AbstractRoutingDataSource

AbstractRoutingDataSource是spring-jdbc包提供的一个了AbstractDataSource的抽象类，它实现了DataSource接口的用于获取数据库连接的方法。下面是其源码：

 @Override public Connection getConnection() throws SQLException { return determineTargetDataSource().getConnection(); } @Override public Connection getConnection(String username, String password) throws SQLException { return determineTargetDataSource().getConnection(username, password); } protected DataSource determineTargetDataSource() { Assert.notNull(this.resolvedDataSources, "DataSource router not initialized"); // 获取指定数据源关键字 Object lookupKey = determineCurrentLookupKey(); DataSource dataSource = this.resolvedDataSources.get(lookupKey); if (dataSource == null && (this.lenientFallback || lookupKey == null)) { dataSource = this.resolvedDefaultDataSource; } if (dataSource == null) { throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]"); } return dataSource; } public void setTargetDataSources(Map targetDataSources) { this.targetDataSources = targetDataSources; }

可以看出，其数据源之间的切换主要 determineTargetDataSource()方法决定，其维护了一个名为targetDataSources的Map，并提供set方法，决定其具体从哪个数据源中获取链接；

下面，我们来看下具体实现代码：

1、先看数据库：

此处，我们有两个数据库，分别是cookie和cxq，其内部皆存在一张结构相同的user表，查看出数据如图：

2、配置文件 application.yml：

server : port : 9001spring : datasource: primary : jdbc-url: jdbc:mysql://xxx:82/cookie?serverTimezone=UTC&useUnicode=true&characterEncoding=UTF-8&useSSL=false username: root password: xxx driver-class-name: com.mysql.cj.jdbc.Driver second : jdbc-url: jdbc:mysql://xxx:82/cxq?serverTimezone=UTC&useUnicode=true&characterEncoding=UTF-8&useSSL=false username: root password: xxx driver-class-name: com.mysql.cj.jdbc.Drivermybatis: type-aliases-package: com.cookie.modellogging: level: root: INFO org.hibernate: INFO org.hibernate.type.descriptor.sql.BasicBinder: TRACE org.hibernate.type.descriptor.sql.BasicExtractor: TRACE com.itmuch.youran.persistence: ERROR

3、新建 DataSourceContextHolder，配置数据源

package com.cookie;/** * author : cxq * Date : 2019/5/15 */public class DataSourceContextHolder { /** * 默认数据源 */ public static final String primaryDataSource = "primaryDataSource"; public static final String secondDataSource = "secondDataSource"; // 使用ThreadLocal 可以有效避免多线程时contextHolder被更改，导致访问出错的问题 // 每一个ThreadLocal能够放一个线程级别的变量，可是它本身能够被多个线程共享使用，并且又能够达到线程安全的目的，且绝对线程安全 private static final ThreadLocal contextHolder = new ThreadLocal<>(); // 设置数据源名 public static void setDB(String dbType) { contextHolder.set(dbType); } // 获取数据源名 public static String getDB() { return (contextHolder.get()); } // 清除数据源名 public static void clearDB() { contextHolder.remove(); }}

4、新建DynamicDataSource

package com.cookie;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;/** * author : cxq * Date : 2019/5/15 */public class DynamicDataSource extends AbstractRoutingDataSource { private final static Logger logger = LoggerFactory.getLogger(DynamicDataSource.class); @Override protected Object determineCurrentLookupKey() { logger.info(" datasource : " + ( DataSourceContextHolder.getDB() == null ? DataSourceContextHolder.secondDataSource : DataSourceContextHolder.getDB() ) ); return DataSourceContextHolder.getDB(); }}

该类继承了AbstractRoutingDataSource，重写determineCurrentLookupKey,在该方法中注入实际应用的dataSource,下面，我们需要创建bean；

5、配置bean

package com.cookie;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 org.springframework.jdbc.datasource.DataSourceTransactionManager;import org.springframework.transaction.PlatformTransactionManager;import javax.sql.DataSource;import java.util.HashMap;import java.util.Map;/** * author : cxq * Date : 2019/5/15 */@Configurationpublic class CommonConfig { @Bean(name = "primaryDataSource") @ConfigurationProperties(prefix = "spring.datasource.primary") public DataSource primaryDataSource (){ return DataSourceBuilder.create().build(); } @Bean(name = "secondDataSource") @ConfigurationProperties(prefix = "spring.datasource.second") public DataSource secondDataSource (){ return DataSourceBuilder.create().build(); } /** * 动态数据源 ：通过AOP在不同数据源之间切换 * @return */ @Primary @Bean(name = "dynamicDataSource") public DataSource dynamicDataSource() { DynamicDataSource dynamicDataSource = new DynamicDataSource(); // 默认数据源 dynamicDataSource.setDefaultTargetDataSource(secondDataSource()); // 配置多数据源 Map dsMap = new HashMap<>(); dsMap.put("primaryDataSource