[FIXED] Accessing Restful webservice using restful Client in Spring 3

Issue

I have created web service with restful in spring 3.0 and it's working good but I am unable to create restful client to access this web service. I searched lot on google for it but nothing useful. Here I created web service. Controller:

package com.nmmc.ws.controller;
import java.util.List;
import javax.inject.Inject;
import javax.inject.Named;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import com.nmmc.ws.model.Corporator;
import com.nmmc.ws.serviceImpl.CorporatorServiceImpl;

@Controller
public class WSDemoController
{
    @Inject
    @Named("wsCorporator")
    private CorporatorServiceImpl corporatorServiceImpl;

    @RequestMapping(value = "/corporator.webService", method = RequestMethod.GET)
    @ResponseBody
    public List<Corporator> getAllCorporators() {

        List list = corporatorServiceImpl.getAllCorporators();
        System.out.println("list" + list);
        return list;
    }
}

ServiceImpl:

package com.nmmc.ws.serviceImpl;
import java.util.ArrayList;
import java.util.List;
import javax.inject.Inject;
import javax.inject.Named;
import com.nmmc.ws.daoImpl.CorporatorDAOImpl;
import com.nmmc.ws.model.Corporator;
@Named("wsCorporator")
public class CorporatorServiceImpl
{
    @Inject
    @Named("wsCorporatorDAO")
    private CorporatorDAOImpl corporatorDAOImpl;    
    public List<Corporator> getAllCorporators() {       
        List list = corporatorDAOImpl.getAllCorporators();      
        return list; 
    }
}

DAOImpl:

package com.nmmc.ws.daoImpl;
import java.util.ArrayList;
import java.util.List;
import javax.inject.Named;
import com.nmmc.ws.model.Corporator;
@Named("wsCorporatorDAO")
public class CorporatorDAOImpl
{   
    public List<Corporator> getAllCorporators() {           
        List list = new ArrayList();
        list.add("Some testing data...");
        return list; 
    }
}

applicationContext.xml:

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xmlns:context="http://www.springframework.org/schema/context"
            xmlns:util="http://www.springframework.org/schema/util"
            xmlns:mvc="http://www.springframework.org/schema/mvc"
            xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
            http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
            http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">

            <import resource="works-servlet.xml" />

        <context:component-scan base-package="com.nmmc.ws"/>
        <!--<context:component-scan base-package="com.nmmc.works.web" />     
        --><bean id="xstreamMarshaller" class="org.springframework.oxm.xstream.XStreamMarshaller"/>  
        <bean id="marshallingHttpMessageConverter"            class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter">
            <property name="marshaller" ref="xstreamMarshaller"/>
            <property name="unmarshaller" ref="xstreamMarshaller"/>
        </bean>

        <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
            <property name="messageConverters">
                <util:list id="beanList">
                    <ref bean="marshallingHttpMessageConverter"/>
                </util:list>
            </property>
        </bean>  
        <mvc:annotation-driven/>     
    </beans>

I have created restfulClient in another module as given above just application.xml and controller as: application.xml:

<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
        <property name="messageConverters">
            <list>
                <!-- We only have one message converter for the RestTemplate, namely 
                    the XStream Marshller -->
                <bean
                    class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter">
                    <constructor-arg>
                        <bean class="org.springframework.oxm.xstream.XStreamMarshaller">
                            <!-- Explicitly define the aliases -->
                            <!-- <property name="aliases"> <props> <prop key="article">com.informit.articleservice.model.Article</prop> 
                                <prop key="category">com.informit.articleservice.model.Category</prop> </props> 
                                </property> -->

                            <!-- Tell XStream to find the alias names in the following classes -->
                            <property name="annotatedClasses">
                                <list>
                                    <value>com.nmmc.ws.model.Corporator</value>
                                </list>
                            </property>
                        </bean>
                    </constructor-arg>
                </bean>
            </list>
        </property>
    </bean>


    <mvc:annotation-driven />

ClientController:

package com.nmmc.ws.controller;

import java.util.ArrayList;
import java.util.List;

import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.client.RestTemplate;

import com.nmmc.ws.model.Corporator;
@Controller
//@RequestMapping("/clientController")
@Component( "articleClient" )
public class WSClientController
{
    protected RestTemplate restTemplate;
    private final static String articleServiceUrl = "http://myPortNo:8080/Works_Web/corporator.webService";
    @SuppressWarnings( "unchecked" )
    @RequestMapping(value = "/corporator.etenderingWS", method = RequestMethod.GET)
    public List<Corporator> getAllCorporators()
    {
        System.out.println("URI for request..." + articleServiceUrl);
        List list = new ArrayList();
        try{
            System.out.println("In try block...");
            Corporator result =  (Corporator) restTemplate.getForObject(articleServiceUrl, List.class); 
            list = (List) result;

        }catch(Exception e){
            e.printStackTrace();
        }
        return list;
    }   
}

When I run application it gives error:

java.lang.NullPointerException
    at com.nmmc.ws.controller.WSClientController.getAllCorporators(WSClientController.java:49)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.doInvokeMethod(HandlerMethodInvoker.java:710)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:167)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:414)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:402)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:771)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:552)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:636)

Solution

I think maybe you forgot the dependency injection annotation for your RestTemplate bean in your client controller.

Answered By - sdouglass