MyBatis - 如何创建w动态WHERE子句

Question

该服务获取一个包含三个值列表的未知对象[column,operator,value]例如,EMAIL - like - "TEST"

基于结果列表来构建我有的WHERE子句但我也能够构建如下的条件(例如)

WHERE(电子邮件,如'test'和user_id <> 5)或(trans_id <100 AND session_id> 500)

有谁可以帮我怎么做？

Answer 1

我自己长期缺席后一直在重新发现MyBatis(我曾经一度熟悉iBatis).Rolf的例子看起来可能是.Net实现,我可能错了,但我认为Java符号现在看起来不像.Rolf关于文字字符串的提示非常有用.

我创建了一个小类来保存你的列,运算符和值,并将它们传递给MyBatis来进行处理.列和运算符是字符串文字,但我将值保留为sql参数(我想MyBatis可以进行任何必要的类型转换).

public class TestAnswer {
    public static void main(String[] args) {
            ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
            SqlSessionFactory sqlFactory = (SqlSessionFactory) ctx.getBean("sqlSessionFactory");            
            MappedStatement statement = sqlFactory.getConfiguration().getMappedStatement("testAnswer");                        

            ArrayList<Clause> params1 = new ArrayList<Clause>();
            params1.add(new Clause("email","like","test"));
            params1.add(new Clause("user","<>",5));

            ArrayList<Clause> params2 = new ArrayList<Clause>();
            params2.add(new Clause("trans_id","<",100));
            params2.add(new Clause("session_id",">",500));

            HashMap params = new HashMap();
            params.put("params1", params1);
            params.put("params2", params2);

            BoundSql boundSql = statement.getBoundSql(params);
            System.out.println(boundSql.getSql());             
    }

    static class Clause{        
        private String column;
        private String operator;
        private Object value;

        public Clause(String column, String operator, Object value){
            this.column = column;
            this.operator = operator;
            this.value = value;
        }

        public void setColumn(String column) {this.column = column;}
        public void setOperator(String operator) {this.operator = operator;}
        public void setValue(Object value) {this.value = value;}
        public String getColumn() {return column;}
        public String getOperator() {return operator;}
        public Object getValue() {return value;}        
    }    
}

正如您所看到的,我使用Spring但我希望类似的东西可能在Spring环境之外工作.

<?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.stackoverflow.TestMapper">

    <select id="testAnswer" parameterType="map" resultType="hashmap">
      select *
    FROM somewhere
        <where>
            <foreach item="clause" collection="params1" separator=" AND " open="(" close=")"> 
                ${clause.column} ${clause.operator} #{clause.value} 
            </foreach>            
            OR
            <foreach item="clause" collection="params2" separator=" AND " open="(" close=")"> 
                ${clause.column} ${clause.operator} #{clause.value} 
            </foreach>    
        </where>
    </select>

</mapper>

Answer 2

这个答案有两个关键部分。一个是“动态”元素，另一个是问题中“运算符”周围的 $$ 文字元素。

  <select id="yourSelect" parameterClass="Map" resultMap="somethingsomething" >
    select * from YOURTABLE
      <dynamic prepend="WHERE">
        <isNotNull prepend="AND" property="email">
          email $operator$ #testvalue#
        </isNotNull>
      </dynamic>
  </select>

另请参阅有关此主题的DataMapper 动态 SQL 文档。