SpringBoot+Mybatis-Plus实现mysql读写分离方案的示例代码

1. 引入mybatis-plus相关包，pom.xml文件

2. 配置文件application.property增加多库配置

mysql 数据源配置

spring . datasource . primary . jdbc - url = jdbc : mysql : //xx.xx.xx.xx:3306/portal?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC&characterEncoding=utf8&serverTimezone=GMT%2B8 spring . datasource . primary . username = root spring . datasource . primary . password = root spring . datasource . primary . driver - class - name = com . mysql . cj . jdbc . Driver #mysql slave 数据源配置   spring . datasource . slave . jdbc - url = jdbc : mysql : //xx.xx.xx.xx:3306/portal?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC&characterEncoding=utf8&serverTimezone=GMT%2B8 spring . datasource . slave . username = root spring . datasource . slave . password = root spring . datasource . slave . driver - class - name = com . mysql . cj . jdbc . Driver

3. 配置数据源及注解

数据源配置 MultiDataSourceConfig.Java

/** * 配置多数据源 */ @Profile ( "dev" ) //开发模式配置文件 @Configuration @MapperScan ( basePackages = "com.csc.portal.mapper" ) //扫描包 public class MultiDataSourceConfig {   /** * 主数据源 * @return */ @Bean @ConfigurationProperties ( prefix = "spring.datasource.primary" ) public DataSource masterDataSource () { return DataSourceBuilder . create (). build (); }   /** * 从数据源 * @return */ @Bean @ConfigurationProperties ( prefix = "spring.datasource.slave" ) public DataSource slaveDataSource () { return DataSourceBuilder . create (). build (); }   /** * 路由数据源，前面两个数据源是为了创建此数据源 * @param masterDataSource 主数据源 * @param slaveDataSource 从数据源 * @return */ @Bean public DataSource myRoutingDataSource ( @Qualifier ( "masterDataSource" ) DataSource masterDataSource , @Qualifier ( "slaveDataSource" ) DataSource slaveDataSource ) { Map < Object , Object > targetDataSources = new HashMap <>(); targetDataSources . put ( DBTypeEnum . MASTER , masterDataSource ); targetDataSources . put ( DBTypeEnum . SLAVE , slaveDataSource ); MyRoutingDataSource myRoutingDataSource = new MyRoutingDataSource (); myRoutingDataSource . setDefaultTargetDataSource ( slaveDataSource ); //设置默认数据源 myRoutingDataSource . setTargetDataSources ( targetDataSources ); //设置路由表，使用map的key，value方式得到对应数据源 return myRoutingDataSource ; }

数据库枚举类

public enum DBTypeEnum { MASTER , SLAVE ; }

注解

@Target ({ ElementType . METHOD }) @Retention ( RetentionPolicy . RUNTIME ) public @interface Master { } @Target ({ ElementType . METHOD }) @Retention ( RetentionPolicy . RUNTIME ) public @interface Slave { }

4. Mybatis-plus配置

@EnableTransactionManagement @Configuration @MapperScan ( basePackages = "com.csc.portal.mapper" ) public class MybatisPlusConfig { /** * 分页插件 */ @Bean public PaginationInterceptor paginationInterceptor () { return new PaginationInterceptor (); }   @Resource ( name = "myRoutingDataSource" ) private DataSource myRoutingDataSource ; /** * 使用MyBatis Plus的sqlSessionFactory代替， * 此处注意mybatis与mybatisPlus的配置不同，不然扫描不到对数据操作的方法。会报未绑定错误 * @return sqlSessionFactory * @throws Exception */ @Bean public SqlSessionFactory sqlSessionFactory () throws Exception { MybatisSqlSessionFactoryBean sqlSessionFactoryBean = new MybatisSqlSessionFactoryBean (); sqlSessionFactoryBean . setDataSource ( myRoutingDataSource ); sqlSessionFactoryBean . setMapperLocations ( new PathMatchingResourcePatternResolver (). getResources ( "classpath:mapper/*.xml" )); MybatisConfiguration mybatisConfiguration = new MybatisConfiguration (); sqlSessionFactoryBean . setConfiguration ( mybatisConfiguration ); return sqlSessionFactoryBean . getObject (); }   /** * 此处为使用mybatis时的sqlsessionFactory配置 * @return * @throws Exception */ /* @Bean public SqlSessionFactory sqlSessionFactory() throws Exception { SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean(); sqlSessionFactoryBean.setDataSource(myRoutingDataSource); sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml")); return sqlSessionFactoryBean.getObject(); } */   /** * 事务配置 * @return 事务管理器 */ @Bean public DataSourceTransactionManager transactionManager () { DataSourceTransactionManager tx = new DataSourceTransactionManager (); tx . setDataSource ( myRoutingDataSource ); return tx ; }

