学习记录mybatis_01

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本文详细介绍了如何在Java环境中搭建MyBatis框架，包括工程结构的建立、配置文件的设置、实体类的创建、Mapper接口及XML文件的编写，以及最终的测试验证，为初学者提供了完整的MyBatis应用实例。

Mybatis学习记录（1）
一个简单应用的案列：
1.创建一个java工程
并把目录结构变成这样（只是为了和以后的maven的项目结构一致，养成一个规范）
在这里插入图片描述

2在com.mybatis目录下创建包lib,里面加入jar包，然后右键弹出一个目录，点add to libray
在这里插入图片描述

3在resource目录下添加mybatis的配置文件conf.xml


```java
<?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>

    <!--开启驼峰命名-->
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true" />
    </settings>
//配置数据源
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/zpark?characterEncoding=utf-8" />
                <property name="username" value="root" />
                <property name="password" value="123456" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/mybatis/dao/UserMapper.xml" />
</mappers>
</configuration>


4.在com.mybatis_01.entity包中创建一个User实体类

```java
package com.mybatis.entity;

import java.util.Date;

public class User {
  private Integer userId;
  private String userName;
  private String userPassword;
  private String userEmail;
  private Integer userSex;
  private String userPhoto;
  private Date userBirthday;

    public User() {
    }

    public User(Integer userId, String userName, String userPassword, String userEmail, Integer userSex, String userPhoto, Date userBirthday) {
        this.userId = userId;
        this.userName = userName;
        this.userPassword = userPassword;
        this.userEmail = userEmail;
        this.userSex = userSex;
        this.userPhoto = userPhoto;
        this.userBirthday = userBirthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userPassword='" + userPassword + '\'' +
                ", userEmail='" + userEmail + '\'' +
                ", userSex=" + userSex +
                ", userPhoto='" + userPhoto + '\'' +
                ", userBirthday=" + userBirthday +
                '}';
    }


    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPassword() {
        return userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }

    public String getUserEmail() {
        return userEmail;
    }

    public void setUserEmail(String userEmail) {
        this.userEmail = userEmail;
    }

    public Integer getUserSex() {
        return userSex;
    }

    public void setUserSex(Integer userSex) {
        this.userSex = userSex;
    }

    public String getUserPhoto() {
        return userPhoto;
    }

    public void setUserPhoto(String userPhoto) {
        this.userPhoto = userPhoto;
    }

    public Date getUserBirthday() {
        return userBirthday;
    }

    public void setUserBirthday(Date userBirthday) {
        this.userBirthday = userBirthday;
    }
}

5在com.mybatis_01.dao包下创建一个UserMapper接口，往里面写一个方法根据id查询用户：


ackage com.mybatis.dao;

import com.mybatis.entity.User;

public interface UserMapper {

        User selectById(Integer userId);//根据id查询用户

}

 6 在com.mybatis_01.dao包下创建一个UserMapper.xml文件来写UserMapper中方法要执行的sql语句。

```java
<?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.mybatis.dao.UserMapper">


     <select id="selectById" parameterType="java.lang.Integer"
             resultType="com.mybatis.entity.User">
         select * from user where user_id=#{userId}
     </select>

</mapper>

7 测试：在com.mybatis_01.test包下创建一个Test类来测试：

package com.mybatis;

import com.mybatis.dao.UserMapper;
import com.mybatis.entity.User;
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 java.io.IOException;
import java.io.InputStream;

public class Test {
    public static void main(String[] args) {
    //1 设置加载配置文件
        String resource = "conf.xml";
       
        InputStream input = Test.class.getClassLoader().getResourceAsStream(resource);
        //2 创建SqlSessionFactory 
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(input);


           /* InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
            SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
            SqlSessionFactory factory = builder.build(in);*/
   //3 开启session
        SqlSession sqlSession= factory.openSession();
        //从session中拿到mapper
        try {
        //4 使用getMapper方法获取接口，就可以调用里面的方法
            UserMapper mapper=sqlSession.getMapper(UserMapper.class);
            User user= mapper.selectById(1);
            System.out.println(user);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException();
        } finally {
        //5关闭session
            sqlSession.close();
        }
    }
}