[ONOS-5012] implement RESTconf server

 - fix javadoc longer than 80 char limit
 - fix javadoc that missing @params
 - chain calls to StringBuilder.append()
 - combine constant strings in place

Change-Id: Ie2ef4fd4c19e955ad2d5a5584f5017a842abb790

@@ -2,6 +2,7 @@ BUNDLES = [
     '//protocols/restconf/server/api:onos-protocols-restconf-server-api',
     '//protocols/restconf/server/restconfmgr:onos-protocols-restconf-server-restconfmgr',
     '//protocols/restconf/server/rpp:onos-protocols-restconf-server-rpp',
+    '//protocols/restconf/server/utils:onos-protocols-restconf-server-utils',
 ]
 
 onos_app (

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.protocol.restconf.server.api;
+
+import javax.ws.rs.HttpMethod;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates that the annotated method responds to HTTP PATCH requests.
+ */
+@Target({ElementType.METHOD})
+@Retention(RetentionPolicy.RUNTIME)
+@HttpMethod("PATCH")
+public @interface Patch {
+}
\ No newline at end of file

@@ -25,59 +25,82 @@ import org.glassfish.jersey.server.ChunkedOutput;
 public interface RestconfService {
     /**
      * Processes a GET request against a data resource. The
-     * target data resource is identified by its URI.
+     * target data resource is identified by its URI. If the
+     * GET operation cannot be fulfilled due to reasons such
+     * as the nonexistence of the target resource, then a
+     * RestconfException exception is raised. The proper
+     * HTTP error status code is enclosed in the exception, so
+     * that the caller may return it to the RESTCONF client to
+     * display.
      *
      * @param uri URI of the target data resource
      * @return JSON representation of the data resource
-     * @throws RestconfException if the GET operation cannot be fulfilled due
-     *                           reasons such as the nonexistence of the target
-     *                           resource. The proper HTTP error status code is
-     *                           enclosed in the exception, so that the caller
-     *                           may return it to the RESTCONF client
+     * @throws RestconfException if the GET operation cannot be fulfilled
      */
-    ObjectNode runGetOperationOnDataResource(String uri) throws RestconfException;
+    ObjectNode runGetOperationOnDataResource(String uri)
+            throws RestconfException;
 
     /**
      * Processes a POST request against a data resource. The location of
      * the target resource is passed in as a URI. And the resource's
-     * content is passed in as a JSON ObjectNode.
+     * content is passed in as a JSON ObjectNode. If the POST operation
+     * cannot be fulfilled due to reasons such as wrong input URIs or
+     * syntax errors in the JSON payloads, a RestconfException exception
+     * is raised. The proper HTTP error status code is enclosed in the
+     * exception.
      *
      * @param uri      URI of the data resource to be created
      * @param rootNode JSON representation of the data resource
-     * @throws RestconfException if the POST operation cannot be fulfilled due
-     *                           reasons such as wrong URI or syntax error
-     *                           in JSON payload. The proper HTTP error status
-     *                           code is enclosed in the exception
+     * @throws RestconfException if the POST operation cannot be fulfilled
      */
-    void runPostOperationOnDataResource(String uri, ObjectNode rootNode) throws RestconfException;
+    void runPostOperationOnDataResource(String uri, ObjectNode rootNode)
+            throws RestconfException;
 
     /**
      * Processes a PUT request against a data resource. The location of
      * the target resource is passed in as a URI. And the resource's
-     * content is passed in as a JSON ObjectNode.
+     * content is passed in as a JSON ObjectNode. If the PUT operation
+     * cannot be fulfilled due to reasons such as wrong input URIs or
+     * syntax errors in the JSON payloads, a RestconfException exception
+     * is raised. The proper HTTP error status code is enclosed in the
+     * exception.
      *
      * @param uri      URI of the data resource to be created or updated
      * @param rootNode JSON representation of the data resource
-     * @throws RestconfException if the PUT operation cannot be fulfilled due
-     *                           reasons such as wrong URI or syntax error
-     *                           in JSON payload. The proper HTTP error status
-     *                           code is enclosed in the exception
+     * @throws RestconfException if the PUT operation cannot be fulfilled
      */
-    void runPutOperationOnDataResource(String uri, ObjectNode rootNode) throws RestconfException;
+    void runPutOperationOnDataResource(String uri, ObjectNode rootNode)
+            throws RestconfException;
 
     /**
      * Processes the DELETE operation against a data resource. The target
-     * data resource is identified by its URI.
+     * data resource is identified by its URI. If the DELETE operation
+     * cannot be fulfilled due reasons such as the nonexistence of the
+     * target resource, a RestconfException exception is raised. The
+     * proper HTTP error status code is enclosed in the exception.
      *
      * @param uri URI of the data resource to be deleted
-     * @throws RestconfException if the DELETE operation cannot be fulfilled due
-     *                           reasons such as the nonexistence of the target
-     *                           resource. The proper HTTP error status code is
-     *                           enclosed in the exception
+     * @throws RestconfException if the DELETE operation cannot be fulfilled
      */
     void runDeleteOperationOnDataResource(String uri) throws RestconfException;
 
     /**
+     * Processes a PATCH operation on a data resource. The target data
+     * resource is identified by its URI passed in by the caller.
+     * And the content of the data resource is passed in as a JSON ObjectNode.
+     * If the PATCH operation cannot be fulfilled due reasons such as
+     * the nonexistence of the target resource, a RestconfException
+     * exception is raised. The proper HTTP error status code is
+     * enclosed in the exception.
+     *
+     * @param uri      URI of the data resource to be patched
+     * @param rootNode JSON representation of the data resource
+     * @throws RestconfException if the PATCH operation cannot be fulfilled
+     */
+    void runPatchOperationOnDataResource(String uri, ObjectNode rootNode)
+            throws RestconfException;
+
+    /**
      * Retrieves the RESTCONF Root directory.
      *
      * @return the RESTCONF Root directory
@@ -90,13 +113,18 @@ public interface RestconfService {
      * which is passed in from the caller. (The worker thread blocks if
      * no events arrive.) The ChuckedOutput is a pipe to which this
      * function acts as the writer and the caller the reader.
+     * <p>
+     * If the Event Stream cannot be subscribed due to reasons such as
+     * the nonexistence of the target stream or failure to allocate
+     * worker thread to handle the request, a RestconfException exception
+     * is raised. The proper HTTP error status code is enclosed in the
+     * exception, so that the caller may return it to the RESTCONF client
+     * to display.
      *
      * @param streamId ID of the RESTCONF stream to subscribe
      * @param output   A string data stream
-     * @throws RestconfException if the Event Stream cannot be subscribed due to
-     *                           reasons such as the nonexistence of the target
-     *                           stream or unable to allocate any free worker
-     *                           thread to handle the request
+     * @throws RestconfException if the Event Stream cannot be subscribed
      */
-    void subscribeEventStream(String streamId, ChunkedOutput<String> output) throws RestconfException;
+    void subscribeEventStream(String streamId, ChunkedOutput<String> output)
+            throws RestconfException;
 }

