JAX WS RS using Jersey - returning Collection, Map etc

Question

I'm using Jersey 2.3

My WS endpoint class :

@Path("/employees")
public class EmployeeWSEndpoint {

    @Context
    Request request;

    @GET
    @Path("/allEmployees")
    @Produces(MediaType.APPLICATION_JSON)
    public List<Employee> getAllEmployees() {

        System.out.println("In EmployeeWSEndpoint.getAllEmployees()");

        EmployeeService employeeService = new EmployeeServiceImpl();
        return employeeService.getAllEmployees();
    }

    @GET
    @Path("/allDept")
    @Produces(MediaType.APPLICATION_JSON)
    public List<String> getAllDept() {

        System.out.println("In EmployeeWSEndpoint.getAllDept()");

        List<String> deptNames = new ArrayList<>();
        deptNames.add("CoE");
        deptNames.add("iLabs");

        return deptNames;
    }

    @GET
    @Path("/allDeptPOJO")
    @Produces(MediaType.APPLICATION_JSON)
    public TempPOJO getAllDeptPOJO() {

        System.out.println("In EmployeeWSEndpoint.getAllDeptPOJO");

        TempPOJO tempPOJO = new TempPOJO();

        return tempPOJO;
    }
}

Employee POJO :

public class Employee {

    private int id;
    private String firstName;
    private String middleName;
    private String lastName;
    private Date dob;
    private int deptId;

    public Employee() {

    }

    public Employee(String firstName, String middleName, String lastName,
            Date dob, int deptId) {
        this.firstName = firstName;
        this.middleName = middleName;
        this.lastName = lastName;
        this.dob = dob;
        this.deptId = deptId;
    }

    public Employee(int id, String firstName, String middleName,
            String lastName, Date dob, int deptId) {
        this.id = id;
        this.firstName = firstName;
        this.middleName = middleName;
        this.lastName = lastName;
        this.dob = dob;
        this.deptId = deptId;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getMiddleName() {
        return middleName;
    }

    public void setMiddleName(String middleName) {
        this.middleName = middleName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public Date getDob() {
        return dob;
    }

    public void setDob(Date dob) {
        this.dob = dob;
    }

    public int getDeptId() {
        return deptId;
    }

    public void setDeptId(int deptId) {
        this.deptId = deptId;
    }

    @Override
    public String toString() {
        return firstName + " " + middleName + " " + " " + lastName;
    }
}

A temporary POJO :

public class TempPOJO {

    private List<String> deptNames;

    public List<String> getDeptNames() {

        deptNames = new ArrayList<>();
        deptNames.add("CoE");
        deptNames.add("iLabs");

        return deptNames;
    }

    public void setDeptNames(List<String> deptNames) {
        this.deptNames = deptNames;
    }

}

Listing the output(s) for different methods :

allEmployees

[{"deptId":1,"dob":"1978-06-19","firstName":"Garfield","id":0,"lastName":"Arbuckle","middleName":"John"},{"deptId":1,"dob":"1946-07-07","firstName":"John","id":0,"lastName":"Rambo","middleName":"R"}]

/allDept

In EmployeeWSEndpoint.getAllDept()
Oct 01, 2013 3:31:08 PM org.glassfish.jersey.server.ServerRuntime$Responder mapException
WARNING: WebApplicationException cause:
javax.xml.bind.MarshalException
 - with linked exception:
[Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: Exception [EclipseLink-25007] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: A descriptor for class java.lang.String was not found in the project.  For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.]
    at org.eclipse.persistence.jaxb.JAXBMarshaller.marshal(JAXBMarshaller.java:403)
    at org.eclipse.persistence.jaxb.rs.MOXyJsonProvider.writeTo(MOXyJsonProvider.java:808)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.invokeWriteTo(WriterInterceptorExecutor.java:243)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.aroundWriteTo(WriterInterceptorExecutor.java:230)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:149)
    at org.glassfish.jersey.server.internal.JsonWithPaddingInterceptor.aroundWriteTo(JsonWithPaddingInterceptor.java:103)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:149)
    at org.glassfish.jersey.server.internal.MappableExceptionWrapperInterceptor.aroundWriteTo(MappableExceptionWrapperInterceptor.java:88)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:149)
    at org.glassfish.jersey.message.internal.MessageBodyFactory.writeTo(MessageBodyFactory.java:1139)
    at org.glassfish.jersey.server.ServerRuntime$Responder.writeResponse(ServerRuntime.java:562)
    at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:357)
    at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:347)
    at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:258)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:318)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:235)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:983)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:359)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:372)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:335)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:218)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: Exception [EclipseLink-25007] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: A descriptor for class java.lang.String was not found in the project.  For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.
    at org.eclipse.persistence.exceptions.XMLMarshalException.marshalException(XMLMarshalException.java:97)
    at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:911)
    at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:848)
    at org.eclipse.persistence.jaxb.JAXBMarshaller.marshal(JAXBMarshaller.java:401)
    ... 41 more
Caused by: Exception [EclipseLink-25007] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: A descriptor for class java.lang.String was not found in the project.  For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.
    at org.eclipse.persistence.exceptions.XMLMarshalException.descriptorNotFoundInProject(XMLMarshalException.java:139)
    at org.eclipse.persistence.internal.oxm.Context$ContextState.getSession(Context.java:143)
    at org.eclipse.persistence.oxm.XMLContext$XMLContextState.getSession(XMLContext.java:787)
    at org.eclipse.persistence.oxm.XMLContext$XMLContextState.getSession(XMLContext.java:1)
    at org.eclipse.persistence.internal.oxm.Context.getSession(Context.java:451)
    at org.eclipse.persistence.oxm.XMLContext.getSession(XMLContext.java:356)
    at org.eclipse.persistence.oxm.XMLContext.getSession(XMLContext.java:1)
    at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:568)
    at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:1096)
    at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:869)
    ... 43 more

