基于spring boot 2.0 实现动态数据源切换

1. maven 文件的引用。

<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.mayikt</groupId>
	<artifactId>springboot-mybatis-02</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.2.2.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-aop</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>1.3.2</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>druid</artifactId>
			<version>1.0.23</version>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<version>2.2.2.RELEASE</version>
			</plugin>
		</plugins>
	</build>

</project>

2. 配置文件定义

spring:
  datasource:
    ###可读数据源
    select:
      jdbc-url: jdbc:mysql://192.168.212.206:8066/mycat_testdb
      driver-class-name: com.mysql.jdbc.Driver
      username: user
      password: user
    ####可写数据源  
    update:
      jdbc-url: jdbc:mysql://192.168.212.206:8066/mycat_testdb
      driver-class-name: com.mysql.jdbc.Driver
      username: root
      password: 123456
    type: com.alibaba.druid.pool.DruidDataSource

3. 数据源配置文件

import javax.sql.DataSource;

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;

@Configuration
public class DataSourceConfig {

	// 创建可读数据源
	@Bean(name = "selectDataSource")
	@ConfigurationProperties(prefix = "spring.datasource.select") // application.properteis中对应属性的前缀
	public DataSource dataSource1() {
		return DataSourceBuilder.create().build();
	}

	// 创建可写数据源
	@Bean(name = "updateDataSource")
	@ConfigurationProperties(prefix = "spring.datasource.update") // application.properteis中对应属性的前缀
	public DataSource dataSource2() {
		return DataSourceBuilder.create().build();
	}

}

4. 动态数据源管理类

//在Spring 2.0.1中引入了AbstractRoutingDataSource, 该类充当了DataSource的路由中介, 能有在运行时, 根据某种key值来动态切换到真正的DataSource上。

import java.util.HashMap;
import java.util.Map;

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Primary;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import org.springframework.stereotype.Component;

@Component
@Primary
public class DynamicDataSource extends AbstractRoutingDataSource {
	@Autowired
	@Qualifier("selectDataSource")
	private DataSource selectDataSource;

	@Autowired
	@Qualifier("updateDataSource")
	private DataSource updateDataSource;

	/**
	 * 这个是主要的方法，返回的是生效的数据源名称
	 */
	@Override
	protected Object determineCurrentLookupKey() {
		System.out.println("DataSourceContextHolder：：：" + DataSourceContextHolder.getDbType());
		return DataSourceContextHolder.getDbType();
	}

	/**
	 * 配置数据源信息
	 */
	@Override
	public void afterPropertiesSet() {
		Map<Object, Object> map = new HashMap<>();
		map.put("selectDataSource", selectDataSource);
		map.put("updateDataSource", updateDataSource);
		setTargetDataSources(map);
		setDefaultTargetDataSource(updateDataSource);
		super.afterPropertiesSet();
	}
}

import org.springframework.context.annotation.Lazy;
import org.springframework.stereotype.Component;

@Component
@Lazy(false)
public class DataSourceContextHolder {
	// 采用ThreadLocal 保存本地多数据源
	private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

	// 设置数据源类型
	public static void setDbType(String dbType) {
		contextHolder.set(dbType);
	}

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

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

}

5. 动态数据源使用

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.context.annotation.Lazy;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import com.hou.config.DataSourceContextHolder;

@Aspect
@Component
@Lazy(false)
@Order(0) // Order设定AOP执行顺序 使之在数据库事务上先执行
public class SwitchDataSourceAOP {
	// 这里切到你的方法目录
	@Before("execution(* com.hou.service.*.*(..))")
	public void process(JoinPoint joinPoint) {
		String methodName = joinPoint.getSignature().getName();
		if (methodName.startsWith("get") || methodName.startsWith("count") || methodName.startsWith("find")
				|| methodName.startsWith("list") || methodName.startsWith("select") || methodName.startsWith("check")) {
			// 读
			DataSourceContextHolder.setDbType("selectDataSource");
		} else {
			// 切换dataSource
			DataSourceContextHolder.setDbType("updateDataSource");
		}
	}
}

总结：

  上面的案例是实现，读写分离的一种数据源动态切换的方案。

   后面会补充一下，通过注解实现数据源动态切换的。