Spring4.3.7注解 @Autowired java.lang.NullPointerException

Question

UserAction中通过@Autowired注入UserServiceImpl无效，得到对象为空
UserAction.java

@Namespace("/")
@ParentPackage("struts-default")
@Controller
public class UserAction extends ActionSupport implements ModelDriven<User> {
    private User user = new User();

    public User getModel() {
        return this.user;
    }

    // *****************************
    @Autowired
    private UserService userService;

    @Action(value = "userAction_add", results = { @Result(name = "add", location = "/success.jsp") })
    public String add() {
        this.userService.saveUser(user);
        return "add";
    }
}

UserServiceImpl.java

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserDao userDao;

    @Transactional
    public void saveUser(User user) {
        this.userDao.save(user);
    }

    @Transactional
    public void updateUser(User user) {
        this.userDao.update(user);
    }

    @Transactional
    public void deleteUser(User user) {
        this.userDao.delete(user);
    }

    @Transactional(readOnly = true)
    public User findUserById(Integer id) {
        return this.userDao.findById(id);
    }

    @Transactional(readOnly = true)
    public List<User> findAllUser() {
        return this.userDao.findAll();
    }
}

配置文件

<?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" 
    xmlns:aop="http://www.springframework.org/schema/aop"
    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
            http://www.springframework.org/schema/aop 
            http://www.springframework.org/schema/aop/spring-aop.xsd">
    <!-- 扫描 com包-->
    <context:component-scan base-package="com"></context:component-scan>
    <context:annotation-config/>
    <!-- 
    <context:property-placeholder location="classpath:redis.properties"/>
    <bean id="jedisPoolConfig" class="redis.clients.jedis.JedisPoolConfig">  
        <property name="maxIdle" value="${redis.pool.maxIdle}" />  
        <property name="maxTotal" value="${redis.pool.maxActive}" />   
        <property name="maxWaitMillis" value="${redis.pool.maxWaitMillis}" />   
        <property name="testOnBorrow" value="${redis.pool.testOnBorrow}" />  
        <property name="testOnReturn" value="${redis.pool.testOnReturn}" />  
    </bean>  -->
    
    <!--  加载c3p0-db.properties -->
    <context:property-placeholder location="classpath:c3p0-db.properties" />
    <!-- 配置dataSource数据源 -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="${jdbc.driverClass}"></property>
        <property name="jdbcUrl" value="${jdbc.jdbcUrl}"></property>
        <property name="user" value="${jdbc.user}"></property>
        <property name="password" value="${jdbc.password}"></property>
    </bean>
    
    <!-- 1 配置SessionFactory -->
    <bean id="sessionFactory"
        class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
        <!-- 1.1 配置数据源 -->
        <property name="dataSource" ref="dataSource"></property>
        <!-- 1.2 其他配置项 ,要使用hibernate全属性名，如果hibernate.不要省略 -->
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">
                    org.hibernate.dialect.MySQL5Dialect
                 </prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
                <prop key="javax.persistence.validation.mode">none</prop>
                <prop key="hibernate.current_session_context_class">thread</prop>
                <prop key=""></prop>
            </props>
        </property>
        
        <!-- 配置实体类 -->
        <property name="packagesToScan">
            <list>
                <value>com.entity</value>
            </list>
        </property>        
    </bean>
    <!-- 配置hibernate模板，必须使用模板 -->
    <bean id="hibernateTemplate" class="org.springframework.orm.hibernate5.HibernateTemplate">
        <!-- 通过工厂获得session，操作PO类 -->
        <property name="sessionFactory" ref="sessionFactory"></property>
    </bean>
    <!-- 事务管理 -->
    <!-- 事务管理器,就是平台，spring工具产生， 依赖于使用 持久方案（hibernate、jdbc等） -->
    <bean id="txManager"
        class="org.springframework.orm.hibernate5.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory"></property>
    </bean>
    <!-- 将事务管理注册spring * proxy-target-class="true": 
    使用cglib * proxy-target-class="false":有接口将使用 jdk -->
    <tx:annotation-driven transaction-manager="txManager" />
</beans>

Answer 1

请保证UserServiceImpl在被扫描的包内。

Answer 2

注解的扫描有问题

Answer 3

我建议你看看UserDao是否正确注入，这条链子上有一个注入失败了就会导致整体创建失败