Java REST调用TOMCAT中的访问DAO

我想在使用REST调用时通过dao访问数据。我的dao与webapp配合得很好。但是当我使用我创建的Web服务时，我有一个空指针异常

这是我的密码：

@Path("/hello")

public class HelloWorldResource {

@Inject
private IAppDao appDao;

@GET
@Produces(MediaType.APPLICATION_XML)
@Path("/{idApp}/{currentVersion}")
public Object checkUpdate(@PathParam("idApp") String idApp,
        @PathParam("currentVersion") String currentVersion) {
    if(idApp == null || idApp.isEmpty() || currentVersion == null || currentVersion.isEmpty())
    {
        ErrorResponse error = new ErrorResponse();
        error.setCode(400);
        error.setMessage("bad_request_error");
        error.setReturnUrl(false);
        return Response.status(400).entity(error).build();
    }

    App app = appDao.findAppByName(idApp);
    if(app != null)
    {
        AppResponse response = new AppResponse();
        response.setDataVersion(app.getDataVersion());
        response.setName(app.getName());
        response.setUpdatable(app.isUpdatable());
        response.setVersion(app.getVersion());
        return Response.status(200).entity(response).build();   
    }
    else
    {
        ErrorResponse error = new ErrorResponse();
        error.setCode(400);
        error.setMessage("bad_app_name_error");
        error.setReturnUrl(false);
        return Response.status(400).entity(error).build();
    }
}

和错误堆栈：

12 mars 2014 15:42:33 com.sun.jersey.spi.container.ContainerResponse mapMappableContainerException
GRAVE: The RuntimeException could not be mapped to a response, re-throwing to the HTTP container
java.lang.NullPointerException
    at com.mlwebanddev.website.front.jersey.HelloWorldResource.checkUpdate(HelloWorldResource.java:38)
    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.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
    at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ObjectOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:258)
    at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
    at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:302)
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
    at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
    at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1542)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1473)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1419)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1409)
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:409)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:540)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:715)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:113)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tapestry5.TapestryFilter.doFilter(TapestryFilter.java:175)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at com.mlwebanddev.website.tools.Log4jFilter.doFilter(Log4jFilter.java:49)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:695)

空指针位于该行上：

App app = appDao.findAppByName(idApp);

有办法解决这个问题吗

---

谢谢

我的applicationContext.xml中的配置是：

<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="persistenceUnitName" value="resthub" />
<property name="persistenceUnitManager" ref="scanningPersistenceUnitManager" />
<property name="jpaDialect">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
</property>
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="showSql" value="false" />
</bean>
</property>
<property name="jpaProperties">
<map>
<entry key="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
<!-- Utile juste pour créer les tables EN LOCAL, ne pas commiter décommenté -->
<entry key="hibernate.hbm2ddl.auto" value="update" />
</map>
</property>
</bean>

---

我的@Stateless EJB也遇到了同样的问题

我解决了在我的公共类声明上方添加@Stateless的问题。像这样：

@Path("/hello")
@Stateless
public class HelloWorldResource {

@EJB
private DaoHello daoHello;


(...)

---

你的刀没有正确注射。您使用的依赖项注入系统是什么？它是如何配置的以提供

IAppDao

对象的？EJB与Tomcat中的部署有什么关系？Tomcat不支持在其中部署EJB？我使用的是Glassfish。我写这篇文章只是为了分享我是如何处理这个问题的。也许它可以为第一个问题指出一个解决方案的开端，或者帮助其他面临同样问题的人。你不明白我的意思：我不在乎你用的是玻璃鱼。OP使用的是Tomcat，因此您的答案完全不相关。这就是为什么我指定“可能是它可以……或者帮助其他面临同样问题的glassfish”。你的工作是发布无意义的信息吗？！我是说你还有别的事要做吗？无需回答…显然您不了解Stackoverflow是如何工作的。这不是一个讨论论坛。