三个数据库：master主库、back_one从库1、back_two从库2

1.application.yml配置三个数据库信息

spring:datasource:driver-class-name : com.mysql.jdbc.Driver# 主库master:jdbcUrl : jdbc:mysql://xxx:3306/master?useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&serverTimezone=GMT%2b8&allowMultiQueries=trueusername : xxxpassword : xxxname :# 从库1slave:enabled: true  # 从数据源开关/默认关闭jdbcUrl: jdbc:mysql://xxx:3306/back_one?useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true&serverTimezone=GMT%2b8username: xxxpassword: xxxname :# 从库2slave2:enabled: true  # 从数据源开关/默认关闭jdbcUrl: jdbc:mysql://xxx:3306/back_two?useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true&serverTimezone=GMT%2b8username: xxxpassword: xxxname :druid.maxActive : 150druid.initialSize : 5druid.minIdle : 5druid.maxWait : 60000druid.filters : statdruid.timeBetweenEvictionRunsMillis : 60000druid.minEvictableIdleTimeMillis : 300000druid.validationQuery : SELECT 1    #多个数据源时配置：select count(*) from dualdruid.testWhileIdle : truedruid.testOnBorrow : falsedruid.testOnReturn : falsedruid.poolPreparedStatements : falsedruid.maxPoolPreparedStatementPerConnectionSize : -1druid.timeBetweenLogStatsMillis : 0druid.keep-alive : truedruid.connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000;druid.stat.logSlowSql=true

注意：

一个数据源时：validationQuery: SELECT 1；

多个数据源时：validationQuery: select count(*) from dual

2.代码

（1）DataSource

import java.lang.annotation.*;@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSource {DataSourceType value() default DataSourceType.MASTER;}

（2）DataSourceAspect

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;import java.lang.reflect.Method;@Aspect
@Order(1)
@Component
public class DataSourceAspect {@Pointcut("execution(public * com.xxx.mapper..*.*(..))")public void pointcut() {}@Before("pointcut()")public void doBefore(JoinPoint joinPoint){Method method = ((MethodSignature)joinPoint.getSignature()).getMethod();DataSource dataSource = method.getAnnotation(DataSource.class);  //获取方法上的注解if(dataSource == null){Class<?> clazz= joinPoint.getTarget().getClass().getInterfaces()[0];dataSource =clazz.getAnnotation(DataSource.class);  //获取类上面的注解if(dataSource == null) return;}if (dataSource != null) {DynamicDataSourceContextHolder.setDataSourceType(dataSource.value().name());}}@After("pointcut()")public void after(JoinPoint point) {//清理掉当前设置的数据源，让默认的数据源不受影响DynamicDataSourceContextHolder.clearDataSourceType();}
}

