shardindjdbc-hint策略

HintShardingStrategy
不需要分片键的强制分片策略。这个分片策略，简单来理解就是说，他的分片键不再跟SQL语句相关联，而是用程序另行指定。对于一些复杂的情况，例如select count(*) from (select userid from t_user where userid in (1,3,5,7,9))这样的SQL语句，就没法通过SQL语句来指定一个分片键。这个时候就可以通过程序，给他另行执行一个分片键，例如在按userid奇偶分片的策略下，可以指定
1作为分片键，然后自行指定他的分片策略。
配置参数：hint.algorithm-class-name 分片算法实现类。
sql和源码
https://gitee.com/zhangjijige/shardingjdbc.git
配置文件

spring:
  main:
    allow-bean-definition-overriding: true
  shardingsphere:
    # 参数配置，显示 sql
    props:
      sql:
        show: true
    datasource:
      # 数据源别名
      names: db0, db1, db2, db3
      # db0数据源信息
      db0:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/order_db_0?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
        username: root
        password: root
      db1:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/order_db_1?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
        username: root
        password: root
      db2:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/order_db_2?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
        username: root
        password: root
      db3:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/order_db_3?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
        username: root
        password: root
    sharding:
      default-database-strategy:
        hint:
          algorithm-class-name: com.example.shardingjdbc.sharding.algorithm.HintShardingTableAlgorithm
      tables:
        # 逻辑表名
        tbl_order:
          # 指定数据节点
          actual-data-nodes: db$->{0..3}.tbl_order_$->{0..3}
          # 分库策略
          database-strategy:
            hint:
              algorithm-class-name: com.example.shardingjdbc.sharding.algorithm.HintShardingDataBaseKeyAlgorithm
          # 分表策略
          table-strategy:
            hint:
              algorithm-class-name: com.example.shardingjdbc.sharding.algorithm.HintShardingTableKeyAlgorithm

mybatis:
  mapper-locations: classpath:mapper/*.xml

HintShardingDataBaseKeyAlgorithm 分库策略

public class HintShardingDataBaseKeyAlgorithm implements HintShardingAlgorithm {
 
    /**
     * 自定义Hint 实现算法
     * 能够保证绕过Sharding-JDBC SQL解析过程
     * @param availableTargetNames
     * @param shardingValue 不再从SQL 解析中获取值，而是直接通过hintManager.addTableShardingValue("t_order", 1)参数指定
     * @return
     */
    @Override
    public Collection doSharding(Collection availableTargetNames, HintShardingValue shardingValue){
        System.out.println(shardingValue.toString());
         return Lists.newArrayList("db0");
    }
}

HintShardingTableKeyAlgorithm 分表策略

public class HintShardingTableKeyAlgorithm implements HintShardingAlgorithm {
 
    /**
     * 自定义Hint 实现算法
     * 能够保证绕过Sharding-JDBC SQL解析过程
     * @param availableTargetNames
     * @param shardingValue 不再从SQL 解析中获取值，而是直接通过hintManager.addTableShardingValue("t_order", 1)参数指定
     * @return
     */
    @Override
    public Collection doSharding(Collection availableTargetNames, HintShardingValue shardingValue){
        System.out.println(shardingValue.toString());
         return Lists.newArrayList(shardingValue.getLogicTableName()+"_0");
    }
}

数据查询示例

    public void getOrderHint(){
//hint的策略规则是通过ThreadLocal方式,通过线程传递参数
//首先将上一次策略删除掉
        HintManager.clear();
//创建instance 
        HintManager instance = HintManager.getInstance();
//不管是分库还是分表第一个参数都要是表的名称
        instance.addDatabaseShardingValue("tbl_order","1");
        instance.addTableShardingValue("tbl_order","2");
        Long orderId = 1418875911339507713L;
        OrderDto queryOrderDto = new OrderDto();
        queryOrderDto.setOrderId(orderId);
        List orderDtoList = orderMapper.getOrdersComplex(queryOrderDto);
        System.out.println(orderDtoList.toString());
//删除策略
        instance.close();
    }

Hint的特点就是不在需要依赖sql了,首先确定要分哪个表,比如这里是tbl_order表,去配置文件中查找tbl_order的配置,分库分表个子的algorithm-class-name