@@ -22,4 +22,5 @@
     <artifact>mvn:${project.groupId}/onos-restconf-server-api/${project.version}</artifact>
     <artifact>mvn:${project.groupId}/onos-restconf-server-restconfmanager/${project.version}</artifact>
     <artifact>mvn:${project.groupId}/onos-restconf-server-rpp/${project.version}</artifact>
+    <artifact>mvn:${project.groupId}/onos-restconf-server-utils/${project.version}</artifact>
 </app>

@@ -21,5 +21,6 @@
         <bundle>mvn:${project.groupId}/onos-restconf-server-api/${project.version}</bundle>
         <bundle>mvn:${project.groupId}/onos-restconf-server-restconfmanager/${project.version}</bundle>
         <bundle>mvn:${project.groupId}/onos-restconf-server-rpp/${project.version}</bundle>
+        <bundle>mvn:${project.groupId}/onos-restconf-server-utils/${project.version}</bundle>
     </feature>
 </features>

@@ -51,5 +51,10 @@
             <artifactId>onos-restconf-server-rpp</artifactId>
             <version>${project.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-restconf-server-utils</artifactId>
+            <version>${project.version}</version>
+        </dependency>
     </dependencies>
 </project>

@@ -34,6 +34,7 @@
         <module>restconfmgr</module>
         <module>rpp</module>
         <module>app</module>
+        <module>utils</module>
     </modules>
 
     <description>RESTCONF Server Module</description>

@@ -6,6 +6,8 @@ COMPILE_DEPS = [
     '//utils/rest:onlab-rest',
     '//core/store/serializers:onos-core-serializers',
     '//protocols/restconf/server/api:onos-protocols-restconf-server-api',
+    '//protocols/restconf/server/utils:onos-protocols-restconf-server-utils',
+    '//apps/yms/api:onos-apps-yms-api',
 ]
 
 osgi_jar_with_tests (

@@ -58,6 +58,16 @@
             <groupId>org.apache.felix</groupId>
             <artifactId>org.apache.felix.scr.annotations</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-restconf-server-utils</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-app-yms-api</artifactId>
+            <version>${project.version}</version>
+        </dependency>
     </dependencies>
     <build>
         <plugins>

@@ -19,6 +19,7 @@ package org.onosproject.protocol.restconf.server.rpp;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 import org.glassfish.jersey.server.ChunkedOutput;
+import org.onosproject.protocol.restconf.server.api.Patch;
 import org.onosproject.protocol.restconf.server.api.RestconfException;
 import org.onosproject.protocol.restconf.server.api.RestconfService;
 import org.onosproject.rest.AbstractWebResource;
@@ -39,8 +40,11 @@ import javax.ws.rs.core.UriInfo;
 import java.io.IOException;
 import java.io.InputStream;
 
+import static javax.ws.rs.core.Response.Status.BAD_REQUEST;
+import static javax.ws.rs.core.Response.Status.INTERNAL_SERVER_ERROR;
 import static org.slf4j.LoggerFactory.getLogger;
 
+
 /*
  * This class is the main implementation of the RESTCONF Protocol
  * Proxy module. Currently it only handles some basic operations
@@ -134,7 +138,8 @@ public class RestconfWebResource extends AbstractWebResource {
     @Consumes(MediaType.APPLICATION_JSON)
     @Produces(MediaType.APPLICATION_JSON)
     @Path("data/{identifier : .+}")
-    public Response handlePostRequest(@PathParam("identifier") String uriString, InputStream stream) {
+    public Response handlePostRequest(@PathParam("identifier") String uriString,
+                                      InputStream stream) {
 
         log.debug("handlePostRequest: {}", uriString);
 
@@ -145,14 +150,14 @@ public class RestconfWebResource extends AbstractWebResource {
             return Response.created(uriInfo.getRequestUri()).build();
         } catch (JsonProcessingException e) {
             log.error("ERROR: handlePostRequest ", e);
-            return Response.status(Response.Status.BAD_REQUEST).build();
+            return Response.status(BAD_REQUEST).build();
         } catch (RestconfException e) {
             log.error("ERROR: handlePostRequest: {}", e.getMessage());
             log.debug("Exception in handlePostRequest:", e);
             return e.getResponse();
         } catch (IOException ex) {
             log.error("ERROR: handlePostRequest ", ex);
-            return Response.status(Response.Status.INTERNAL_SERVER_ERROR).build();
+            return Response.status(INTERNAL_SERVER_ERROR).build();
         }
     }
 
@@ -174,7 +179,8 @@ public class RestconfWebResource extends AbstractWebResource {
     @Consumes(MediaType.APPLICATION_JSON)
     @Produces(MediaType.APPLICATION_JSON)
     @Path("data/{identifier : .+}")
-    public Response handlePutRequest(@PathParam("identifier") String uriString, InputStream stream) {
+    public Response handlePutRequest(@PathParam("identifier") String uriString,
+                                     InputStream stream) {
 
         log.debug("handlePutRequest: {}", uriString);
 
@@ -185,14 +191,14 @@ public class RestconfWebResource extends AbstractWebResource {
             return Response.created(uriInfo.getRequestUri()).build();
         } catch (JsonProcessingException e) {
             log.error("ERROR: handlePutRequest ", e);
-            return Response.status(Response.Status.BAD_REQUEST).build();
+            return Response.status(BAD_REQUEST).build();
         } catch (RestconfException e) {
             log.error("ERROR: handlePutRequest: {}", e.getMessage());
             log.debug("Exception in handlePutRequest:", e);
             return e.getResponse();
         } catch (IOException ex) {
             log.error("ERROR: handlePutRequest ", ex);
-            return Response.status(Response.Status.INTERNAL_SERVER_ERROR).build();
+            return Response.status(INTERNAL_SERVER_ERROR).build();
         }
     }
 
