REST服务中的EJB返回空指针异常

时间：2014-01-06 20:01:26

标签： rest java-ee jboss ejb

我试图用Resteasy和Jboss as7实现REST服务，我有会话bean通过DAO从DB获取数据（它适用于JSF +托管bean），我想用@注入该会话bean EJB，但它返回null，我做错了吗？

MyRESTApplication.java：

public class MyRESTApplication extends Application {

    private Set<Object> singletons = new HashSet<Object>();
    private Set<Class<?>> empty = new HashSet<Class<?>>();
    public MyRESTApplication(){
         singletons.add(new TablesResource());
    }
    @Override
    public Set<Class<?>> getClasses() {
         return empty;
    }
    @Override
    public Set<Object> getSingletons() {
         return singletons;
    }
}

TablesResource.java：

@Path("/RESTService")
public class TablesResource {

    @EJB
    private TablesSB tablesSB;

    @GET
    @Produces("application/xml")
    @Path("/table")
    public Tables getTable() {
        return tablesSB.getTable(28);
    }
}

会话bean：

@Stateless
@LocalBean
public class TablesSB {

    @PersistenceContext
    private EntityManager em;

    private TablesDAO tablesDao;
    private TablesDAOxml tablesDaoXml;

    public TablesSB() {
    }

    @PostConstruct
    public void init(){
        //tablesDao = new TablesDAO(em);
        tablesDaoXml = new TablesDAOxml();
    }

    public Tables getTable(int tableId) {
        return tablesDaoXml.getTable(tableId);
    }
    ...
}

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" 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>BarBar</display-name>
  <welcome-file-list>
    <welcome-file>index.xhtml</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>Resteasy</servlet-name>
    <servlet-class>org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Resteasy</servlet-name>
    <url-pattern>/*</url-pattern>
  </servlet-mapping>
  <context-param>
    <param-name>javax.ws.rs.Application</param-name>
    <param-value>ws.MyRESTApplication</param-value>
  </context-param>
  <listener>
    <listener-class>org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap</listener-class>
  </listener>
</web-app>

堆栈跟踪：

20:59:06,820 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/BarBar].[Resteasy]] (http-localhost-127.0.0.1-8080-1) Servlet.service() for servlet Resteasy threw exception: org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
    at org.jboss.resteasy.core.ExceptionHandler.handleApplicationException(ExceptionHandler.java:76) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ExceptionHandler.handleException(ExceptionHandler.java:212) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:149) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:372) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:179) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:220) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51) [resteasy-jaxrs-3.0.6.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.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
    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.Http11Processor.process(Http11Processor.java:877) [jbossweb-7.0.13.Final.jar:]
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671) [jbossweb-7.0.13.Final.jar:]
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930) [jbossweb-7.0.13.Final.jar:]
    at java.lang.Thread.run(Unknown Source) [rt.jar:1.7.0_45]
Caused by: java.lang.NullPointerException
    at ws.TablesResource.getTable(TablesResource.java:30) [classes:]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_45]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_45]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.7.0_45]
    at java.lang.reflect.Method.invoke(Unknown Source) [rt.jar:1.7.0_45]
    at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:137) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:280) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:234) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:221) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:356) [resteasy-jaxrs-3.0.6.Final.jar:]
    ... 19 more

3 个答案:

答案 0 :(得分：2)

我认为原因是因为您明确使用了RestEasy。它不能注入EJB，因为它不知道它。您可以尝试替换上面的整个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" 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>BarBar</display-name>
    <welcome-file-list>
        <welcome-file>index.xhtml</welcome-file>
    </welcome-file-list>

    <servlet-mapping>
        <servlet-name>yourcompany.yourpackage.MyRESTApplication</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>

（即用JAX-RS的标准servlet映射替换所有RestEasy东西 - 参见JAX-RS 1.1规范，ch.2.3.2;显然用{{1}的真正完全定义的名称替换yourcompany.yourpackage.MyRESTApplication }}）

或者，使用MyRESTApplication注释您的应用程序类，并从web.xml中删除所有相关配置：

javax.ws.rs.ApplicationPath

答案 1 :(得分：2)

来自Nikos的提示完全正确。但是奇怪的是代码适合你。 在您的代码中，您可以“手动”创建 TablesResource 类的引用。你可以明确地调用构造函数。

public MyRESTApplication(){
     singletons.add(new TablesResource());
}

类 MyRESTApplication 应更改如下。关键是要显示容器应该使用哪些类。它必须自己调用构造函数。

public class MyRESTApplication extends Application {

   private Set<Object> singletons = new HashSet<Object>();
   private Set<Class<?>> classes = new HashSet<Class<?>>();

   public MyRESTApplication(){
        classes.add(TablesResource.class); 
        // singletons.add(new TablesResource());
   }

   @Override
   public Set<Class<?>> getClasses() {
        return classes;
    }

   @Override
   public Set<Object> getSingletons() {
        return singletons;
   }
}

（我遇到了类似的问题，我通过上述更改解决了这个问题。问题是Eclipse JBoss Tool自动生成的代码“创建示例RESTful服务”。）

答案 2 :(得分：0)

请在WEB-INF文件夹中添加bean.xml文件，并将以下代码粘贴到bean.xml文件中。

 (/zipcodes {
 ep = 12345;
 sp = 12345;
 })
 Optional(<null>)
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