Mybatis学习笔记(十八)【spring和mybatis整合】

Contents

• 整合思路
• 整合环境
• sqlSessionFactory
• 原始dao开发(和spring整合后)
• mapper代理开发
• 遇到的问题

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本文主要将如何将spring和mybatis整合，只是作简单的示例，没有使用Maven构建。并展示mybatis与spring整合后如何进行原始dao开发和mapper代理开发。

整合思路

需要spring通过单例方式管理SqlSessionFactory。

spring和mybatis整合生成代理对象，使用SqlSessionFactory创建SqlSession。（spring和mybatis整合自动完成）

持久层的mapper都需要由spring进行管理。

整合环境

创建一个新的java工程（接近实际开发的工程结构）

jar包：

• mybatis3.2.7的jar包
• spring3.2.0的jar包
• mybatis和spring的整合包：早期ibatis和spring整合是由spring官方提供，mybatis和spring整合由mybatis提供。

sqlSessionFactory

在applicationContext.xml配置sqlSessionFactory和数据源

sqlSessionFactory在mybatis和spring的整合包下。

<beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"       xmlns:context="http://www.springframework.org/schema/context"       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"       xsi:schemaLocation="http://www.springframework.org/schema/beans        http://www.springframework.org/schema/beans/spring-beans-3.2.xsd        http://www.springframework.org/schema/mvc        http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd        http://www.springframework.org/schema/context        http://www.springframework.org/schema/context/spring-context-3.2.xsd        http://www.springframework.org/schema/aop        http://www.springframework.org/schema/aop/spring-aop-3.2.xsd        http://www.springframework.org/schema/tx        http://www.springframework.org/schema/tx/spring-tx-3.2.xsd ">    <!-- 加载配置文件 -->    <context:property-placeholder location="classpath:db.properties" />    <!-- 数据源，使用dbcp -->    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"          destroy-method="close">        <property name="driverClassName" value="${jdbc.driver}" />        <property name="url" value="${jdbc.url}" />        <property name="username" value="${jdbc.username}" />        <property name="password" value="${jdbc.password}" />        <property name="maxActive" value="10" />        <property name="maxIdle" value="5" />    </bean>    <!-- sqlSessinFactory -->    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">        <!-- 加载mybatis的配置文件 -->        <property name="configLocation" value="mybatis/SqlMapConfig.xml" />        <!-- 数据源 -->        <property name="dataSource" ref="dataSource" />    </bean></beans>

原始dao开发(和spring整合后)

• User.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"><!-- namespace 命名空间，作用就是对sql进行分类化管理,理解为sql隔离 注意：使用mapper代理方法开发，namespace有特殊重要的作用 --><mapper namespace="test">    <!-- 在映射文件中配置很多sql语句 -->    <!--需求:通过id查询用户表的记录 -->    <!-- 通过select执行数据库查询     id:标识映射文件中的sql，称为statement的id     将sql语句封装到mappedStatement对象中，所以将id称为statement的id     parameterType:指定输入参数的类型     #{}标示一个占位符,     #{value}其中value表示接收输入参数的名称，如果输入参数是简单类型，那么#{}中的值可以任意。     resultType：指定sql输出结果的映射的java对象类型，select指定resultType表示将单条记录映射成java对象     -->    <select id="findUserById" parameterType="int" resultType="com.iot.ssm.po.User">        SELECT * FROM  user  WHERE id=#{value}    </select></mapper>

在SqlMapconfig.xml中加载User.xml

 <!-- 加载映射文件--><mappers>    <mapper resource="sqlmap/User.xml"/></mappers>  

• dao(实现类继承SqlSessionDaoSupport)

public interface UserDao {    //根据id查询用户信息    public User findUserById(int id) throws Exception;}

dao接口实现类需要注入SqlSessoinFactory，通过spring进行注入。这里spring声明配置方式，配置dao的bean

让UserDaoImpl实现类继承SqlSessionDaoSupport

public class UserDaoImpl extends SqlSessionDaoSupport implements UserDao{    @Override    public User findUserById(int id) throws Exception {        //继承SqlSessionDaoSupport，通过this.getSqlSession()得到sqlSessoin        SqlSession sqlSession = this.getSqlSession();        User user = sqlSession.selectOne("test.findUserById",id);        return user;    }}

• 配置dao

在applicationContext.xml中配置dao

<!-- 原始dao接口 --><bean id="userDao" class="com.iot.ssm.dao.UserDaoImpl">    <property name="sqlSessionFactory" ref="sqlSessionFactory"/></bean>

