Mybatis学习笔记1

mybatis是一个orm持久化框架，mybatis专注于sql的操作
从3.0开始名字改变了:ibatis-mybatis
 对象关系映射（Object Relational Mapping）

一、Mybatis搭建

1、导包

2、mybatis-config.xml配置文件

<?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>
 <environments default="development">
 <environment id="development">
 <transactionManager type="JDBC"/>
 <dataSource type="POOLED"><!-- 四大组件 --><!--池  提高效率管理连接  节省连接过程中消耗的资源 -->
 <property name="driver" value="com.mysql.jdbc.Driver"/>
 <property name="url" value="jdbc:mysql://localhost:3306/crm"/>
 <property name="username" value="root"/>
 <property name="password" value="123456"/>
 </dataSource>
 </environment>
 </environments>
 <mappers><!-- 映射文件  现在不要配 ，有映射文件需要配在这里  包名前面的不要-->
 <mapper resource="com/zy/mapper/UserMapper.xml"/>
 </mappers>
</configuration>

3、创建表

4、创建实体类

package com.zy.entity;

public class User {
    private Integer uid;
    private String username;
    private String password;
    private String address;

    public User() {
        super();
        // TODO Auto-generated constructor stub
    }

    public User(Integer uid, String username, String password, String address) {
        super();
        this.uid = uid;
        this.username = username;
        this.password = password;
        this.address = address;
    }

    public Integer getUid() {
        return uid;
    }
    public void setUid(Integer uid) {
        this.uid = uid;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User [uid=" + uid + ", username=" + username + ", password=" + password + ", address=" + address + "]";
    }

}

5、搭建映射文件

UserMapper.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">
 <!--
    namespace唯一表示此名字下的crud语句
 -->
<mapper namespace="myuser"><!-- 无规律，起个代号就行，不要重复 -->
 <!-- 提供了增删改查的相关标签 -->
 <!-- 以后的sql都会写在这个配置文件中 -->
 <!--<select id=""></select>
 <insert id=""></insert>
 <delete id=""></delete>
 <update id=""></update>  -->

 <!-- 查询 -->        <!-- 如果结果是集合也填集合的泛型 -->
 <!--
        id:在此命名空间下唯一标识
        resultType:查询结果的返回类型或者集合的泛型
     -->
 <select id="selectUser" resultType="com.zy.entity.User">
 SELECT * FROM t_user
 </select>
 <delete id="deleteUser">
 DELETE FROM t_user WHERE uid=1
 </delete>

 <insert id="insertUseer">
INSERT INTO t_user VALUES(NULL,'bbbb','1234','德国')
 </insert>

 <update id="updateUser">
 UPDATE t_user SET username='武磊' WHERE uid=4
 </update>

 <!-- 根据id查询用户 -->
 <select id="selectUserByid" resultType="com.zy.entity.User">
 SELECT * FROM t_user WHERE uid=#{id}<!-- 一个参数#{}占位符，里面写什么无所谓 -->
 </select>

 <!-- 根据用户名和密码查询用户 -->
 <select id="selectUserByNP" resultType="com.zy.entity.User">
 SELECT * FROM t_user WHERE username=#{uu}  AND password=#{pp}
 </select>

 <!-- 特殊字符的转义   <![CDATA[]]>  -->
 <!-- xml把小于号当做标签  在sql语句中直接写小于号会报错 -->
 <!-- The content of elements must consist of well-formed character data or markup. -->
 <select id="selectUser007" resultType="com.zy.entity.User">
 <![CDATA[ SELECT * FROM t_user WHERE uid<9 ]]>
 </select>

 <!-- 多条件查询之对象传值  占位符要与对象属性保持一致,不然传不上去 -->
 <insert id="insertUser007">
 INSERT INTO t_user VALUES(NULL,#{username},#{password},#{address})

 </insert>
</mapper>

<!-- 该实体类与表中列名有不一致的  使用as命别名解决 -->
<select id="uu" resultType="com.zy.entity.UU">
SELECT uid id,username name,password,address from t_user
</select>

