Springboot MyBatis多数据源切换

在实际开发中，我们一个项目可能会用到多个数据库，通常一个数据库对应一个数据源。本示例，通过两种方式实现多数据源切换
1）手动切换
2）使用注解进行切换

代码结构：

简要原理：

1）DataSourceType列出所有的数据源的key—key

2）DataSourceContextHolder是一个线程安全的DataSourceEnum容器，并提供了向其中设置和获取DataSourceEnum的方法

3）DynamicDataSource继承AbstractRoutingDataSource并重写其中的方法determineCurrentLookupKey()，在该方法中使用DatabaseContextHolder获取当前线程的DatabaseType

4）MyBatisConfig中生成2个数据源DataSource的bean—value

5）MyBatisConfig中将1）和4）组成的key-value对写入到DynamicDataSource动态数据源的targetDataSources属性（当然，同时也会设置2个数据源其中的一个为DynamicDataSource的defaultTargetDataSource属性中）

6）将DynamicDataSource作为primary数据源注入到SqlSessionFactory的dataSource属性中去，并且该dataSource作为transactionManager的入参来构造DataSourceTransactionManager

7）使用的时候，在dao层或service层先使用DatabaseContextHolder设置将要使用的数据源key，然后再调用mapper层进行相应的操作，建议放在dao层去做（当然也可以使用spring aop+自定注解去做）

8）定义了一个DataSourceTypeAnno注解，用于说明方法执行时使用的数据源

9）DataSourceAspect切面用于捕获DataSourceTypeAnno注解的方法，根据DataSourceTypeAnno注解内对应的值设置数据源

注意：在mapper层进行操作的时候，会先调用determineCurrentLookupKey()方法获取一个数据源（获取数据源：先根据设置去targetDataSources中去找，若没有，则选择defaultTargetDataSource），之后在进行数据库操作。

Maven依赖

<?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.example.springboot</groupId>    <artifactId>multi-datasource</artifactId>    <version>1.0-SNAPSHOT</version>    <parent>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-parent</artifactId>        <version>1.5.2.RELEASE</version>        <relativePath/>     </parent>    <dependencies>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-jdbc</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-tomcat</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-autoconfigure</artifactId>        </dependency>        <dependency>            <groupId>org.mybatis.spring.boot</groupId>            <artifactId>mybatis-spring-boot-starter</artifactId>            <version>1.2.0</version>        </dependency>        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>5.1.41</version>        </dependency>        <!-- 使用aspectj时需要 -->        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-aop</artifactId>        </dependency>    </dependencies>    <build>        <plugins>            <plugin>                <groupId>org.springframework.boot</groupId>                <artifactId>spring-boot-maven-plugin</artifactId>            </plugin>        </plugins>    </build></project>

application.properties配置

#the master datasourcedatasource.master.driverClassName=com.mysql.jdbc.Driverdatasource.master.url=jdbc:mysql://localhost:3306/master?zeroDateTimeBehavior=convertToNull&useUnicode=true&characterEncoding=utf-8datasource.master.username=rootdatasource.master.password=123456#the slaver datasourcedatasource.slaver.driverClassName=com.mysql.jdbc.Driverdatasource.slaver.url=jdbc:mysql://localhost:3306/slaver?zeroDateTimeBehavior=convertToNull&useUnicode=true&characterEncoding=utf-8datasource.slaver.username=rootdatasource.slaver.password=123456# mybatis接口文件位置#mybatis.typeAliasesPackage=# mybatis *.xml文件的位置#mybatis.mapperLocations=
1

mysql数据库数据准备

#向master和slaver两个数据库中各建立一张表CREATE TABLE t_shop (    id        INT PRIMARY KEY,    shop_name CHAR(64) NOT NULL);# 向master库中插入一条记录INSERT INTO t_shop(id, shop_name) VALUES (1, 'MasterShop');# 向slaver库中插入一条记录INSERT INTO t_shop(id, shop_name) VALUES (1, 'SlaverShop');

