使用springboot+mybatis-plus+（Druid/Hikari）實現(xiàn)多數(shù)據(jù)源配置

操作步驟：

1. 引入相應(yīng)的maven坐標(biāo)
2. 編寫mybatis配置，集成mybatis或mybatis-plus（如果已集成可跳過）
3. 編寫數(shù)據(jù)源配置類
4. 編寫注解，并通過aop進行增強（編寫數(shù)據(jù)源切換代碼）
5. 類或方法中使用注解，對數(shù)據(jù)源進行切換

第一步：引入需要相應(yīng)maven坐標(biāo)

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- aop注解實現(xiàn)aspectjweaver依賴 -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.9.6</version>
        </dependency>
        <!-- mysql-plus 依賴 -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.0</version>
        </dependency>
        <!-- Mysql驅(qū)動包 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--阿里數(shù)據(jù)庫連接池 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.14</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

第二步：編寫mybatis-plus配置集成

server:
  port: 8000

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    master:
      url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8&allowMultiQueries=true
      username: root
      password: 123456
    slaver:
      # 從數(shù)據(jù)源開關(guān)/默認關(guān)閉
      enabled: false
      url: jdbc:mysql://localhost:3306/slave?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8&allowMultiQueries=true
      username: root
      password: 123456
    druid:
      # 初始連接數(shù)
      initial-size: 5
      # 最小連接池數(shù)量
      min-idle: 10
      # 最大連接池數(shù)量
      max-active: 20
      # 獲取連接等待超時時間
      max-wait: 60000
mybatis-plus:
  mapper-locations: classpath*:mapper/*Mapper.xml

logging:
  level:
    com.example.demo: debug

以下是集成mp相關(guān)的代碼，不需要可直接跳過?。?！(以user表為例)

userMapper

package com.example.demo.datesource.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.example.demo.datesource.domain.User;

import java.util.List;

public interface UserService extends IService<User> {

    List<User> getUserList();
    List<User> getUserListByXml();

    List<User> testSlave();
}

userMapper.xml

<?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.demo.datesource.mapper.UserMapper">


    <select id="getUserListByXml" resultType="com.example.demo.datesource.domain.User">
        select * from user
    </select>
</mapper>

userService

package com.example.demo.datesource.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.example.demo.datesource.domain.User;

import java.util.List;

public interface UserService extends IService<User> {

    List<User> getUserList();
    List<User> getUserListByXml();

    List<User> testSlave();
}

userServiceImpl

package com.example.demo.datesource.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.demo.datesource.annotation.UseDataSource;
import com.example.demo.datesource.domain.User;
import com.example.demo.datesource.enums.DataSourceType;
import com.example.demo.datesource.mapper.UserMapper;
import com.example.demo.datesource.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

    @Autowired
    private UserMapper userMapper;

    @Override
    public List<User> getUserList() {
        return list();
    }

    @Override
    public List<User> getUserListByXml(){
        return userMapper.getUserListByXml();
    }

    @Override
    public List<User> testSlave() {
        return list();
    }
}

User

package com.example.demo.datesource.domain;

import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

@Data
@TableName("user")
public class User {

    @TableId
    private Long id;

    private String name;

    private String sex;

    private int age;
}

mybatis-plus 集成完畢！

第三步：編寫數(shù)據(jù)源的配置類（例：Druid、Hikari）

一、@ConfigurationProperties要和配置文件中的配置對應(yīng)上

（1）Druid：

package com.example.demo.datesource.config;

import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;
import com.alibaba.druid.spring.boot.autoconfigure.properties.DruidStatProperties;
import com.example.demo.datesource.config.properties.DruidPropertiesConfig;
import com.example.demo.datesource.datasource.DynamicDataSource;
import com.example.demo.datesource.enums.DataSourceType;
import com.example.demo.datesource.utils.SpringUtils;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
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 javax.sql.DataSource;
import javax.swing.*;
import java.util.HashMap;
import java.util.Map;

