mybatis主要流程和高阶用法简介

这里是引用

一、主要流程

1、通过解析两个xml文件，将他们共同变成一个configuration对象。不同的mapper.xml生成不同的configuration对象
2、通过configuration创建sessionFactory对象
3、再由sessionFactory生成sqlsession对象。它包含一组statement，可以理解为一个方法就是一个会话
4、statement是核心，一次sql语句的执行就是一个statement
5、通过两个handler将参数和结果封装进statement

二、高阶用法

（一）动态sql

主要利用@SelectProvider等注解

1、Dao类

package com.anmining.truck.dispatch.modules.report.dao;

import com.anmining.truck.dispatch.modules.report.entity.TruckReportData;
import com.anmining.truck.dispatch.modules.report.utils.MapperSql;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.SelectProvider;

import java.sql.Timestamp;
import java.util.List;
import java.util.Map;

@Mapper
public interface ReportDao {

   @SelectProvider(type = MapperSql.class, method = "getUnloadAndExcavator")
    List<Map<String, Object>> getUnloadAndExcavator(Map s);
}

2、MapperSql类

package com.anmining.truck.dispatch.modules.report.utils;



import java.util.List;
import java.util.Map;

public class MapperSql {



    public String getUnloadAndExcavator(Map map) throws IllegalAccessException {
        StringBuilder sql = new StringBuilder();
        List<Map<String,String>> unloadList = (List) map.get("allUnloadName");
        String startTime = map.get("startTime").toString();
        String endTime = map.get("endTime").toString();
        sql.append("select tb.excavator_name,tb.excavator_code,");

        for (int i=0;i<unloadList.size();i++){
            Map unload = unloadList.get(i);
            sql.append("MAX ( CASE tb.unloading_name WHEN '"+unload.get("unloading_name")+"' THEN tb.yield ELSE 0 END ) \""+unload.get("unloading_name")+"\",");
            if (i==unloadList.size()-1){
                //去掉最后的，
                sql.deleteCharAt(sql.length()-1);
            }
        }
        sql.append(" FROM\n" +
                "\t(\n" +
                "\tSELECT\n" +
                "\t\te.excavator_name,\n" +
                "\t\tu.unloading_name,e.excavator_code,\n" +
                "\t\tcount ( w.yield ) yield \n" +
                "\tFROM\n" +
                "\t\tp_workflow_statistical_table w\n" +
                "\t\tLEFT JOIN b_excavator_base_info e ON w.excavator_code = e.excavator_code\n" +
                "\t\tLEFT JOIN b_unloading_base_info u ON w.unloading_code = u.unloading_code\n" +
                "\t\tLEFT JOIN b_truck_base_info T ON w.truck_code = T.truck_code \n" +
                "\tWHERE\n" +
                "\t\tcreate_time >= '" +startTime+"' "+
                "\t\tAND create_time <= '" +endTime+"' "+
                "\tGROUP BY\n" +
                "\t\te.excavator_name,\n" +
                "\t\tu.unloading_name,e.excavator_code \n" +
                "\t) tb \n" +
                "GROUP BY\n" +
                "\ttb.excavator_name,tb.excavator_code  ORDER BY tb.excavator_name");

        return sql.toString();
    }
}

（二）mybatis拦截器

https://blog.csdn.net/qq_36881887/article/details/111589294