Java Spring中entityManager上的NullPointerException_Java_Spring_Hibernate_Spring Mvc_Jpa

Java Spring中entityManager上的NullPointerException

java spring hibernate spring-mvc jpa

Java Spring中entityManager上的NullPointerException,java,spring,hibernate,spring-mvc,jpa,Java,Spring,Hibernate,Spring Mvc,Jpa,我的问题是无法从LocalContainerEntityManagerFactoryBean获取entityManager。我找到了一个临时解决方案，而不是在源代码中获取Factory，然后在代码中使用Factory实例创建manager，但我认为这对于spring应用程序是错误的方法。代码如下： ManDAOImpl： public class ManDAOImpl implements ManDAO{ //can't obtain EntityManager by that ann

我的问题是无法从LocalContainerEntityManagerFactoryBean获取entityManager。我找到了一个临时解决方案，而不是在源代码中获取Factory，然后在代码中使用Factory实例创建manager，但我认为这对于spring应用程序是错误的方法。代码如下：

ManDAOImpl：

public class ManDAOImpl implements ManDAO{

    //can't obtain EntityManager by that annotation
    @PersistenceContext
    private EntityManager entityManager;

    //It's temporary solution instead of the above, but dont mind
    private EntityManagerFactory emf;

    public void setEmf(EntityManagerFactory emf) {
        this.emf = emf;
    }

    @Override
    public int save(Man man) {
        //temporary solution
//      entityManager = this.emf.createEntityManager();

        entityManager.getTransaction().begin();      //NullPointerException on this line
        entityManager.persist(man);
        entityManager.getTransaction().commit();

        return man.getId();
    }

    @Override
    public void remove(Man man) {
        //temporary solution
//      entityManager = this.emf.createEntityManager();

        entityManager.getTransaction().begin();
        entityManager.remove(man);
        entityManager.getTransaction().commit();
    }

}

root-context.xml中的My Bean：

<?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/tx 
      http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">

    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"
        >
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/tutorialbase" />
        <property name="username" value="tutorial" />
        <property name="password" value="password" />
    </bean>

    <bean id="myEmf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
      <property name="dataSource" ref="dataSource" />
      <property name="packagesToScan" value="com.tutorial.myapp.domain" />
      <property name="jpaVendorAdapter">
         <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
      </property>
      <property name="jpaProperties">
         <props>
            <prop key="hibernate.hbm2ddl.auto">create</prop>
            <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>
            <prop key="hibernate.current_session_context_class">thread</prop>
            <prop key="hibernate.show_sql">false</prop>
         </props>
      </property>
   </bean>

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

   <bean id="ManDAO" class="com.tutorial.myapp.daos.ManDAOImpl">
   <property name="emf" ref="myEmf" />
   </bean>

   <bean id="persistenceExceptionTranslationPostProcessor"
      class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />

</beans>

在HomeController.java.43中，我正在尝试保存一行：

Man man = new Man();

        man.setFirstName("Janusz");
        man.setLastName("Soft");
        man.setCountry("Polska");

        **manDao.save(man);**

这是我的pom.xml：

<?xml version="1.0" encoding="UTF-8"?>
<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.tutorial</groupId>
    <artifactId>myapp</artifactId>
    <name>Test</name>
    <packaging>war</packaging>
    <version>1.0.0-BUILD-SNAPSHOT</version>
    <properties>
        <java-version>1.6</java-version>
        <org.springframework-version>3.1.1.RELEASE</org.springframework-version>
    </properties>
    <dependencies>
        <!-- Spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${org.springframework-version}</version>
            </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <!-- Servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.0</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <!-- Hibernate -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.36</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>4.3.10.Final</version>
        </dependency>

        <dependency>
    <groupId>javax.ejb</groupId>
    <artifactId>ejb-api</artifactId>
    <version>3.0</version>
</dependency>

加

或

在root context.xml中添加

或

在root context.xml中，向我们展示HomeController的代码，特别是您获取ManDAO实例的方式。好的，我发布了它，@jbnizets向我们展示HomeController的代码，特别是您获取ManDAO实例的方式。好的，我发布了它，@jbnizets感谢它解决了我的问题

<?xml version="1.0" encoding="UTF-8"?>
<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.tutorial</groupId>
    <artifactId>myapp</artifactId>
    <name>Test</name>
    <packaging>war</packaging>
    <version>1.0.0-BUILD-SNAPSHOT</version>
    <properties>
        <java-version>1.6</java-version>
        <org.springframework-version>3.1.1.RELEASE</org.springframework-version>
    </properties>
    <dependencies>
        <!-- Spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${org.springframework-version}</version>
            </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <!-- Servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.0</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <!-- Hibernate -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.36</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>4.3.10.Final</version>
        </dependency>

        <dependency>
    <groupId>javax.ejb</groupId>
    <artifactId>ejb-api</artifactId>
    <version>3.0</version>
</dependency>

@Controller
public class HomeController {

    @Autowired
    private ManDAO manDao;
    /**
     * Simply selects the home view to render by returning its name.
     */
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String home(Locale locale, Model model) {

        Date date = new Date();
        DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, locale);

        String formattedDate = dateFormat.format(date);

        model.addAttribute("serverTime", formattedDate );

        Man man = new Man();

        man.setFirstName("Janusz");
        man.setLastName("Soft");
        man.setCountry("Polska");

        manDao.save(man);

        return "home";
    }

}

<context:annotation-config/>

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