@Configuration
public class DruidConfig {

    @Bean
    @ConfigurationProperties("spring.datasource.master")
    public DataSource masterDataSource(DruidPropertiesConfig propertiesConfig){
        DruidDataSource dataSource = DruidDataSourceBuilder.create().build();
        return propertiesConfig.setDataSourceProperties(dataSource);
    }

    @Bean
    @ConfigurationProperties("spring.datasource.slaver")
    @ConditionalOnProperty(prefix = "spring.datasource.slaver", name = "enabled", havingValue = "true")
    public DataSource slaverDataSource(DruidPropertiesConfig propertiesConfig){
        DruidDataSource dataSource = DruidDataSourceBuilder.create().build();
        return propertiesConfig.setDataSourceProperties(dataSource);
    }

    @Bean
    @Primary
    public DynamicDataSource dataSource(DataSource masterDataSource){
        Map<Object,Object> targetDataSource = new HashMap<>();
        targetDataSource.put(DataSourceType.MASTER.name(),masterDataSource);
        setDataSource(targetDataSource,DataSourceType.SLAVE.name(),"slaverDataSource");
        return new DynamicDataSource(masterDataSource,targetDataSource);
    }

    public void setDataSource(Map<Object,Object> targetDataSource,String sourceName,String beanName){
        try {
            DataSource dataSource = SpringUtils.getBean(beanName);
            targetDataSource.put(sourceName,dataSource);
        }catch (Exception e){

        }
    }

}

增加DruidPropertiesConfig類，用于給數(shù)據(jù)源配置上配置文件對應(yīng)的屬性

package com.example.demo.datesource.config.properties;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;

@Configuration
public class DruidPropertiesConfig {

    @Value("${spring.datasource.druid.initial-size}")
    private int initialSize;

    @Value("${spring.datasource.druid.min-idle}")
    private int minIdle;

    @Value("${spring.datasource.druid.max-active}")
    private int maxActive;

    @Value("${spring.datasource.druid.max-wait}")
    private int maxWait;

    public DruidDataSource setDataSourceProperties(DruidDataSource dataSource){
        dataSource.setInitialSize(this.initialSize);
        dataSource.setMinIdle(this.minIdle);
        dataSource.setMaxActive(this.maxActive);
        dataSource.setMaxWait(this.maxWait);
        return dataSource;
    }

}

（2）Hikari：配置上基本和druid相同，只需把配置類改為如下且配置文件的“url”改為“jdbc-url”即可

二、增加SpringUtils類，用于讀取spring中的bean

package com.example.demo.datesource.utils;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.stereotype.Component;

@Component
public class SpringUtils implements BeanFactoryPostProcessor {

    private static ConfigurableListableBeanFactory beanFactory;

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
        SpringUtils.beanFactory = configurableListableBeanFactory;
    }


    public static <T> T getBean(String name){
        return (T) beanFactory.getBean(name);
    }


}

三、添加DynamicDataSource類

（1）此類是用來配置動態(tài)數(shù)據(jù)源的關(guān)鍵。該類繼承spring的抽象類AbstractRoutingDataSource，通過這個類可以實現(xiàn)動態(tài)數(shù)據(jù)源切換。其中維護著默認數(shù)據(jù)源（defaultTargetDataSource）和數(shù)據(jù)源列表（targetDataSources），通過afterPropertiesSet()方法對數(shù)據(jù)源列表進行解析以及設(shè)置數(shù)據(jù)源。
程序每次對數(shù)據(jù)庫發(fā)起連接時，都會訪問到AbstractRoutingDataSource的getConnection()方法，此方法會調(diào)用determineCurrentLookupKey的相應(yīng)實現(xiàn)，此處實現(xiàn)為獲取線程變量。

package com.example.demo.datesource.datasource;

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);
        super.afterPropertiesSet();
    }

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

（2）添加DynamicDataSourceContextHolder類，此類用于切換數(shù)據(jù)源，根據(jù)ThreadLocal做多線程數(shù)據(jù)隔離，每一次切換都能保證不影響其他線程的正常運行

package com.example.demo.datesource.datasource;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DynamicDataSourceContextHolder {

    public static final Logger log = LoggerFactory.getLogger(DynamicDataSourceContextHolder.class);

