JBoss 中的 JAX-RS (RestEasy) 和 EJB3 集成答案

【问题标题】：JAX-RS (RestEasy) and EJB3 integration in JBossJBoss 中的 JAX-RS (RestEasy) 和 EJB3 集成
【发布时间】：2016-06-27 14:26:10
【问题描述】：

我已经构建了一个 maven 项目(packaging:war) 用于学习 jax-rs 和 ejb 集成。主要有以下文件：

无状态 Bean

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 服务应用程序路径类

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;
    }
}

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>

现在当我点击 url "http://127.0.0.1:8080/J2EEDemo/home/eb/s1" 时，总是会抛出以下空指针异常：

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:]
    ...

更尴尬的是，当我点击“http://127.0.0.1:8080/J2EEDemo/home/eb/s2”时，有时会按照我的意愿工作（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。

【问题讨论】：

首先，考虑到您正在处理的上下文，没有必要有一个 web.xml。看看this 的帖子。关于您的s1 bean，因为它不是managed bean，所以您不能使用@Inject 注释注入它。关于你的s2 bean，你为什么要指定@Local 注释？
@aribeiro，我正在关注docs.jboss.org/resteasy/docs/2.0.0.GA/userguide/html/… 进行整合。它使用带有 web.xml 的“@Local”注释。另外，我可能要从web.xml中配置很多东西，所以使用它。
@aribeiro，即使删除了“@Local”，行为仍然保持不变
我在这里看到了downvote。请提供评论，以便我更正自己

标签： web-services jax-rs jboss7.x resteasy ejb-3.1

【解决方案1】：

我通过在 WEB-INF (Configuring CDI Application) 中添加 'beans.xml' 虚拟文件解决了这个问题。（启用 CDI）

但问题仍然悬而未决。为什么http://127.0.0.1:8080/J2EEDemo/home/eb/s2 在添加 beans.xml 之前偶尔工作？

【讨论】：