@@ -223,4 +229,41 @@ public class RestconfWebResource extends AbstractWebResource {
         }
     }
 
+    /**
+     * Handles a RESTCONF PATCH operation against a data resource.
+     * If the PATCH request succeeds, a "200 OK" status-line is returned if
+     * there is a message-body, and "204 No Content" is returned if no
+     * response message-body is sent.
+     *
+     * @param uriString URI of the data resource
+     * @param stream    Input JSON object
+     * @return HTTP response
+     */
+    @Patch
+    @Consumes(MediaType.APPLICATION_JSON)
+    @Produces(MediaType.APPLICATION_JSON)
+    @Path("data/{identifier : .+}")
+    public Response handlePatchRequest(@PathParam("identifier") String uriString,
+                                       InputStream stream) {
+
+        log.debug("handlePatchRequest: {}", uriString);
+
+        try {
+            ObjectNode rootNode = (ObjectNode) mapper().readTree(stream);
+
+            service.runPatchOperationOnDataResource(uriString, rootNode);
+            return Response.ok().build();
+        } catch (JsonProcessingException e) {
+            log.error("ERROR: handlePatchRequest ", e);
+            return Response.status(BAD_REQUEST).build();
+        } catch (RestconfException e) {
+            log.error("ERROR: handlePatchRequest: {}", e.getMessage());
+            log.debug("Exception in handlePatchRequest:", e);
+            return e.getResponse();
+        } catch (IOException ex) {
+            log.error("ERROR: handlePatchRequest ", ex);
+            return Response.status(INTERNAL_SERVER_ERROR).build();
+        }
+    }
+
 }

+COMPILE_DEPS = [
+ '//lib:CORE_DEPS',
+ '//apps/yms/api:onos-apps-yms-api',
+]
+
+osgi_jar_with_tests (
+    deps = COMPILE_DEPS,
+)

