帶你了解mybatis如何實(shí)現(xiàn)讀寫分離

更新時(shí)間：2021年08月04日 10:44:12 作者：alexander137

本篇文章主要介紹了MyBatis實(shí)現(xiàn)數(shù)據(jù)讀寫分離的實(shí)例代碼，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下，希望能給你帶來幫助

1、spring aop實(shí)現(xiàn)

首先application-test.yml增加如下數(shù)據(jù)源的配置

spring:
  datasource:
    master:
      jdbc-url: jdbc:mysql://master域名:3306/test
      username: root
      password: 123456
      driver-class-name: com.mysql.jdbc.Driver
    slave1:
      jdbc-url: jdbc:mysql://slave域名:3306/test
      username: root   # 只讀賬戶
      password: 123456
      driver-class-name: com.mysql.jdbc.Driver
    slave2:
      jdbc-url: jdbc:mysql://slave域名:3306/test
      username: root   # 只讀賬戶
      password: 123456
      driver-class-name: com.mysql.jdbc.Driver

package com.cjs.example.enums;
public enum DBTypeEnum {
    MASTER, SLAVE1, SLAVE2;
}

定義ThreadLocal上下文，將當(dāng)前線程的數(shù)據(jù)源進(jìn)行動(dòng)態(tài)修改

public class DBContextHolder {
    private static  volatile ThreadLocal<DBTypeEnum> contextHolder = new ThreadLocal<>();
    public static synchronized void set(DBTypeEnum dbType) {
        contextHolder.set(dbType);
    }
    public static synchronized DBTypeEnum get() {
        return contextHolder.get();
    }
    public static void master() {
        set(DBTypeEnum.MASTER);
    }
    public static void slave() {
        set(DBTypeEnum.SLAVE1);
    }
    public static void slave2(){ set(DBTypeEnum.SLAVE2); }
    // 清除數(shù)據(jù)源名
    public static void clearDB() {
        contextHolder.remove();
    }
}

重寫mybatis數(shù)據(jù)源路由接口，在此修改數(shù)據(jù)源為我們上一塊代碼設(shè)置的上下文的數(shù)據(jù)源

public class MyRoutingDataSource extends AbstractRoutingDataSource {
    @Nullable
    @Override
    protected Object determineCurrentLookupKey() {
        DBTypeEnum dbTypeEnum=DBContextHolder.get();
        return dbTypeEnum;
    }
}

將yml配置的多數(shù)據(jù)源手動(dòng)指定注入

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

sqlsession注入以上我們配置的datasource路由

@EnableTransactionManagement
@Configuration
@Import({TableSegInterceptor.class})
public class MyBatisConfig {
    @Resource(name = "myRoutingDataSource")
    private DataSource myRoutingDataSource;
    @Autowired
    private MybatisConfigProperty mybatisConfigProperty;
    @Autowired
    private TableSegInterceptor tableSegInterceptor;
    @Bean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(myRoutingDataSource);
        // SpringBoot項(xiàng)目集成mybatis打包為jar運(yùn)行時(shí)setTypeAliasesPackage無效解決
        VFS.addImplClass(SpringBootVFS.class);
        sqlSessionFactoryBean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources(mybatisConfigProperty.getMapperLocations()));
        sqlSessionFactoryBean.setTypeAliasesPackage(mybatisConfigProperty.getTypeAliasesPackage());
        sqlSessionFactoryBean.setConfigLocation(
                new PathMatchingResourcePatternResolver().getResource(mybatisConfigProperty.getConfigLocation()));
        sqlSessionFactoryBean.setPlugins(new Interceptor[]{tableSegInterceptor});
        return sqlSessionFactoryBean.getObject();
    }
    @Bean
    public PlatformTransactionManager platformTransactionManager() {
        return new DataSourceTransactionManager(myRoutingDataSource);
    }
}

