MyBatis学习（2）【主要是记录学习中出现的问题】

落日映苍穹つ 2021-09-27 18:22 285阅读 0赞

弄了个web project项目

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjcxNzkyOA_size_16_color_FFFFFF_t_70][]

UserMapper.java代码

package cn.dao;
    
    import cn.pojo.User;
    
    public interface UserMapper {
    	int add(User user);
    }

UserMapper.xml代码

<?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="cn.dao.UserMapper">
    	<insert id="saveUser" parameterType="user" useGeneratedKeys="true">
    		INSERT INTO TB_USER(name,sex,age) VALUES(#{name},#{sex},#{age})
    	</insert>
    
    	<select id="selectUser" parameterType="int" resultType="user">
    		SELECT *from TB_USER WHERE id=#{id}
    	</select>
    	
    	<update id="modifyUser" parameterType="user">
    		UPDATE TB_USER SET name=#{name},sex=#{sex},age=#{age} WHERE id=#{id}
    	</update>
    	
    	<delete id="removeUser" parameterType="int">
    		DELETE FROM TB_USER WHERE id=#{id}
    	</delete>
    	
    	<insert id="add" parameterType="user">
      		INSERT INTO TB_USER(`name`,`sex`,`age`) VALUES(#{name},#{sex},#{age})
      	</insert>
      	
      	<select id="selectAll" resultType="User">
      		SELECT *FROM TB_USER
      	</select>
    
    </mapper>

User.java代码

package cn.pojo;
    
    import java.io.Serializable;
    
    import org.apache.ibatis.type.Alias;
    
    /**
     * @author AUSU
     *
     */
    //@Alias("user")
    public class User implements Serializable{
    	/**
    	 * 
    	 */
    	private static final long serialVersionUID = 1L;
    	private Integer id;            //用户标识
    	private String name;           //用户姓名
    	private String sex;            //用户性别
    	private Integer age;           //用户年龄
    	
    	
    	
    	@Override
    	public String toString() {
    		return "User [id=" + id + ", name=" + name + ", sex=" + sex + ", age=" + age + "]";
    	}
    
    	//无参数的构造方法       
    	public User() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    	
    	//有参数的构造方法
    	public User(String name, String sex, Integer age) {
    		super();
    		this.name = name;
    		this.sex = sex;
    		this.age = age;
    	}
    
    	
    	//setter和getter
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public String getSex() {
    		return sex;
    	}
    
    	public void setSex(String sex) {
    		this.sex = sex;
    	}
    
    	public Integer getAge() {
    		return age;
    	}
    
    	public void setAge(Integer age) {
    		this.age = age;
    	}
    	
    	
    }

在这里注意一下：

@Alias("user")，我注释掉了，如果有注解，则别名为其注解值user

Test.java代码

package cn.test;
    
    import java.io.InputStream;
    import java.text.Normalizer.Form;
    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.apache.jasper.tagplugins.jstl.core.ForEach;
    
    import cn.util.MyBatisUtil;
    import cn.dao.UserMapper;
    import cn.pojo.User;
    
    public class Test {
    	public static void main(String[] args) {
    //创建SqlSession实例,赋给SqlSession变量		
    		SqlSession sqlSession = MyBatisUtil.getSqlSession();
    //方法一：将User对象作为参数调用SqlSession的insert方法，MyBatis会找到cn.dao.UserMapper命名空间下
    //id="saveUser"的元素,执行该元素的SQL语句
    		//User user=new User("jack","男",55);
    		//int count=sqlSession.insert("cn.dao.UserMapper.saveUser",user);
    
    //根据id查询User对象
    		User user=sqlSession.selectOne("cn.dao.UserMapper.selectUser",5);
    		System.out.println(user);
    		
    //修改User对象的属性值
    		user.setName("chyyy");
    		user.setAge(65);
    //修改User对象
    		sqlSession.update("cn.dao.UserMapper.modifyUser",user);
    		System.out.println(user);
    		
    //删除id为1的User对象
    		sqlSession.delete("cn.dao.UserMapper.removeUser",1);
    		
    //查询表中所有数据返回List集合，集合中的每个元素都是一个Map
    //List<Map<String,Object>> list=sqlSession.selectList("cn.dao.UserMapper.selectAll");
    //遍历List集合，打印每一个Map集合
    //list.forEach(row->System.out.println(row););  在这里用不了，要1.8才行,而且UserMapper里面的resultType.xml的参数值要改为map
    		//我这样也行，不过UserMapper.xml里面的resultType的参数值要改为User
    		List<User> list=sqlSession.selectList("cn.dao.UserMapper.selectAll");		
    		System.out.println(list);    //方法一输出，不过不好看
    		for (User list1 : list) {    //方法二输出，这种用在第一个好像不行
    			System.out.println(list1);
    		}
    		
    		
    //方法二：我在UserMapper.java里面自己写一个增加的方法，然后通过getMapper去调用		
    		//User user=new User("tom","女",52);
    		//int count=sqlSession.getMapper(UserMapper.class).add(user);
    		sqlSession.commit();    //提交事务
    		//System.out.println("增加了"+count+"条数据！");
    		MyBatisUtil.closeSession(sqlSession);
    	