+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>onos-restconf-server</artifactId>
+        <groupId>org.onosproject</groupId>
+        <version>1.8.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>onos-restconf-server-utils</artifactId>
+    <packaging>bundle</packaging>
+    <dependencies>
+        <dependency>
+            <groupId>org.onosproject</groupId>
+            <artifactId>onos-app-yms-api</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.easymock</groupId>
+            <artifactId>easymock</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.protocol.restconf.server.utils.exceptions;
+
+/**
+ * Represents class of errors related to Json parse utils.
+ */
+public class JsonParseException extends RuntimeException {
+
+    /**
+     * Constructs an exception with the specified message.
+     *
+     * @param message the message describing the specific nature of the error
+     */
+    public JsonParseException(String message) {
+        super(message);
+    }
+
+    /**
+     * Constructs an exception with the specified message and the underlying
+     * cause.
+     *
+     * @param message the message describing the specific nature of the error
+     * @param cause   the underlying cause of this error
+     */
+    public JsonParseException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.protocol.restconf.server.utils.exceptions;
+
+/**
+ * Represents class of errors related to YDT parse utils.
+ */
+public class YdtParseException extends RuntimeException {
+    /**
+     * Constructs an exception with the specified message.
+     *
+     * @param message the message describing the specific nature of the error
+     */
+    public YdtParseException(String message) {
+        super(message);
+    }
+
+    /**
+     * Constructs an exception with the specified message and the underlying
+     * cause.
+     *
+     * @param message the message describing the specific nature of the error
+     * @param cause   the underlying cause of this error
+     */
+    public YdtParseException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Parse utils custom exceptions.
+ */
+package org.onosproject.protocol.restconf.server.utils.exceptions;
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.protocol.restconf.server.utils.parser.api;
+
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+import java.util.Set;
+
+/**
+ * Abstraction of an entity which provides interfaces to build and obtain JSON
+ * data tree.
+ */
+public interface JsonBuilder {
+
+    /**
+     * Adds a to half (a left brace/bracket and the field name) of a JSON
+     * object/array to the JSON tree. This method is used by protocols which
+     * knows the nature (object/array) of node.
+     *
+     * @param fieldName name of child to be added
+     * @param nodeType  the type of the child
+     */
+    void addNodeTopHalf(String fieldName, JsonNodeType nodeType);
+
+    /**
+     * Adds a child with value and a comma to the JSON tree.
+     * Protocols unaware of nature of node (single/multiple) will use it to add
+     * both single instance and multi instance node. Protocols aware of nature
+     * of node will use it for single instance value node addition.
+     *
+     * @param fieldName name of child to be added
+     * @param value     the type of the child
+     */
+    void addNodeWithValueTopHalf(String fieldName, String value);
+
+    /**
+     * Adds a child with list of values to JSON data tree. This method is
+     * used by protocols which knows the nature (object/array) of node for
+     * ArrayNode addition.
+     *
+     * @param fieldName name of child to be added
+     * @param sets      the value list of the child
+     */
+    void addNodeWithSetTopHalf(String fieldName, Set<String> sets);
+
+    /**
+     * Adds the bottom half(a right brace/bracket) of  a JSON object/array to
+     * the JSON tree. for the text, a comma should be taken out.
+     *
+     * @param nodeType the type of the child
+     */
+    void addNodeBottomHalf(JsonNodeType nodeType);
+
+    /**
+     * Returns the JSON tree after build operations in the format of string.
+     *
+     * @return the final string JSON tree after build operations
+     */
+    String getTreeString();
+
+    /**
+     * Returns the JSON tree after build operations in the format of ObjectNode.
+     *
+     * @return the final ObjectNode JSON tree after build operations
+     */
+    ObjectNode getTreeNode();
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.protocol.restconf.server.utils.parser.api;
+
+
+import com.fasterxml.jackson.databind.JsonNode;
+
+/**
+ * Abstraction of an entity which provide call back methods which are called
+ * by JSON walker while walking the JSON data tree. This interface needs to be
+ * implemented by protocol implementing listener's based call backs while JSON
+ * walk.
+ */
+public interface JsonListener {
+
+    /**
+     * Callback invoked during a node entry.
+     * All the related information about the node can be obtain from the JSON
+     * object.
+     *
+     * @param fieldName the field name of the JSON Node value
+     * @param node      the JsonNode which is walked through
+     */
+    void enterJsonNode(String fieldName, JsonNode node);
+
+    /**
+     * Callback invoked during a node exit.
+     * All the related information about the node can be obtain from the JSON
+     * node.
+     *
+     * @param jsonNode JSON node which has been walked through
+     */
+    void exitJsonNode(JsonNode jsonNode);
+
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.protocol.restconf.server.utils.parser.api;
+
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+/**
+ * Abstraction of an entity which provides interfaces for Json walk.
+ * This interface serve as common tools for anyone who needs to parse
+ * the json node with depth-first algorithm.
+ */
+public interface JsonWalker {
+
+    /**
+     * Walks the JSON data tree. Protocols implements JSON listener service
+     * and walks JSON tree with input as implemented object. JSON walker
+     * provides call backs to implemented methods. For the original json
+     * node(come from NB), there is a field name which is something like the
+     * module name of a YANG model. If not, the fieldName can be null.
+     *
+     * @param jsonListener Json listener implemented by the user
+     * @param fieldName    the original object node field
+     * @param node         the json node which needs to be walk
+     */
+    void walk(JsonListener jsonListener, String fieldName, ObjectNode node);
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Provider json related process interface.
+ */
+package org.onosproject.protocol.restconf.server.utils.parser.api;
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.protocol.restconf.server.utils.parser.json;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.onosproject.protocol.restconf.server.utils.exceptions.JsonParseException;
+import org.onosproject.protocol.restconf.server.utils.parser.api.JsonBuilder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Set;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Strings.isNullOrEmpty;
+
+/**
+ * Represents implementation of interfaces to build and obtain JSON data tree.
+ */
+public class DefaultJsonBuilder implements JsonBuilder {
+
+    private static final String LEFT_BRACE = "{";
+    private static final String RIGHT_BRACE = "}";
+    private static final String LEFT_BRACKET = "[";
+    private static final String RIGHT_BRACKET = "]";
+    private static final String COMMA = ",";
+    private static final String COLON = ":";
+    private static final String QUOTE = "\"";
+    private static final String E_UNSUP_TYPE = "Unsupported node type %s " +
+            "field name is %s fieldName";
+
