如何在java ee 6框架中持久化JAX服务中的数据？
如何在java ee 6框架中持久化JAX服务中的数据？
提问于 2013-09-27 11:45:36
我在java 6框架中有一个J2EE项目。使用EJB和War模块。我想在EJB模块中添加一个服务来操作数据库中的一些数据，所以我需要访问Service方法中的DAO方法。但它还错了！
@WebService(serviceName = "AddUserService")
@Stateless()
public class AddUserService {
@PersistenceContext(unitName = "UserRegistrationService-ejbPU")
EntityManager em;
@WebMethod(operationName = "registerUser")
public String registerUser(BasicUserInfo basicUserInfo) {
UserEJB userEJB=new UserEJB(em);
String retValue = "";
User user = new User();
user.setAge(basicUserInfo.getAge());
user.setUserName(userName);
userEJB.addUser(user);
retValue = " User Registered with user_ID:" + user.getId().toString() + " and userName:" + user.getUserName();
return retValue;
}
}EJB类代码是：
@TransactionManagement(TransactionManagementType.CONTAINER)
@Stateless
public class UserEJB {
@PersistenceContext(unitName = "UserRegistrationService-ejbPU")
EntityManager em;
public UserEJB() {
}
public UserEJB(EntityManager em) {
this.em = em;
}
public void addUser(User user) {
em.persist(user);
}
}在服务器上测试服务时会出现以下错误：
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
at dao.UserEJB.addUser(UserEJB.java:34)
at app.Services.AddUserService.registerUser2(AddUserService.java:60)
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 org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052)
at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124)
at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5388)
at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144)
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.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861)回答 2
Stack Overflow用户
回答已采纳
发布于 2013-09-27 15:02:04
您的EntityManger不会被容器注入，因为您已经自己创建了UserEJB对象！你打破了注射链。在使用DI时，必须让容器为您创建对象。试着这样做：
@WebService(serviceName = "AddUserService")
@Stateless()
public class AddUserService {
//actually you don't need this here, you'll get that injected inside the UserEJB
@PersistenceContext(unitName = "UserRegistrationService-ejbPU")
EntityManager em;
@Inject
UserEJB userEjb;
@WebMethod(operationName = "registerUser")
public String registerUser(BasicUserInfo basicUserInfo) {
//you don't need this line, the container will instantiate the object for you!
//UserEJB userEJB=new UserEJB(em);
String retValue = "";
User user = new User();
user.setAge(basicUserInfo.getAge());
user.setUserName(userName);
userEJB.addUser(user);
retValue = " User Registered with user_ID:" + user.getId().toString() + " and userName:" + user.getUserName();
return retValue;
}
}Stack Overflow用户
发布于 2013-09-27 12:03:15
错误发生在第34行的类UserEJB.java中，因此请将该代码发布。
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原文链接：
https://stackoverflow.com/questions/19049951
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