怎么用SpringBoot + Mybatis多数据源配置实现读写分离

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应用场景：项目中有一些报表统计与查询功能，对数据实时性要求不高，因此考虑对报表的统计与查询去操作slave db，减少对master的压力。

根据网上多份资料测试发现总是使用master数据源，无法切换到slave，经过多次调试修改现已完美通过，现整理下详细步骤和完整代码如下：

实现方式：配置多个数据源，使用Spring AOP实现拦截注解实现数据源的动态切换。

1. application.yml数据库配置：

druid:  type: com.alibaba.druid.pool.DruidDataSource  master:    url: jdbc:mysql://127.0.0.1:3306/test?characterEncoding=UTF-8&autoReconnect=true&zeroDateTimeBehavior=convertToNull&useUnicode=true    driver-class-name: com.mysql.jdbc.Driver    username: test    password: 123    initial-size: 5    max-active: 10    min-idle: 5    max-wait: 60000    time-between-eviction-runs-millis: 3000    min-evictable-idle-time-millis: 300000    validation-query: SELECT 'x' FROM DUAL    test-while-idle: true    test-on-borrow: true    test-on-return: false    filters: stat,wall,log4j2  slave:    url: jdbc:mysql://127.0.0.1:3307/test?characterEncoding=UTF-8&autoReconnect=true&zeroDateTimeBehavior=convertToNull&useUnicode=true    driver-class-name: com.mysql.jdbc.Driver    username: test    password: 123    initial-size: 5    max-active: 10    min-idle: 5    max-wait: 60000    time-between-eviction-runs-millis: 3000    min-evictable-idle-time-millis: 300000    validation-query: SELECT 'x' FROM DUAL    test-while-idle: true    test-on-borrow: true    test-on-return: false    filters: stat,wall,log4j2

2. 通过MybatisAutoConfiguration实现多数据源注入:

@Configuration@EnableTransactionManagementpublic class DataSourceConfiguration extends MybatisAutoConfiguration {    @Value("${druid.type}")    private Class dataSourceType;    @Bean(name = "masterDataSource")    @Primary    @ConfigurationProperties(prefix = "druid.master")    public DataSource masterDataSource(){        return DataSourceBuilder.create().type(dataSourceType).build();    }    @Bean(name = "slaveDataSource")    @ConfigurationProperties(prefix = "druid.slave")    public DataSource slaveDataSource(){        return DataSourceBuilder.create().type(dataSourceType).build();    }    @Bean    @Override    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {        return super.sqlSessionFactory(dataSource());    }    @Bean(name = "dataSource")    public AbstractRoutingDataSource dataSource() {        MasterSlaveRoutingDataSource proxy = new MasterSlaveRoutingDataSource();        Map targetDataResources = new HashMap<>();        targetDataResources.put(DbContextHolder.DbType.MASTER, masterDataSource());        targetDataResources.put(DbContextHolder.DbType.SLAVE, slaveDataSource());        proxy.setDefaultTargetDataSource(masterDataSource());        proxy.setTargetDataSources(targetDataResources);        proxy.afterPropertiesSet();        return proxy;    }}

3. 基于 AbstractRoutingDataSource 和 AOP 的多数据源的配置

我们自己定义一个DataSource类，来继承 AbstractRoutingDataSource：

public class MasterSlaveRoutingDataSource extends AbstractRoutingDataSource {    @Override    protected Object determineCurrentLookupKey() {        return DbContextHolder.getDbType();    }}

这里通过determineCurrentLookupKey（）返回的不同key到sqlSessionFactory中获取对应数据源然后使用ThreadLocal来存放线程的变量，将不同的数据源标识记录在ThreadLocal中

public class DbContextHolder {    public enum DbType{        MASTER, SLAVE    }    private static final ThreadLocal contextHolder = new ThreadLocal<>();    public static void setDbType(DbType dbType){        if (dbType==null) {            throw new NullPointerException();        }        contextHolder.set(dbType);    }    public static DbType getDbType(){        return contextHolder.get()==null?DbType.MASTER:contextHolder.get();    }    public static void clearDbType(){        contextHolder.remove();    }}

4. 注解实现

@Target({ElementType.METHOD, ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)public @interface ReadOnlyConnection {}@Aspect@Componentpublic class ReadOnlyConnectionInterceptor implements Ordered {    @Around("@annotation(readOnlyConnection)")    public Object proceed(ProceedingJoinPoint proceedingJoinPoint, ReadOnlyConnection readOnlyConnection) throws Throwable {        try {            DbContextHolder.setDbType(DbContextHolder.DbType.SLAVE);            Object result = proceedingJoinPoint.proceed();            return result;        }finally {            DbContextHolder.clearDbType();        }    }    @Override    public int getOrder() {        return 0;    }}

5. 应用方式：

service层接口增加ReadOnlyConnection注解即可：

@ReadOnlyConnectionpublic CommonPagingVOpagingByCondition(GroupGoodsCondition condition, int pageNum, int pageSize) {   Page page = PageHelper.startPage(pageNum, pageSize).doSelectPage(() -> groupGoodsMapper.listByCondition(condition));    return CommonPagingVO.get(page,page.getResult()); }

对于未加ReadOnlyConnection注解的默认使用masterDataSource。

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