5. 增加数据源管理类

DBContextHolder.java

public class DBContextHolder {   /** * 外部一个请求将会产生一个线程与之对应，每个线程的变量可用ThreadLocal进行存储 */ private static final ThreadLocal < DBTypeEnum > contextHolder = new ThreadLocal <>();   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 ( "切换到master" ); }   public static void slave () { set ( DBTypeEnum . SLAVE ); System . out . println ( "切换到slave" ); }   }

指定选择数据源

MyRoutingDataSource.java 方法determineCurrentLookupKey决定最终使用哪个数据源进行操作，若为空则使用默认数据源。

public class MyRoutingDataSource extends AbstractRoutingDataSource { @Nullable @Override protected Object determineCurrentLookupKey () { System . out . println ( "线程名：" + Thread . currentThread (). getName ()+ ":" + DBContextHolder . get ()); return DBContextHolder . get (); /* if (DBContextHolder.get() != null) { System.out.println("线程名："+Thread.currentThread().getName()+":"+DBContextHolder.get()); return DBContextHolder.get(); } else { System.out.println("未匹配到指定数据库,默认切换到Master"); return DBTypeEnum.MASTER; }*/ //return DBContextHolder.get(); }   }

6. 增加aop切面

@Aspect @Component @Order ( 0 ) //配置注解优先级，优于事物注解@Transactional先进行数据源切换， //不然在事物中进行数据源切换无效 public class DataSourceAop {   @Pointcut ( /*"!@annotation(com.csc.portal.annotation.Master) " + "&& (execution(* com.csc.portal.service..*.select*(..)) " + "|| execution(* com.csc.portal.service..*.get*(..))"+*/ " @annotation(com.csc.portal.annotation.Slave)" ) public void readPointcut () {   }   @Pointcut ( "@annotation(com.csc.portal.annotation.Master) " //+ /* "|| execution(* com.csc.portal.service..*.insert*(..)) " + "|| execution(* com.csc.portal.service..*.add*(..)) " + "|| execution(* com.csc.portal.service..*.update*(..)) " + "|| execution(* com.csc.portal.service..*.edit*(..)) " + "|| execution(* com.csc.portal.service..*.delete*(..)) " + "|| execution(* com.csc.portal.service..*.remove*(..))"*/ ) public void writePointcut () {   }   @Before ( "readPointcut()" ) public void read () { //获取拦截类 DBContextHolder . slave (); System . out . println ( Thread . currentThread (). getName ()+ DBContextHolder . get ()); }   @Before ( "writePointcut()" ) public void write () { //获取拦截类 /* String className = pjp.getTarget().getClass().getName(); System.out.println("当前线程"+Thread.currentThread().getName()+" 拦截类为：" + className);   //获取拦截的方法名 MethodSignature msig = (MethodSignature) pjp.getSignature(); Method currentMethod = null; try { currentMethod = pjp.getTarget().getClass().getMethod(msig.getName(), msig.getParameterTypes()); } catch (NoSuchMethodException e) { e.printStackTrace(); } String methodName = currentMethod.getName(); System.out.println("拦截方法名为：" + methodName);*/ DBContextHolder . master (); System . out . println ( Thread . currentThread (). getName ()+ DBContextHolder . get ()); } }

6. 实际应用

在service层方法前增加注解@Master表示使用主库，进行增删改的操作使用主库。 在service层方法前增加注解@Slave表示使用从库，进行查的操作使用从库，默认使用从库，可不配置。 @ Transactional注解加到service层，增加了@Transactional注解后，启用事务后，一个事务内部的connection是复用的，所以就算AOP切了数据源字符串，但是数据源并不会被真正修改。所以@Transactional注解不要写在controller层，不然在service层也切换不了数据源。 @Transactional与@Master可同时使用，已经配置@Master注解的优先级较高，先切换数据源后执行事务。

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原文链接：https://blog.csdn.net/AAAAABBBBBYYYYY/article/details/110875245

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