【Java】自动获取某表某列的最大ID数

使用场景：

当需要往数据库插入数据时，表的主键需要接着已经有的数据后面进行自增。比如已经wq_customer表里，主键为TBL_ID，如果是空表，那么插入的数据TBL_ID设置为1，如果已经有n条数据，那么插入的数据TBL_ID设置为n+1。

SQL语句为

SELECT
    CASE
WHEN MAX(TBL_ID) IS NULL THEN
    1
ELSE
    MAX(TBL_ID) + 1
END AS MAXID
FROM
    wq_customer
WHERE
    TBL_ID < 100000

单纯查询某表某列MAX为：

SELECT
    MAX(TBL_ID)
FROM
    wq_customer
WHERE
    TBL_ID < 100000;

mybatis的相关代码如下（仅供参考）：

调用代码如下：

 package com.msk.batch.wq.logic;

 import com.msk.batch.wq.bean.BWQ201701Bean;
 import com.msk.batch.wq.bean.BWQ201701Bean2;
 import com.msk.batch.wq.bean.BWQ201701Bean3;
 import com.msk.common.logic.CommonLogic;
 import com.msk.core.base.BaseDao;
 import com.msk.core.base.BaseLogic;
 import com.msk.core.bean.BaseParam;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;

 import java.util.List;

 /**
  * Created by fjm on 2017/1/9.
  */
 public class BWQ201701Logic extends BaseLogic{

     private static Logger logger = LoggerFactory.getLogger(BWQ201701Logic.class);

     public interface SqlId {
         static final String SQLID_INSERT_OMSDATA = "insertCmCustomer";
     }

     @Autowired
     @Override
     public void setBaseDao(BaseDao baseDao) {
         super.setBaseDao(baseDao);
     }
     @Autowired
     CommonLogic commonLogic;

     public void insertCmCustomer(List<BWQ201701Bean3> bwq201701BeanList){

         for(BWQ201701Bean3 bwq201701Beans:bwq201701BeanList){
             BWQ201701Bean bwq201701Bean = new BWQ201701Bean();
             long id=commonLogic.maxId("WQ_CUSTOMER","TBL_ID");
             bwq201701Bean.setTblId(id);
             bwq201701Bean.setCmId(bwq201701Beans.getCm_id());
             bwq201701Bean.setCmName(bwq201701Beans.getCm_name());
             bwq201701Bean.setCmCode(bwq201701Beans.getCm_code());
             bwq201701Bean.setCmType(bwq201701Beans.getCm_type());
             bwq201701Bean.setCmManager(bwq201701Beans.getCm_manager());
             super.save(SqlId.SQLID_INSERT_OMSDATA, bwq201701Bean);
         }
     }

 }

共通代码如下：

 package com.msk.common.logic;

 import java.util.List;

 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;

 import com.msk.core.base.BaseDao;
 import com.msk.core.base.BaseLogic;
 import com.msk.core.bean.BaseParam;

 /**
  * CommonLogic
  *
  * @author fjm
  * @version 1.0
  **/
 @Service("commonLogic")
 public class CommonLogic extends BaseLogic {
     /**
      * logger
      */
     private static Logger logger = LoggerFactory.getLogger(CommonLogic.class);

     /**
      * SQL Id
      */
     interface SqlId {
         /** 获得最大Max Id */
         String SQL_ID_MAX_ID = "maxId";
     }

     /**
      * 获得Max Id
      *
      * @param tableName 表名
      * @param tableFiled 字段名称
      * @return Max Id
      */
     @Transactional(readOnly = true)
     public Long maxId(String tableName, String tableFiled) {
         logger.debug("获得Max Id");
         BaseParam param = new BaseParam();
         param.setFilter("tableName", tableName);
         param.setFilter("tableFiled", tableFiled);
         return (Long) super.findObject(SqlId.SQL_ID_MAX_ID, param);
     }

     @Autowired
     @Override
     public void setBaseDao(BaseDao baseDao) {
         super.setBaseDao(baseDao);
     }
 }

xml代码如下：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.msk.common.logic.CommonLogic">
    <sql id="maxIdSql">
        SELECT
              CASE
              WHEN MAX(${filterMap.tableFiled}) IS NULL THEN 1
              ELSE MAX(${filterMap.tableFiled})+1 END AS MAXID
        FROM ${filterMap.tableName}
        WHERE ${filterMap.tableFiled} <![CDATA[<]]> 100000
    </sql>
    <select id="maxId" parameterType="BaseParam" resultType="java.lang.Long">
        <include refid="maxIdSql"/>
    </select>
</mapper>