首先考慮使用快取來處理，如果快取不夠用，再使用讀寫分離來實現

application.yml配置兩個資料來源

#預設使用配置
spring:
  profiles:
    active: dev

---

#開發配置
spring:
  profiles: dev
  datasource:
    master:
      jdbc-url: jdbc:mysql://localhost:3812/test
      username: user
      password: pwd
      driver-class-name: com.mysql.jdbc.Driver
      type: com.alibaba.druid.pool.DruidDataSource
    slave:
      jdbc-url: jdbc:mysql://localhost:3812/test
      username: user
      password: pwd
      driver-class-name: com.mysql.jdbc.Driver
      type: com.alibaba.druid.pool.DruidDataSource
 

Application.java 注意Mapper上加@Mapper註解，然後可以被掃描到

@SpringBootApplication
@EnableAutoConfiguration
@MapperScan("com.xx.mobile.group.dao")
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

DataSourceConfig.java 注意有三個DataSource

@Configuration
public class DataSourceConfig {

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

    @Bean
    @ConfigurationProperties("spring.datasource.slave")
    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.SLAVE, slave1DataSource);
        DataSourceRouting myRoutingDataSource = new DataSourceRouting();
        myRoutingDataSource.setDefaultTargetDataSource(masterDataSource);
        myRoutingDataSource.setTargetDataSources(targetDataSources);
        return myRoutingDataSource;
    }

}
 

DBType

public enum DBTypeEnum {
    MASTER, SLAVE;
}

MybatisConfig 注意注入的DataSource，注意事務註解的order

@EnableTransactionManagement(order = 2)
@Configuration
public 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);
    }
}

DataSourceRouting

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

DBContextHolder

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() {
        set(DBTypeEnum.SLAVE);
        System.out.println("切換到slave");
    }

}

使用從庫註解UseSlaveDatabase

public @interface UseSlaveDatabase {
}

DataSourceAop 注意此切面的Order

@Aspect
@Component
public class DataSourceAop implements Ordered{
    @Override
    public int getOrder() {
        return 0;
    }

    @Before("readPointcut()")
    public void read() {
        DBContextHolder.slave();
    }

    @Pointcut("@annotation(com.xx.mobile.config.UseSlaveDatabase)")
    public void readPointcut() {

    }
}

測試類

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class TestTask {
    @Autowired
    private ITaskService taskService;

    @Test
	public void save() throws Exception {
		
	}
	@Test
	public void query() throws Exception {
		//query方法可以用上面的註解
	}
}

相關的service dao mapper entity沒有寫 原理：多個數據源彙集到一個數據源上（myRoutingDataSource），然後定義切面，遇到有UseSlaveDatabase註解就設定資料來源為從庫，預設使用主庫，因為myRoutingDataSource.setDefaultTargetDataSource(masterDataSource); 注意資料來源選擇要在是事務之前，所以切