我试图使用netbeans IDE在jpa中创建多对多映射。我有许多实体类，例如User，Comment，Post，LikeDislike。
通过Comment，LikeDislike，Watched链接的User和Post实体之间存在多对多的关系。一个用户可能对一个帖子有很多评论，一个帖子可能会从单个/多个用户获得许多评论。但是，当我第一次注册用户时，他/她将不会发表评论，比如说喜欢。所以我只想注册用户
问题是当我试图保存没有评论的用户时，我得到nullpointer异常。为了保存用户，我有一个名为UserDao的DAO类，它有一个save方法，用于接收用户对象并调用JPA persist方法。为了调用这个方法，我有一个名为Tester的单例类，它创建一个用户并调用UsarDao save方法。
这是我的代码：
Tester class:
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.List;
import javax.annotation.PostConstruct;
import javax.ejb.EJB;
import javax.ejb.Singleton;
import javax.ejb.Startup;
import tube_application.manager.Comment;
import tube_application.manager.LikeDislike;
import tube_application.manager.User;
import tube_application.manager.UserDaoLocal;
import tube_application.manager.Watched;
@Singleton
@Startup
public class Tester {
@EJB
UserDaoLocal userDao;
@PostConstruct
void start_here(){
User user=new User();
user.setAge(18);
user.setEmail("biliyala.ezd2@gmail.com");
user.setGender("m");
user.setName("Ezedin");
user.setPassword("password");
user.setUserName("username");
userDao.saveUser(user);
}
}
UserDaoLocal interface:
import javax.ejb.Local;
@Local
public interface UserDaoLocal {
void saveUser(User user);
void saveCategory(Catigory cat);
}
UserDao class:
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
@Stateless
public class UserDao implements UserDaoLocal {
@PersistenceContext(unitName = "tube_application_tube-ejb_ejb_1.0-SNAPSHOTPU")
EntityManager em;
@Override
public void saveUser(User user) {
try {
em.persist(em);
} catch (Exception e) {
e.setStackTrace(null);
}
}
}
User calss:
import java.io.Serializable;
import java.util.List;
import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.validation.constraints.Size;
@Entity
@Table(name = "user")
@NamedQueries({
@NamedQuery(name = "User.findAll", query = "SELECT u FROM User u")})
public class User implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "id")
private Integer id;
@Size(max = 45)
@Column(name = "name")
private String name;
// @Pattern(regexp="[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?", message="Invalid email")//if the field contains email address consider using this annotation to enforce field validation
@Size(max = 45)
@Column(name = "email")
private String email;
@Column(name = "age")
private Integer age;
@Size(max = 45)
@Column(name = "user_name")
private String userName;
@Size(max = 45)
@Column(name = "password")
private String password;
@Size(max = 5)
@Column(name = "gender")
private String gender;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "postedBy")
private List<Post> postList;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
private List<LikeDislike> likeDislikeList;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
private List<Comment> commentList;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
private List<Watched> watchedList;
public User() {
}
public User(Integer id) {
this.id = id;
}
getters and setters .....