/allDeptPOJO

{"deptNames":["CoE","iLabs"]}

I have some queries :

1. I guess since Jersey 2.3, annotation 'XmlRootElement' isn't necessary for POJOs - I haven't done it, yet, the calls work. Please confirm
2. In case of a List of a pojo(Employee) or a pojo having a List, the response is proper but for List, Map etc. it fails(basically, for Java types) - why is this so? If it works for Employee, why doesn't it work for Java types? Is there a need to write an XmlAdapter?

Note : I want the response in JSON in most of the cases.

Modifying the web.xml to use Jackson :

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <display-name>Jersey</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>

    <servlet>
        <servlet-name>Jersey REST Service</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>jersey.config.server.provider.packages</param-name>
            <param-value>com.ws.jaxrs.jersey</param-value>
        </init-param>
        <init-param>
            <param-name>jersey.config.disableMoxyJson.server</param-name>
            <param-value>true</param-value>
        </init-param>

        <init-param>
            <param-name>jersey.config.server.provider.packages</param-name>
            <param-value>com.ws.jaxrs.jersey;org.codehaus.jackson.jaxrs</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>Jersey REST Service</servlet-name>
        <url-pattern>/rest/*</url-pattern>
    </servlet-mapping>


</web-app>

I got the following exception :

In EmployeeWSEndpoint.getAllDept()
Nov 07, 2013 10:04:12 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [Jersey REST Service] in context with path [/Jersey] threw exception [org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyWriter not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.List<java.lang.String>.] with root cause
org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyWriter not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.List<java.lang.String>.
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.aroundWriteTo(WriterInterceptorExecutor.java:227)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:149)
    at org.glassfish.jersey.server.internal.JsonWithPaddingInterceptor.aroundWriteTo(JsonWithPaddingInterceptor.java:103)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:149)
    at org.glassfish.jersey.server.internal.MappableExceptionWrapperInterceptor.aroundWriteTo(MappableExceptionWrapperInterceptor.java:88)
    at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:149)
    at org.glassfish.jersey.message.internal.MessageBodyFactory.writeTo(MessageBodyFactory.java:1139)
    at org.glassfish.jersey.server.ServerRuntime$Responder.writeResponse(ServerRuntime.java:562)
    at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:357)
    at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:347)
    at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:258)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:318)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:235)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:983)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:359)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:372)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:335)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:218)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:964)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

Answer 1

Jackson is the best solution for me at the moment.

To use Jackson as your JSON provider you need to add jersey-media-json-jackson module to your pom.xml file:

<dependency>
    <groupId>org.glassfish.jersey.media</groupId>
    <artifactId>jersey-media-json-jackson</artifactId>
    <version>2.7</version>
</dependency>

Note: Auto-discovery feature does not work.

Building client with Jackson JSON feature enabled:

final Client client = ClientBuilder.newBuilder()
                    .register(JacksonFeature.class)
                    .build();

Creating JAX-RS server application with Jackson JSON feature enabled:

final Application application = new ResourceConfig()
                              .packages("my.rest.package")
                              .register(JacksonFeature.class);

Also check official Jersey json-jackson example.

Answer 2

Use a different JSON provider

I don't know why jersey startet to adopt MOXy as their default JSON provider, but it's obviously a bad idea.

The problems you (and me - and others) are experiencing are the result of MOXy beeing unable to map collections of simple Java types (like String) - that's just ridiculous imho. Other providers (like jackson) do not have this problem, so switching will definitely help.

Here is what I did:

1. Tell Jersey not to use MOXy. Add this to your web.xml:

   <init-param>
       <param-name>jersey.config.disableMoxyJson.server</param-name>
       <param-value>true</param-value>
   </init-param>
   

2. Add Jackson to your pom. Something like this will do:

   <dependency>
       <groupId>org.codehaus.jackson</groupId>
       <artifactId>jackson-jaxrs</artifactId>
       <version>1.9.12</version>
   </dependency>
   

3. Tell jersey to scan the jackson jackson packages. It will find (and use) the json providers provided by jackson:

   <init-param>
       <param-name>jersey.config.server.provider.packages</param-name>
       <param-value>com.example.your.package;org.codehaus.jackson.jaxrs</param-value>
   </init-param>