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✨ spring-boot-demo-multi-datasource-mybatis 完成
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‎spring-boot-demo-multi-datasource-mybatis/README.md

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# spring-boot-demo-multi-datasource-mybatis
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> 此 demo 主要演示了 Spring Boot 如何集成 Mybatis 的多数据源。可以自己基于AOP实现多数据源，这里基于 Mybatis-Plus 提供的一个优雅的开源的解决方案来实现。
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## 准备工作
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准备两个数据源，分别执行如下建表语句
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```mysql
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DROP TABLE IF EXISTS `multi_user`;
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CREATE TABLE `multi_user`(
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`id` bigint(64) NOT NULL,
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`name` varchar(50) DEFAULT NULL,
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`age` int(30) DEFAULT NULL,
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PRIMARY KEY (`id`) USING BTREE
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) ENGINE = InnoDB
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AUTO_INCREMENT = 1
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CHARACTER SET = utf8
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COLLATE = utf8_general_ci;
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```
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## 导入依赖
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>spring-boot-demo-multi-datasource-mybatis</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<packaging>jar</packaging>
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<name>spring-boot-demo-multi-datasource-mybatis</name>
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<description>Demo project for Spring Boot</description>
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<parent>
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<groupId>com.xkcoding</groupId>
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<artifactId>spring-boot-demo</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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</parent>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
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<java.version>1.8</java.version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter</artifactId>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-test</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>mysql</groupId>
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<artifactId>mysql-connector-java</artifactId>
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</dependency>
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<dependency>
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<groupId>com.baomidou</groupId>
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<artifactId>dynamic-datasource-spring-boot-starter</artifactId>
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<version>2.5.0</version>
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</dependency>
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<dependency>
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<groupId>com.baomidou</groupId>
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<artifactId>mybatis-plus-boot-starter</artifactId>
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<version>3.0.7.1</version>
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</dependency>
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<dependency>
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<groupId>org.projectlombok</groupId>
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<artifactId>lombok</artifactId>
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<optional>true</optional>
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</dependency>
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<dependency>
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<groupId>cn.hutool</groupId>
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<artifactId>hutool-all</artifactId>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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</dependency>
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</dependencies>
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<build>
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<finalName>spring-boot-demo-multi-datasource-mybatis</finalName>
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<plugins>
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<plugin>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-maven-plugin</artifactId>
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</plugin>
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</plugins>
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</build>
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</project>
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```
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## 准备实体类
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`User.java`
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> 1. @Data / @NoArgsConstructor / @AllArgsConstructor / @Builder 都是 lombok 注解
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> 2. @TableName("multi_user") 是 Mybatis-Plus 注解，主要是当实体类名字和表名不满足 **驼峰和下划线互转** 的格式时，用于表示数据库表名
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> 3. @TableId(type = IdType.ID_WORKER) 是 Mybatis-Plus 注解，主要是指定主键类型，这里我使用的是 Mybatis-Plus 基于 twitter 提供的 雪花算法
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```java
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/**
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* <p>
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* User实体类
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* </p>
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*
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* @package: com.xkcoding.multi.datasource.mybatis.model
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* @description: User实体类
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* @author: yangkai.shen
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* @date: Created in 2019-01-21 14:19
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* @copyright: Copyright (c) 2019
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* @version: V1.0
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* @modified: yangkai.shen
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*/
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@Data
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@TableName("multi_user")
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@NoArgsConstructor
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@AllArgsConstructor
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@Builder
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public class User implements Serializable {
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private static final long serialVersionUID = -1923859222295750467L;
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/**
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* 主键
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*/
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@TableId(type = IdType.ID_WORKER)
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private Long id;
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/**
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* 姓名
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*/
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private String name;
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/**
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* 年龄
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*/
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private Integer age;
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}
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```
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## 数据访问层
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`UserMapper.java`
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> 不需要建对应的xml，只需要继承 BaseMapper 就拥有了大部分单表操作的方法了。
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```java
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/**
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* <p>
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* 数据访问层
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* </p>
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*
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* @package: com.xkcoding.multi.datasource.mybatis.mapper
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* @description: 数据访问层
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* @author: yangkai.shen
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* @date: Created in 2019-01-21 14:28
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* @copyright: Copyright (c) 2019
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* @version: V1.0
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* @modified: yangkai.shen
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*/
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public interface UserMapper extends BaseMapper<User> {
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}
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```
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## 数据服务层
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### 接口
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`UserService.java`
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```java
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/**
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* <p>
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* 数据服务层
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* </p>
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*
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* @package: com.xkcoding.multi.datasource.mybatis.service
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* @description: 数据服务层
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* @author: yangkai.shen
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* @date: Created in 2019-01-21 14:31
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* @copyright: Copyright (c) 2019
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* @version: V1.0
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* @modified: yangkai.shen
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*/
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public interface UserService extends IService<User> {
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/**
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* 添加 User
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*
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* @param user 用户
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*/
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void addUser(User user);
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}
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```
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### 实现
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`UserServiceImpl.java`
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> 1. @DS: 注解在类上或方法上来切换数据源，方法上的@DS优先级大于类上的@DS