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

    /**
     * 設(shè)置數(shù)據(jù)源的變量
     */
    public static void setDataSourceType(String dsType){
        log.info("切換到{}數(shù)據(jù)源",dsType);
        CONTEXT_HOLDER.set(dsType);
    }


    /**
     * 獲得數(shù)據(jù)源的變量
     */
    public static String getDataSourceType()
    {
        return CONTEXT_HOLDER.get();
    }

    /**
     * 清空數(shù)據(jù)源變量,此方法可調(diào)動gc對線程進行清除
     */
    public static void clearDataSourceType()
    {
        CONTEXT_HOLDER.remove();
    }

}

AbstractRoutingDataSource切換線程變量來切換數(shù)據(jù)源源碼。
此處就是獲取之前在DynamicDataSourceContextHolder中set到線程中的數(shù)據(jù)源名，通過數(shù)據(jù)源名獲取維護的數(shù)據(jù)源列表中對應(yīng)的數(shù)據(jù)源

第四步：使用

大致思路：定義一個切換數(shù)據(jù)源注解，通過注解aop的形式對數(shù)據(jù)源進行切換，在類或方法中使用注解，設(shè)置對應(yīng)的數(shù)據(jù)源名稱以此來達到數(shù)據(jù)源切換

一、定義一個切換數(shù)據(jù)源注解

package com.example.demo.datesource.annotation;

import com.example.demo.datesource.enums.DataSourceType;

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

@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface UseDataSource {

    public DataSourceType dataSource() default DataSourceType.MASTER;

}

二、編寫aop代碼

@within：此注解可以作用于類中的所有方法，如果@UseDataSource放到類上，此類下的所有的方法都會被當(dāng)做切點攔截
@Order(1)：提升組件注冊到spring中的優(yōu)先級
point.proceed()：原來執(zhí)行的程序，也就是原請求，想要做環(huán)繞增強就再這周圍寫就可以了

package com.example.demo.datesource.aspectj;

import com.example.demo.datesource.annotation.UseDataSource;
import com.example.demo.datesource.datasource.DynamicDataSourceContextHolder;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.Signature;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import javax.sql.DataSource;
import java.util.Objects;

@Aspect
@Order(1)
@Component
public class DataSourceAspect {

    @Pointcut("@annotation(com.example.demo.datesource.annotation.UseDataSource) || @within(com.example.demo.datesource.annotation.UseDataSource)")
    public void pointCut(){}

    @Around("pointCut()")
    public Object around(ProceedingJoinPoint point) throws Throwable{
        UseDataSource useDataSource = getDataSource(point);
        if(Objects.nonNull(useDataSource)){
            DynamicDataSourceContextHolder.setDataSourceType(useDataSource.dataSource().name());
        }
        try {
            return point.proceed();
        }finally {
            //清空threadlocalMap的entry。避免內(nèi)存泄漏
            DynamicDataSourceContextHolder.clearDataSourceType();
        }

    }

    public UseDataSource getDataSource(ProceedingJoinPoint point){
        MethodSignature signature = (MethodSignature) point.getSignature();
        UseDataSource annotation = AnnotationUtils.findAnnotation(signature.getMethod(), UseDataSource.class);
        if(Objects.nonNull(annotation)){
            return annotation;
        }
        return AnnotationUtils.findAnnotation(signature.getDeclaringType(),UseDataSource.class);
    }

}

三、編寫注解到類或方法上

運行結(jié)果：

至此，數(shù)據(jù)源切換成功?。?！

另外，如果需要增加新的數(shù)據(jù)源需要的操作：
1、啟動配置文件中增加新的數(shù)據(jù)源參數(shù)
2、數(shù)據(jù)源配置類中，新增配置源bean，并且把數(shù)據(jù)源set到targetDataSource中
3、DataSourceType枚舉類中，添加新數(shù)據(jù)源的枚舉
如圖所示：

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