朗讀SpringBoot + MyBatis + MySQL讀寫分離實踐！第SpringBoot + MyBatis + MySQL讀寫分離實踐！

《SpringBoot + MyBatis + MySQL讀寫分離實踐！》
酷扯兒《酷扯兒》官方帳號2.  AbstractRoutingDataSource基於特定的查找key路由到特定的數據源。它內部維護了一組目標數據源，並且做了路由key與目標數據源之間的映射，提供基於key查找數據源的方法。
3.  實踐3.1.  maven依賴<?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>com.cjs.example</groupId>    <artifactId>cjs-datasource-demo</artifactId>    <version>0.0.1-SNAPSHOT</version>    <packaging>jar</packaging>    <name>cjs-datasource-demo</name>    <description></description>    <parent>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-parent</artifactId>        <version>2.0.5.RELEASE</version>        <relativePath/>     </parent>    <properties>        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>        <java.version>1.8</java.version>    </properties>    <dependencies>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-aop</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-jdbc</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>        <dependency>            <groupId>org.mybatis.spring.boot</groupId>            <artifactId>mybatis-spring-boot-starter</artifactId>            <version>1.3.2</version>        </dependency>        <dependency>            <groupId>org.apache.commons</groupId>            <artifactId>commons-lang3</artifactId>            <version>3.8</version>        </dependency>        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <scope>runtime</scope>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>            <scope>test</scope>        </dependency>    </dependencies>    <build>        <plugins>            <plugin>                <groupId>org.springframework.boot</groupId>                <artifactId>spring-boot-maven-plugin</artifactId>            </plugin>                    </plugins>    </build></project>3.2.  數據源配置application.ymlspring:datasource:    master:      jdbc-url: jdbc:mysql://192.168.102.31:3306/test      username: root      password: 123456      driver-class-name: com.mysql.jdbc.Driver    slave1:      jdbc-url: jdbc:mysql://192.168.102.56:3306/test      username: pig   # 只讀賬戶      password: 123456      driver-class-name: com.mysql.jdbc.Driver    slave2:      jdbc-url: jdbc:mysql://192.168.102.36:3306/test      username: pig   # 只讀賬戶      password: 123456      driver-class-name: com.mysql.jdbc.Driver多數據源配置package com.cjs.example.config;import com.cjs.example.bean.MyRoutingDataSource;import com.cjs.example.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 javax.sql.DataSource;import java.util.HashMap;import java.util.Map;/*** 關於數據源配置，參考SpringBoot官方文檔第79章《Data Access》 * 79. Data Access * 79.1 Configure a Custom DataSource * 79.2 Configure Two DataSources */@Configurationpublic 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    @ConfigurationProperties("spring.datasource.slave2")    public DataSource slave2DataSource() {        return DataSourceBuilder.create().build();    }    @Bean    public DataSource myRoutingDataSource(@Qualifier("masterDataSource") DataSource masterDataSource,                                          @Qualifier("slave1DataSource") DataSource slave1DataSource,                                          @Qualifier("slave2DataSource") DataSource slave2DataSource) {        Map<Object, Object> targetDataSources = new HashMap<>();        targetDataSources.put(DBTypeEnum.MASTER, masterDataSource);        targetDataSources.put(DBTypeEnum.SLAVE1, slave1DataSource);        targetDataSources.put(DBTypeEnum.SLAVE2, slave2DataSource);        MyRoutingDataSource myRoutingDataSource = new MyRoutingDataSource();        myRoutingDataSource.setDefaultTargetDataSource(masterDataSource);        myRoutingDataSource.setTargetDataSources(targetDataSources);        return myRoutingDataSource;    }}這裏，我們配置了4個數據源，1個master，2兩個slave，1個路由數據源。前3個數據源都是為了生成第4個數據源，而且後續我們只用這最後一個路由數據源。MyBatis配置package com.cjs.example.config;import org.apache.ibatis.session.SqlSessionFactory;import org.mybatis.spring.SqlSessionFactoryBean;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.core.io.support.PathMatchingResourcePatternResolver;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;@EnableTransactionManagement@Configurationpublic class MyBatisConfig {@Resource(name = "myRoutingDataSource")    private DataSource myRoutingDataSource;    @Bean    public SqlSessionFactory sqlSessionFactory() throws Exception {        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();        sqlSessionFactoryBean.setDataSource(myRoutingDataSource);        sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml"));        return sqlSessionFactoryBean.getObject();    }    @Bean    public PlatformTransactionManager platformTransactionManager() {        return new DataSourceTransactionManager(myRoutingDataSource);    }}由於Spring容器中現在有4個數據源，所以我們需要為事務管理器和MyBatis手動指定一個明確的數據源。3.3 設置路由key / 查找數據源目標數據源就是那前3個這個我們是知道的，但是使用的時候是如果查找數據源的呢？