Spring boot添加多数据源实现读写分离

配置如下

spring:datasource:master:type: com.alibaba.druid.pool.DruidDataSourceurl: jdbc:mysql://x.x.x.x:3306/leaf?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghaiusername: rootpassword: 123456driver-class-name: com.mysql.cj.jdbc.Driver# 配置初始值initial-size: 5min-idle: 10max-active: 20slave:type: com.alibaba.druid.pool.DruidDataSourceurl: jdbc:mysql://x.x.x.x:3316/leaf?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghaiusername: leafpassword: 123456driver-class-name: com.mysql.cj.jdbc.Driver# 配置初始值initial-size: 5min-idle: 10max-active: 20

流程概述如下：

1、添加数据源配置类，注入三个数据源master、slave和dataSourceRouter，在dataSourceRouter中加上@Primary提高优先级；

2、在dataSourceRouter中创建一个AbstractRoutingDataSource的实例DataSourceRouter，然后把master和slave设置到dataSourceRouter中，设置默认数据库为master，并且返回dataSourceRouter；

3、在进行数据库操作前都会调用dataSourceRouter类的方法determineCurrentLookupKey，在该方法中返回key就会选择相应的数据源。

4、创建一个注解类，类型分为master和slave，然后创建一个切面类，在service方法调用前查看注解类型，根据注解类型动态切换数据源。

具体代码如下：

创建DataSourceEnum枚举类

package com.funheng.leaf.client.datasource;/*** @author ：leaf* @date ：Created in 2020/6/5 2:42 PM* @description：* @modified By：*/
public enum DataSourceEnum {MASTER("master"),SLAVE("slave");private String name;private DataSourceEnum(String name) {this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}}

创建自定义注解

package com.funheng.leaf.client.datasource;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** @author ：leaf* @date ：Created in 2020/6/5 2:43 PM* @description：* @modified By：* 数据源选择，自定义注解*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface DataSourceAnnotation {DataSourceEnum value() default DataSourceEnum.MASTER;    // 默认主表master}

创建切面类

package com.funheng.leaf.client.datasource;/*** @author ：leaf* @date ：Created in 2020/6/5 2:45 PM* @description：* @modified By：*/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.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;import java.lang.reflect.Method;/*** AOP根据注解给上下文赋值*/
@Aspect
@Order(1)    // 数据源的切换要在数据库事务之前, 设置AOP执行顺序(需要在事务之前，否则事务只发生在默认库中, 数值越小等级越高)
@Component
public class DataSourceAspect {private Logger log = LoggerFactory.getLogger(DataSourceAspect.class);// 切点, 注意这里是在service层@Pointcut("execution(* com.funheng.leaf.client.service.*.*(..))")public void aspect() {}@Before("aspect()")private void before(JoinPoint point) {log.info("-----------调用service----");Object target = point.getTarget();String method = point.getSignature().getName();Class<?> classz = target.getClass();Class<?>[] parameterTypes = ((MethodSignature) point.getSignature()).getMethod().getParameterTypes();try {Method m = classz.getMethod(method, parameterTypes);if (m != null && m.isAnnotationPresent(DataSourceAnnotation.class)) {DataSourceAnnotation data = m.getAnnotation(DataSourceAnnotation.class);DataSourceContextHolder.putDataSource(data.value().getName());log.info("-----------切换数据源, 上下文准备赋值-----:{}", data.value().getName());log.info("-----------切换数据源, 数据源上下文实际赋值-----:{}", DataSourceContextHolder.getCurrentDataSource());}} catch (Exception e) {e.printStackTrace();}}// 切面结束, 重置线程变量@After("aspect()")public void after(JoinPoint joinPoint) {DataSourceContextHolder.removeCurrentDataSource();log.info("重置数据源: Restore DataSource to [{}] in Method [{}]", DataSourceContextHolder.getCurrentDataSource(), joinPoint.getSignature());}}

创建动态数据源切换的上下文

package com.funheng.leaf.client.datasource;/*** @author ：leaf* @date ：Created in 2020/6/5 2:58 PM* @description：* @modified By：*/
public class DataSourceContextHolder {private final static ThreadLocal<String> local = new ThreadLocal<>();public static void putDataSource(String name) {local.set(name);}public static String getCurrentDataSource() {return local.get();}public static void removeCurrentDataSource() {local.remove();}}

