问题
I hope you can help me with this: I have a WebProject created with Eclipse as a dynamic web project, running on a Glassfish3 Server. I’m using EJB 3.0 to create a stateless Façade(@stateless Annotation) that implements my business logic:
@Stateless
public class Facade {
public void test(){
System.out.println("test hat geklappt!!");
}
}
Additionally I’m using a RESTRessource to offer my REST WS that uses my EJB with (@EJB Annotation) the business logic:
@RequestScoped
@Path("/prescriptions")
public class Ressource {
@EJB
private Facade facade;
public Ressource() {
super();
}
@GET
@Path("/user/{userid}")
@Produces(MediaType.APPLICATION_JSON)
public void getUser(@PathParam("userid") String userid) {
facade.test();
}
}
Although I can get into the REST WS and call it, my EJB is always null and I cant find a reason why.
I would really appreciate it if you could help me. In case you need more information about the code or something just ask.
Thanks in advance, Florian
PS: I always get the following error in my log:
INFO: Portable JNDI names for EJB Facade : [java:global/TestProject/Facade,java:global/TestProject/Facade!webservices.Facade]
INFO: Portable JNDI names for EJB Facade : [java:global/TestProject/Facade, java:global/TestProject/Facade!webservices.Facade]
INFO: Scanning for root resource and provider classes in the packages:
webservices
INFO: Root resource classes found:
class webservices.Ressource
INFO: No provider classes found.
INFO: Initiating Jersey application, version 'Jersey: 1.5 01/14/2011 12:36 PM'
SCHWERWIEGEND: The RuntimeException could not be mapped to a response, re-throwing to the HTTP container
java.lang.NullPointerException
at webservices.Ressource.getUser(Ressource.java:40)
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 com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$VoidOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:150)
at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:70)
at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:279)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:136)
at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:86)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:136)
at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:74)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1347)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1279)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1229)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1219)
at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:419)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1534)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98)
at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:326)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:227)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:170)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:822)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:719)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1013)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:662)
回答1:
Ideally RESTFul class design should be stateless, as explained in this article:
A stateless service not only performs better, it shifts most of the responsibility of maintaining state to the client application
If you add the Stateless annotation to your Ressource class, you can inject your Facade session bean, and the container will care of the lifecycle of your session bean.
This will make your code run smoothly without the exception.
Don't forget to make your getUser method return a value!
public String getUser(@PathParam("userid") String userid) {
facade.test();
return "{" + userid + "}";
}
来源：https://stackoverflow.com/questions/8839824/ejb3-stateless-bean-is-always-null-in-rest-webservice-glassfish3-ejb3-statele