• 测试程序

public class UserDaoImplTest {    private ApplicationContext applicationContext;    //在setUp这个方法得到spring容器    @Before    public void setUp() throws Exception {        applicationContext = new ClassPathXmlApplicationContext("classpath:spring/applicationContext.xml");    }    @Test    public void testFindUserById() throws Exception {        // 创建UserDao的对象        UserDao userDao = (UserDao)applicationContext.getBean("userDao");        // 调用UserDao的方法        User user = userDao.findUserById(1);        System.out.println(user);    }}

mapper代理开发

• mapper.java

public interface UserMapper {    //根据id查询用户信息    User findUserById(int id) throws Exception;}

• mapper.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"><!-- namespace 命名空间，作用就是对sql进行分类化管理,理解为sql隔离 注意：使用mapper代理方法开发，namespace有特殊重要的作用 --><mapper namespace="com.iot.ssm.mapper.UserMapper">    <!-- 在映射文件中配置很多sql语句 -->    <select id="findUserById" parameterType="int" resultType="user">        SELECT * FROM  user  WHERE id=#{value}    </select></mapper>

• 通过MapperFactoryBean创建代理对象

 <!-- mapper配置    MapperFactoryBean：根据mapper接口生成代理对象    --><bean id="userMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">        //mapperInterface指定mapper接口        <property name="mapperInterface" value="com.iot.ssm.mapper.UserMapper"/>        <property name="sqlSessionFactory" ref="sqlSessionFactory"/></bean>

此方法问题：需要针对每个mapper进行配置，麻烦。

• 通过MapperScannerConfigurer进行mapper扫描（建议使用）

<!-- mapper批量扫描，从mapper包中扫描出mapper接口，自动创建代理对象并且在spring容器中注册    遵循规范：将mapper.java和mapper.xml映射文件名称保持一致，且在一个目录 中    自动扫描出来的mapper的bean的id为mapper类名（首字母小写）    --><bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">    <!-- 指定扫描的包名    如果扫描多个包，每个包中间使用半角逗号分隔    -->    <property name="basePackage" value="com.iot.ssm.mapper"/>    <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/></bean>

• 测试代码

package com.iot.mybatis.mapper;import com.iot.ssm.mapper.UserMapper;import com.iot.ssm.po.User;import org.junit.Before;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class UserMapperTest {    private ApplicationContext applicationContext;    //在setUp这个方法得到spring容器    @Before    public void setUp() throws Exception {        applicationContext = new ClassPathXmlApplicationContext("classpath:spring/applicationContext.xml");    }    @Test    public void testFindUserById() throws Exception {        UserMapper userMapper = (UserMapper)applicationContext.getBean("userMapper");        //调用userMapper的方法        User user = userMapper.findUserById(1);        System.out.println(user);    }}

遇到的问题

org.springframework.beans.factory.BeanDefinitionStoreException: Failed to read candidate component class: file [D:\intellij\workspace\spring-mybatis\out\production\spring-mybatis\com\iot\ssm\mapper\UserMapper.class]; nested exception is java.lang.IllegalArgumentException    at org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider.findCandidateComponents(ClassPathScanningCandidateComponentProvider.java:281)    at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.doScan(ClassPathBeanDefinitionScanner.java:242)    at org.mybatis.spring.mapper.ClassPathMapperScanner.doScan(ClassPathMapperScanner.java:155)    at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.scan(ClassPathBeanDefinitionScanner.java:220)    at org.mybatis.spring.mapper.MapperScannerConfigurer.postProcessBeanDefinitionRegistry(MapperScannerConfigurer.java:315)    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:630)    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:461)    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)    at com.iot.mybatis.mapper.UserMapperTest.setUp(UserMapperTest.java:17)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)    at java.lang.reflect.Method.invoke(Method.java:483)    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:27)    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:69)    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:48)    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)    at org.junit.runners.ParentRunner.run(ParentRunner.java:292)    at org.junit.runner.JUnitCore.run(JUnitCore.java:157)    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)    at java.lang.reflect.Method.invoke(Method.java:483)    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)Caused by: java.lang.IllegalArgumentException    at org.springframework.asm.ClassReader.<init>(Unknown Source)    at org.springframework.asm.ClassReader.<init>(Unknown Source)    at org.springframework.asm.ClassReader.<init>(Unknown Source)    at org.springframework.core.type.classreading.SimpleMetadataReader.<init>(SimpleMetadataReader.java:52)    at org.springframework.core.type.classreading.SimpleMetadataReaderFactory.getMetadataReader(SimpleMetadataReaderFactory.java:80)    at org.springframework.core.type.classreading.CachingMetadataReaderFactory.getMetadataReader(CachingMetadataReaderFactory.java:101)    at org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider.findCandidateComponents(ClassPathScanningCandidateComponentProvider.java:257)    ... 35 more

• 搜到的答案

• BeanDefinitionStoreException Failed to read candidate component class
• Failed to read candidate component错误

总结起来就是java 8 和spring 3 不能一起用，我在IDEA的project settings里把project language level换成7就好了。具体原因还不清楚