首先，我們定義一個枚舉來代表這三個數據源package com.cjs.example.enums;public enum DBTypeEnum {MASTER, SLAVE1, SLAVE2;}接下來，通過ThreadLocal將數據源設置到每個線程上下文中package com.cjs.example.bean;import com.cjs.example.enums.DBTypeEnum;import java.util.concurrent.atomic.AtomicInteger;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);        System.out.println("切換到master");    }    public static void slave() {        //  輪詢        int index = counter.getAndIncrement() % 2;        if (counter.get() > 9999) {            counter.set(-1);        }        if (index == 0) {            set(DBTypeEnum.SLAVE1);            System.out.println("切換到slave1");        }else {            set(DBTypeEnum.SLAVE2);            System.out.println("切換到slave2");        }    }}獲取路由keypackage com.cjs.example.bean;import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;import org.springframework.lang.Nullable;public class MyRoutingDataSource extends AbstractRoutingDataSource {@Nullable    @Override    protected Object determineCurrentLookupKey() {        return DBContextHolder.get();    }}設置路由key默認情況下，所有的查詢都走從庫，插入/修改/刪除走主庫。我們通過方法名來區分操作類型（CRUD）package com.cjs.example.aop;import com.cjs.example.bean.DBContextHolder;import org.apache.commons.lang3.StringUtils;import org.aspectj.lang.JoinPoint;import org.aspectj.lang.annotation.Aspect;import org.aspectj.lang.annotation.Before;import org.aspectj.lang.annotation.Pointcut;import org.springframework.stereotype.Component;@Aspect@Componentpublic class DataSourceAop {@Pointcut("!@annotation(com.cjs.example.annotation.Master) " +            "&& (execution(* com.cjs.example.service..*.select*(..)) " +            "|| execution(* com.cjs.example.service..*.get*(..)))")    public void readPointcut() {    }    @Pointcut("@annotation(com.cjs.example.annotation.Master) " +            "|| execution(* com.cjs.example.service..*.insert*(..)) " +            "|| execution(* com.cjs.example.service..*.add*(..)) " +            "|| execution(* com.cjs.example.service..*.update*(..)) " +            "|| execution(* com.cjs.example.service..*.edit*(..)) " +            "|| execution(* com.cjs.example.service..*.delete*(..)) " +            "|| execution(* com.cjs.example.service..*.remove*(..))")    public void writePointcut() {    }    @Before("readPointcut()")    public void read() {        DBContextHolder.slave();    }    @Before("writePointcut()")    public void write() {        DBContextHolder.master();    }    /**     * 另一種寫法：ifelse  判斷哪些需要讀從數據庫，其餘的走主數據庫     *///    @Before("execution(* com.cjs.example.service.impl.*.*(..))")//    public void before(JoinPoint jp) {//        String methodName = jp.getSignature().getName();////        if (StringUtils.startsWithAny(methodName, "get", "select", "find")) {//            DBContextHolder.slave();//        }else {//            DBContextHolder.master();//        }//    }}有一般情況就有特殊情況，特殊情況是某些情況下我們需要強制讀主庫，針對這種情況，我們定義一個主鍵，用該注解標注的就讀主庫package com.cjs.example.annotation;public @interface Master {}例如，假設我們有一張表memberpackage com.cjs.example.service.impl;import com.cjs.example.annotation.Master;import com.cjs.example.entity.Member;import com.cjs.example.entity.MemberExample;import com.cjs.example.mapper.MemberMapper;import com.cjs.example.service.MemberService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import org.springframework.transaction.annotation.Transactional;import java.util.List;@Servicepublic class MemberServiceImpl implements MemberService {@Autowired    private MemberMapper memberMapper;    @Transactional    @Override    public int insert(Member member) {        return memberMapper.insert(member);    }    @Master    @Override    public int save(Member member) {        return memberMapper.insert(member);    }    @Override    public List<Member> selectAll() {        return memberMapper.selectByExample(new MemberExample());    }    @Master    @Override    public String getToken(String appId) {        //  有些讀操作必須讀主數據庫        //  比如，獲取微信access_token，因為高峰時期主從同步可能延遲        //  這種情況下就必須強制從主數據讀        return null;    }}4.  測試package com.cjs.example;import com.cjs.example.entity.Member;import com.cjs.example.service.MemberService;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.test.context.junit4.SpringRunner;@RunWith(SpringRunner.class)@SpringBootTestpublic class CjsDatasourceDemoApplicationTests {@Autowired    private MemberService memberService;    @Test    public void testWrite() {        Member member = new Member();        member.setName("zhangsan");        memberService.insert(member);    }    @Test    public void testRead() {        for (int i = 0; i < 4; i++) {            memberService.selectAll();        }    }    @Test    public void testSave() {        Member member = new Member();        member.setName("wangwu");        memberService.save(member);    }    @Test    public void testReadFromMaster() {        memberService.getToken("1234");    }}查看控制台
5.  工程結構
6.  參考https://www.jianshu.com/p/f2f4256a2310http://www.cnblogs.com/gl-developer/p/6170423.htmlhttps://www.cnblogs.com/huangjuncong/p/8576935.htmlhttps://blog.csdn.net/liu976180578/article/details/77684583
《SpringBoot + MyBatis + MySQL讀寫分離實踐！》完，請繼續朗讀精采文章。
喜歡 小編的世界 e4to.com，請記得按讚、收藏及分享！