为我的EntityManager获取nullpointerexception

时间：2016-11-12 09:24:18

标签： java postgresql hibernate wildfly entitymanager

使用Wildfly 10进行以下操作：使用hibernate通过DAO对象访问postgresql数据库的JSON Web服务。

更具体地说，我的POJO User.java：

@Entity (name="User")
@Table(name = "users")
public class User {


    @Id @GeneratedValue
    @Column(name="id")
    private int id;

    @Column(name="username")
    private String userName;

    @Column(name="password")
    private String password;

    @Column(name="email")
    private String emailAddress;

    public User(String userName, String password, String emailAddress) {
        super();
        this.userName = userName;
        this.password = password;
        this.emailAddress = emailAddress;
    }

    public User() {
        super();
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

我的用户道：

@Stateless
public class UserDao {

    @PersistenceContext (unitName="librarysoftjpa")
    private EntityManager entityManager;

    public List<User> getAllUsers(){
List<User> allUsers=null;

        CriteriaBuilder criteriaBuilder = this.entityManager.getCriteriaBuilder();
        CriteriaQuery<User> criteria = criteriaBuilder.createQuery(User.class);
        criteria.from(User.class);

        TypedQuery<User>query = entityManager.createQuery(criteria);
        allUsers = query.getResultList();
        return allUsers;    
    }
}

我的网络服务：

@RequestScoped
@Path("/users")
@Produces("application/json")
@Consumes("application/json")
public class UserWebService {


    private UserDao userDao;


    public UserWebService(){
        this.userDao=new UserDao();
    }
@GET
    @Path("/all")
    public List<User> getAllUsers(){
        List<User>users=this.userDao.getAllUsers();
        return users;
    }
}

我的persistence.xml：

<persistence version="2.1"
   xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="
        http://xmlns.jcp.org/xml/ns/persistence
        http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
   <persistence-unit name="librarysoftjpa" transaction-type="JTA">
    <jta-data-source>java:/PostGreLibrarySoftDS</jta-data-source>
    <class>org.declercq.librarysoftbackend.models.Permission</class>
    <class>org.declercq.librarysoftbackend.models.Role</class>
    <class>org.declercq.librarysoftbackend.models.User</class>
      <properties>
         <!-- Properties for Hibernate -->
         <property name="hibernate.hbm2ddl.auto" value="update" />
         <property name="hibernate.show_sql" value="true" />
         <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
         <property name="hibernate.format_sql" value="true"/>

      </properties>
   </persistence-unit>
</persistence>

所以我使用Wildfly 10管理的容器管理持久性。 但是，当访问webservice时，我的entitymanager得到了一个nullpointer异常：

10:17:10,095 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 62) WFLYUT0021: Registered web context: /librarysoftbackend
10:17:10,174 INFO  [org.jboss.as.server] (ServerService Thread Pool -- 34) WFLYSRV0010: Deployed "librarysoftbackend.war" (runtime-name : "librarysoftbackend.war")
10:17:10,341 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0060: Http management interface listening on http://127.0.0.1:9990/management
10:17:10,342 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0051: Admin console listening on http://127.0.0.1:9990
10:17:10,343 INFO  [org.jboss.as] (Controller Boot Thread) WFLYSRV0025: WildFly Full 10.1.0.Final (WildFly Core 2.2.0.Final) started in 14178ms - Started 422 of 670 services (404 services are lazy, passive or on-demand)
10:17:18,898 ERROR [io.undertow.request] (default task-3) UT005023: Exception handling request to /librarysoftbackend/rest/users/all: org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
    at org.jboss.resteasy.core.ExceptionHandler.handleApplicationException(ExceptionHandler.java:77)
    at org.jboss.resteasy.core.ExceptionHandler.handleException(ExceptionHandler.java:220)
    at org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:175)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:418)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:209)
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:221)
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56)
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
    at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
    at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
    at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
    at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:805)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
    at org.declercq.librarysoftbackend.dao.UserDao.getAllUsers(UserDao.java:64)
    at org.declercq.librarysoftbackend.rest.UserWebService.getAllUsers(UserWebService.java:69)
    at org.declercq.librarysoftbackend.rest.UserWebService$Proxy$_$$_WeldClientProxy.getAllUsers(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:139)
    at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:295)
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:249)
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:236)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:402)
    ... 43 more