+    private Logger log = LoggerFactory.getLogger(getClass());
+
+    private StringBuilder treeString;
+
+    /**
+     * Creates a Default Json Builder with a specific root name.
+     *
+     * @param rootName the start string of the Json builder
+     */
+    public DefaultJsonBuilder(String rootName) {
+        checkNotNull(rootName);
+        treeString = new StringBuilder(rootName);
+    }
+
+    /**
+     * Creates a Default Json Builder with a default root name.
+     */
+    public DefaultJsonBuilder() {
+        treeString = new StringBuilder(LEFT_BRACE);
+    }
+
+    @Override
+    public void addNodeTopHalf(String fieldName, JsonNodeType nodeType) {
+
+        appendField(fieldName);
+
+        switch (nodeType) {
+            case OBJECT:
+                treeString.append(LEFT_BRACE);
+                break;
+            case ARRAY:
+                treeString.append(LEFT_BRACKET);
+                break;
+            default:
+                throw new JsonParseException(String.format(E_UNSUP_TYPE,
+                                                           nodeType, fieldName));
+        }
+    }
+
+    @Override
+    public void addNodeWithValueTopHalf(String fieldName, String value) {
+        if (isNullOrEmpty(fieldName)) {
+            return;
+        }
+        appendField(fieldName);
+        if (value.isEmpty()) {
+            return;
+        }
+        treeString.append(QUOTE)
+                .append(value)
+                .append(QUOTE + COMMA);
+    }
+
+    @Override
+    public void addNodeWithSetTopHalf(String fieldName, Set<String> sets) {
+        if (isNullOrEmpty(fieldName)) {
+            return;
+        }
+        appendField(fieldName);
+        treeString.append(LEFT_BRACKET);
+        for (String el : sets) {
+            treeString.append(QUOTE)
+                    .append(el)
+                    .append(QUOTE + COMMA);
+        }
+    }
+
+    @Override
+    public void addNodeBottomHalf(JsonNodeType nodeType) {
+
+        switch (nodeType) {
+            case OBJECT:
+                removeCommaIfExist();
+                treeString.append(RIGHT_BRACE + COMMA);
+                break;
+
+            case ARRAY:
+                removeCommaIfExist();
+                treeString.append(RIGHT_BRACKET + COMMA);
+                break;
+
+            case BINARY:
+            case BOOLEAN:
+            case MISSING:
+            case NULL:
+            case NUMBER:
+            case POJO:
+            case STRING:
+                log.debug("Unimplemented node type {}", nodeType);
+                break;
+
+            default:
+                throw new JsonParseException("Unsupported json node type " +
+                                                     nodeType);
+        }
+    }
+
+    @Override
+    public String getTreeString() {
+        removeCommaIfExist();
+        return treeString.append(RIGHT_BRACE).toString();
+    }
+
+    @Override
+    public ObjectNode getTreeNode() {
+        ObjectNode node = null;
+        try {
+            node = (ObjectNode) (new ObjectMapper()).readTree(getTreeString());
+        } catch (IOException e) {
+            log.error("Parse json string failed {}", e.getMessage());
+        }
+        return node;
+    }
+
+
+    private void appendField(String fieldName) {
+        if (!isNullOrEmpty(fieldName)) {
+            treeString.append(QUOTE)
+            .append(fieldName)
+            .append(QUOTE + COLON);
+        }
+    }
+
+    private void removeCommaIfExist() {
+        int lastIndex = treeString.length() - 1;
+        if (treeString.charAt(lastIndex) == COMMA.charAt(0)) {
+            treeString.deleteCharAt(lastIndex);
+        }
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.protocol.restconf.server.utils.parser.json;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.onosproject.protocol.restconf.server.utils.parser.api.JsonWalker;
+import org.onosproject.protocol.restconf.server.utils.parser.api.JsonListener;
+
+import java.util.Iterator;
+import java.util.Map;
+
+/**
+ * Represents implementation of JSON walk, which walks the JSON object node.
+ */
+public class DefaultJsonWalker implements JsonWalker {
+    @Override
+    public void walk(JsonListener jsonListener, String fieldName,
+                     ObjectNode objectNode) {
+
+        //enter the object node, the original ObjectNode should have a module
+        //name as fieldName.
+        jsonListener.enterJsonNode(fieldName, objectNode);
+        //the node has no children, then exist and return.
+        if (!objectNode.isContainerNode()) {
+            jsonListener.exitJsonNode(objectNode);
+            return;
+        }
+
+        Iterator<Map.Entry<String, JsonNode>> fields = objectNode.fields();
+        while (fields.hasNext()) {
+            //get the children entry of the node
+            Map.Entry<String, JsonNode> currentChild = fields.next();
+            String key = currentChild.getKey();
+            JsonNode value = currentChild.getValue();
+            //if the entry's value has its own children, do a recursion.
+            //if the entry has no children, store the key and value.
+            //for we don't know the specific type of the entry's value, we
+            // should give it to a method which can handle JsonNode
+            if (value.isContainerNode()) {
+                walkJsonNode(jsonListener, key, value);
+            } else {
+                jsonListener.enterJsonNode(key, value);
+                jsonListener.exitJsonNode(value);
+            }
+        }
+        jsonListener.exitJsonNode(objectNode);
+    }
+
+    /**
+     * Walks the JSON data tree. This method is called when we don't know
+     * the exact type of a json node.
+     *
+     * @param jsonListener Json listener implemented by the user
+     * @param fieldName    the original object node field
+     * @param rootNode     the json node which needs to be walk
+     */
+    private void walkJsonNode(JsonListener jsonListener, String fieldName,
+                              JsonNode rootNode) {
+        if (rootNode.isObject()) {
+            walk(jsonListener, fieldName, (ObjectNode) rootNode);
+            return;
+        }
+
+        if (rootNode.isArray()) {
+            walkArrayNode(jsonListener, fieldName, (ArrayNode) rootNode);
+        }
+    }
+
+    /**
+     * Walks the JSON data tree. This method is called when the user knows the
+     * json node type is ArrayNode.
+     *
+     * @param jsonListener Json listener implemented by the user
+     * @param fieldName    the original object node field
+     * @param rootNode     the json node which needs to be walk
+     */
+    private void walkArrayNode(JsonListener jsonListener, String fieldName,
+                               ArrayNode rootNode) {
+        if (rootNode == null) {
+            return;
+        }
+        //enter the array node.
+        jsonListener.enterJsonNode(fieldName, rootNode);
+        Iterator<JsonNode> children = rootNode.elements();
+        while (children.hasNext()) {
+            JsonNode currentChild = children.next();
+            if (currentChild.isContainerNode()) {
+                walkJsonNode(jsonListener, null, currentChild);
+            }
+        }
+        jsonListener.exitJsonNode(rootNode);
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.protocol.restconf.server.utils.parser.json;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import org.onosproject.protocol.restconf.server.utils.exceptions.JsonParseException;
+import org.onosproject.protocol.restconf.server.utils.parser.api.JsonListener;
+import org.onosproject.yms.ydt.YdtBuilder;
+import org.onosproject.yms.ydt.YdtContext;
+import org.slf4j.Logger;
+
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Set;
+
