Error while Implementing HATEOAS in Spring

Question

I am trying to implement REstful Web Services with Spring MVC. I first did it without using HATEOAS concept. i was returning the domain objects and it was working fine. Now i am trying to implement HATEOAS for the same methods in the Controller and it is giving error. Could someone please help me out?

My Domain Class is below:

import javax.xml.bind.annotation.XmlRootElement;
import org.springframework.hateoas.ResourceSupport;

/**
* The {@link XmlRootElement} annotation is needed for the XML representation.
* 
* @author Daniel Sawano
* 
*/
@XmlRootElement(name = "user")
public class User extends ResourceSupport{

private int userId;
private String name;

public User() {
}

public int getUserId() {
    return userId;
}

public void setUserId(int userId) {
    this.userId = userId;
}

public User(int id, String name) {
    this.userId = id;
    this.name = name;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

}

My Controller Class is

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.hateoas.Link;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import static org.springframework.hateoas.mvc.ControllerLinkBuilder.*;
import static org.springframework.hateoas.mvc.ControllerLinkBuilder.methodOn;
import static org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo;

@Controller
@RequestMapping("/users")
public class RESTController {
Userlist obj2; //userlist is just a class with list of users. this too extends ResourceSupport.
boolean flag=false;
private Logger logger = LoggerFactory.getLogger(getClass());

@RequestMapping(value = "/{id}",method = RequestMethod.GET)
@ResponseBody
public User getUser(@PathVariable int id, @RequestHeader("Accept") String acceptHeader) {
    User temp = new User();
    if(obj2==null)
    {
        temp= new User(0, "Null");
    }
    else   {
        Set<User> set1= obj2.getUsers();
        for(User a:set1)
        {
            if(id==a.getUserId()) temp=a;
        }
      }
//temp.add(new Link("http://localhost:7001/spring-examples-json-xml-ws/users/"+id)); This is working perfectly fine.
//temp.add(linkTo(methodOn(RESTController.class).getUser(id,acceptHeader)).withSelfRel());This gives **error 1**

//temp.add(linkTo(RESTController.class).slash(temp.getUserId()).withSelfRel()); This gave **error 2**

return temp;
}

The Error 1 is below

Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.113 sec <<< FAILURE!
returnedUserShouldHaveCorrectId(se.sawano.spring.examples.jsonxmlws.RESTControllerTest)  Time elapsed: 0.02 sec  <<< ERROR!
java.lang.NoClassDefFoundError: org/springframework/cglib/proxy/MethodInterceptor
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at org.springframework.hateoas.core.DummyInvocationUtils.methodOn(DummyInvocationUtils.java:143)
at org.springframework.hateoas.mvc.ControllerLinkBuilder.methodOn(ControllerLinkBuilder.java:129)
at se.sawano.spring.examples.jsonxmlws.RESTController.getUser(RESTController.java:47)
at se.sawano.spring.examples.jsonxmlws.RESTControllerTest.returnedUserShouldHaveCorrectId(RESTControllerTest.java:25)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.apache.maven.surefire.junit4.JUnit4TestSet.execute(JUnit4TestSet.java:35)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:115)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:97)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.maven.surefire.booter.ProviderFactory$ClassLoaderProxy.invoke(ProviderFactory.java:103)
at $Proxy0.invoke(Unknown Source)
at org.apache.maven.surefire.booter.SurefireStarter.invokeProvider(SurefireStarter.java:150)
at org.apache.maven.surefire.booter.SurefireStarter.runSuitesInProcess(SurefireStarter.java:91)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:69)
Caused by: java.lang.ClassNotFoundException: org.springframework.cglib.proxy.MethodInterceptor
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 46 more

The Error 2 is below

Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.11 sec <<< FAILURE!
returnedUserShouldHaveCorrectId(se.sawano.spring.examples.jsonxmlws.RESTControllerTest)  Time elapsed: 0.019 sec  <<< ERROR!
java.lang.IllegalStateException: Could not find current request via RequestContextHolder
at org.springframework.util.Assert.state(Assert.java:384)
at org.springframework.hateoas.mvc.ControllerLinkBuilder.getCurrentRequest(ControllerLinkBuilder.java:201)
at org.springframework.hateoas.mvc.ControllerLinkBuilder.getBuilder(ControllerLinkBuilder.java:167)
at org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo(ControllerLinkBuilder.java:80)
at org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo(ControllerLinkBuilder.java:64)
at se.sawano.spring.examples.jsonxmlws.RESTController.getUser(RESTController.java:47)
at se.sawano.spring.examples.jsonxmlws.RESTControllerTest.returnedUserShouldHaveCorrectId(RESTControllerTest.java:25)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.apache.maven.surefire.junit4.JUnit4TestSet.execute(JUnit4TestSet.java:35)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:115)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:97)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.maven.surefire.booter.ProviderFactory$ClassLoaderProxy.invoke(ProviderFactory.java:103)
at $Proxy0.invoke(Unknown Source)
at org.apache.maven.surefire.booter.SurefireStarter.invokeProvider(SurefireStarter.java:150)
at org.apache.maven.surefire.booter.SurefireStarter.runSuitesInProcess(SurefireStarter.java:91)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:69)

As we can see when i add the Hard-coded link it works but when i try to fetch i get an error. Could some one please tell me what i have done wrong? Thank you for your time.

Answer 1

Returned user has incorrect ID.

Possible scenario: If parameter id is not found in UserList obj2, empty instance of User is used and it's id is null.