更具体地说：

Caused by: java.lang.NullPointerException
    at org.declercq.librarysoftbackend.dao.UserDao.getAllUsers(UserDao.java:64)

指向：

CriteriaBuilder criteriaBuilder = this.entityManager.getCriteriaBuilder();

在UserDao.java中。

知道我在这里做错了吗？

更新：此处链接的主题可能是重复的，绝对没有任何关系。我的问题是容器管理持久化上下文并在我的应用程序中注入实体管理器，而不是不知道如何初始化对象。

UPDATE2：我稍微改变了我的代码，在阅读Adam Bien的这篇文章后，通过添加注释@Stateless来考虑我的UserDao为Bean：http://www.adam-bien.com/roller/abien/entry/ejb_3_persistence_jpa_for。基本上说JPA不再需要DAO，EJB更好。但是，在同一位置仍然是nullpointerexception。 （尝试了@Stateful，同样的结果）。

UPDATE3： 在Wildfly的standalone.xml中配置我的数据源：

<datasources>
                <datasource jndi-name="java:/PostGreLibrarySoftDS" pool-name="PostgrePool">
                    <connection-url>jdbc:postgresql://127.0.0.1:5432/librarysoft</connection-url>
                    <driver>postgres</driver>
                    <security>
                        <user-name>test</user-name>
                        <password>test</password>
                    </security>
                </datasource>
                <drivers>
                    <driver name="postgres" module="org.postgres">
                        <driver-class>org.postgresql.Driver</driver-class>
                    </driver>
                </drivers>

解决即可。 解决方案是将@Stateless表示法添加到我的UserDao类中，使其成为一个bean。 接下来，在UserWebService中，添加属性：

@EJB
private UserDao userDao;

使用@EJB在这里注入bean是解决方案。

2 个答案:

答案 0 :(得分：0)

您的UserDao不受任何框架管理。请注意，在您提供的示例中，Movies对象上有@Stateful。这告诉容器它应该注入依赖项：在你的情况下是PersistenceManager。

答案 1 :(得分：0)

在您的<?php if(isset($_GET["checkIfLoggedIn"]) && boolval($_GET["checkIfLoggedIn"]) === true) { header("Content-Type: text/json"); die(json_encode(array("isLoggedIn" => $_COOKIE["isLoggedIn"]))); exit(); } else { var_dump($_COOKIE); } ?> <html> <head> <script type="text/javascript" src="jquery-3.1.1.min.js"></script> <script type="text/javascript" src="js.cookie.js"></script> </head> <body> <script type="text/javascript"> function checkIfLoggedIn() { console.log("checking..."); jQuery.post("?checkIfLoggedIn=1", function(data) { if(data.isLoggedIn == true) { alert("Logged im."); } else { alert("NOT logged in!"); } }); } </script> <a href="#" onclick="Cookies.set('isLoggedIn', 'true'); checkIfLoggedIn(); return false;">Set logged in to true</a><br/> <a href="#" onclick="Cookies.set('isLoggedIn', 'false'); checkIfLoggedIn(); return false;">Set logged in to false</a> </body> </html> 资源中，您正在实例化UserWebService，如下所示：

UserDao

您的public UserWebService(){ this.userDao=new UserDao(); } 是UserDao EJB（具有本地无界面视图）。

因此，让EJB容器按如下方式注入@Stateless EJB：

UserDao

您现在可以删除@EJB private UserDao userDao; 构造函数。

我希望这会有所帮助。

相关问题
最新问题