}
Comment class:
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.JoinColumn;
import javax.persistence.Lob;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.validation.constraints.Size;
@Entity
@Table(name = "comment")
@NamedQueries({
@NamedQuery(name = "Comment.findAll", query = "SELECT c FROM Comment c")})
public class Comment implements Serializable {
private static final long serialVersionUID = 1L;
@EmbeddedId
protected CommentPK commentPK;
@Lob
@Size(max = 2147483647)
@Column(name = "comment")
private String comment;
@JoinColumn(name = "user_id", referencedColumnName = "id", insertable = false, updatable = false)
@ManyToOne(optional = false)
private User user=new User();
@JoinColumn(name = "post_id", referencedColumnName = "id")
@ManyToOne(optional = false)
private Post postId;
public Comment() {
}
public Comment(CommentPK commentPK) {
this.commentPK = commentPK;
}
public Comment(int id, int userId) {
this.commentPK = new CommentPK(id, userId);
}
public CommentPK getCommentPK() {
return commentPK;
}
public void setCommentPK(CommentPK commentPK) {
this.commentPK = commentPK;
}
public String getComment() {
return comment;
}
public void setComment(String comment) {
this.comment = comment;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public Post getPostId() {
return postId;
}
public void setPostId(Post postId) {
this.postId = postId;
}
}
CommentPK class:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package tube_application.manager;
import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Embeddable;
import javax.validation.constraints.NotNull;
@Embeddable
public class CommentPK implements Serializable {
@Basic(optional = false)
@Column(name = "id")
private int id;
@Basic(optional = false)
@NotNull
@Column(name = "user_id")
private int userId;
public CommentPK() {
}
public CommentPK(int id, int userId) {
this.id = id;
this.userId = userId;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
}
**the error is:**
WARNING: EJB5184:A system exception occurred during an invocation on EJB UserDao, method: public void tube_application.manager.UserDao.saveUser(tube_application.manager.User)
WARNING: javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean
at com.sun.ejb.containers.EJBContainerTransactionManager.checkExceptionClientTx(EJBContainerTransactionManager.java:662)
at com.sun.ejb.containers.EJBContainerTransactionManager.postInvokeTx(EJBContainerTransactionManager.java:507)
at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:4475)
at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2009)
at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1979)
at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:220)
at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:88)
at com.sun.proxy.$Proxy495.saveUser(Unknown Source)
at tube_application.tests.Tester.start_here(Tester.java:43)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.BeanCallbackInterceptor.intercept(InterceptorManager.java:1035)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:72)
at com.sun.ejb.containers.interceptors.CallbackInvocationContext.proceed(CallbackInvocationContext.java:205)
at org.jboss.weld.ejb.AbstractEJBRequestScopeActivationInterceptor.aroundInvoke(AbstractEJBRequestScopeActivationInterceptor.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.CallbackInterceptor.intercept(InterceptorManager.java:986)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:72)
at com.sun.ejb.containers.interceptors.CallbackInvocationContext.proceed(CallbackInvocationContext.java:205)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doCall(SystemInterceptorProxy.java:163)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.init(SystemInterceptorProxy.java:125)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.CallbackInterceptor.intercept(InterceptorManager.java:986)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:72)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:412)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:375)
at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:1949)
at com.sun.ejb.containers.AbstractSingletonContainer.createSingletonEJB(AbstractSingletonContainer.java:475)
at com.sun.ejb.containers.AbstractSingletonContainer.access$000(AbstractSingletonContainer.java:81)
at com.sun.ejb.containers.AbstractSingletonContainer$SingletonContextFactory.create(AbstractSingletonContainer.java:654)
at com.sun.ejb.containers.AbstractSingletonContainer.instantiateSingletonInstance(AbstractSingletonContainer.java:396)
at org.glassfish.ejb.startup.SingletonLifeCycleManager.initializeSingleton(SingletonLifeCycleManager.java:219)
at org.glassfish.ejb.startup.SingletonLifeCycleManager.initializeSingleton(SingletonLifeCycleManager.java:180)
at org.glassfish.ejb.startup.SingletonLifeCycleManager.doStartup(SingletonLifeCycleManager.java:158)
at org.glassfish.ejb.startup.EjbApplication.start(EjbApplication.java:166)
at org.glassfish.internal.data.EngineRef.start(EngineRef.java:122)
at org.glassfish.internal.data.ModuleInfo.start(ModuleInfo.java:291)
at org.glassfish.internal.data.ApplicationInfo.start(ApplicationInfo.java:352)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:497)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:527)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:523)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:356)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:522)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:546)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1423)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1500(CommandRunnerImpl.java:108)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1762)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1674)