接下来创建数据源配置类

package com.funheng.leaf.client.datasource;import com.alibaba.druid.pool.DruidDataSource;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
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 ：leaf* @date ：Created in 2020/6/5 2:51 PM* @description：数据源配置* @modified By：*/@Configuration
@Slf4j
public class DataSourceConfig {public final static String masterTransactionManager = "masterTransactionManager";public final static String slaveTransactionManager = "slaveTransactionManager";/**** 注意这里用的 Druid 连接池*/@Bean(name = "dbMaster")@ConfigurationProperties(prefix = "spring.datasource.master")public DataSource dbMaster() {log.info("master数据源");return new DruidDataSource();}@Bean(name = "dbSlave")@ConfigurationProperties(prefix = "spring.datasource.slave")public DataSource dbSlave() {log.info("slave数据源");return new DruidDataSource();}/**** @Primary： 相同的bean中，优先使用用@Primary注解的bean.* @Qualifier:： 这个注解则指定某个bean有没有资格进行注入。*/@Primary@Bean(name = "dataSourceRouter") // 对应Bean: DataSourceRouterpublic DataSource dataSourceRouter(@Qualifier("dbMaster") DataSource master, @Qualifier("dbSlave") DataSource slave) {DataSourceRouter dataSourceRouter = new DataSourceRouter();//配置多数据源Map<Object, Object> map = new HashMap<>(5);map.put(DataSourceEnum.MASTER.getName(), master);    // key需要跟ThreadLocal中的值对应map.put(DataSourceEnum.SLAVE.getName(), slave);// master 作为默认数据源dataSourceRouter.setDefaultTargetDataSource(master);dataSourceRouter.setTargetDataSources(map);return dataSourceRouter;}// 注入动态数据源 DataSourceTransactionManager 用于事务管理(事务回滚只针对同一个数据源)@Bean(name = "transactionManager")public PlatformTransactionManager transactionManager(@Qualifier("dataSourceRouter") DataSource dataSource) {return new DataSourceTransactionManager(dataSource);}
}

最后创建数据源实现类

package com.funheng.leaf.client.datasource;import lombok.extern.slf4j.Slf4j;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;/*** @author ：leaf* @date ：Created in 2020/6/5 2:58 PM* @description：* @modified By：*/
/**** AbstractRoutingDataSource抽象类, 实现AOP动态切换的关键* 		1.AbstractRoutingDataSource中determineTargetDataSource()方法中获取数据源 * 			Object lookupKey = determineCurrentLookupKey();* 			DataSource dataSource = this.resolvedDataSources.get(lookupKey);* 			根据determineCurrentLookupKey()得到Datasource,并且此方法是抽象方法,应用可以实现*     2.resolvedDataSources 的值根据 targetDataSources 所得 afterPropertiesSet()方法[该方法在@Bean所在方法执行完成后执行]中:* 			Map.Entry<Object, Object> entry : this.targetDataSources.entrySet()*     3.然后在xml中使用<bean>或者代码中@Bean 设置 dataSource 的defaultTargetDataSource(默认数据源)和 targetDataSources(多数据源)*     4.利用自定义注解，AOP拦截动态的设置ThreadLocal的值*     5.在DAO层与数据库建立连接时会根据ThreadLocal的key得到数据源*/// 在访问数据库前会调用该类的 determineCurrentLookupKey() 方法获取数据库实例的 key
@Slf4j
public class DataSourceRouter extends AbstractRoutingDataSource {@Overrideprotected Object determineCurrentLookupKey() {log.info(" 当前数据源: " + DataSourceContextHolder.getCurrentDataSource());return DataSourceContextHolder.getCurrentDataSource();}
}

之后在service层的方法上添加@DataSourceAnnotation(value = DataSourceEnum.SLAVE)即可

package com.funheng.leaf.client.service.impl;import com.funheng.leaf.client.dao.BusinessDao;
import com.funheng.leaf.client.datasource.DataSourceAnnotation;
import com.funheng.leaf.client.datasource.DataSourceEnum;
import com.funheng.leaf.client.domain.BusinessHomeQuery;
import com.funheng.leaf.client.domain.BusinessResultCommon;
import com.funheng.leaf.client.service.BsnBusinessService;
import com.funheng.leaf.mapper.BsnBusinessMapper;
import com.funheng.leaf.model.BsnBusiness;
import com.funheng.leaf.model.BsnBusinessExample;
import com.github.pagehelper.PageHelper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.List;/*** @author ：leaf* @date ：Created in 2020/4/27 11:20 AM* @description：* @modified By：*/
@Service
public class BsnBusinessServiceImpl implements BsnBusinessService {@AutowiredBusinessDao businessDao;@Override@DataSourceAnnotation(value = DataSourceEnum.SLAVE)public List<BusinessResultCommon> getList(Integer pageSize, Integer pageNum, BusinessHomeQuery businessHomeQuery) {return businessDao.getBusinessByDistance(businessHomeQuery, (pageNum - 1) * pageSize, pageSize);}}