+import static com.fasterxml.jackson.databind.node.JsonNodeType.ARRAY;
+import static com.google.common.base.Strings.isNullOrEmpty;
+import static org.onosproject.yms.ydt.YdtType.MULTI_INSTANCE_NODE;
+import static org.onosproject.yms.ydt.YdtType.SINGLE_INSTANCE_NODE;
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Represents default implementation of codec JSON listener.
+ */
+public class JsonToYdtListener implements JsonListener {
+
+    private static final String INPUT_FIELD_NAME = "input";
+    private static final String COLON = ":";
+    private static final int INPUT_FIELD_LENGTH = 2;
+    private static final String E_UNSUP_TYPE = "Unsupported node type %s " +
+            "field name is %s fieldName";
+
+    private Logger log = getLogger(getClass());
+
+    private YdtBuilder ydtBuilder;
+    private String defaultMultiInsNodeName;
+    private YdtContext rpcModule;
+
+    /**
+     * Creates a listener for the process of a Json Object, the listener will
+     * try to transfer the JSON object to a Ydt builder.
+     *
+     * @param ydtBuilder the YDT builder to build a YDT object
+     */
+    public JsonToYdtListener(YdtBuilder ydtBuilder) {
+        this.ydtBuilder = ydtBuilder;
+    }
+
+    @Override
+    public void enterJsonNode(String fieldName, JsonNode node) {
+        if (isNullOrEmpty(fieldName)) {
+            if (!isNullOrEmpty(defaultMultiInsNodeName)) {
+                ydtBuilder.addChild(defaultMultiInsNodeName, null,
+                                    MULTI_INSTANCE_NODE);
+            }
+            return;
+        }
+        JsonNodeType nodeType = node.getNodeType();
+        switch (nodeType) {
+            case OBJECT:
+                processObjectNode(fieldName);
+                break;
+
+            case ARRAY:
+                processArrayNode(fieldName, node);
+                break;
+
+            //TODO for now, just process the following three node type
+            case STRING:
+            case NUMBER:
+            case BOOLEAN:
+                ydtBuilder.addLeaf(fieldName, null, node.asText());
+                break;
+
+            case BINARY:
+            case MISSING:
+            case NULL:
+            case POJO:
+                log.debug("Unimplemented node type {}", nodeType);
+                break;
+
+            default:
+                throw new JsonParseException(String.format(E_UNSUP_TYPE,
+                                                           nodeType, fieldName));
+        }
+    }
+
+    @Override
+    public void exitJsonNode(JsonNode jsonNode) {
+        if (jsonNode.getNodeType() == ARRAY) {
+            return;
+        }
+        ydtBuilder.traverseToParent();
+        YdtContext curNode = ydtBuilder.getCurNode();
+        //if the current node is the RPC node, then should go to the father
+        //for we have enter the RPC node and Input node at the same time
+        //and the input is the only child of RPC node.
+
+        if (curNode == null) {
+            return;
+        }
+        String name = curNode.getName();
+        if (rpcModule != null && name.equals(rpcModule.getName())) {
+            ydtBuilder.traverseToParent();
+        }
+    }
+
+    private void processObjectNode(String fieldName) {
+        String[] segments = fieldName.split(COLON);
+        Boolean isLastInput = segments.length == INPUT_FIELD_LENGTH &&
+                segments[INPUT_FIELD_LENGTH - 1].equals(INPUT_FIELD_NAME);
+        int first = 0;
+        int second = 1;
+        if (isLastInput) {
+            ydtBuilder.addChild(segments[first], null, SINGLE_INSTANCE_NODE);
+            rpcModule = ydtBuilder.getCurNode();
+            ydtBuilder.addChild(segments[second], null, SINGLE_INSTANCE_NODE);
+        } else {
+            ydtBuilder.addChild(fieldName, null, SINGLE_INSTANCE_NODE);
+        }
+    }
+
+    private void processArrayNode(String fieldName, JsonNode node) {
+        ArrayNode arrayNode = (ArrayNode) node;
+        Set<String> sets = new HashSet<>();
+        Iterator<JsonNode> elements = arrayNode.elements();
+        boolean isLeafList = true;
+        while (elements.hasNext()) {
+            JsonNode element = elements.next();
+            JsonNodeType eleType = element.getNodeType();
+
+            if (eleType == JsonNodeType.STRING ||
+                    eleType == JsonNodeType.NUMBER ||
+                    eleType == JsonNodeType.BOOLEAN) {
+                sets.add(element.asText());
+            } else {
+                isLeafList = false;
+            }
+        }
+        if (isLeafList) {
+            //leaf-list
+            ydtBuilder.addLeaf(fieldName, null, sets);
+        } else {
+            this.defaultMultiInsNodeName = fieldName;
+        }
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.protocol.restconf.server.utils.parser.json;
+
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.google.common.base.Splitter;
+import com.google.common.collect.Lists;
+import org.onosproject.protocol.restconf.server.utils.exceptions.JsonParseException;
+import org.onosproject.protocol.restconf.server.utils.parser.api.JsonBuilder;
+import org.onosproject.yms.ydt.YdtBuilder;
+import org.onosproject.yms.ydt.YdtContext;
+import org.onosproject.yms.ydt.YdtContextOperationType;
+import org.onosproject.yms.ydt.YdtListener;
+import org.onosproject.yms.ydt.YdtType;
+import org.onosproject.yms.ydt.YdtWalker;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLDecoder;
+import java.util.ArrayList;
+import java.util.List;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.onosproject.yms.ydt.YdtContextOperationType.NONE;
+
+/**
+ * Utils to complete the conversion between JSON and YDT(YANG DATA MODEL).
+ */
+public final class ParserUtils {
+
+    private static final Splitter SLASH_SPLITTER = Splitter.on('/');
+    private static final Splitter COMMA_SPLITTER = Splitter.on(',');
+    private static final String EQUAL = "=";
+    private static final String COMMA = ",";
+    private static final String COLON = ":";
+    private static final String URI_ENCODING_CHAR_SET = "ISO-8859-1";
+    private static final String ERROR_LIST_MSG = "List/Leaf-list node should be " +
+            "in format \"nodeName=key\"or \"nodeName=instance-value\"";
+    private static final String ERROR_MODULE_MSG = "First node should be in " +
+            "format \"moduleName:nodeName\"";
+
+    // no instantiation
+    private ParserUtils() {
+    }
+
+    /**
+     * Converts  URI identifier to YDT builder.
+     *
+     * @param id      the uri identifier from web request
+     * @param builder the base ydt builder
+     * @param opType  the ydt operation type for the uri
+     */
+    public static void convertUriToYdt(String id,
+                                       YdtBuilder builder,
+                                       YdtContextOperationType opType) {
+        checkNotNull(id, "uri identifier should not be null");
+        List<String> paths = urlPathArgsDecode(SLASH_SPLITTER.split(id));
+        if (!paths.isEmpty()) {
+            processPathSegments(paths, builder, opType);
+        }
+    }
+
+    /**
+     * Converts  JSON objectNode to YDT builder. The objectNode can be any
+     * standard JSON node, node just for RESTconf payload.
+     *
+     * @param objectNode the objectNode from web request
+     * @param builder    the base ydt builder
+     */
+    public static void convertJsonToYdt(ObjectNode objectNode,
+                                        YdtBuilder builder) {
+
+        JsonToYdtListener listener = new JsonToYdtListener(builder);
+        new DefaultJsonWalker().walk(listener, null, objectNode);
+    }
+
+    /**
+     * Converts a Ydt context tree to a JSON object.
+     *
+     * @param rootName the name of the YdtContext from which the YdtListener
