java - 实体管理器为空

Question

我是 EJB 的新手，创建一个有趣/学习 EJB 的应用程序，下面是代码。

@Entity
@Table(name = "PERSON", schema = "experiment")
@NamedQuery(name = "Person.fetchAllPerson" , query = "select p from Person p")
public class Person implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;
    @Column(name = "name", length = 500)
    private String name;
    @Column(name = "age")
    private Integer age;

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Person)) {
            return false;
        }
        Person other = (Person) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "Person id ::: "+this.id + " | "+"name ::: "+this.name+" | "+"age ::: "+this.age;
    }
}

上面是Entity类:::下面是我的bean(SessionBean)::

    @Stateless
public class PersonSessionBean implements PersonSessionBeanLocal {

    @PersistenceContext(unitName = "OCDPU")
    private EntityManager em;

    private static final Logger LOGGER = Logger.getLogger(PersonSessionBean.class);

    public void addPerson(Person p) {
        LOGGER.info("ENTITY MANAGER ::: "+em);
        em.persist(p);
    }

    public static PersonSessionBean getPersonSessionBean() {
        return new PersonSessionBean();
    }
}

下面是我的persistence.xml :::

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
  <persistence-unit name="OCDPU" transaction-type="JTA">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <jta-data-source>java:/jndi_postgresql2</jta-data-source>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
      <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
      <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
      <property name="hibernate.show_sql" value="true" />
    </properties>
  </persistence-unit>
</persistence>

以下是我的 .zul 文件控制器 :::

    public class Index2Controller extends GenericForwardComposer<Component> {

    private final static Logger LOGGER = Logger.getLogger(Index2Controller.class);

    private Textbox idTB,personTB,ageTB;
    private Button btn;
    private Window win;

//    @Inject
//    private  PersonDao pd;

    private PersonSessionBean psb;

    {
        psb = PersonSessionBean.getPersonSessionBean();
        LOGGER.info("PersonSessionBean ::: "+psb);
    }

    public void onClick$btn(Event e) {
        if(personTB.getText().equals("") ||ageTB.getText().equals("")){ 
            //| idTB.getText().equals("")) {
            this.alert("Enter all values");
            return;
        }

        LOGGER.info("ONCLICK ::: PersonSessionBean ::: "+this.psb);

        Integer i;
        i = Integer.valueOf(Integer.parseInt(ageTB.getText()));
        Person p = new Person();
        p.setName(personTB.getText());
        p.setAge(i);
        LOGGER.error("Person is ::: "+p);
        psb.addPerson(p);
        personTB.setRawValue(null);
        ageTB.setRawValue(null);
        showNotification("Saved", win);
    }

   public void showNotification(String msg, Component ref) {
       Clients.showNotification(msg, "info", ref, 700, 0, 1000);
   }
}

错误 ：：：：

18:33:27,395 INFO  [com.discusit.ctrl.Index2Controller] (http--0.0.0.0-8080-5) ONCLICK ::: PersonSessionBean ::: com.discusit.bean.PersonSessionBean@3f2c4ca
18:33:27,396 ERROR [com.discusit.ctrl.Index2Controller] (http--0.0.0.0-8080-5) Person is ::: Person id ::: null | name ::: Naman | age ::: 26
18:33:27,397 INFO  [com.discusit.bean.PersonSessionBean] (http--0.0.0.0-8080-5) ENTITY MANAGER ::: null
18:33:27,400 SEVERE [org.zkoss] (http--0.0.0.0-8080-5) >>java.lang.NullPointerException
>>  at com.discusit.bean.PersonSessionBean.addPerson(PersonSessionBean.java:27)
>>  at com.discusit.ctrl.Index2Controller.onClick$btn(Index2Controller.java:60)
>>  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>>  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>>  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>>  at java.lang.reflect.Method.invoke(Method.java:606)
>>  at org.zkoss.zk.ui.event.GenericEventListener.onEvent(GenericEventListener.java:88)
>>  at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:2742)
>>  at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2713)
>>  at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2654)
>>  at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:136)
>>  at org.zkoss.zk.ui.event.Events.sendEvent(Events.java:325)
>>  at org.zkoss.zk.ui.event.Events.sendEvent(Events.java:348)
>>  at org.zkoss.zk.ui.AbstractComponent$ForwardListener.onEvent(AbstractComponent.java:3180)
>>  at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:2742)
>>  at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2713)
>>  at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2654)
>>  at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:136)
>>  at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1717)
>>  at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1502)
>>  at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1212)
>>  at org.zkoss.zk.au.http.DHtmlUpdateServlet.process(DHtmlUpdateServlet.java:600)
>>  at org.zkoss.zk.au.http.DHtmlUpdateServlet.doGet(DHtmlUpdateServlet.java:482)
>>  at org.zkoss.zk.au.http.DHtmlUpdateServlet.doPost(DHtmlUpdateServlet.java:491)
>>  at javax.servlet.http.HttpServlet.service(HttpServlet.java:754)
>>  at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
>>  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329)
>>  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
>>  at org.jboss.weld.servlet.ConversationPropagationFilter.doFilter(ConversationPropagationFilter.java:62)
>>  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
>>  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
>>  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275)
>>  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
>>  at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50)
>>  at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153)
>>  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
>>  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
>>  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
>>  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368)
>>  at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877)
>>  at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671)
>>  at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930)
>>  at java.lang.Thread.run(Thread.java:724)

