java - PersistenceContext 为空

Question

我创建了一个 PersonDao 对象，它是一个应该使用注入(inject)实体管理器的可注入(inject) bean。问题是 @PersistenceContext() 没有注入(inject)我的对象并将其保留为 null。我正在使用 JBoss 独立 eap 6.2。下面是我的文件:

hello.dao/PersonDao:

package hello.dao;

import java.util.List;

import javax.ejb.Stateless;
import javax.inject.Inject;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import hello.entity.Location;
import hello.entity.Person;

@Stateless
public class PersonDao {
    @PersistenceContext(unitName="helloPersistence")
    static EntityManager em;
    Person person;

    @Inject
    public PersonDao() {

    }

    public void addLocation(Location location) {
        // em is always null
        System.out.println(em.toString());
        em.persist(person);
        em.persist(location);
        person.getLocations().add(location);
        location.getPersons().add(person);
        em.flush();
    }

    public void setPerson(Person person) {
        this.person = person;
    }

    public void savePerson() {
        em.persist(person);
        em.flush();
    }

    public static List<?> list() {
        List<?> results = em.createNativeQuery("SELECT * FROM PERSON").getResultList();
        return results;
    }
}

持久性.xml

<?xml version="1.0" encoding="UTF-8" ?>
<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"
    version="2.0" xmlns="http://java.sun.com/xml/ns/persistence">
    <persistence-unit name="helloPersistence">
        <jta-data-source>java:jboss/datasources/MySqlDS</jta-data-source>
        <class>hello.dao.LocationDao</class>
        <class>hello.dao.PersonDao</class>
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
            <property name="javax.persistence.schema-generation.database.action"
                  value="drop-and-create" />
        </properties>
    </persistence-unit>
</persistence>

Standalone.xml 数据源:

             <datasources>
                <datasource jta="true" jndi-name="java:jboss/datasources/MySqlDS" pool-name="java:jboss/datasources/MySqlDS_Pool" enabled="true" use-java-context="true" use-ccm="true">
                    <connection-url>jdbc:mysql://localhost:3306/hello</connection-url>
                    <driver>mysql</driver>
                    <pool>
                        <min-pool-size>10</min-pool-size>
                        <max-pool-size>100</max-pool-size>
                        <prefill>true</prefill>
                    </pool>
                    <security>
                        <user-name>root</user-name>
                        <password>password</password>
                    </security>
                </datasource>
                <drivers>
                    <driver name="mysql" module="com.mysql.connectorj">
                        <driver-class>com.mysql.jdbc.Driver</driver-class>
                        <xa-datasource-class>com.mysql.jdbc.jdbc2.optional.MysqlXADataSource</xa-datasource-class>
                    </driver>
                    <driver name="db2" module="com.ibm.db2">
                        <driver-class>com.ibm.db2.jcc.DB2Driver</driver-class>
                        <xa-datasource-class>com.ibm.db2.jcc.DB2XADataSource</xa-datasource-class>
                    </driver>
                </drivers>
           </datasources>

standalone.sh 上的 War 部署

13:19:39,530 INFO  [org.jboss.as.server.deployment] (MSC service thread 1-14) JBAS015876: Starting deployment of "hello.war" (runtime-name: "hello.war")
13:19:39,871 INFO  [org.jboss.as.jpa] (MSC service thread 1-14) JBAS011401: Read persistence.xml for helloPersistence
13:19:39,912 INFO  [org.jboss.weld.deployer] (MSC service thread 1-11) JBAS016002: Processing weld deployment hello.war
13:19:39,915 INFO  [org.jboss.as.ejb3.deployment.processors.EjbJndiBindingsDeploymentUnitProcessor] (MSC service thread 1-11) JNDI bindings for session bean named PersonDao in deployment unit deployment "hello.war" are as follows:

    java:global/hello/PersonDao!hello.dao.PersonDao
    java:app/hello/PersonDao!hello.dao.PersonDao
    java:module/PersonDao!hello.dao.PersonDao
    java:global/hello/PersonDao
    java:app/hello/PersonDao
    java:module/PersonDao

13:20:07,809 INFO  [org.jboss.as.connector.deployers.jdbc] (MSC service thread 1-9) JBAS010404: Deploying non-JDBC-compliant driver class com.mysql.jdbc.Driver (version 5.1)
13:20:07,810 INFO  [org.jboss.as.connector.deployers.jdbc] (MSC service thread 1-9) JBAS010404: Deploying non-JDBC-compliant driver class com.mysql.fabric.jdbc.FabricMySQLDriver (version 5.1)
13:20:07,810 INFO  [org.jboss.weld.deployer] (MSC service thread 1-9) JBAS016005: Starting Services for CDI deployment: hello.war
13:20:07,813 INFO  [org.jboss.as.jpa] (ServerService Thread Pool -- 436) JBAS011402: Starting Persistence Unit Service 'hello.war#helloPersistence'
13:20:07,814 INFO  [org.jboss.weld.deployer] (MSC service thread 1-4) JBAS016008: Starting weld service for deployment hello.war
13:20:07,814 INFO  [org.hibernate.ejb.Ejb3Configuration] (ServerService Thread Pool -- 436) HHH000204: Processing PersistenceUnitInfo [
    name: helloPersistence
    ...]
13:20:07,823 INFO  [org.hibernate.service.jdbc.connections.internal.ConnectionProviderInitiator] (ServerService Thread Pool -- 436) HHH000130: Instantiating explicit connection provider: org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider
13:20:07,825 INFO  [org.hibernate.dialect.Dialect] (ServerService Thread Pool -- 436) HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
13:20:07,829 INFO  [org.hibernate.engine.transaction.internal.TransactionFactoryInitiator] (ServerService Thread Pool -- 436) HHH000268: Transaction strategy: org.hibernate.engine.transaction.internal.jta.CMTTransactionFactory
13:20:07,829 INFO  [org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory] (ServerService Thread Pool -- 436) HHH000397: Using ASTQueryTranslatorFactory
13:20:07,890 INFO  [org.jboss.web] (ServerService Thread Pool -- 446) JBAS018210: Register web context: /helloMan
13:20:07,908 INFO  [org.jboss.as.server] (DeploymentScanner-threads - 2) JBAS018565: Replaced deployment "hello.war" with deployment "hello.war"

Answer 1

我必须检查 JPA 规范，但我敢打赌容器根本不喜欢那个static。你能尝试一下吗:

@PersistenceContext(unitName="helloPersistence")
private EntityManager em; // Not a static but an instance field

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