Spring-Mybatis读写分离笔记整理

1. 编写Spring动态数据源实现类

   public class ReadWriteDataSource extends AbstractRoutingDataSource {
       @Nullable
       @Override
       protected Object determineCurrentLookupKey() {
           return DsTypeHolder.get().getCode();
       }
   }
   

2. 编写Mybatis拦截器切换数据源

   @Intercepts({
      @Signature(type = Executor.class, method = "update",
              args = {MappedStatement.class, Object.class}),
      @Signature(type = Executor.class, method = "query",
              args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
      @Signature(type = Executor.class, method = "query",
              args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class, CacheKey.class, BoundSql.class})
   })
   public class DynamicDataSourceInterceptor implements Interceptor {
       private static final String REGEX = ".*insert\\u0020.*|.*delete\\u0020.*|.*update\\u0020.*" ;
       @Override
       public Object intercept(Invocation invocation) throws Throwable {
           boolean transactionActive = TransactionSynchronizationManager.isActualTransactionActive();
           DsType dsType = DsType.MASTER;
           if (!transactionActive){
               Object[] args = invocation.getArgs();
               MappedStatement ms = (MappedStatement) args[0] ;
               if (ms.getSqlCommandType().equals(SqlCommandType.SELECT)){
                   // 如果selectKey为自增id查询主键，使用主库
                   if (ms.getId().contains(SelectKeyGenerator.SELECT_KEY_SUFFIX)){
                       dsType = DsType.MASTER;
                   }else {
                       BoundSql boundSql = ms.getSqlSource().getBoundSql(args[1]);
                       String sql = boundSql.getSql().toLowerCase(Locale.CHINA).replaceAll("[\\t\\n\\r]]", "");
                       // 如果是更新操作则切换到主库
                       if (sql.matches(REGEX)){
                           dsType = DsType.MASTER;
                       }else {
                           // 非更新操作则使用从库
                           dsType = DsType.SLAVE;
                       }
                   }
               }
           }else {
               dsType = DsType.MASTER;
           }
           DsTypeHolder.set(dsType);
           return invocation.proceed();
       }
       @Override
       public Object plugin(Object target) {
           if (target instanceof Executor){
               return Plugin.wrap(target, this);
           }
           return target ;
       }
   }
   

3. 数据源切换工具类

   @Getter
   public enum DsType {
       MASTER("master"),
       SLAVE("slave");
   
       private final String code ;
   
       DsType(String code){
           this.code = code ;
       }
   }
   public class DsTypeHolder {
       private static ThreadLocal<DsType> dsTypeThreadLocal = new ThreadLocal<>();
   
       public static void set(DsType dsType) {
           dsTypeThreadLocal.set(dsType);
       }
   
       public static DsType get() {
           if (dsTypeThreadLocal.get() == null){
               return DsType.MASTER ;
           }
           return dsTypeThreadLocal.get();
       }
   
       public static void clear() {
           dsTypeThreadLocal.remove();
       }
   }
   

4. 编写数据源配置

   spring:
     application:
       name: hello-read-write-app
     jackson:
       time-zone: GMT+8
     datasource:
       master:
         driver-class-name: com.mysql.cj.jdbc.Driver
         jdbc-url: jdbc:mysql://127.0.0.1:3306/test
         username: root
         password: root
       slave:
         driver-class-name: com.mysql.cj.jdbc.Driver
         jdbc-url: jdbc:mysql://127.0.0.1:3306/test
         username: root
         password: root
   logging:
     level:
       root: info
       com.yicj.study.rw.repository.mapper: debug
   mybatis-plus:
     mapper-locations: classpath:/mapper/*Mapper.xml
   

5. 将数据源注入到spring容器中

   @Configuration
   public class DataSourceConfig {
       @Bean
       @ConfigurationProperties("spring.datasource.master")
       public DataSource masterDataSource() {
           return DataSourceBuilder.create().build();
       }
   
       @Bean
       @ConfigurationProperties("spring.datasource.slave")
       public DataSource slaveDataSource() {
           return DataSourceBuilder.create().build();
       }
   
       @Bean
       public ReadWriteDataSource readWriteDataSource(
               @Qualifier("masterDataSource") DataSource masterDataSource,
               @Qualifier("slaveDataSource") DataSource slaveDataSource) {
           Map<Object, Object> targetDataSources = new HashMap<>();
           targetDataSources.put(DsType.MASTER.getCode(), masterDataSource);
           targetDataSources.put(DsType.SLAVE.getCode(), slaveDataSource);
           //
           ReadWriteDataSource readWriteDataSource = new ReadWriteDataSource();
           readWriteDataSource.setDefaultTargetDataSource(masterDataSource);
           readWriteDataSource.setTargetDataSources(targetDataSources);
           return readWriteDataSource;
       }
   }
   

6. Mybatis-plus配置

   @Configuration
   public class MyBatisConfig {
   
       @Autowired
       private ReadWriteDataSource readWriteDataSource ;
   
       @Bean
       public SqlSessionFactory sqlSessionFactory() throws Exception {
           MybatisSqlSessionFactoryBean sqlSessionFactory = new MybatisSqlSessionFactoryBean();
           sqlSessionFactory.setDataSource(readWriteDataSource);
           MybatisConfiguration configuration = new MybatisConfiguration();
           configuration.setJdbcTypeForNull(JdbcType.NULL);
           configuration.setMapUnderscoreToCamelCase(true);
           configuration.setCacheEnabled(false);
           // 动态数据源拦截器配置
           configuration.addInterceptor(new DynamicDataSourceInterceptor());
           //如果配置多个插件,切记分页最后添加
           MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
           interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
           configuration.addInterceptor(interceptor);
           sqlSessionFactory.setConfiguration(configuration);
           return sqlSessionFactory.getObject();
       }
   
       @Bean
       public PlatformTransactionManager platformTransactionManager() {
           return new DataSourceTransactionManager(readWriteDataSource);
       }
   }