JPA不是自动装配

Question

当我尝试自动装配我的DAO对象时，我得到一个空指针异常。让我告诉你代码（我正在使用maven + hibernate + spring + jpa）：

@Repository
public class DAOFriendImp implements DAOFriend{

    private EntityManagerFactory emf = Persistence.createEntityManagerFactory("persistence");
    private EntityManager entityManager = emf.createEntityManager();

    @PersistenceContext(unitName = "persistence")
    public void setEntityManager(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    @Override
    public boolean save(Person person, Person friend) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public List<Person> getAllFriendOfPersonWithId(int id) {
        Person person = entityManager.find(Person.class, id);
        return person.getFriends();
    }

    @Override
    public boolean delete(Person person, Person friend) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

}

正如您所看到的，我正在手动初始化我的entityManager。那是因为如果我使用persistenceContext，我也会得到一个空指针异常。也许是因为DAOFriendImp没有正确获得自动装配？我真的不知道。

现在让我告诉你我在哪里得到空指针：

public class FriendListLogic {

@Autowired
DAOFriendImp dao;

public List<Person> getEntrys(int userId) {
    List<Person> result = dao.getAllFriendOfPersonWithId(userId); //here
    return result;
}
}

我不知道为什么不注射！在配置XML中，一切似乎都没问题。我将添加其余的文件（pom，persistence，applicationcontext和servlet.xml）

的persistence.xml：

<persistence 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_1_0.xsd"
    version="1.0">

<persistence-unit name="persistence" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>com.divux.onex.model.Person</class>
    <class>com.divux.onex.model.CircleOfConnection</class>
    <properties>
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
        <property name="javax.persistence.jdbc.driver"   value="com.mysql.jdbc.Driver"   />
        <property name="javax.persistence.jdbc.url"        value="jdbc:mysql://localhost:3306/onex" />
        <property name="javax.persistence.jdbc.user"     value="root" />
        <property name="javax.persistence.jdbc.password" value="bterra" />
    </properties>
</persistence-unit>
</persistence>

注意：我在这里有我的jdbc用户密码驱动程序和url，因为我在applicationContext中的dataSource bean中遇到了问题...如果我在那里有这个信息就不行了（不知道为什么）

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans     http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context     http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/tx    http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">

<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

<context:annotation-config />
<bean  class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor"/> 
<bean id="dataSource"  class="org.springframework.jdbc.datasource.DriverManagerDataSource">
</bean>

<bean id="entityManagerFactory"   class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="persistenceUnitName" value="persistence" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="database" value="MYSQL" />
            <property name="showSql" value="false" /> 
            <property name="generateDdl" value="false" />
            <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"  />
        </bean>
    </property>
    <property name="loadTimeWeaver">  
        <bean class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver"></bean>  
    </property>
</bean>

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor"></bean>  

<tx:annotation-driven transaction-manager="transactionManager" />


</beans>

servlet.xml中

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd
    http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">

<context:component-scan base-package="com.divux.onex.controller"></context:component-scan>
<context:component-scan base-package="com.divux.onex.daoImp"></context:component-scan>

<context:property-placeholder location="classpath*:resources/properties/*.properties"/>

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/jsp/"/>
    <property name="suffix" value=".jsp"/>
</bean>

<mvc:annotation-driven/>
<mvc:view-controller path="/" view-name="index"/>
<mvc:resources mapping="/resources/**" location="/resources/"/>

  <import resource="applicationContext.xml" />

</beans>

最后是pom.xml（只是其中的一部分）

<properties>
    <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <org.springframework.version>3.0.5.RELEASE</org.springframework.version>
    <aspectj.version>1.6.11</aspectj.version>
    <org.slf4j-version>1.5.8</org.slf4j-version>
    <hibernate.version>3.6.7.Final</hibernate.version>
    <hibernate-search.version>4.0.0.Final</hibernate-search.version>
</properties>
<!-- JPA with Hibernate Persistence -->             
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.16</version>
    </dependency>
   <!-- Persistance -->
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>${hibernate.version}</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>${hibernate.version}</version>
        <exclusions>
            <exclusion>
                <groupId>cglib</groupId>
                <artifactId>cglib</artifactId>
            </exclusion>
            <exclusion>
                <groupId>dom4j</groupId>
                <artifactId>dom4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-ehcache</artifactId>
        <version>${hibernate.version}</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-search</artifactId>
        <version>${hibernate-search.version}</version>
    </dependency>
<!-- <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-jmx</artifactId> 
<version>${hibernate-jmx.version}</version> </dependency> -->
    <dependency>
        <groupId>org.hibernate.javax.persistence</groupId>
        <artifactId>hibernate-jpa-2.0-api</artifactId>
        <version>1.0.0.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-jpamodelgen</artifactId>
        <version>1.1.1.Final</version>
        <scope>provided</scope>
<!-- only need at compile time -->
    </dependency>
    <dependency>
        <groupId>cglib</groupId>
        <artifactId>cglib-nodep</artifactId>
        <version>2.2</version>
    </dependency>
    <dependency>
        <groupId>javax.transaction</groupId>
        <artifactId>jta</artifactId>
        <version>1.1</version>
    </dependency>


<!-- validation -->
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-validator</artifactId>
        <version>4.1.0.Final</version>
        <exclusions>
            <exclusion>
                <groupId>javax.xml.bind</groupId>
                <artifactId>jaxb-api</artifactId>
            </exclusion>
            <exclusion>
                <groupId>com.sun.xml.bind</groupId>
                <artifactId>jaxb-impl</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>javax.validation</groupId>
        <artifactId>validation-api</artifactId>
        <version>1.0.0.GA</version>
    </dependency>

<!-- AspectJ -->
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>${aspectj.version}</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>${aspectj.version}</version>
    </dependency>

</dependencies>

如果您需要更多信息，请告诉我们！我不会添加错误输出，因为我认为这是不必要的。如果您需要，请告诉我。

Answer 1

啊，您需要使用界面DAOFriend自动装配：

@Autowired
DAOFriend dao;

这是因为Spring使用Java代理机制将您的存储库bean包装到事务感知层中。使用这种方法，只有其他bean可以看到接口。

@Autowired也有“必需”的默认行为。这意味着您的FriendListLogic实例不受Spring管理：您需要使用@Component注释此类（并确保它位于组件扫描路径中）或通过String上下文显式创建它。

Answer 2

尝试在app-context.xml中添加FriendImpl作为bean。您需要使用完全限定的类名替换`xxx.yyy.zzz.FriendImpl'。

<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

<context:annotation-config />
<bean  class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor"/> 
<bean id="dataSource"  class="org.springframework.jdbc.datasource.DriverManagerDataSource">
</bean>

<bean id="entityManagerFactory"   class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="persistenceUnitName" value="persistence" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="database" value="MYSQL" />
            <property name="showSql" value="false" /> 
            <property name="generateDdl" value="false" />
            <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"  />
        </bean>
    </property>
    <property name="loadTimeWeaver">  
        <bean class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver"></bean>  
    </property>
</bean>

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor"></bean>  

<bean id="friendDao" class="xxx.yyy.zzz.FriendImpl"/>

<tx:annotation-driven transaction-manager="transactionManager" />