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我已经构建了一个用于学习jax-rs和ejb集成的maven项目（packaging：war）。它主要以下文件：JBoss中的JAX-RS（RestEasy）和EJB3集成
无国籍豆
package org.eb.stateless;
import javax.annotation.PostConstruct;
import javax.ejb.Stateless;
@Stateless
public class StatelessBeanDemo
{
@PostConstruct
public void init()
{
System.out.println("I M POST-CONSTRUCT");
}
public void printData()
{
System.out.println("I M Stateless");
}
}
资源接口
package org.webservice.rs;
import javax.ejb.Local;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.core.Response;
@Local
@Path("/home")
public interface IHelloWorldService
{
@GET
@Path("/eb/s1")
Response callSL1();
@GET
@Path("/eb/s2")
Response callSL2();
}
资源
package org.webservice.rs;
import javax.ejb.EJB;
import javax.ejb.Stateless;
import javax.inject.Inject;
import javax.ws.rs.core.Response;
import org.eb.stateless.StatelessBeanDemo;
@Stateless
public class HelloWorldService implements IHelloWorldService
{
@Inject // Use of "Inject"
private StatelessBeanDemo sl; // Always Null
@EJB // Use of "EJB"
private StatelessBeanDemo s2; // Sometime Null, Sometime Not
public Response callSL1()
{
sl.printData();
return Response.status(201).entity("DONE").build();
}
public Response callSL2()
{
s2.printData();
return Response.status(201).entity("DONE").build();
}
}
Web服务应用程序Path类
package org.webservice.rs;
import java.util.HashSet;
import java.util.Set;
import javax.ws.rs.core.Application;
public class RestServiceLocator extends Application
{
public Set<Class<?>> getClasses()
{
Set<Class<?>> s = new HashSet<Class<?>>();
s.add(HelloWorldService.class);
return s;
}
}
的web.xml
<?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
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>J2EEDemo</display-name>
<context-param>
<param-name>resteasy.jndi.resources</param-name>
<param-value>java:module/HelloWorldService</param-value>
</context-param>
<listener>
<listener-class>org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap</listener-class>
</listener>
<servlet>
<servlet-name>Resteasy</servlet-name>
<servlet-class>
org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher
</servlet-class>
<init-param>
<param-name>javax.ws.rs.Application</param-name>
<param-value>org.webservice.rs.RestServiceLocator</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Resteasy</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>
现在，当我打的网址 “http://127.0.0.1:8080/J2EEDemo/home/eb/s1”，这是继空指针异常ALWAYS投掷：
13:59:08,695 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/J2EEDemo].[Resteasy]] (http-0.0.0.0-0.0.0.0-8080-2) Servlet.service() for servlet Resteasy threw exception: org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
at org.jboss.resteasy.core.SynchronousDispatcher.handleApplicationException(SynchronousDispatcher.java:340) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.SynchronousDispatcher.handleException(SynchronousDispatcher.java:214) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.SynchronousDispatcher.handleInvokerException(SynchronousDispatcher.java:190) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:540) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:502) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:119) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:208) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:55) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:50) [resteasy-jaxrs-2.3.2.Final.jar:]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [jboss-servlet-api_3.0_spec-1.0.0.Final.jar:1.0.0.Final]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) [jbossweb-7.0.13.Final.jar:]
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153) [jboss-as-web-7.1.1.Final.jar:7.1.1.Final]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:897) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:626) [jbossweb-7.0.13.Final.jar:]
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:2039) [jbossweb-7.0.13.Final.jar:]
at java.lang.Thread.run(Thread.java:744) [rt.jar:1.7.0_51]
Caused by: java.lang.NullPointerException
at org.webservice.rs.HelloWorldService.callSL1(HelloWorldService.java:26) [classes:]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_51]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [rt.jar:1.7.0_51]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_51]
at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_51]
at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:155) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.ResourceMethod.invokeOnTarget(ResourceMethod.java:257) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:222) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:211) [resteasy-jaxrs-2.3.2.Final.jar:]
at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:525) [resteasy-jaxrs-2.3.2.Final.jar:]
...
更奇怪的是当我点击“http://127.0.0.1:8080/J2EEDemo/home/eb/s2”时，它是有时候按照我的意愿工作（打印“DONE”并执行注入的bean方法），有时会抛出相同的空指针异常。我无法理解发生了什么。
首先，考虑到您正在处理的上下文，不需要有* web.xml *。看看[这]（http://stackoverflow.com/questions/9373081/how-to-set-up-jax-rs-application-using-annotations-only-no-web-xml）后。关于你的's1' bean，因为它不是[托管bean]（http://stackoverflow.com/questions/8138232/should-i-use-ejb-or-inject），你不能注入它'@Inject'注释。关于你的's2' bean，你为什么要指定'@ Local'注释？ – aribeiro
@aribeiro，我正在关注http://docs.jboss.org/resteasy/docs/2.0.0.GA/userguide/html/RESTEasy_EJB_Integration.html的integartion。它在web.xml中使用'@Local'注释。另外，我可能必须从web.xml配置很多东西，所以使用它。 – user811602
@aribeiro，即使删除'@Local'后，行为仍然相同 – user811602