（3）DataSourceConfig

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.DependsOn;
import org.springframework.context.annotation.Primary;import javax.sql.DataSource;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;@Configuration
public class DataSourceConfig {//主数据源@Value("${spring.datasource.master.jdbcUrl}")private String masterJdbcUrl;@Value("${spring.datasource.master.username}")private String masterUsername;@Value("${spring.datasource.master.password}")private String masterPassword;@Value("${spring.datasource.driver-class-name}")private String masterDriverClassName;@Value("${spring.datasource.master.name}")private String name;//从数据源1@Value("${spring.datasource.slave.jdbcUrl}")private String slaveJdbcUrl1;@Value("${spring.datasource.slave.username}")private String slaveUsername1;@Value("${spring.datasource.slave.password}")private String slavePassword1;@Value("${spring.datasource.driver-class-name}")private String slaveDriverClassName1;@Value("${spring.datasource.slave.name}")private String slaveName;//从数据源2@Value("${spring.datasource.slave2.jdbcUrl}")private String slaveJdbcUrl2;@Value("${spring.datasource.slave2.username}")private String slaveUsername2;@Value("${spring.datasource.slave2.password}")private String slavePassword2;@Value("${spring.datasource.driver-class-name}")private String slaveDriverClassName2;@Value("${spring.datasource.slave2.name}")private String slaveName2;//其他相关配置@Value("${spring.datasource.druid.initialSize}")private int initialSize;@Value("${spring.datasource.druid.minIdle}")private int minIdle;@Value("${spring.datasource.druid.maxWait}")private int maxWait;@Value("${spring.datasource.druid.filters}")private String filters;@Value("${spring.datasource.druid.timeBetweenEvictionRunsMillis}")private int timeBetweenEvictionRunsMillis;@Value("${spring.datasource.druid.minEvictableIdleTimeMillis}")private int minEvictableIdleTimeMillis;@Value("${spring.datasource.druid.validationQuery}")private String validationQuery;@Value("${spring.datasource.druid.testWhileIdle}")private boolean testWhileIdle;@Value("${spring.datasource.druid.testOnBorrow}")private boolean testOnBorrow;@Value("${spring.datasource.druid.testOnReturn}")private boolean testOnReturn;@Value("${spring.datasource.druid.poolPreparedStatements}")private boolean poolPreparedStatements;@Value("${spring.datasource.druid.maxPoolPreparedStatementPerConnectionSize}")private int maxPoolPreparedStatementPerConnectionSize;@Value("${spring.datasource.druid.timeBetweenLogStatsMillis}")private int timeBetweenLogStatsMillis;@Value("${spring.datasource.druid.keep-alive}")private boolean keepAlive;@Value("${spring.datasource.druid.connectionProperties}")private String connectionProperties;@Beanpublic DataSource masterDataSource() {return generateDataSource(masterJdbcUrl,masterUsername,masterPassword,masterDriverClassName,name);}@Bean@ConditionalOnProperty(prefix = "spring.datasource.slave", name = "enabled", havingValue = "true")public DataSource slaveDataSource1() {return generateDataSource(slaveJdbcUrl1,slaveUsername1,slavePassword1,slaveDriverClassName1,slaveName);}@Bean@ConditionalOnProperty(prefix = "spring.datasource.slave2", name = "enabled", havingValue = "true")public DataSource slaveDataSource2() {return generateDataSource(slaveJdbcUrl2,slaveUsername2,slavePassword2,slaveDriverClassName2,slaveName2);}private DruidDataSource generateDataSource(String url,String username,String password,String driverClassName,String name){DruidDataSource datasource = new DruidDataSource();datasource.setUrl(url);datasource.setUsername(username);datasource.setPassword(password);datasource.setDriverClassName(driverClassName);datasource.setName(name);datasource.setInitialSize(initialSize);datasource.setMinIdle(minIdle);datasource.setMaxWait(maxWait);datasource.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);datasource.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);datasource.setValidationQuery(validationQuery);datasource.setTestWhileIdle(testWhileIdle);datasource.setTestOnBorrow(testOnBorrow);datasource.setTestOnReturn(testOnReturn);datasource.setPoolPreparedStatements(poolPreparedStatements);datasource.setMaxPoolPreparedStatementPerConnectionSize(maxPoolPreparedStatementPerConnectionSize);datasource.setKeepAlive(keepAlive);try {datasource.setFilters(filters);} catch (SQLException e) {System.err.println("druid configuration initialization filter: " + e);}datasource.setConnectionProperties(connectionProperties);datasource.setTimeBetweenLogStatsMillis(timeBetweenLogStatsMillis);return datasource;}@Bean(name = "dynamicDataSource")@DependsOn({"masterDataSource", "slaveDataSource1", "slaveDataSource2"})  //如果不加这个，会报错：The dependencies of some of the beans in the application context form a cycle@Primarypublic DynamicDataSource dataSource(DataSource masterDataSource, DataSource slaveDataSource1, DataSource slaveDataSource2) {Map<Object, Object> targetDataSources = new HashMap<>();targetDataSources.put(DataSourceType.MASTER.name(), masterDataSource);targetDataSources.put(DataSourceType.BACKONE.name(), slaveDataSource1);targetDataSources.put(DataSourceType.BACKTWO.name(), slaveDataSource2);return new DynamicDataSource(masterDataSource, targetDataSources);}}

（4）DataSourceType

public enum DataSourceType {/*** 主库*/MASTER,/*** 从库1*/BACKONE,/*** 从库2*/BACKTWO;
}

（5）DynamicDataSource

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;import javax.sql.DataSource;
import java.util.Map;public class DynamicDataSource extends AbstractRoutingDataSource {public DynamicDataSource(DataSource defaultTargetDataSource, Map<Object, Object> targetDataSources) {super.setDefaultTargetDataSource(defaultTargetDataSource);super.setTargetDataSources(targetDataSources);// afterPropertiesSet()方法调用时用来将targetDataSources的属性写入resolvedDataSources中的super.afterPropertiesSet();}/*** 根据Key获取数据源的信息*/@Overrideprotected Object determineCurrentLookupKey() {return DynamicDataSourceContextHolder.getDataSourceType();}}

（6）DynamicDataSourceContextHolder

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;public class DynamicDataSourceContextHolder {public static final Logger log = LoggerFactory.getLogger(DynamicDataSourceContextHolder.class);/*** 使用ThreadLocal维护变量，ThreadLocal为每个使用该变量的线程提供独立的变量副本，*  所以每一个线程都可以独立地改变自己的副本，而不会影响其它线程所对应的副本。*/private static final ThreadLocal<String> CONTEXT_HOLDER = new ThreadLocal<>();/*** 设置数据源变量*/public static void setDataSourceType(String dataSourceType){log.info("切换到{}数据源", dataSourceType);CONTEXT_HOLDER.set(dataSourceType);}/*** 获取数据源变量*/public static String getDataSourceType(){return CONTEXT_HOLDER.get();}/*** 清空数据源变量*/public static void clearDataSourceType(){CONTEXT_HOLDER.remove();}}

3.使用

（1）调用从库1

/*** 调用从库1*/
@Component
@DataSource(value = DataSourceType.BACKONE)
public interface TestOneMapper {}

（2）调用从库2

/*** 调用从库2*/
@Component
@DataSource(value = DataSourceType.BACKTWO)
public interface TestTwoMapper {}

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