SSM 整合

荒流2021年4月15日大约 3 分钟约 941 字

1. 生硬整合

在没有新技术的加入之前，整合 SSM（主要是 Spring 与 MyBatis）只能靠生硬的进行，如这里的工程：

这里的主要特点是 Service 层的编写，Service 业务方法中含有重复性代码，即使将其封装为一个 MyBtatisUtils 也非佳作：

package com.chuan.ssm.service.impl;

import com.chuan.ssm.domain.Account;
import com.chuan.ssm.mapper.AccountMapper;
import com.chuan.ssm.service.AccountService;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.springframework.stereotype.Service;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @author chuan
 * @date 2021/4/15 19:37
 */
@Service("accountService")
public class AccountServiceImpl implements AccountService {
    
    @Override
    public void save(Account account) {
        try {
            InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
            SqlSession sqlSession = sqlSessionFactory.openSession();
            AccountMapper mapper = sqlSession.getMapper(AccountMapper.class);
            mapper.save(account);
            sqlSession.commit();
            sqlSession.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    @Override
    public List<Account> findAll() {
        try {
            InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
            SqlSession sqlSession = sqlSessionFactory.openSession();
            AccountMapper mapper = sqlSession.getMapper(AccountMapper.class);
            List<Account> accountList = mapper.findAll();
            sqlSession.close();
            return accountList;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

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:context="http://www.springframework.org/schema/context" 
    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
">
    <!--组件扫描：service 和 mapper-->
    <context:component-scan base-package="com.chuan.ssm">
        <!--排除 controller 的扫描-->
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    </context:component-scan>
</beans>

sqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org/DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--加载 properties 文件-->
    <properties resource="jdbc.properties"/>
    <!--定义别名-->
    <typeAliases>
        <!--方法 1：逐个编写别名-->
        <typeAlias type="com.chuan.ssm.domain.Account" alias="account"/>
        <!--方法 2：包扫描定义别名，该包中每个类的别名被定义为首字母小写后的类名-->
        <!--<package name="com.chuan.ssm.domain"/>-->
    </typeAliases>
    <!--环境-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--加载映射-->
    <mappers>
        <!--方法 1：逐个添加映射文件-->
        <!--<mapper resource="com/chuan/mapper/AccountMapper.xml"/>-->
        <!--方法 2：包扫描-->
        <package name="com.chuan.ssm.mapper"/>
    </mappers>
</configuration>

2. 实际整合

Spring 整合 MyBatis 的思路：

将 SqlSessionFactory 配置到 Spring 容器中：

<!-- 加载 jdbc.properties -->
<context:property-placeholder location="classpath:jdbc.properties" />
<!-- 配置数据源 -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
	<property name="driverClass" value="${jdbc.driver}" />
	<property name="jdbcUrl" value="${jdbc.url}" />
	<property name="user" value="${jdbc.username}" />
	<property name="password" value="${jdbc.password}" />
</bean>
<!-- 配置 MyBatis 的 SqlSessionFactory -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
	<property name="dataSource" ref="dataSource" />
	<property name="configLocation" value="classpath:sqlMapConfig.xml" />
</bean>

具体地，相对上节生硬整合的代码改动如下（减少了 mybatis 核心配置文件的配置、增加了 spring 的配置、优化了业务层代码）：