at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:534)
at com.sun.enterprise.v3.admin.AdminAdapter.onMissingResource(AdminAdapter.java:224)
at org.glassfish.grizzly.http.server.StaticHttpHandler.service(StaticHttpHandler.java:297)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:246)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.NullPointerException
SEVERE: Exception while invoking class org.glassfish.ejb.startup.EjbApplication start method
javax.ejb.EJBException: javax.ejb.CreateException: Initialization failed for Singleton Tester
at com.sun.ejb.containers.AbstractSingletonContainer$SingletonContextFactory.create(AbstractSingletonContainer.java:656)
at com.sun.ejb.containers.AbstractSingletonContainer.instantiateSingletonInstance(AbstractSingletonContainer.java:396)
at org.glassfish.ejb.startup.SingletonLifeCycleManager.initializeSingleton(SingletonLifeCycleManager.java:219)
at org.glassfish.ejb.startup.SingletonLifeCycleManager.initializeSingleton(SingletonLifeCycleManager.java:180)
at org.glassfish.ejb.startup.SingletonLifeCycleManager.doStartup(SingletonLifeCycleManager.java:158)
at org.glassfish.ejb.startup.EjbApplication.start(EjbApplication.java:166)
at org.glassfish.internal.data.EngineRef.start(EngineRef.java:122)
at org.glassfish.internal.data.ModuleInfo.start(ModuleInfo.java:291)
at org.glassfish.internal.data.ApplicationInfo.start(ApplicationInfo.java:352)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:497)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:527)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:523)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:356)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:522)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:546)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1423)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1500(CommandRunnerImpl.java:108)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1762)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1674)
at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:534)
at com.sun.enterprise.v3.admin.AdminAdapter.onMissingResource(AdminAdapter.java:224)
at org.glassfish.grizzly.http.server.StaticHttpHandler.service(StaticHttpHandler.java:297)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:246)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
at java.lang.Thread.run(Thread.java:744)
Caused by: javax.ejb.CreateException: Initialization failed for Singleton Tester
at com.sun.ejb.containers.AbstractSingletonContainer.createSingletonEJB(AbstractSingletonContainer.java:483)
at com.sun.ejb.containers.AbstractSingletonContainer.access$000(AbstractSingletonContainer.java:81)
at com.sun.ejb.containers.AbstractSingletonContainer$SingletonContextFactory.create(AbstractSingletonContainer.java:654)
... 42 more
Caused by: javax.ejb.EJBTransactionRolledbackException
at com.sun.ejb.containers.BaseContainer.mapLocal3xException(BaseContainer.java:2279)
at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2060)
at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1979)
at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:220)
at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:88)
at com.sun.proxy.$Proxy495.saveUser(Unknown Source)
at tube_application.tests.Tester.start_here(Tester.java:43)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.BeanCallbackInterceptor.intercept(InterceptorManager.java:1035)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:72)
at com.sun.ejb.containers.interceptors.CallbackInvocationContext.proceed(CallbackInvocationContext.java:205)
at org.jboss.weld.ejb.AbstractEJBRequestScopeActivationInterceptor.aroundInvoke(AbstractEJBRequestScopeActivationInterceptor.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.CallbackInterceptor.intercept(InterceptorManager.java:986)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:72)
at com.sun.ejb.containers.interceptors.CallbackInvocationContext.proceed(CallbackInvocationContext.java:205)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doCall(SystemInterceptorProxy.java:163)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.init(SystemInterceptorProxy.java:125)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.CallbackInterceptor.intercept(InterceptorManager.java:986)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:72)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:412)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:375)
at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:1949)
at com.sun.ejb.containers.AbstractSingletonContainer.createSingletonEJB(AbstractSingletonContainer.java:475)
... 44 more
Caused by: javax.ejb.TransactionRolledbackLocalException: Exception thrown from bean
at com.sun.ejb.containers.EJBContainerTransactionManager.checkExceptionClientTx(EJBContainerTransactionManager.java:662)
at com.sun.ejb.containers.EJBContainerTransactionManager.postInvokeTx(EJBContainerTransactionManager.java:507)
at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:4475)
at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2009)
... 76 more
Caused by: java.lang.NullPointerException
答案 0 :(得分：0)
您应该从修复代码开始：
em.persist(em);
您应该保留user对象而不是EntityManger。
em.persist(user);
如果错误仍然存在，请提供完整的堆栈跟踪。