+     *                 start to builder a Json Object
+     * @param context  a abstract data model for YANG data
+     * @param walker   abstraction of an entity which provides interfaces for
+     *                 YDT walk
+     * @return the JSON node corresponding the YANG data
+     */
+    public static ObjectNode convertYdtToJson(String rootName,
+                                              YdtContext context,
+                                              YdtWalker walker) {
+        JsonBuilder builder = new DefaultJsonBuilder();
+        YdtListener listener = new YdtToJsonListener(rootName, builder);
+        walker.walk(listener, context);
+        return builder.getTreeNode();
+    }
+
+    /**
+     * Converts a list of path segments to a YDT builder tree.
+     *
+     * @param paths   the list of path segments split from URI
+     * @param builder the base YDT builder
+     * @param opType  the YDT operation type for the Path segment
+     * @return the YDT builder with the tree info of paths
+     */
+    private static YdtBuilder processPathSegments(List<String> paths,
+                                                  YdtBuilder builder,
+                                                  YdtContextOperationType opType) {
+        if (paths.isEmpty()) {
+            return builder;
+        }
+        boolean isLastNode = paths.size() == 1;
+        YdtContextOperationType opTypeForThisNode = isLastNode ? opType : NONE;
+
+        String path = paths.iterator().next();
+        if (path.contains(COLON)) {
+            addModule(builder, path);
+            addNode(path, builder, opTypeForThisNode);
+        } else if (path.contains(EQUAL)) {
+            addListOrLeafList(path, builder, opTypeForThisNode);
+        } else {
+            addLeaf(path, builder, opTypeForThisNode);
+        }
+
+        if (isLastNode) {
+            return builder;
+        }
+        List<String> remainPaths = paths.subList(1, paths.size());
+        processPathSegments(remainPaths, builder, opType);
+
+        return builder;
+    }
+
+    private static YdtBuilder addModule(YdtBuilder builder, String path) {
+        String moduleName = getPreSegment(path, COLON);
+        if (moduleName == null) {
+            throw new JsonParseException(ERROR_MODULE_MSG);
+        }
+        builder.addChild(moduleName, null, YdtType.SINGLE_INSTANCE_NODE);
+        return builder;
+    }
+
+    private static YdtBuilder addNode(String path, YdtBuilder builder,
+                                      YdtContextOperationType opType) {
+        String nodeName = getLatterSegment(path, COLON);
+        builder.addChild(nodeName,
+                         null,
+                         YdtType.SINGLE_INSTANCE_NODE,
+                         opType);
+        return builder;
+    }
+
+    private static YdtBuilder addListOrLeafList(String path,
+                                                YdtBuilder builder,
+                                                YdtContextOperationType opType) {
+        String nodeName = getPreSegment(path, EQUAL);
+        String keyStr = getLatterSegment(path, EQUAL);
+        if (keyStr == null) {
+            throw new JsonParseException(ERROR_LIST_MSG);
+        }
+        builder.setDefaultEditOperationType(opType);
+        if (keyStr.contains(COMMA)) {
+            List<String> keys = Lists.
+                    newArrayList(COMMA_SPLITTER.split(keyStr));
+            builder.addMultiInstanceChild(nodeName, null, keys);
+        } else {
+            builder.addMultiInstanceChild(nodeName, null,
+                                          Lists.newArrayList(keyStr));
+        }
+        return builder;
+    }
+
+    private static YdtBuilder addLeaf(String path, YdtBuilder builder,
+                                      YdtContextOperationType opType) {
+        checkNotNull(path);
+        builder.addChild(path, null, opType);
+        return builder;
+    }
+
+    /**
+     * Returns the previous segment of a path which is separated by a split char.
+     * For example:
+     * <pre>
+     * "foo:bar", ":"   -->  "foo"
+     * </pre>
+     *
+     * @param path      the original path string
+     * @param splitChar char used to split the path
+     * @return the previous segment of the path
+     */
+    private static String getPreSegment(String path, String splitChar) {
+        int idx = path.indexOf(splitChar);
+        if (idx == -1) {
+            return null;
+        }
+
+        if (path.indexOf(splitChar, idx + 1) != -1) {
+            return null;
+        }
+
+        return path.substring(0, idx);
+    }
+
+    /**
+     * Returns the latter segment of a path which is separated by a split char.
+     * For example:
+     * <pre>
+     * "foo:bar", ":"   -->  "bar"
+     * </pre>
+     *
+     * @param path      the original path string
+     * @param splitChar char used to split the path
+     * @return the latter segment of the path
+     */
+    private static String getLatterSegment(String path, String splitChar) {
+        int idx = path.indexOf(splitChar);
+        if (idx == -1) {
+            return path;
+        }
+
+        if (path.indexOf(splitChar, idx + 1) != -1) {
+            return null;
+        }
+
+        return path.substring(idx + 1);
+    }
+
+    /**
+     * Converts a list of path from the original format to ISO-8859-1 code.
+     *
+     * @param paths the original paths
+     * @return list of decoded paths
+     */
+    public static List<String> urlPathArgsDecode(Iterable<String> paths) {
+        try {
+            List<String> decodedPathArgs = new ArrayList<>();
+            for (String pathArg : paths) {
+                String decode = URLDecoder.decode(pathArg,
+                                                  URI_ENCODING_CHAR_SET);
+                decodedPathArgs.add(decode);
+            }
+            return decodedPathArgs;
+        } catch (UnsupportedEncodingException e) {
+            throw new JsonParseException("Invalid URL path arg '" +
+                                                 paths + "': ", e);
+        }
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.protocol.restconf.server.utils.parser.json;
+
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import org.onosproject.protocol.restconf.server.utils.exceptions.YdtParseException;
+import org.onosproject.protocol.restconf.server.utils.parser.api.JsonBuilder;
+import org.onosproject.yms.ydt.YdtContext;
+import org.onosproject.yms.ydt.YdtListener;
+
+import static com.google.common.base.Strings.isNullOrEmpty;
+
+/**
+ * Represents implementation of codec YDT listener.
+ */
+public class YdtToJsonListener implements YdtListener {
+
+    private static final String EMPTY = "";
+    private JsonBuilder jsonBuilder;
+    //the root name of the json
+    //the input YdtContext is usually a total tree of a YANG resource
+    //this property is used to mark the start of the request node.
+    private String rootName;
+    //the parse state
+    private boolean isBegin;
+
+    /**
+     * Creates a listener for the process of a Ydt, the listener will try to
+     * transfer the Ydt to a JSON Object.
+     *
+     * @param rootName    the name of a specific YdtContext begin to  process
+     * @param jsonBuilder the JSON builder to build a JSON object
+     */
+    public YdtToJsonListener(String rootName, JsonBuilder jsonBuilder) {
+        this.jsonBuilder = jsonBuilder;
+        this.rootName = rootName;
+        this.isBegin = isNullOrEmpty(rootName);
+    }
+
+    @Override
+    public void enterYdtNode(YdtContext ydtContext) {
+        String name = ydtContext.getName();
+
+        if (!isBegin && name.equals(rootName)) {
+            isBegin = true;
+        }
+        if (!isBegin) {
+            return;
+        }
+