Shop实例类

package com.example.springboot.multidatasource.domain;/** * Author: 王俊超 * Date: 2017-04-09 08:58 * All Rights Reserved !!! */public class Shop {    private int id;    private String shopName;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getShopName() {        return shopName;    }    public void setShopName(String shopName) {        this.shopName = shopName;    }    @Override    public String toString() {        return "Shop{" +                "id=" + id +                ", shopName='" + shopName + '\'' +                '}';    }}

DataSourceEnum

作用：列举数据源的key

package com.example.springboot.multidatasource.common;/** * Author: 王俊超 * Date: 2017-04-09 08:30 * All Rights Reserved !!! */public enum DataSourceEnum {    master,slaver;}

DataSourceContextHolder

作用：构建一个DataSourceEnum容器，并提供了向其中设置和获取DataSorceEnum的方法

package com.example.springboot.multidatasource.common;/** * Author: 王俊超 * Date: 2017-04-09 08:30 * All Rights Reserved !!! */public class DataSourceContextHolder {    private static final ThreadLocal<DataSourceEnum> CONTEXT_HOLDER = new ThreadLocal<DataSourceEnum>() {        @Override        protected DataSourceEnum initialValue() {            return DataSourceEnum.master;        }    };    public static void setDataSourceType(DataSourceEnum type) {        CONTEXT_HOLDER.set(type);    }    public static DataSourceEnum getDataSourceType() {        return CONTEXT_HOLDER.get();    }    public static void resetDataSourceType() {        CONTEXT_HOLDER.set(DataSourceEnum.master);    }}

DynamicDataSource

作用：使用DatabaseContextHolder获取当前线程的DataSoureEnum

package com.example.springboot.multidatasource.common;import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;/** * Author: 王俊超 * Date: 2017-04-09 08:30 * All Rights Reserved !!! */public class DynamicDataSource extends AbstractRoutingDataSource {    protected Object determineCurrentLookupKey() {        return DataSourceContextHolder.getDataSourceType();    }}

MyBatisConfig

通过读取application.properties文件生成两个数据源（masterDataSource，slaverDataSource）
使用以上生成的两个数据源构造动态数据源dataSource
@Primary：指定在同一个接口有多个实现类可以注入的时候，默认选择哪一个，而不是让@Autowire注解报错（一般用于多数据源的情况下）
@Qualifier：指定名称的注入，当一个接口有多个实现类的时候使用（在本例中，有三个DataSource类型的实例，DynamicDataSource也是一种DataSource，需要指定名称注入）
@Bean：生成的bean实例的名称是方法名（例如上边的@Qualifier注解中使用的名称是前边两个数据源的方法名，而这两个数据源也是使用@Bean注解进行注入的）
通过动态数据源构造SqlSessionFactory和事务管理器（如果不需要事务，后者可以去掉）

