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我是春天的新手。我正在尝试使用 Spring 3.1.3 和 JPA 2.0 设置简单的 Web 应用程序，我已将所有必要的库添加到 WEB-INF/lib。启动过程中没有错误，但我的 DaoImpl 文件中的 entityManager 为空。所以，这是我的配置：

持久性.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="fcmsServer" transaction-type="RESOURCE_LOCAL">
</persistence-unit>
</persistence>

fcms-servlet.xml

<?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"
xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd">

<!-- the application context definition for the fcmsServer DispatcherServlet -->

<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="persistenceUnitName" value="fcmsServer" />
    <property name="dataSource" ref="dataSource" />
    <property name="jpaDialect">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
    </property>
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="showSql" value="true" />
            <property name="generateDdl" value="true" />
            <property name="databasePlatform" value="org.hibernate.dialect.H2Dialect" />
        </bean>
    </property>
    <property name="persistenceUnitManager">
        <bean
            class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
            <property name="defaultDataSource" ref="dataSource" />
        </bean>
    </property>
</bean>

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
    destroy-method="close">
    <property name="driverClassName" value="org.h2.Driver" />
    <property name="url" value="jdbc:h2:tcp://localhost/~/fcms" />
    <property name="username" value="sa" />
    <property name="password" value="sa" />
</bean>

<tx:annotation-driven transaction-manager="transactionManager" />
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
    <property name="dataSource" ref="dataSource" />
</bean>

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


<bean id="userDao" class="fcms.data.user.UserDAOImpl">
</bean>

<bean name="/user.htm" class="fcms.controller.UserController">
</bean>

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

DaoImpl 类：

@Repository
public class UserDAOImpl implements UserDAO {
@PersistenceContext(unitName = "fcmsServer")
private EntityManager entityManager;

public void setEntityManager(EntityManager entityManager) {
    this.entityManager = entityManager;
}

@Override
public User getUserById(long id) {
    return entityManager.find(User.class,id);
}

@Override
public void addUser(User u) {
    entityManager.persist(u);
}
}

用户类

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


@Id  @GeneratedValue
private long id;
@Column(name = "lastName", nullable = false)
private String lastName;
@Column(name = "firstName", nullable = false)
private String firstName;
@Column(name = "birthDate", nullable = true)
private Date birthDate;
private static final long serialVersionUID = 1L;

}

因此，当我尝试在 UserController 中调用 addUser() 时，在持久化期间出现 NullPointerException。

4

2 回答 2

2

我认为您缺少告诉 spring 搜索注释的配置（在<beans>元素之间的任何位置添加以下内容：

<context:annotation-config />

也许您还需要添加以下内容，指定您拥有 DAO 的包。但我认为这不是必需的。

<context:component-scan base-package="your.package" />
于 2013-02-13T14:31:34.760 回答
1

这是一段工作代码：

春天.xml：

<?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: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.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/tx 
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
        <context:annotation-config />
        <context:component-scan base-package="com.package.dao" />
        <tx:annotation-driven transaction-manager="transactionManager" />
        <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
                <property name="persistenceUnitName" value="fcmsServer" />
        </bean>
        <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
                <property name="entityManagerFactory" ref="entityManagerFactory" />
        </bean>        
</beans>

豆豆：

@Repository
public class UserDaoBean implements UserDao {
        @PersistenceContext
        protected EntityManager em;         
}

持久性.xml：

<?xml version="1.0" encoding="UTF-8" ?>
<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="fcmsServer" transaction-type="RESOURCE_LOCAL">

        <class>com.package.entity.</class>
        <properties>
            <property name="javax.persistence.jdbc.url"
                 value="jdbc:mysql://localhost:3306/db_name"/>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.user" value="admin"/>
            <property name="javax.persistence.jdbc.password" value="admin"/>
        </properties>
    </persistence-unit>
</persistence>
于 2013-02-13T16:03:50.913 回答