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> 2. baseMapper: mapper 对象，即`UserMapper`，可获得CRUD功能
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> 3. 默认走从库: `@DS(value = "slave")`在类上，默认走从库，除非在方法在添加`@DS(value = "master")`才走主库
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```java
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/**
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* <p>
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* 数据服务层 实现
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* </p>
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*
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* @package: com.xkcoding.multi.datasource.mybatis.service.impl
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* @description: 数据服务层 实现
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* @author: yangkai.shen
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* @date: Created in 2019-01-21 14:37
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* @copyright: Copyright (c) 2019
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* @version: V1.0
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* @modified: yangkai.shen
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*/
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@Service
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@DS("slave")
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public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
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/**
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* 类上 {@code @DS("slave")} 代表默认从库，在方法上写 {@code @DS("master")} 代表默认主库
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*
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* @param user 用户
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*/
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@DS("master")
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@Override
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public void addUser(User user) {
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baseMapper.insert(user);
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}
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}
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```
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## 启动类
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`SpringBootDemoMultiDatasourceMybatisApplication.java`
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> 启动类上方需要使用@MapperScan扫描 mapper 类所在的包
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```java
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/**
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* <p>
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* 启动器
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* </p>
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*
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* @package: com.xkcoding.multi.datasource.mybatis
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* @description: 启动器
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* @author: yangkai.shen
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* @date: Created in 2019-01-21 14:19
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* @copyright: Copyright (c) 2019
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* @version: V1.0
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* @modified: yangkai.shen
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*/
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@SpringBootApplication
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@MapperScan(basePackages = "com.xkcoding.multi.datasource.mybatis.mapper")
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public class SpringBootDemoMultiDatasourceMybatisApplication {
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public static void main(String[] args) {
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SpringApplication.run(SpringBootDemoMultiDatasourceMybatisApplication.class, args);
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}
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}
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```
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## 配置文件
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`application.yml`
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```yaml
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spring:
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datasource:
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dynamic:
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datasource:
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master:
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username: root
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password: root
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url: jdbc:mysql://127.0.0.1:3306/spring-boot-demo?useUnicode=true&characterEncoding=UTF-8&useSSL=false&autoReconnect=true&failOverReadOnly=false&serverTimezone=GMT%2B8
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driver-class-name: com.mysql.cj.jdbc.Driver
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slave:
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username: root
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password: root
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url: jdbc:mysql://127.0.0.1:3306/spring-boot-demo-2?useUnicode=true&characterEncoding=UTF-8&useSSL=false&autoReconnect=true&failOverReadOnly=false&serverTimezone=GMT%2B8
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driver-class-name: com.mysql.cj.jdbc.Driver
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mp-enabled: true
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logging:
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level:
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com.xkcoding.multi.datasource.mybatis: debug
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```
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## 测试类
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```java
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/**
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* <p>
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* 测试主从数据源
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* </p>
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*
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* @package: com.xkcoding.multi.datasource.mybatis.service.impl
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* @description: 测试主从数据源
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* @author: yangkai.shen
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* @date: Created in 2019-01-21 14:45
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* @copyright: Copyright (c) 2019
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* @version: V1.0
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* @modified: yangkai.shen
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*/
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@Slf4j
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public class UserServiceImplTest extends SpringBootDemoMultiDatasourceMybatisApplicationTests {
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@Autowired
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private UserService userService;
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/**
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* 主从库添加
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*/
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@Test
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public void addUser() {
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User userMaster = User.builder().name("主库添加").age(20).build();
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userService.addUser(userMaster);
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User userSlave = User.builder().name("从库添加").age(20).build();
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userService.save(userSlave);
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}
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/**
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* 从库查询
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*/
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@Test
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public void testListUser() {
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List<User> list = userService.list(new QueryWrapper<>());
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log.info("【list】= {}", JSONUtil.toJsonStr(list));
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}
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}
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```
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### 测试结果
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主从数据源加载成功
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```java
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2019-01-21 14:55:41.096 INFO 7239 --- [ main] com.zaxxer.hikari.HikariDataSource : master - Starting...
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2019-01-21 14:55:41.307 INFO 7239 --- [ main] com.zaxxer.hikari.HikariDataSource : master - Start completed.
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2019-01-21 14:55:41.308 INFO 7239 --- [ main] com.zaxxer.hikari.HikariDataSource : slave - Starting...
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2019-01-21 14:55:41.312 INFO 7239 --- [ main] com.zaxxer.hikari.HikariDataSource : slave - Start completed.
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2019-01-21 14:55:41.312 INFO 7239 --- [ main] c.b.d.d.DynamicRoutingDataSource : 初始共加载 2 个数据源
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2019-01-21 14:55:41.313 INFO 7239 --- [ main] c.b.d.d.DynamicRoutingDataSource : 动态数据源-加载 slave 成功
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2019-01-21 14:55:41.313 INFO 7239 --- [ main] c.b.d.d.DynamicRoutingDataSource : 动态数据源-加载 master 成功
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2019-01-21 14:55:41.313 INFO 7239 --- [ main] c.b.d.d.DynamicRoutingDataSource : 当前的默认数据源是单数据源，数据源名为 master
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_ _ |_ _ _|_. ___ _ | _
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| | |\/|_)(_| | |_\ |_)||_|_\
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/ |
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3.0.7.1
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```
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**主**库 **建议** 只执行 **INSERT** **UPDATE** **DELETE** 操作
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![image-20190121153211509](assets/image-20190121153211509.png)
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**从**库 **建议** 只执行 **SELECT** 操作
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![image-20190121152825859](assets/image-20190121152825859.png)
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> 生产环境需要搭建 **主从复制**
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## 参考
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1. Mybatis-Plus 多数据源文档：https://mybatis.plus/guide/dynamic-datasource.html
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2. Mybatis-Plus 多数据源集成官方 demo：https://gitee.com/baomidou/dynamic-datasource-spring-boot-starter/tree/master/samples

‎spring-boot-demo-multi-datasource-mybatis/assets/image-20190121152825859.png

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