package com.example.springboot.multidatasource.config;import com.example.springboot.multidatasource.common.DataSourceEnum;import com.example.springboot.multidatasource.common.DynamicDataSource;import org.apache.ibatis.session.SqlSessionFactory;import org.mybatis.spring.SqlSessionFactoryBean;import org.mybatis.spring.annotation.MapperScan;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.beans.factory.annotation.Value;import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;import org.springframework.boot.context.properties.ConfigurationProperties;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.Primary;import org.springframework.jdbc.datasource.DataSourceTransactionManager;import javax.sql.DataSource;import java.util.HashMap;import java.util.Map;/** * Author: 王俊超 * Date: 2017-04-09 08:30 * All Rights Reserved !!! */@Configuration@MapperScan(basePackages = "com.example.springboot.multidatasource.mapper")public class MyBatisConfig {    /**     * @return     * @throws Exception     * @Primary 该注解表示在同一个接口有多个实现类可以注入的时候，默认选择哪一个，而不是让@autowire注解报错     */    @Primary    @Bean("masterDataSource")    @ConfigurationProperties(prefix = "datasource.master")    public DataSource masterDataSource() throws Exception {        return DataSourceBuilder.create().build();    }    @Bean("slaverDataSource")    @ConfigurationProperties(prefix = "datasource.slaver")    public DataSource slaverDataSource() throws Exception {        return DataSourceBuilder.create().build();    }    /**     * @Qualifier 根据名称进行注入，通常是在具有相同的多个类型的实例的一个注入（例如有多个DataSource类型的实例）     */    @Bean("dynamicDataSource")    public DynamicDataSource dynamicDataSource(@Qualifier("masterDataSource") DataSource masterDataSource,                                               @Qualifier("slaverDataSource") DataSource slaverDataSource) {        Map<Object, Object> targetDataSources = new HashMap<Object, Object>();        targetDataSources.put(DataSourceEnum.master, masterDataSource);        targetDataSources.put(DataSourceEnum.slaver, slaverDataSource);        DynamicDataSource dataSource = new DynamicDataSource();        dataSource.setTargetDataSources(targetDataSources);// 该方法是AbstractRoutingDataSource的方法        dataSource.setDefaultTargetDataSource(masterDataSource);// 默认的datasource设置为myTestDbDataSource        return dataSource;    }    /**     * 根据数据源创建SqlSessionFactory     */    @Bean    public SqlSessionFactory sqlSessionFactory(@Qualifier("dynamicDataSource") DynamicDataSource dynamicDataSource,                                               @Value("mybatis.typeAliasesPackage") String typeAliasesPackage,                                               @Value("mybatis.mapperLocations") String mapperLocations) throws Exception {        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();        factoryBean.setDataSource(dynamicDataSource);// 指定数据源(这个必须有，否则报错)        // 下边两句仅仅用于*.xml文件，如果整个持久层操作不需要使用到xml文件的话（只用注解就可以搞定），则不加//        factoryBean.setTypeAliasesPackage(typeAliasesPackage);// 指定基包//        factoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(mapperLocations));//        return factoryBean.getObject();    }    /**     * 配置事务管理器     */    @Bean    public DataSourceTransactionManager transactionManager(DynamicDataSource dataSource) throws Exception {        return new DataSourceTransactionManager(dataSource);    }}

ShopMapper

数据映射文件

package com.example.springboot.multidatasource.mapper;import com.example.springboot.multidatasource.domain.Shop;import org.apache.ibatis.annotations.Param;import org.apache.ibatis.annotations.Result;import org.apache.ibatis.annotations.Results;import org.apache.ibatis.annotations.Select;/** * Author: 王俊超 * Date: 2017-04-09 08:58 * All Rights Reserved !!! */public interface ShopMapper {    @Select("SELECT * FROM t_shop WHERE id = #{id}")    @Results(value = { @Result(id = true, column = "id", property = "id"),            @Result(column = "shop_name", property = "shopName") })    public Shop getShop(@Param("id") int id);}

ShopDao

package com.example.springboot.multidatasource.service;import com.example.springboot.multidatasource.annotation.DataSourceTypeAnno;import com.example.springboot.multidatasource.common.DataSourceEnum;import com.example.springboot.multidatasource.dao.ShopDao;import com.example.springboot.multidatasource.domain.Shop;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;/** * Author: 王俊超 * Date: 2017-04-09 09:09 * All Rights Reserved !!! */@Service("shopService")public class ShopService {    @Autowired    private ShopDao dao;    public Shop getShop(int id) {        return dao.getShop(id);    }    public Shop getMasterShopByHandle(int id) {        return dao.getMasterShopByHandle(id);    }    public Shop getSlaverShopByHandle(int id) {        return dao.getSlaverShopByHandle(id);    }    @DataSourceTypeAnno(DataSourceEnum.master)    public Shop getMasterShopByAnnotation(int id) {        return dao.getMasterShopByAnnotation(id);    }    @DataSourceTypeAnno(DataSourceEnum.slaver)    public Shop getSlaverShopByAnnotation(int id) {        return dao.getSlaverShopByAnnotation(id);    }}

