Severe: Java class not found util. Message body writer for ArrayList and mime media types application / JSON

I'm testing the restful service. When I execute, I get an exception. Although there are the following jars in my classpath (WEB-INF / LIB), I don't use Maven. My JDK version is 1.5 Other questions about this problem did not help solve the problem

code snippet

@GET
@Produces("application/json")    
//@Produces({MediaType.APPLICATION_JSON}) tried this,didn't work either
public List<Emp> getEmployees() {        
    List<Emp> empList = myDAO.getAllEmployees();
    log.info("size   " + empList.size());
    return empList;
}

@XmlRootElement
public class Emp {
......

web. In XML

<servlet>
    <servlet-name>Jersey Web Application</servlet-name>
    <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
    <init-param>
        <param-name>com.sun.jersey.config.property.packages</param-name>
        <param-value>test.employees</param-value>
    </init-param>
    <init-param>
        <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
        <param-value>true</param-value>
    </init-param>
</servlet>

 <servlet-mapping>
    <servlet-name>Jersey Web Application</servlet-name>
    <url-pattern>/rest/*</url-pattern>
</servlet-mapping>

Jar list

jersey-server-1.2.jar
jersey-core-1.2.jar
jsr311-api-1.1.jar
asm-3.1.jar
jaxb-api-2.0.jar
jaxb-impl-2.0.jar
jackson-xc-1.2.0.jar
jackson-jaxrs-1.2.0.jar
jackson-mapper-asl-1.2.0.jar
jackson-core-asl-1.2.0.jar
jettison-1.2.jar
jersey-client-1.2.jar
jersey-servlet-1.10.jar
jersey-json-1.8.jar

Exception stack

SEVERE: A message body writer for Java class java.util.ArrayList,and Java type java.util.List<test.Emp>,and MIME media type application/json was not found
Nov 21,2013 11:47:26 AM com.sun.jersey.spi.container.ContainerResponse traceException
SEVERE: Mapped exception to response: 500 (Internal Server Error)

javax.ws.rs.WebApplicationException
    at javax.ws.rs.WebApplicationException.<init>(WebApplicationException.java:97)
    at javax.ws.rs.WebApplicationException.<init>(WebApplicationException.java:55)
    at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:267)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1035)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:947)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:939)
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:399)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:478)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:663)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
    at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:719)
    at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:376)
    at com.evermind.server.http.HttpRequestHandler.doProcessRequest(HttpRequestHandler.java:870)
    at com.evermind.server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:451)
    at com.evermind.server.http.HttpRequestHandler.serveOneRequest(HttpRequestHandler.java:218)
    at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:119)
    at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:112)
    at oracle.oc4j.network.ServerSocketReadHandler$SafeRunnable.run(ServerSocketReadHandler.java:260)
    at oracle.oc4j.network.ServerSocketAcceptHandler.procClientSocket(ServerSocketAcceptHandler.java:230)
    at oracle.oc4j.network.ServerSocketAcceptHandler.access$800(ServerSocketAcceptHandler.java:33)
    at oracle.oc4j.network.ServerSocketAcceptHandler$AcceptHandlerHorse.run(ServerSocketAcceptHandler.java:831)
    at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:303)
    at java.lang.Thread.run(Thread.java:595)

How to solve this problem?

Solution

Make sure you do not have multiple Jersey versions in your project From the list you provided, there are three different versions of modules (1.2, 1.10, 1.8) For some modules, Jersey checks whether the version of the module is the same as the core version If not, the provider of the module (such as messagebodyreaders and messagebodywriters) is not registered at runtime This may be a problem in your setup – JSON vs core (1.8 vs 1.2)