Spring Boot + MyBatis 实现读写分离

Spring Boot + MyBatis 实现读写分离

MySQL主从复制配置

项目下载

一、技术栈

1、 Spring Boot：2.2.2.Release

<parent>
	<groupId>org.springframework.bootgroupId>
	<artifactId>spring-boot-starter-parentartifactId>
	<version>2.2.2.RELEASEversion>
	<relativePath/> 
parent>

2、MyBatis：2.1.1

<dependency>
	<groupId>org.mybatis.spring.bootgroupId>
	<artifactId>mybatis-spring-boot-starterartifactId>
	<version>2.1.1version>
dependency>

3、 MySQL：5.7.x

4、MiniUI

二、yml配置文件

三、代码实现

1、添加枚举类，用于区分主、从库

package com.productmanage.enums;

/**
 * 用于主从切换时区分主、从库
 * @author xzkui
 * @create 2022-03-04
 */
public enum DBTypeEnum {
    MASTER, SLAVE;
}

2、DBContextHolder，用于切换、获取当前使用的数据库

package com.productmanage.config;

import com.productmanage.enums.DBTypeEnum;
import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * 通过ThreadLocal将数据源设置到每个线程上下文中，如果主、从库较多，需使用原子类
 * @author xzkui
 * @create 2022-03-04
 */
@Slf4j
public class DBContextHolder {


    private static final ThreadLocal<DBTypeEnum> contextHolder = new ThreadLocal<>();

    private static final AtomicInteger counter = new AtomicInteger(-1);

    public static void set(DBTypeEnum dbType) {
        contextHolder.set(dbType);
    }

    public static DBTypeEnum get() {
        return contextHolder.get();
    }

    public static void master() {
        set(DBTypeEnum.MASTER);
        log.info("切换到master");
    }

    public static void slave() {
        set(DBTypeEnum.SLAVE);
        log.info("切换到slave");

        //  如果有多个从库，可通过轮询进行切换
//        int index = counter.getAndIncrement() % 2;
//        if (counter.get() > 9999) {
//            counter.set(-1);
//        }
//        if (index == 0) {
//            set(DBTypeEnum.SLAVE1);
//            log.info("切换到slave1");
//        }else {
//            set(DBTypeEnum.SLAVE2);
//            log.info("切换到slave2");
//        }
    }
}

3、数据源配置类：DataSourceConfig

package com.productmanage.config;

import com.productmanage.enums.DBTypeEnum;
import org.springframework.beans.factory.annotation.Qualifier;
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 javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;

/**
 * 数据源配置类，配置多个数据源
 * 多个数据源使用@Bean、@Qualifier指定名称，
 * @Primary：默认使用该数据库
 * @ConfigurationProperties：指定配置文件中对应的数据库配置信息
 * @author xzkui
 * @create 2022-03-04
 */
@Configuration
public class DataSourceConfig {

    @Primary
    @Bean(name = "masterDataSource")
    @Qualifier("masterDataSource")
    @ConfigurationProperties("spring.datasource.master")
    public DataSource masterDataSource(){
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "slaveDataSource")
    @Qualifier("slaveDataSource")
    @ConfigurationProperties("spring.datasource.slave")
    public DataSource slaveDataSource(){
        return DataSourceBuilder.create().build();
    }

    @Bean
    public DataSource myRouteDataSource(@Qualifier("masterDataSource") DataSource masterDataSource,
                                        @Qualifier("slaveDataSource") DataSource slaveDataSource){
        Map<Object, Object> targetDataSource = new HashMap<>();
        targetDataSource.put(DBTypeEnum.MASTER, masterDataSource);
        targetDataSource.put(DBTypeEnum.SLAVE, slaveDataSource);
        MyRouteDataSource myRouteDataSource = new MyRouteDataSource();
        myRouteDataSource.setDefaultTargetDataSource(masterDataSource);
        myRouteDataSource.setTargetDataSources(targetDataSource);
        return myRouteDataSource;
    }
}

4、路由数据源：MyRouteDataSource

package com.productmanage.config;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import org.springframework.lang.Nullable;

/**
 * 用于获取当前使用的数据库
 * @author xzkui
 * @create 2022-03-04
 */
public class MyRouteDataSource extends AbstractRoutingDataSource {

    @Nullable
    @Override
    protected Object determineCurrentLookupKey() {
        return DBContextHolder.get();
    }
}

5、自定义主、从注解

（1）Master.java

package com.productmanage.annotation;

/**
 * 自定义主库注解，标记了该注解的方法都走主库
 * @author xzkui
 * @create 2022-03-04
 */
public @interface Master {
}

（2）Slave.java

package com.productmanage.annotation;

/**
 * 自定义从库注解，标记了该注解的方法都走从库
 * @author xzkui
 * @create 2022-03-04
 */
public @interface Slave {
}

6、AOP切面，@Before，在方法调用前切换数据源

package com.productmanage.aspect;

import com.productmanage.config.DBContextHolder;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

/**
 * aop切面，读操作都使用slave，写操作使用master
 * @author xzkui
 * @create 2022-03-04
 */
@Aspect
@Component
public class DataSourceAspect {

    @Pointcut("!@annotation(com.productmanage.annotation.Slave) " +
            "&& (execution(* com.productmanage.service..*.select*(..)) " +
            "|| execution(* com.productmanage.service..*.find*(..)))")
    public void readPointCut(){}

    @Pointcut("@annotation(com.productmanage.annotation.Master) " +
            "|| execution(* com.productmanage.service..*.insert*(..)) " +
            "|| execution(* com.productmanage.service..*.add*(..)) " +
            "|| execution(* com.productmanage.service..*.update*(..)) " +
            "|| execution(* com..productmanage.service..*.edit*(..)) " +
            "|| execution(* com.productmanage.service..*.delete*(..)) " +
            "|| execution(* com.productmanage.service..*.remove*(..))")
    public void writePointCut(){}

    @Before("readPointCut()")
    public void read() {
        DBContextHolder.slave();
    }

    @Before("writePointCut()")
    public void write() {
        DBContextHolder.master();
    }
}

四、FAQ

1、多数据源配置启动报错

file [H:\XZKUI\GoodGoodStudyDayDayUp\CODE\productmanagement\target\classes\com\productmanage\mapper\UserMapper.class] required a single bean, but 3 were found:
	- masterDataSource: defined by method 'masterDataSource' in class path resource [com/productmanage/config/DataSourceConfig.class]
	- slaveDataSource: defined by method 'slaveDataSource' in class path resource [com/productmanage/config/DataSourceConfig.class]
	- myRouteDataSource: defined by method 'myRouteDataSource' in class path resource [com/productmanage/config/DataSourceConfig.class]

Action:

Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

• 报错分析：很明显，Bean重复了，翻译一下Action：考虑将其中一个bean标记为@Primary，更新使用者以接受多个bean，或者使用@Qualifier来标识应该被消费的bean
• 解决：在数据源配置类（DataSourceConfig）中，给每个数据源添加一个唯一的名称，并在主库中添加@Primary注解，表示默认使用该数据库

2、项目运行时，从库被关闭，主库正常

• 项目正常运行，读写都在主库

3、项目运行时，从库被关闭，主库正常，此时更改主库数据

• 从库重新启动后，会读取主库中的binlog二进制文件，并将读取的数据保存到从库的relay-log日志文件中，并解析成sql语句逐一执行