6、在配置文件中引用映射文件

 <mapper resource="com/zy/mapper/UserMapper.xml"/>

7、得到会话

package com.zy.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
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 com.zy.entity.User;

public class UserTest {
    public static void main(String[] args) throws Exception {
        //1读取配置文件得到会话工厂
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        //2sql会话工厂创建者
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        //3生成sql会话工厂
        SqlSessionFactory sf = sqlSessionFactoryBuilder.build(resourceAsStream);
        //4得到mybatis和数据库会话对象
        SqlSession session = sf.openSession();

        //完成一个查询任务
/*//        List<User> selectList = session.selectList("myuser.selectUser");
//        for (User user : selectList) {
//            System.out.println(user);
//        }

        //完成一个删除任务(增删改需要提交事务commit)
//        int delete = session.delete("myuser.deleteUser");
//        session.commit();//相当于应用改变

        //完成一个添加
//        session.insert("myuser.insertUseer");
//        session.commit();

        //完成一个修改
//        session.update("myuser.updateUser");
//        session.commit();

        //带一个参数的查询
//        User uu = session.selectOne("myuser.selectUserByid",2);
//        System.out.println(uu);

        //带两个参数的查询
        //解决方案1把参数放对象中   2把参数放map中[map中的键需要与占位符一致]  灵活度更高
//        Map<Object, Object> map = new HashMap();
//        map.put("uu", "rose");
//        map.put("pp", "654321");
//
//        User uu = session.selectOne("myuser.selectUserByNP", map);
//        System.out.println(uu);

        //调用带<号的
//        List<User> selectList = session.selectList("myuser.selectUser007");
//        for (User uu : selectList) {
//            System.out.println(uu);
//        }
*/
        //用对象传递参数
        session.insert("myuser.insertUser007",new User(null, "哈哈", "111111", "郑州"));
        session.commit();

    }

}

8、使用mapper代理的方式

1）.在实现的时候，查询字符串，需要namespace.sqlid,容易拼接出错，硬编码
2）.参数是object类型，如果参数传入有问题，在编译的时候不报错
3）.selectOne和seletList还需要判断

上述写法，有很多吐槽点，所以需要改成主流的方法

使用mapper代理的方式

package com.zy.mapper;

import java.util.List;

import com.zy.entity.User;

public interface UserMapper {
    //UserMapper.java接口和UserMapper.xml配套使用----关系密切
    //查询用户
    public List<User> getList();

    //根据id删除用户
    public void deleteById(int id);

}

UserMapper.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.zy.mapper.UserMapper">
<!-- 查询用户
1 namespace必须是接口全名称
2 id名必须和方法名一致
3 resultType和方法名的返回值保持一致，如果是集合和集合的泛型保持一致
4 接口和xml名字一致，放在同一包下
-->
<select id="getList" resultType="com.zy.entity.User">
SELECT * FROM t_user
</select>

<delete id="deleteById">
DELETE FROM t_user WHERE uid=#{id}
</delete>
</mapper>

package com.zy.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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 com.zy.entity.User;
import com.zy.mapper.UserMapper;

public class Test {

    public static void main(String[] args) throws Exception {
        //新形势下，使用mapper代理完成调用
        //1读取配置文件得到会话工厂
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        //2sql会话工厂创建者
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        //3生成sql会话工厂
        SqlSessionFactory sf = sqlSessionFactoryBuilder.build(resourceAsStream);
        //4得到mybatis和数据库会话对象
        SqlSession session = sf.openSession();
        //---------------------------
        //旧的
        //完成一个查询任务
        //        List<User> selectList = session.selectList("myuser.selectUser");
        //        for (User user : selectList) {
        //            System.out.println(user);
        //        }
        //------------------------------------

        //新的

        //得到一个mapper代理
//        UserMapper mapper = session.getMapper(UserMapper.class);//反射  UserMapper为接口
//        //代理调用方法去查询
//        List<User> list = mapper.getList();
//        //遍历
//        for (User user : list) {
//            System.out.println(user);
//
//        }
        //------------------------

        UserMapper mapper = session.getMapper(UserMapper.class);
        mapper.deleteById(4);
        session.commit();
    }

}