Spring Boot 实现多数据源配置

一、配置流程

在 Spring Boot 中实现多数据源配置通常用于需要连接多个数据库的场景。主要有以下几个步骤：

配置多个数据源的连接信息。
定义多个数据源的 Bean。
为每个数据源配置MyBatis的SqlSessionFactory和事务管理器。
为每个数据源定义Mapper接口和Mapper XML文件。
在服务类中使用不同的Mapper接口操作对应的数据源。

二、详细步骤

2.1 添加依赖

首先，在pom.xml中添加MyBatis、数据库驱动和Spring Boot的JDBC依赖。

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<dependencies>
    <!-- Spring Boot Starter Web (可选，如果需要使用Web功能) -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- MyBatis Starter -->
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.2.2</version>
    </dependency>

    <!-- MySQL 驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>

    <!-- Spring Boot Starter JDBC -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>
</dependencies>

2.2 配置多数据源

在application.properties或application.yml中配置多个数据源的连接信息。

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spring:
  datasource:
    primary:
      jdbc-url: jdbc:mysql://localhost:3306/db1
      username: root
      password: password
      driver-class-name: com.mysql.cj.jdbc.Driver
    secondary:
      jdbc-url: jdbc:mysql://localhost:3306/db2
      username: root
      password: password
      driver-class-name: com.mysql.cj.jdbc.Driver

2.3 配置数据源Bean

在Spring Boot中，通过@Configuration类来配置多个数据源的Bean。

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import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;

@Configuration
public class DataSourceConfig {

    // 主数据源
    @Bean(name = "primaryDataSource")
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    // 次数据源
    @Bean(name = "secondaryDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.secondary")
    public DataSource secondaryDataSource() {
        return DataSourceBuilder.create().build();
    }
}

2.4 配置MyBatis的SqlSessionFactory和事务管理器

为每个数据源配置独立的SqlSessionFactory和DataSourceTransactionManager。

PrimaryDataSourceConfig .java

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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.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

@Configuration
@MapperScan(basePackages = "com.example.mapper.primary", sqlSessionFactoryRef = 	"primarySqlSessionFactory")
public class PrimaryDataSourceConfig {

	@Bean(name = "primarySqlSessionFactory")
	@Primary
	public SqlSessionFactory primarySqlSessionFactory(@Qualifier("primaryDataSource") DataSource dataSource) throws Exception {
    	SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
    	sessionFactory.setDataSource(dataSource);
    	// 设置MyBatis的Mapper XML文件路径
    	sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
            	.getResources("classpath:mapper/primary/*.xml"));
    	return sessionFactory.getObject();
	}

	@Bean(name = "primaryTransactionManager")
	@Primary
    public DataSourceTransactionManager primaryTransactionManager(@Qualifier("primaryDataSource") DataSource dataSource) {
    	return new DataSourceTransactionManager(dataSource);
	}
}

SecondaryDataSourceConfig.java

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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.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

@Configuration
@MapperScan(basePackages = "com.example.mapper.secondary", sqlSessionFactoryRef = "secondarySqlSessionFactory")
public class SecondaryDataSourceConfig {

	@Bean(name = "secondarySqlSessionFactory")
	public SqlSessionFactory secondarySqlSessionFactory(@Qualifier("secondaryDataSource") DataSource dataSource) throws Exception {
    	SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
    	sessionFactory.setDataSource(dataSource);
    	// 设置MyBatis的Mapper XML文件路径
    	sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
            	.getResources("classpath:mapper/secondary/*.xml"));
    	return sessionFactory.getObject();
	}

	@Bean(name = "secondaryTransactionManager")
	public DataSourceTransactionManager secondaryTransactionManager(@Qualifier("secondaryDataSource") DataSource dataSource) {
    	return new DataSourceTransactionManager(dataSource);
	}
}

2.5 配置Mapper接口和XML文件

将Mapper接口和XML文件分别放在不同的包中，以区分不同的数据源。

主数据源Mapper接口

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package com.example.mapper.primary;

import com.example.model.User;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;

@Mapper
public interface PrimaryUserMapper {
	List<User> findAll();
}

次数据源Mapper接口

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package com.example.mapper.secondary;

import com.example.model.Product;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;

@Mapper
public interface SecondaryProductMapper {
	List<Product> findAll();
}

主数据源Mapper XML文件

在src/main/resources/mapper/primary目录下创建UserMapper.xml：

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<?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.example.mapper.primary.PrimaryUserMapper">
	<select id="findAll" resultType="com.example.model.User">
    	SELECT * FROM user
	</select>
</mapper>

次数据源Mapper XML文件

在src/main/resources/mapper/secondary目录下创建ProductMapper.xml：

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<?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.example.mapper.secondary.SecondaryProductMapper">
	<select id="findAll" resultType="com.example.model.Product">
    	SELECT * FROM product
	</select>
</mapper>

2.6 使用多数据源

在Service中注入对应的Mapper接口，并使用@Transactional注解指定事务管理器。

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import com.example.mapper.primary.PrimaryUserMapper;
import com.example.mapper.secondary.SecondaryProductMapper;
import com.example.model.User;
import com.example.model.Product;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

@Service
public class MyService {

    @Autowired
    private PrimaryUserMapper primaryUserMapper;

    @Autowired
    private SecondaryProductMapper secondaryProductMapper;

    @Transactional("primaryTransactionManager")
    public List<User> getUsers() {
        return primaryUserMapper.findAll();
    }

    @Transactional("secondaryTransactionManager")
    public List<Product> getProducts() {
        return secondaryProductMapper.findAll();
    }
}

三、动态数据源切换

如果需要动态切换数据源，可以通过以下步骤：

动态数据源配置

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import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class DynamicDataSource extends AbstractRoutingDataSource {

	@Override
	protected Object determineCurrentLookupKey() {
    	return DataSourceContextHolder.getDataSourceType();
	}
}

数据源上下文持有者

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public class DataSourceContextHolder {

	private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

	public static void setDataSourceType(String dataSourceType) {
    	contextHolder.set(dataSourceType);
	}

	public static String getDataSourceType() {
    	return contextHolder.get();
	}

	public static void clearDataSourceType() {
    	contextHolder.remove();
	}
}

AOP切面

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import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class DataSourceAspect {

	@Before("@annotation(dataSource)")
	public void switchDataSource(DataSource dataSource) {
    	DataSourceContextHolder.setDataSourceType(dataSource.value());
	}
}

自定义注解

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import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DataSource {
	String value();
}

使用动态数据源

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@Service
public class MyService {

	@DataSource("primary")
	public List<User> getUsers() {
    	return primaryUserMapper.findAll();
	}

	@DataSource("secondary")
	public List<Product> getProducts() {
    	return secondaryProductMapper.findAll();
	}
}