spring aop攔截指定前綴的service方法，并設(shè)置對(duì)應(yīng)所屬的上下文

@Aspect
@Component
public class DataSourceAop {
    @Pointcut("!@annotation(com.ask.student.interceptor.annotation.Master) " +
            "&& (execution(* com.ask.student.service..*.select*(..)) " +
            "|| execution(* com.ask.student.service..*.get*(..))" +
            "|| execution(* com.ask.student.service..*.find*(..))" +
            ")")
    public void readPointcut() {
    }
    @Pointcut("@annotation(com.ask.student.interceptor.annotation.Master) " +
            "|| execution(* com.ask.student.service..*.insert*(..)) " +
            "|| execution(* com.ask.student.service..*.clean*(..)) " +
            "|| execution(* com.ask.student.service..*.reset*(..)) " +
            "|| execution(* com.ask.student.service..*.add*(..)) " +
            "|| execution(* com.ask.student.service..*.update*(..)) " +
            "|| execution(* com.ask.student.service..*.edit*(..)) " +
            "|| execution(* com.ask.student.service..*.delete*(..)) " +
            "|| execution(* com.ask.student.service..*.remove*(..))")
    public void writePointcut() {
    }
    @Before("readPointcut()")
    public void read() {
        DBContextHolder.slave();
    }
    @Before("writePointcut()")
    public void write() {
        DBContextHolder.master();
    }
    @After("readPointcut()||writePointcut()")
    public void afterSwitchDS(){
        DBContextHolder.clearDB();
    }
}

以上最后一個(gè)方法的作用，在攔截器中獲取后及時(shí)清除避免導(dǎo)致來回切換當(dāng)前線程變量延遲問題導(dǎo)致某些操作的數(shù)據(jù)源錯(cuò)誤

DBContextHolder.clearDB();

@After("readPointcut()||writePointcut()")

public void afterSwitchDS(){

DBContextHolder.clearDB();

}

2、mybatis-plus的實(shí)現(xiàn)方式

這個(gè)方式配置簡(jiǎn)單，代碼少，很多事情mybatis-plus都已經(jīng)做好了，推薦使用

yml配置如下

  datasource:
    dynamic:
      primary: master  #設(shè)置默認(rèn)的數(shù)據(jù)源或者數(shù)據(jù)源組,默認(rèn)值即為master
      strict: false #設(shè)置嚴(yán)格模式,默認(rèn)false不啟動(dòng). 啟動(dòng)后在未匹配到指定數(shù)據(jù)源時(shí)候會(huì)拋出異常,不啟動(dòng)則使用默認(rèn)數(shù)據(jù)源.
      datasource:
        master:
          url: jdbc:mysql://xxx:3306/db0?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&useSSL=false&zeroDateTimeBehavior=convertToNull&serverTimezone=Asia/Shanghai
          username: admin
          password: 123456
          driver-class-name: com.mysql.cj.jdbc.Driver
          type: com.zaxxer.hikari.HikariDataSource
          hikari:
            minimum-idle: 5
            maximum-pool-size: 15
            auto-commit: true
            idle-timeout: 30000
            pool-name: springHikariCP
            max-lifetime: 1800000
            connection-timeout: 30000
            connection-test-query: SELECT 1
        slave1:
          url: jdbc:mysql://xxx:3306/db2?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&useSSL=false&zeroDateTimeBehavior=convertToNull&serverTimezone=Asia/Shanghai
          username: admin
          password: 123456
          driver-class-name: com.mysql.cj.jdbc.Driver
          type: com.zaxxer.hikari.HikariDataSource
          hikari:
            minimum-idle: 5
            maximum-pool-size: 15
            auto-commit: true
            idle-timeout: 30000
            pool-name: springHikariCP
            max-lifetime: 1800000
            connection-timeout: 30000
            connection-test-query: SELECT 1
        slave2:
          url: jdbc:mysql://xxx:3306/db3?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&useSSL=false&zeroDateTimeBehavior=convertToNull&serverTimezone=Asia/Shanghai
          username: admin
          password: 123456
          driver-class-name: com.mysql.cj.jdbc.Driver
          type: com.zaxxer.hikari.HikariDataSource
          hikari:
            minimum-idle: 5
            maximum-pool-size: 15
            auto-commit: true
            idle-timeout: 30000
            pool-name: springHikariCP
            max-lifetime: 1800000
            connection-timeout: 30000
            connection-test-query: SELECT 1

使用起來非常簡(jiǎn)單，只需要加上這個(gè)master的注解即可

    @Override
    @DS("master")
    public DestMedia getOneByCodeFromEpg(String code) {
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.eq("code", code);
        return super.getOne(queryWrapper);
    }