Question

我正在学习春天和 mybatis 。

我遇到了一个问题。我主要从officail tutorial学习。但我无法得到我的意思。

春天无法在 ServiceImpl 中自动装配 UserMapper 。

还有一个例外

java.lang.NullPointerException

    main.java.cn.qingtianr.service.impl.UserServiceImpl.findByUserName(UserServiceImpl.java:23)
    main.java.cn.qingtianr.action.UserAction.execute(UserAction.java:22)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:498)
    ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:870)
    ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1293)
    ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)
    com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:117)
    com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:108)
    ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1369)
    ognl.ASTMethod.getValueBody(ASTMethod.java:90)
    ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
    ognl.SimpleNode.getValue(SimpleNode.java:258)
    ognl.Ognl.getValue(Ognl.java:494)

还有其他来源。

的applicationContext.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:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                        http://www.springframework.org/schema/context
                        http://www.springframework.org/schema/context/spring-context-3.1.xsd
                        http://www.springframework.org/schema/mvc
                        http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <bean id="archivesi" class="main.java.cn.qingtianr.service.impl.ArchiveServiceImpl"/>
    <bean id="articlesi" class="main.java.cn.qingtianr.service.impl.ArticleServiceImpl"/>
    <bean id="usersi" class="main.java.cn.qingtianr.service.impl.UserServiceImpl"/>

    <!--<aop:aspectj-autoproxy proxy-target-class="true" />-->
    <!-- 自动扫描 -->
    <!--<context:component-scan base-package="main.java.cn.qingtianr" />-->
    <!-- 引入配置文件 -->
    <bean id="propertyConfigurer"
          class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location" value="classpath:main/resources/jdbc.properties" />
    </bean>

    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
          destroy-method="close">
        <property name="driverClassName" value="${driver}" />
        <property name="url" value="${url}" />
        <property name="username" value="${username}" />
        <property name="password" value="${password}" />
        <!-- 初始化连接大小 -->
        <property name="initialSize" value="${initialSize}"></property>
        <!-- 连接池最大数量 -->
        <property name="maxActive" value="${maxActive}"></property>
        <!-- 连接池最大空闲 -->
        <property name="maxIdle" value="${maxIdle}"></property>
        <!-- 连接池最小空闲 -->
        <property name="minIdle" value="${minIdle}"></property>
        <!-- 获取连接最大等待时间 -->
        <property name="maxWait" value="${maxWait}"></property>
    </bean>

    <!-- spring和MyBatis完美整合，不需要mybatis的配置映射文件 -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
    </bean>

    <bean id="userdao" class="org.mybatis.spring.mapper.MapperFactoryBean">
        <property name="mapperInterface" value="main.java.cn.qingtianr.dao.UserDao" />
        <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    </bean>


        </beans>

UserServiceImpl.java

package main.java.cn.qingtianr.service.impl;

import main.java.cn.qingtianr.dao.UserDao;
import main.java.cn.qingtianr.dbc.MybatisSqlSessionFactory;
import main.java.cn.qingtianr.model.User;
import main.java.cn.qingtianr.service.UserService;

/**
 * Created by jack on 16-3-29.
 */
public class UserServiceImpl implements UserService{

    private UserDao userdao;

    public User findByUserName(String username) throws Exception
    {
        User user = null;
        try
        {
            if(userdao == null){
                System.out.println("11111111111");
            }
            user = this.userdao.findByUserName(username);
        }
        catch (Exception e)
        {
            e.printStackTrace();
            throw e;
        }
        finally
        {
            MybatisSqlSessionFactory.closeSession();
        }
        return user;
    }

    public UserDao getUserdao() {
        System.out.println("It is in getUserdao");
        return userdao;
    }

    public void setUserdao(UserDao userdao) {
        System.out.println("It is in setUserdao");
        this.userdao = userdao;
    }
}

UserDao.java

package main.java.cn.qingtianr.dao;

import main.java.cn.qingtianr.model.User;

/**
 * Created by jack on 16-3-29.
 */
public interface UserDao {
    public User findByUserName(String username) throws Exception;
}

UserDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="main.java.cn.qingtianr.dao.UserDao">

    <select id="findByUserName" parameterType="int" resultType="main.java.cn.qingtianr.model.User">
        SELECT * FROM user WHERE username = #{username}
    </select>

</mapper>

如果spring autowire mybatis Mapper，则会在 UserServiceImpl.java 中打印It is in setUserdao或getUserdao。

但11111111为空时只有userdao。

那么有人可以帮助我吗？ THX。

Answer 1

<bean id="usersi" class="main.java.cn.qingtianr.service.impl.UserServiceImpl">
    <property name="userdao" ref = "userdao"/>
</bean >

Answer 2

您没有在usersi bean定义中设置userDao bean。请点击此处了解更多信息：http://www.mybatis.org/spring/mappers.html

spring无法在mybatis中自动装配NullPointerException

2 个答案: