[Java知识库]SpringBoot: 通过AOP实现对主从复制的MySQL进行读写分离操作

一、创建SpringBoot项目并添加依赖，完整pom如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>cn.edu.tju</groupId>
    <artifactId>springbootmysqlmasterslave</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.14</version>
        </dependency>


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

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


        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>2.9.0</version>
        </dependency>

        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.6</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.30</version>
        </dependency>

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

        <!-- https://mvnrepository.com/artifact/org.springframework.cloud/spring-cloud-starter-openfeign -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
            <version>2.1.5.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.13</version>
        </dependency>

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/io.springfox/springfox-swagger2 -->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>3.0.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/io.springfox/springfox-swagger-ui -->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>3.0.0</version>
        </dependency>

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


        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>





    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>

        </plugins>
    </build>


</project>

二、在application.properties中配置主数据源和从数据源：

server.port=9093
spring.datasource.master.jdbc-url=jdbc:mysql://139.xxx.xxx.xxx:3306/test?useUnicode=true&characterEncoding=utf8&tinyInt1isBit=false&useSSL=false&serverTimezone=GMT
spring.datasource.master.username=root
spring.datasource.master.password=xxx
spring.datasource.master.driver-class-name=com.mysql.jdbc.Driver

spring.datasource.slave1.jdbc-url=jdbc:mysql://139.xxx.xxx.xxx:3306/test?useUnicode=true&characterEncoding=utf8&tinyInt1isBit=false&useSSL=false&serverTimezone=GMT
spring.datasource.slave1.username=root
spring.datasource.slave1.password=xxx
spring.datasource.slave1.driver-class-name=com.mysql.jdbc.Driver

三、创建枚举，分别表示主数据源和从数据源

package cn.edu.tju.config;



public enum DataSourceEnum {
    MASTER, SLAVE1
}

四、创建Holder静态类，持有上述枚举,并提供修改功能

package cn.edu.tju.config;


public class DataSourceContextHolder {

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

    public static void setDataSource(DataSourceEnum dataSourceEnum) {
        contextHolder.set(dataSourceEnum);
    }

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


    public static void switchToMasterDatabase() {
        setDataSource(DataSourceEnum.MASTER);
        System.out.println("switch to master");
    }


    public static void switchToSlaveDatabase() {
        setDataSource(DataSourceEnum.values()[1]);
        System.out.println("switch to "+DataSourceEnum.values()[1]);
    }


    public static void remove(){
        contextHolder.remove();
    }
}

五、定义AbstractRoutingDataSource的子类，通过上述Holder类，来实现数据源的切换

package cn.edu.tju.config;


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


public class MyRoutingDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return DataSourceContextHolder.get();
    }

}

六、定义主数据源bean、从数据源bean、RoutingDataSource bean;

package cn.edu.tju.config;

import java.util.Map;
import java.util.HashMap;
import javax.sql.DataSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;



@Configuration
public class DataSourceConfig {

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

    @Bean
    @ConfigurationProperties("spring.datasource.slave1")
    public DataSource slave1DataSource() {
        return DataSourceBuilder.create().build();
    }



    @Bean("targetDataSources")
    public DataSource getRoutingDataSource(@Qualifier("masterDataSource") DataSource masterDataSource,
                                          @Qualifier("slave1DataSource") DataSource slave1DataSource) {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceEnum.MASTER, masterDataSource);
        targetDataSources.put(DataSourceEnum.SLAVE1, slave1DataSource);
        MyRoutingDataSource myRoutingDataSource = new MyRoutingDataSource();
        myRoutingDataSource.setDefaultTargetDataSource(masterDataSource);
        myRoutingDataSource.setTargetDataSources(targetDataSources);
        return myRoutingDataSource;
    }

}

7、定义SqlSessionFactory

package cn.edu.tju.config;

import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import javax.annotation.Resource;
import javax.sql.DataSource;


@Configuration
@MapperScan(basePackages = "cn.edu.tju.mapper", sqlSessionFactoryRef = "sqlSessionFactory")
@EnableTransactionManagement
public class SqlSessionFactoryConfig {

    @Resource(name = "targetDataSources")
    private DataSource dataSource;

    @Bean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource);
        sqlSessionFactoryBean.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
        return sqlSessionFactoryBean.getObject();
    }

    @Bean
    public PlatformTransactionManager platformTransactionManager(){
        return new DataSourceTransactionManager(dataSource);
    }
}

八、定义一个用来强制路由到主数据源的注解

package cn.edu.tju.aop;

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

@Retention(RetentionPolicy.RUNTIME)
public @interface SelectMasterDatabase {
}

九、定义Aspect，用来对控制器的请求进行增强处理，读请求路由到从数据源，写请求路由到主数据源

package cn.edu.tju.aop;

import cn.edu.tju.config.DataSourceContextHolder;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class DataSourceSelectAop {
    @Pointcut("!@annotation(cn.edu.tju.aop.SelectMasterDatabase) && (execution(* cn.edu.tju.service.*.get*(..)))")
    public void readPointcut() {
    }
    @Pointcut("@annotation(cn.edu.tju.aop.SelectMasterDatabase) " +
            "|| execution(* cn.edu.tju.service.*.add*(..)) " +
            "|| execution(* cn.edu.tju.service.*.delete*(..)) " +
            "|| execution(* cn.edu.tju.service.*.update*(..)) " )
    public void writePointcut() {
    }

    @Before("readPointcut()")
    public void read() {
        DataSourceContextHolder.switchToSlaveDatabase();
    }

    @Before("writePointcut()")
    public void write() {
        DataSourceContextHolder.switchToMasterDatabase();
    }
}

十、准备启动类\mapper\service\controller，启动程序

package cn.edu.tju;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Start {
    public static void main(String[] args) {
        SpringApplication.run(Start.class,args);
    }
}

package cn.edu.tju.mapper;

import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;

import java.util.Map;

public interface UserMapper {

    @Select("select * from user_info where username like 'cho%'  limit 1")
    Map<String,Object> getUserInfo();

    @Insert("insert into user_info(username,passwd) values(#{arg0},#{arg1})")
    int addUserInfo(String username,String password);
}

package cn.edu.tju.service;

import cn.edu.tju.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.Map;

@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;

    public Map<String,Object> getUser(){
        Map<String,Object>  map=userMapper.getUserInfo();
        return map;
    }

    public int addUserInfo(String username,String password){
        return userMapper.addUserInfo(username,password);
    }
}

package cn.edu.tju.controller;

import cn.edu.tju.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Map;

@RestController
public class UserController {
    @Autowired
    private UserService userService;

    @RequestMapping("/get")
    public Map<String,Object> getUser(){
        return userService.getUser();
    }



    @RequestMapping("/add")
    public int addUser(){
        return userService.addUserInfo("Ludwig","Beethoven1770");
    }



}

十一、调用add接口和get接口并在数据库查看结果:
写入数据会写到主数据源，然后被自动同步到从数据源
读取数据会从从数据源读。
这样就完成了读写分离。

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