MyBatis入门之增删改查+数据库字段和实体字段不一致问题处理方法

当数据库字段和实体bean中属性不一致时

之前数据库Person名字字段是name,PersonBean中属性也是name,但是之后数据库中修改为了user_name,

方法1:通过sql语句的字段起别名,别名和实体中的对象属性一致

SELECt id,user_name as name,sex,age from person

  SELECT id,user_name as name,sex,age from person

方法2: mybatis最强大的地方 : reslutMap对象

添加一个中介reslutMap标签,并将select标签中的resultType改为resultMap,并对应resultMap标签的id.

结果集:resultType 基础类型,int,string,Person,

resultMap 针对中介标签resultMap而存在.

 
 
  
  
  
  
 
 
 
 
  SELECT * from person
 
 
 
  SELECT * FROM person WHERe id = #{id}
 

    mybatis的增删改查

新增人员信息

首先在PersonMapper.xml中添加insert标签,我们的数据库字段user_name,Person实体属性为name,不一致,区别开来.然后在TestMybatis中写入代码.

 
  INSERT INTO person(id,user_name,age,sex) VALUES(#{id},#{name},#{age},#{sex})
 

package test;

import com.luogg.domain.Person;
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.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class TestMybatis {
 //SqlSessionFactory为线程安全的
 private SqlSessionFactory factory;
 @Before
 public void init() throws IOException {
  String resource = "sqlMapConfig.xml";
  InputStream is = Resources.getResourceAsStream(resource);
  factory = new SqlSessionFactoryBuilder().build(is);
 }
 @Test //查询所有
 public void findAll() throws IOException {
  
  SqlSession session = factory.openSession();
  //如何访问PersonMapper.xml中的sql语句呢? 命名空间+ .id
  List list = session.selectList("com.luogg.mapper.PersonMapper.find");
  System.out.println(list.size());
  for(Person p : list){
   System.out.println(p);
  }
 }
 @Test //通过ID查询人员信息
 public void selById(){
  SqlSession session = factory.openSession();
  Person p = session.selectOne("com.luogg.mapper.PersonMapper.selById",1);
  System.out.println(p);
 }
 @Test //添加人员信息
 public void add(){
  SqlSession session = factory.openSession();
  Person p = new Person();
  p.setId(4);
  p.setName("luogg");
  p.setAge(22);
  p.setSex(1);
  int i = session.insert("com.luogg.mapper.PersonMapper.insert",p);
  session.commit();
  if(i==1){
   System.out.print("添加人员成功");
  }
 }
}

修改人员信息 , 查询总的记录条数

prsonMapper.xml文件

 
  UPDATE person SET user_name=#{name},age=#{age} WHERe id=#{id}
 
 
 
  SELECT COUNT(*) FROM person
 

TestMybatis.java文件

@Test //修改人员信息
 public void updatePer(){
  SqlSession session = factory.openSession();
  Person p = new Person();
  p.setId(4);
  p.setName("luoggg");
  //p.setSex(1);
  p.setAge(23);
  int i = session.update("com.luogg.mapper.PersonMapper.update",p);
  session.commit();
  if(i==1){
   System.out.print("修改信息成功");
  }
 }
 @Test //查询总的记录条数
 public void selCount(){
  SqlSession session = factory.openSession();
  int i = session.selectOne("com.luogg.mapper.PersonMapper.count");
  System.out.println(i);
 }

条件查询
根据条件查询


 
  SELECT  FROM person
  where user_name like #{name}
  AND sex=#{sex}
 
@Test //带条 件查询
 public void selByL(){
  SqlSession session = factory.openSession();
  Map map = new HashMap();
  map.put("name","luo%");
  map.put("sex",1);
  List list = session.selectList("com.luogg.mapper.PersonMapper.selByL",map);
  System.out.println(list.size());
  for(Person p : list){
   System.out.println(p);
  }
 }

以上所述是小编给大家介绍的MyBatis入门之增删改查+数据库字段和实体字段不一致问题处理方法，希望对大家有所帮助，如果大家有任何疑问欢迎给我留言，小编会及时回复大家的！