Mabtis (I) basic use of framework

1、 Introduce

MyBatis It's supporting Ordinary SQL Inquire about , stored procedure and Advanced mapping Excellent persistence layer framework for .MyBatis Eliminated almost all of them JDBC Manual setting of code and parameters and retrieval of result sets .MyBatis You can use simple XML Or annotations for configuring and raw mapping , The interface and Java Of POJO（ Entity class object ） Maps to records in the database . Semi automated framework . Must write sql sentence .

2、 Basic use process

2.1 Import jar package

Use mabtis The framework needs to import two jar package , One is database driven jar package , Used to link databases . One is mabtis frame jar package .

maven Warehouse preparation jar Packet dependency

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        
    </dependencies>

2.2 Add the configuration file of the framework conf.xml

<?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" />
            <!-- Configuration of data source :name The value of is fixed   value The value of should be modified according to the customer -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver" />
                <property name="url"    value="jdbc:mysql://localhost:3306/mydb?serverTimezone=Asia/Shanghai" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>

</configuration>

2.3 Write entity class

package com.xrx.entity;

import org.omg.CORBA.StringHolder;

public class User {
    private int id;
    private String userName;
    private String password;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                '}';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    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;
    }
}

2.4 Definition User Tabular sql The mapping file 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.ykq.mybatis_test.test1.userMapper">
        <select id="getUser" parameterType="int" resultType="User">
            select * from users where id=#{id}
        </select>
    </mapper>

2.5 stay conf.xml Register in the file UserMapper.xml

<mappers>
<mapper resource="userMapper.xml"/>
</mappers>

 2.6 Write a test class to execute SQL sentence

public class Test {
    public static void main(String[] args) throws IOException {
        String resource = "conf.xml";
        // load  mybatis  Configuration file for （ It also loads the associated mapping file ）
        Reader reader = Resources.getResourceAsReader(resource);
        // structure  sqlSession  Our factory 
        SqlSessionFactory sessionFactory = new
        SqlSessionFactoryBuilder().build(reader);
        // Create executable mapping file  sql  Of  sqlSession
        SqlSession session = sessionFactory.openSession();
        // mapping  sql  The identity string of 
        String statement = "com.atguigu.mybatis.bean.userMapper"+".selectUser";
        // Executing the query returns a unique  user  Object's  sql
        User user = session.selectOne(statement, 1);
        System.out.println(user);
    }
}

  increase 、 Delete 、 Change , These operations are all in UserMapper.xml Written in Chinese sql, Then test execution sql That's it

// increase sql
<insert id="insertUser" parameterType="User">
    insert into users(name, age) values(#{name}, #{age});
</insert>

// Delete sql
<delete id="deleteUser" parameterType="int">
    delete from users where id=#{id}
</delete>

// modify sql
<update id="updateUser" parameterType="com.ykq.ibatis.bean.User">
    update users set name=#{name},age=#{age} where id=#{id}
</update>