我正在使用 JBoss AS 7.1.1 final。我在其中创建了一个连接池。它连接到我局域网上的数据库。无法弄清楚出了什么问题。先感谢您。

我想我在 pom.xml 中遗漏了一些东西，这是我的 pom :::

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.discusit</groupId>
    <artifactId>OrgChartDemo</artifactId>
    <version>1.0</version>
    <packaging>war</packaging>

    <name>OrgChartDemo</name>

    <properties>
        <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>6.0</version>
            <scope>provided</scope>
        </dependency>

        <!-- ZK DEPENDENCIES -->
        <dependency>
            <groupId>org.zkoss.zk</groupId>
            <artifactId>zkplus</artifactId>
            <version>6.5.2</version>
        </dependency>
        <dependency>
            <groupId>org.zkoss.zk</groupId>
            <artifactId>zhtml</artifactId>
            <version>6.5.2</version>
        </dependency>
        <dependency>
            <groupId>org.zkoss.zk</groupId>
            <artifactId>zkbind</artifactId>
            <version>6.5.2</version>
        </dependency>
        <dependency>
            <groupId>org.zkoss.zk</groupId>
            <artifactId>zul</artifactId>
            <version>6.5.2</version>
        </dependency> 
        <!-- ZK Dependencies ends -->

        <!-- log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <!-- log4j ends -->

        <!-- javax.persistence 2.0 implementation -->
        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.0-api</artifactId>
            <version>1.0.1.Final</version>
        </dependency>
        <!-- javax.persistence 2.0 ends -->
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                    <compilerArguments>
                        <endorseddirs>${endorsed.dir}</endorseddirs>
                    </compilerArguments>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.1.1</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.1</version>
                <executions>
                    <execution>
                        <phase>validate</phase>
                        <goals>
                            <goal>copy</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${endorsed.dir}</outputDirectory>
                            <silent>true</silent>
                            <artifactItems>
                                <artifactItem>
                                    <groupId>javax</groupId>
                                    <artifactId>javaee-endorsed-api</artifactId>
                                    <version>6.0</version>
                                    <type>jar</type>
                                </artifactItem>
                            </artifactItems>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Answer 1

资源注入如下：

@PersistenceContext(unitName = "OCDPU")
private EntityManager em;

仅适用于生命周期由容器管理的客户端类，即 EJB、JSF ManagedBean、CDI bean 或 servlet。在您的情况下，客户端类PersonSessionBean 是 EJB，这没关系。错误在于PersonSessionBean：

psb = PersonSessionBean.getPersonSessionBean();

这一行是错误的，因为 EJB 应该通过@EJB注解注入：

@EJB PersonSessionBean psb;

或通过 JNDI 查找检索。

但是您还必须注意，客户端类Index2Controller也是容器管理的，从发布的代码来看，情况并非如此。

有用的链接：从 Oracle 的 Java EE 6 教程访问 Enterprise Beans 。