mybatis动态sql之修改(学习set标签)
时间:2022-07-23
本文章向大家介绍mybatis动态sql之修改(学习set标签),主要内容包括其使用实例、应用技巧、基本知识点总结和需要注意事项,具有一定的参考价值,需要的朋友可以参考一下。
EmployeeMapperDynamicSql.java
package com.gong.mybatis.mapper;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.MapKey;
import com.gong.mybatis.bean.Employee;
public interface EmployeeMapperDynamicSql {
public List<Employee> getEmpByConditionIf(Employee employee);
public 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>
<when test="lastName!=null">
last_name like #{lastName}
</when>
<when test="email!=null">
email=#{email}
</when>
<otherwise>
</otherwise>
</choose>
</where>
</select>
<update id="updateEmp">
update tbl_employee
set
<if test="lastName!=null">
last_name=#{lastName},
</if>
<if test="gender!=null and gender == 0 or gender == 1">
gender=#{gender},
</if>
<if test="email!=null">
email=#{email}
</if>
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:
package com.gong.mybatis.test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import com.gong.mybatis.bean.Employee;
import com.gong.mybatis.mapper.EmployeeMapperDynamicSql;
public class TestMybatis3 {
public SqlSessionFactory getSqlSessionFactory() throws IOException {
String resource = "mybatis-config.xml";
InputStream is = Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(is);
}
@Test
public void test() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try {
EmployeeMapperDynamicSql mapper = openSession.getMapper(EmployeeMapperDynamicSql.class);
Employee employee = new Employee();
employee.setId(1);
employee.setLastName("hanbin");
// employee.setGender("0");
// employee.setEmail("dema@qq.com");
mapper.updateEmp(employee);
List<Employee> es = mapper.getEmpByConditionIf(new 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 id="updateEmp">
update tbl_employee
<set>
<if test="lastName!=null">
last_name=#{lastName},
</if>
<if test="gender!=null and gender == 0 or gender == 1">
gender=#{gender},
</if>
<if test="email!=null">
email=#{email}
</if>
</set>
where id=#{id}
</update>
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, gender=0, email=hanbin@qq.com, dept=null]
第二种:使用之前学过的trim标签
<update id="updateEmp">
update tbl_employee
<trim prefix="set" suffixOverrides=",">
<if test="lastName!=null">
last_name=#{lastName},
</if>
<if test="gender!=null and gender == 0 or gender == 1">
gender=#{gender},
</if>
<if test="email!=null">
email=#{email}
</if>
</trim>
where id=#{id}
</update>
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 <== Total: 4 (BaseJdbcLogger.java:145)
Employee [id=1, lastName=dema, gender=1, email=dema@qq.com, dept=null]
Employee [id=2, lastName=jack, gender=1, email=675544321@qq.com, dept=null]
Employee [id=3, lastName=小红, gender=0, email=xiaohong@qq.com, dept=null]
Employee [id=4, lastName=小明, gender=0, email=xiaoming@qq.com, dept=null]
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