spring+mybatis整合,实现多数据源配置

项目中需要支持mysql及db2数据库，但是每种数据库有特定的语法，需要对sql做处理来适配各种数据库

解决思路：

（1）使用原生sql，不依赖数据库特性。缺点：可能导致sql语句发杂，执行效率低下

（2）对不同数据库定义不同的mapper文件。缺点：对不依赖数据库的sql语句重复定义

（3）使用mybatis的databaseId，适配多种数据库(本例中使用的方式)

1.依赖配置

<?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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.jb</groupId>
  <artifactId>springIntegrationMybatis</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
    <springVersion>4.3.18.RELEASE</springVersion>
  </properties>

  <dependencies>
    <!-- spring相关依赖 -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-beans</artifactId>
      <version>${springVersion}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>${springVersion}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>${springVersion}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-tx</artifactId>
      <version>${springVersion}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-aop</artifactId>
      <version>${springVersion}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>${springVersion}</version>
    </dependency>

    <!-- mybatis相关依赖 -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.2.2</version>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis-spring</artifactId>
      <version>1.2.3</version>
    </dependency>

    <!-- dbcp数据源 -->
    <dependency>
      <groupId>commons-dbcp</groupId>
      <artifactId>commons-dbcp</artifactId>
      <version>1.4</version>
    </dependency>

    <!-- mysql数据库驱动 -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.9</version>
    </dependency>
   <!-- <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.46</version>
    </dependency>-->
    <!--<dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.11</version>
    </dependency>-->

    <!-- 测试相关依赖 -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-test</artifactId>
      <version>${springVersion}</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <finalName>springIntegrationMybatis</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.0.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.7.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.20.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

2.application.xml配置

<?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:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">
    <!-- IoC配置 -->
    <!-- 扫描类包，将标注Spring注解的类自动转化Bean，同时完成Bean的注入 -->
    <context:component-scan base-package="com.jb.springIntegrationMybatis.service" />
    <!-- 引入配置文件 两种方式-->
    <!--<context:property-placeholder location="classpath:jdbc.properties"/>-->
    <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location" value="classpath: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}" />
    </bean>

    <!-- databaseIdProvider属性配置 -->
    <bean id="vendorProperties"
          class="org.springframework.beans.factory.config.PropertiesFactoryBean">
        <property name="properties">
            <props>
                <prop key="DB2">db2</prop>
                <prop key="MySQL">mysql</prop>
            </props>
        </property>
    </bean>
    <bean id="databaseIdProvider" class="org.apache.ibatis.mapping.VendorDatabaseIdProvider">
        <property name="properties" ref="vendorProperties" />
    </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" />
        <!-- 自动扫描mapping.xml文件，**表示迭代查找 -->
        <property name="mapperLocations" value="classpath:mapper/*.xml" />
        <property name="databaseIdProvider" ref="databaseIdProvider"/>
    </bean>

    <!-- DAO接口所在包名，Spring会自动查找其下的类 ,包下的类需要使用@MapperScan注解,否则容器注入会失败 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.jb.springIntegrationMybatis.dao" />
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
    </bean>

    <!-- 配置事务管理器 -->
    <!--<tx:annotation-driven/>-->
    <!-- (事务管理)transaction manager, use JtaTransactionManager for global tx -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
    </bean>

</beans>

3.jdbc.properties配置

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/mybatislearn?characterEncoding=utf8
username=root
password=root

4.mapper文件配置

<?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="com.jb.springIntegrationMybatis.dao.UserDao">
    <select id="getUser" parameterType="int" resultType="com.jb.springIntegrationMybatis.pojo.User" databaseId="mysql">
      select age, name from user where id=#{id}
    </select>

    <select id="getUser" parameterType="int" resultType="com.jb.springIntegrationMybatis.pojo.User" databaseId="db2">
        select age, name from user where id=#{id}
    </select>

</mapper>

5.java类

dao接口

package com.jb.springIntegrationMybatis.dao;

import com.jb.springIntegrationMybatis.pojo.User;
import org.mybatis.spring.annotation.MapperScan;

/**
 * 这里的@MapperScan就是上面所讲的Mapper扫描器中所需要的配置，会自动生成代理对象。
 * 注意，接口中的方法名称要和对应的MyBatis映射文件中的语句的id值一样，因为生成的
 * 动态代理，会根据这个匹配相应的Sql语句执行。另外就是方法的参数和返回值也需要注
 * 意。接口中的方法如何定义，对应的MyBatis映射文件就应该进行相应的定义。
 * 最后，标注中的userDao是用来作为Spring的Bean的id(或name)进行使用的，方便我
 * 们在Service层进行注入使用。
 */

@MapperScan
public interface UserDao {
    //此处的方法名必须和mapper中的映射文件中的id同名
    //mapper映射文件中通过com.jb.springIntegrationMybatis.dao.UserDao.getUser,即this.getClass().getName()+".getUser"
    public User getUser(int id);

}

service接口

package com.jb.springIntegrationMybatis.service;

import com.jb.springIntegrationMybatis.pojo.User;
import org.springframework.stereotype.Service;

@Service
public interface IUserService {
   User getUser(int id);
}

service实现

package com.jb.springIntegrationMybatis.service;

import com.jb.springIntegrationMybatis.dao.UserDao;
import com.jb.springIntegrationMybatis.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service("userService")
public class UserServiceImpl implements IUserService {

    @Autowired
    private UserDao userDao;

    public User getUser(int id) {
        return userDao.getUser(id);
    }
}

junit测试

package com.jb.springIntegrationMybatis;

import com.jb.springIntegrationMybatis.pojo.User;
import com.jb.springIntegrationMybatis.service.IUserService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:application.xml")
@Transactional
public class TestDatabseIdPrivoder {

    @Autowired
    private IUserService userService;

    @Test
    public void testGetUserListInfo()
    {
        User user = userService.getUser(1);
        System.out.println(user.toString());
    }
}

6.配置说明：

<bean id="vendorProperties"
          class="org.springframework.beans.factory.config.PropertiesFactoryBean">
        <property name="properties">
            <props>
                <prop key="Oracle">oracle</prop>
                <prop key="MySQL">mysql</prop>
            </props>
        </property>
    </bean>
    <bean id="databaseIdProvider" class="org.apache.ibatis.mapping.VendorDatabaseIdProvider">
        <property name="properties" ref="vendorProperties" />
    </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" />
        <!-- 自动扫描mapping.xml文件，**表示迭代查找 -->
        <property name="mapperLocations" value="classpath:mapper/*.xml" />
        <property name="databaseIdProvider" ref="databaseIdProvider"/>
    </bean>

自定义databaseIdProvider，覆盖SqlSessionFactoryBean中默认创建的，项目启动时会根据配置的数据源获取数据库类型

private String getDatabaseName(DataSource dataSource) throws SQLException {
        String productName = this.getDatabaseProductName(dataSource);
        if (this.properties != null) {
            Iterator i$ = this.properties.entrySet().iterator();

            Entry property;
            do {
                if (!i$.hasNext()) {
                    return null;
                }

                property = (Entry)i$.next();
            } while(!productName.contains((String)property.getKey()));

            return (String)property.getValue();
        } else {
            return productName;
        }
    }

sql执行时会找数据库类型与sql标签中配置的databaseId属性相同的sql语句

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