    	}
    }

MyBatisUtil.java代码

package cn.util;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class MyBatisUtil {
    	
    	
    	private static SqlSessionFactory sqlSessionFactory;
    	
    	/**
    	 * 创建SqlSessionFactory   只创建一次
    	 */
    	static{
    		try {
    			String resource = "mybatis-config.xml";
    			InputStream inputStream;
    			inputStream = Resources.getResourceAsStream(resource);
    			//创建SqlSessionFactory对象，读取配置文件
    			sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	
    	}
    	/**
    	 * 获得SqlSessionFactory
    	 * @return SqlSessionFactory
    	 */
    	public static SqlSessionFactory getSqlSessionFactory(){
    		
    		return sqlSessionFactory;
    		
    	}
    	/**
    	 * 获得 SqlSession
    	 * @return SqlSession
    	 */
    	public static SqlSession getSqlSession(){
    		return sqlSessionFactory.openSession(false);
    	}
    	/**
    	 * 關閉sqlSession
    	 * @param sqlSession
    	 */
    	public static void closeSession(SqlSession sqlSession){
    		if(sqlSession!=null){
    			sqlSession.close();
    		}
    	}
    	
    
    }

MyBatis-config.xml代码

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
      PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
      "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
    
    	
    	<properties resource="database.properties"></properties> 
    	
    	<settings>
    		<setting name="logImpl" value="LOG4J" />
    	</settings>
    	
      	<typeAliases>
    		<typeAlias type="cn.pojo.User" alias="User"/>
    	</typeAliases>
    
    	
    
    	
    	<environments default="development">
    		<environment id="development">
    			<transactionManager type="JDBC" />
    			<dataSource type="POOLED">
    				<property name="driver" value="${jdbc.driver}" />
    				<property name="url" value="${jdbc.url}" />
    				<property name="username" value="${jdbc.user}" />
    				<property name="password" value="${jdbc.password}" />
    			</dataSource>
    		</environment>
    	</environments>
    	<mappers>
    		<mapper resource="cn/dao/UserMapper.xml" />
    	</mappers>
    </configuration>

运行结果：

DEBUG \[main\] - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@457e2f02\]  
DEBUG \[main\] - ==>  Preparing: SELECT \*from TB\_USER WHERE id=?   
DEBUG \[main\] - ==> Parameters: 5(Integer)  
User \[id=5, name=chyyy, sex=女, age=65\]  
DEBUG \[main\] - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@457e2f02\]  
DEBUG \[main\] - ==>  Preparing: UPDATE TB\_USER SET name=?,sex=?,age=? WHERE id=?   
DEBUG \[main\] - ==> Parameters: chyyy(String), 女(String), 65(Integer), 5(Integer)  
User \[id=5, name=chyyy, sex=女, age=65\]  
DEBUG \[main\] - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@457e2f02\]  
DEBUG \[main\] - ==>  Preparing: DELETE FROM TB\_USER WHERE id=?   
DEBUG \[main\] - ==> Parameters: 1(Integer)  
DEBUG \[main\] - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@457e2f02\]  
DEBUG \[main\] - ==>  Preparing: SELECT \*FROM TB\_USER   
DEBUG \[main\] - ==> Parameters:   
\[User \[id=2, name=admin, sex=男, age=27\], User \[id=3, name=admin, sex=男, age=39\], User \[id=4, name=admin, sex=男, age=40\], User \[id=5, name=chyyy, sex=女, age=65\], User \[id=6, name=admin, sex=女, age=48\], User \[id=7, name=admin, sex=人, age=48\], User \[id=8, name=admin, sex=人, age=48\], User \[id=9, name=chy, sex=人, age=48\], User \[id=10, name=chy, sex=人, age=48\], User \[id=11, name=chy, sex=人, age=48\], User \[id=12, name=chy, sex=人, age=48\], User \[id=13, name=chy, sex=人, age=48\], User \[id=14, name=chy, sex=人, age=48\], User \[id=15, name=chy, sex=人, age=48\], User \[id=16, name=chy, sex=人, age=48\], User \[id=17, name=chy, sex=人, age=48\], User \[id=18, name=chy, sex=人, age=48\], User \[id=19, name=chy, sex=人, age=48\], User \[id=20, name=jack, sex=男, age=55\], User \[id=21, name=jack, sex=男, age=55\], User \[id=22, name=tom, sex=女, age=52\]\]  
User \[id=2, name=admin, sex=男, age=27\]  
User \[id=3, name=admin, sex=男, age=39\]  
User \[id=4, name=admin, sex=男, age=40\]  
User \[id=5, name=chyyy, sex=女, age=65\]  
User \[id=6, name=admin, sex=女, age=48\]  
User \[id=7, name=admin, sex=人, age=48\]  
User \[id=8, name=admin, sex=人, age=48\]  
User \[id=9, name=chy, sex=人, age=48\]  
User \[id=10, name=chy, sex=人, age=48\]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjcxNzkyOA_size_16_color_FFFFFF_t_70]: /images/20210923/5bcbbb66722645a297a71b24af8beb92.png