mybatis动态sql之修改（学习set标签）

EmployeeMapperDynamicsql.java

package com.gong.mybatis.mapper;

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

 org.apache.ibatis.annotations.MapKey;

 com.gong.mybatis.bean.Employee;

public interface EmployeeMapperDynamicsql {
    public List<Employee> getEmpByConditionIf(Employee employee);
    
    void updateEmp(Employee employee);
}

EmployeeMapperDynamicsql.xml

<?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.gong.mybatis.mapper.EmployeeMapperDynamicsql">
    <!-- 查询，要查那个就带上那个条件 -->
    select id="getEmpByConditionIf" resultType="com.gong.mybatis.bean.Employee">
        select * from tbl_employee 
        where>
            choose>
                when test="id!=null"
                    id=#{id}
                </when="lastName!=null"
                    last_name like #{lastName}
                ="email!=null"
                    email=#{email}
                otherwise>
        select>
    
    update ="updateEmp"
        update tbl_employee 
        set
        if 
            last_name=#{lastName},if="gender!=null and gender == 0 or gender == 1"
            gender=#{gender},1)">
            email=#{email}
        
        where id=#{id}
    update>
mapper>

结合之前的知识，我们在这里不使用set标签：

进行测试：

 com.gong.mybatis.test;

 java.io.IOException;
 java.io.InputStream;
 org.apache.ibatis.io.Resources;
 org.apache.ibatis.session.sqlSession;
 org.apache.ibatis.session.sqlSessionFactory;
 org.apache.ibatis.session.sqlSessionFactoryBuilder;
 org.junit.Test;

 com.gong.mybatis.bean.Employee;
 com.gong.mybatis.mapper.EmployeeMapperDynamicsql;

class TestMybatis3 {
    
    public sqlSessionFactory getsqlSessionFactory() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream is = Resources.getResourceAsStream(resource);
        return new sqlSessionFactoryBuilder().build(is);
    }

    @Test
    void test()  IOException {
        sqlSessionFactory sqlSessionFactory = getsqlSessionFactory();
        sqlSession openSession = sqlSessionFactory.openSession();
        try {
            EmployeeMapperDynamicsql mapper = openSession.getMapper(EmployeeMapperDynamicsql.);
            Employee employee =  Employee();
            employee.setId(1);
            employee.setLastName("hanbin");
//            employee.setGender("0");
            employee.setEmail("dema@qq.com");
            mapper.updateEmp(employee);
            List<Employee> es = mapper.getEmpByConditionIf( Employee());
            for(Employee e:es) {
                System.err.println(e);
            }
            openSession.commit();
        } finally {
            openSession.close();
        }
        
    }
    
}

我们先对Id=1的记录修改last_name=hanbin，结果：会报错，因为sql最后面多了个逗号

DEBUG 01-21 14:31:18,323 ==>  Preparing: update tbl_employee set last_name=?, where id=?   (BaseJdbcLogger.java:145) 
DEBUG 01-21 14:31:18,366 ==> Parameters: hanbin(String),1(Integer)  (BaseJdbcLogger.java:145)

解决方法有两种：

第一种：使用set标签，会自动过滤掉多余的逗号

    
        update tbl_employee 
        set
                last_name=#{lastName},1)">
                gender=#{gender},1)">
                email=#{email}
            >

结果：

DEBUG 01-21 14:46:11,726 ==>  Preparing: select * from tbl_employee   (BaseJdbcLogger.java:145) 
DEBUG 01-21 14:46:11,727 ==> Parameters:   (BaseJdbcLogger.java:145) 
DEBUG 01-21 14:46:11,756 ==      Total: 4  (BaseJdbcLogger.java:145) 
Employee [id=1,lastName=hanbin,1)">gender=0,1)">email=hanbin@qq.com,1)">dept=null]

第二种：使用之前学过的trim标签

    trim prefix="set" suffixOverrides=","trim>

并修改id=1的last_name为dema，gender为1，email为dema@qq.com

            employee.setId(1);
            employee.setLastName("dema");
            employee.setGender("1");
            employee.setEmail("dema@qq.com");

结果：

DEBUG 01-21 14:53:38,851 ==>  Preparing: select * from tbl_employee   (BaseJdbcLogger.java:145) 
DEBUG 01-21 14:53:38,852 ==> Parameters:   (BaseJdbcLogger.java:145) 
DEBUG 01-21 14:53:38,885 =dema,1)">=dema@qq.com,1)">=null]
Employee [id=2,1)">=jack,1)">=675544321@qq.com,1)">=3,1)">=小红,1)">=xiaohong@qq.com,1)">=4,1)">=小明,1)">=xiaoming@qq.com,1)">=null]

mybatis动态sql之修改（学习set标签）

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