+        switch (ydtContext.getYdtType()) {
+
+            case SINGLE_INSTANCE_NODE:
+                jsonBuilder.addNodeTopHalf(name, JsonNodeType.OBJECT);
+                break;
+            case MULTI_INSTANCE_NODE:
+                YdtContext preNode = ydtContext.getPreviousSibling();
+                if (preNode == null || !preNode.getName().equals(name)) {
+                    jsonBuilder.addNodeTopHalf(name, JsonNodeType.ARRAY);
+                }
+                jsonBuilder.addNodeTopHalf(EMPTY, JsonNodeType.OBJECT);
+                break;
+            case SINGLE_INSTANCE_LEAF_VALUE_NODE:
+                jsonBuilder.addNodeWithValueTopHalf(name, ydtContext.getValue());
+                break;
+            case MULTI_INSTANCE_LEAF_VALUE_NODE:
+                jsonBuilder.addNodeWithSetTopHalf(name, ydtContext.getValueSet());
+                break;
+            default:
+                throw new YdtParseException("unknown Ydt type " +
+                                                    ydtContext.getYdtType());
+        }
+
+    }
+
+    @Override
+    public void exitYdtNode(YdtContext ydtContext) {
+
+        if (!isBegin) {
+            return;
+        }
+
+        String curName = ydtContext.getName();
+        YdtContext nextNode = ydtContext.getNextSibling();
+        switch (ydtContext.getYdtType()) {
+
+            case SINGLE_INSTANCE_NODE:
+                jsonBuilder.addNodeBottomHalf(JsonNodeType.OBJECT);
+                break;
+            case MULTI_INSTANCE_NODE:
+                if (nextNode == null || !nextNode.getName().equals(curName)) {
+                    jsonBuilder.addNodeBottomHalf(JsonNodeType.OBJECT);
+                    jsonBuilder.addNodeBottomHalf(JsonNodeType.ARRAY);
+                } else {
+                    jsonBuilder.addNodeBottomHalf(JsonNodeType.OBJECT);
+                }
+                break;
+            case SINGLE_INSTANCE_LEAF_VALUE_NODE:
+                jsonBuilder.addNodeBottomHalf(JsonNodeType.STRING);
+                break;
+            case MULTI_INSTANCE_LEAF_VALUE_NODE:
+                jsonBuilder.addNodeBottomHalf(JsonNodeType.ARRAY);
+                break;
+            default:
+                throw new YdtParseException("Unknown Ydt type " +
+                                                    ydtContext.getYdtType());
+        }
+        if (curName.equals(rootName) &&
+                (nextNode == null || !nextNode.getName().equals(rootName))) {
+            isBegin = false;
+        }
+    }
+}
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Provider utilities to support the data format based encoding and decoding,
+ * used by YMSC to operate on different data format and YDT(YANG DATA TYPE).
+ */
+
+package org.onosproject.protocol.restconf.server.utils.parser.json;
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.restconf.utils.parser.json;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.junit.Before;
+import org.junit.Test;
+import org.onosproject.protocol.restconf.server.utils.parser.api.JsonListener;
+import org.onosproject.protocol.restconf.server.utils.parser.json.DefaultJsonWalker;
+
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+
+public class DefaultJsonWalkerTest {
+
+    private static final String[] EXP_TEXT_ARRAY = {
+            "Enter: type is OBJECT name is null",
+            "Enter: type is STRING name is name",
+            "Exit: type is STRING",
+            "Enter: type is STRING name is surname",
+            "Exit: type is STRING",
+            "Exit: type is OBJECT"
+    };
+
+    private static final String[] EXP_NODE_LIST_ARRAY = {
+            "Enter: type is OBJECT name is null",
+            "Enter: type is STRING name is surname",
+            "Exit: type is STRING",
+            "Enter: type is ARRAY name is networklist",
+            "Exit: type is ARRAY",
+            "Exit: type is OBJECT"
+    };
+
+    private static final String[] EXP_NODE_WITH_ARRAY = {
+            "Enter: type is OBJECT name is null",
+            "Enter: type is STRING name is surname",
+            "Exit: type is STRING",
+            "Enter: type is ARRAY name is networklist",
+            "Enter: type is OBJECT name is null",
+            "Enter: type is STRING name is network-id",
+            "Exit: type is STRING",
+            "Enter: type is STRING name is server-provided",
+            "Exit: type is STRING",
+            "Exit: type is OBJECT",
+            "Enter: type is OBJECT name is null",
+            "Enter: type is STRING name is network-id",
+            "Exit: type is STRING",
+            "Enter: type is STRING name is server-provided",
+            "Exit: type is STRING",
+            "Exit: type is OBJECT",
+            "Enter: type is OBJECT name is null",
+            "Enter: type is STRING name is network-id",
+            "Exit: type is STRING",
+            "Enter: type is STRING name is server-provided",
+            "Exit: type is STRING",
+            "Exit: type is OBJECT",
+            "Exit: type is ARRAY",
+            "Exit: type is OBJECT"
+    };
+    private static final String WRONG_CONTENT_MSG = "Wrong content in array";
+
+    private final List<String> logger = new ArrayList<>();
+
+    DefaultJsonWalker defaultJsonWalker = new DefaultJsonWalker();
+    InternalJsonListener jsonListener = new InternalJsonListener();
+
+    ObjectNode arrayNode;
+    ObjectNode textNode;
+    ObjectNode listNode;
+
+    @Before
+    public void setup() throws Exception {
+        textNode = loadJsonFile("/textNode.json");
+        listNode = loadJsonFile("/listNode.json");
+        arrayNode = loadJsonFile("/arrayNode.json");
+    }
+
+    private ObjectNode loadJsonFile(String path) throws Exception {
+        InputStream jsonStream = getClass().getResourceAsStream(path);
+        ObjectMapper mapper = new ObjectMapper();
+        return (ObjectNode) mapper.readTree(jsonStream);
+    }
+
+    private void assertWalkResult(String[] expectArray, List<String> logger) {
+        for (int i = 0; i < expectArray.length; i++) {
+            assertThat(WRONG_CONTENT_MSG,
+                       true,
+                       is(logger.get(i).contentEquals(expectArray[i])));
+        }
+    }
+
+    @Test
+    public void testWalkTextNode() throws Exception {
+
+        defaultJsonWalker.walk(jsonListener, null, textNode);
+        assertWalkResult(EXP_TEXT_ARRAY, logger);
+    }
+
+    @Test
+    public void testWalkNodeWithList() throws Exception {
+        defaultJsonWalker.walk(jsonListener, null, listNode);
+        assertWalkResult(EXP_NODE_LIST_ARRAY, logger);
+    }
+
+    @Test
+    public void testWalkNodeWithArray() throws Exception {
+        defaultJsonWalker.walk(jsonListener, null, arrayNode);
+        assertWalkResult(EXP_NODE_WITH_ARRAY, logger);
+    }
+
+    private class InternalJsonListener implements JsonListener {
+
+        @Override
+        public void enterJsonNode(String fieldName, JsonNode node) {
+            logger.add("Enter: type is " + node.getNodeType() + " name is " +
+                               fieldName);
+        }
+
+        @Override
+        public void exitJsonNode(JsonNode node) {
+            logger.add("Exit: type is " + node.getNodeType());
+        }
+    }
+}
\ No newline at end of file

+{
+  "surname": "Bangalore",
+  "networklist":[
+    {
+      "network-id": "520",
+      "server-provided": "123"
+    },
+    {
+      "network-id": "521",
+      "server-provided": "124"
+    },
+    {
+      "network-id": "523",
+      "server-provided": "125"
+    }
+
+  ]
+}
\ No newline at end of file

+{
+  "surname": "Bangalore",
+  "networklist":[
+    "0.79",
+    "1.04",
+    "3.14"
+  ]
+}
\ No newline at end of file

+{
+  "name": "Huawei",
+  "surname": "Bangalore"
+}
\ No newline at end of file