ShopController

package com.example.springboot.multidatasource.controller;import com.example.springboot.multidatasource.annotation.DataSourceTypeAnno;import com.example.springboot.multidatasource.common.DataSourceEnum;import com.example.springboot.multidatasource.domain.Shop;import com.example.springboot.multidatasource.service.ShopService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.RestController;/** * Author: 王俊超 * Date: 2017-04-09 09:12 * All Rights Reserved !!! */@RestControllerpublic class ShopController {    @Autowired    private ShopService service;    @RequestMapping(value = "/getShop")    public Shop getShop(@RequestParam("id") int id) {        return service.getShop(id);    }    @RequestMapping(value = "/getMasterShopByHandle")    public Shop getMasterShopByHandle(int id) {        return service.getMasterShopByHandle(id);    }    @RequestMapping(value = "/getSlaverShopByHandle")    public Shop getSlaverShopByHandle(int id) {        return service.getSlaverShopByHandle(id);    }    @RequestMapping(value = "/getMasterShopByAnnotation")    @DataSourceTypeAnno(DataSourceEnum.master)    public Shop getMasterShopByAnnotation(int id) {        return service.getMasterShopByAnnotation(id);    }    @RequestMapping(value = "/getSlaverShopByAnnotation")    public Shop getSlaverShopByAnnotation(int id) {        return service.getSlaverShopByAnnotation(id);    }}

MultiDataSourceApplication

程序启动入口

package com.example.springboot.multidatasource;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.EnableAutoConfiguration;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.web.servlet.config.annotation.EnableWebMvc;/** * Author: 王俊超 * Date: 2017-04-09 09:14 * All Rights Reserved !!! */@SpringBootApplication@EnableAutoConfiguration@EnableWebMvcpublic class MultiDataSourceApplication  {    public static void main(String[] args) {        SpringApplication.run(MultiDataSourceApplication.class, args);    }}

DataSourceTypeAnno数据源类型注解

@Retention(RetentionPolicy.RUNTIME) 说是此注解在运行时可见
@Target(ElementType.METHOD) // 注解可以用在方法上

package com.example.springboot.multidatasource.annotation;import com.example.springboot.multidatasource.common.DataSourceEnum;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * 数据源类型注解 * * Author: 王俊超 * Date: 2017-04-09 09:50 * All Rights Reserved !!! */@Retention(RetentionPolicy.RUNTIME) // 在运行时可见@Target(ElementType.METHOD) // 注解可以用在方法上public @interface DataSourceTypeAnno {    DataSourceEnum value() default DataSourceEnum.master;}

DataSourceAspect 数据源切面

用于捕获使用数据源注解的方法，并且根据注解上的数据源类型进行切换

package com.example.springboot.multidatasource.aspect;import com.example.springboot.multidatasource.annotation.DataSourceTypeAnno;import com.example.springboot.multidatasource.common.DataSourceContextHolder;import com.example.springboot.multidatasource.common.DataSourceEnum;import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.Around;import org.aspectj.lang.annotation.Aspect;import org.aspectj.lang.annotation.Pointcut;import org.aspectj.lang.reflect.MethodSignature;import org.springframework.stereotype.Component;import java.lang.reflect.Method;/** * Author: 王俊超 * Date: 2017-04-09 09:54 * All Rights Reserved !!! */@Component@Aspectpublic class DataSourceAspect {    @Pointcut("execution(* com.example.springboot.multidatasource.dao..*(..)) " +            "&& @annotation(com.example.springboot.multidatasource.annotation.DataSourceTypeAnno)")    public void dataSourcePointcut() {    }    @Around("dataSourcePointcut()")    public Object doAround(ProceedingJoinPoint pjp) {        MethodSignature methodSignature = (MethodSignature) pjp.getSignature();        Method method = methodSignature.getMethod();        DataSourceTypeAnno typeAnno = method.getAnnotation(DataSourceTypeAnno.class);        DataSourceEnum sourceEnum = typeAnno.value();        if (sourceEnum == DataSourceEnum.master) {            DataSourceContextHolder.setDataSourceType(DataSourceEnum.master);        } else if (sourceEnum == DataSourceEnum.slaver) {            DataSourceContextHolder.setDataSourceType(DataSourceEnum.slaver);        }        Object result = null;        try {            result = pjp.proceed();        } catch (Throwable throwable) {            throwable.printStackTrace();        } finally {            DataSourceContextHolder.resetDataSourceType();        }        return result;    }}

执行结果