Complete operaciones CRUD usando el método Mybatis

Complete operaciones CRUD usando el método Mybatis

El desarrollo de Java solía realizarse a través de JDBC al conectarse a bases de datos, lo cual era muy problemático.

Ahora se ha introducido el marco MyBatis, que es un marco de capa de persistencia que simplifica las operaciones de la base de datos.

Beneficios de usar Mybatis:

• Mybatis puede eliminar directamente las operaciones de las tablas de datos (sql, métodos), etc., y escribirlas en archivos de configuración xml para lograr el desacoplamiento del código java.
• MyBatis proporciona un mapeo más flexible entre java y sql

1. Java opera DB en modo Mybatis

1.1 Configurar fuente de datos: crear recursos/mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!--    配置mybatis自带的日志输出-->
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <!--    配置类型别名-->
    <typeAliases>
        <typeAlias type="com.linghu.entity.Monster" alias="Monster"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <!--            配置事务管理器-->
            <transactionManager type="JDBC"/>
            <!--            配置数据源-->
            <dataSource type="POOLED">
                <!--                配置驱动-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!--                配置数据库的链接-->
                <property name="url"
                          value="jdbc:mysql://127.0.0.1:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <!--               数据库的用户名和密码-->
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!--    这里设置我们需要管理的mapper.xml文件-->
    <!--    可以通过快捷键copy这个地址-->
    <mappers>
        <mapper resource="com/linghu/mapper/MonsterMapper.xml"/>
    </mappers>


</configuration>

1.2 Crear Java Bean-Monster

Al crear un bean, debe diseñarlo según los campos de la tabla de la base de datos que diseñó, ¡y deben corresponder uno a uno!

package com.linghu.entity;

import java.util.Date;

/**
 * @author 令狐荣豪
 * @version 1.0
 * Monster类和monster表有对应关系,字段要对应
 * 体现oop
 */
public class Monster {
    
    
    private Integer id;
    private Integer age;
    private String name;
    private String email;
    private Date birthday;
    private double salary;
    private Integer gender;

    public Monster() {
    
    
    }

    public Monster(Integer id, Integer age, String name, String email, Date birthday, double salary, Integer gender) {
    
    
        this.id = id;
        this.age = age;
        this.name = name;
        this.email = email;
        this.birthday = birthday;
        this.salary = salary;
        this.gender = gender;
    }

    @Override
    public String toString() {
    
    
        return "Monster{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                ", email='" + email + '\'' +
                ", birthday=" + birthday +
                ", salary=" + salary +
                ", gender=" + gender +
                '}';
    }

    public Integer getId() {
    
    
        return id;
    }

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

    public Integer getAge() {
    
    
        return age;
    }

    public void setAge(Integer age) {
    
    
        this.age = age;
    }

    public String getName() {
    
    
        return name;
    }

    public void setName(String name) {
    
    
        this.name = name;
    }

    public String getEmail() {
    
    
        return email;
    }

    public void setEmail(String email) {
    
    
        this.email = email;
    }

    public Date getBirthday() {
    
    
        return birthday;
    }

    public void setBirthday(Date birthday) {
    
    
        this.birthday = birthday;
    }

    public double getSalary() {
    
    
        return salary;
    }

    public void setSalary(double salary) {
    
    
        this.salary = salary;
    }

    public Integer getGender() {
    
    
        return gender;
    }

    public void setGender(Integer gender) {
    
    
        this.gender = gender;
    }
}

1.3 Configurar el método de declaración de la interfaz Mapper

package com.linghu.mapper;

import com.linghu.entity.Monster;

import java.util.List;

/**
 * @author 令狐荣豪
 * @version 1.0
 * 定义增删改查的接口方法
 */
public interface MonsterMapper {
    
    
//    添加monster
    public void addMonster(Monster monster);

    //根据id删除一个Monster
    public void delMonster(Integer id);
    //修改 Monster
    public void updateMonster(Monster monster);
    //查询-根据 id
    public Monster getMonsterById(Integer id);

    //查询所有的 Monster
    public List<Monster> findAllMonster();
}

1.4 Configure xxMapper, complete la configuración SQL e implemente operaciones CRUD

Monstermapper.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.linghu.mapper.MonsterMapper">

<!--    <select id="selectBlog" resultType="Blog">-->
<!--        select * from Blog where id = #{id}-->
<!--    </select>-->
<!--    private Integer id;
    private Integer age;
    private String name;
    private String email;
    private Date birthday;
    private double salary;
    private Integer gender;-->
        <insert id="addMonster" parameterType="com.linghu.entity.Monster">
            insert into `monster`
            (`age`,`birthday`,`email`,`gender`,`name`,`salary`)
<!--            values(10,null,'[email protected]',1,'kate',1000),修改成活数据-->
<!--            下面的名称对应的Monster对象的属性名-->
            values(#{age},#{birthday},#{email},#{gender},#{name},#{salary})
        </insert>

    <delete id="delMonster" parameterType="Integer">
        delete from `monster` where id=#{id};
    </delete>

<!--    这里的入参类型最好不要简写！-->
<!--    配置类型别名后这里可以简写Monster-->
<!--    <update id="updateMonster" parameterType="com.linghu.entity.Monster">-->
    <update id="updateMonster" parameterType="Monster">
        update `monster` set `age`=#{age},`birthday`=#{birthday},`email`=#{email},
        `gender`=#{gender},`name`=#{name},`salary`=#{salary}
        where id=#{id}
    </update>

<!--     resultType是个别名-->
    <select id="getMonsterById" parameterType="Integer" resultType="Monster">
        select * from `monster` where id=#{id};
    </select>

<!--    查询全部结果-->
    <select id="findAllMonster" resultType="Monster">
        select * from `monster`;
    </select>

</mapper>

1.5 Prueba de prueba

package com.linghu.mapper;

import com.linghu.entity.Monster;
import com.linghu.util.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Before;
import org.junit.Test;

import java.util.Date;
import java.util.List;

/**
 * @author 令狐荣豪
 * @version 1.0
 */
public class MonsterMapperTest {
    
    
    private SqlSession sqlSession;
    private MonsterMapper monsterMapper;

    @Before
    public void init(){
    
    
        //通过SqlSessionFactory获取一个SqlSession会话
        sqlSession= MyBatisUtils.getSqlSession();
        //获取MonsterMapper接口对象，该对象实现了MonsterMapper
        monsterMapper=sqlSession.getMapper(MonsterMapper.class);
        System.out.println(monsterMapper.getClass());
    }

//    @Test
//    public void t1(){
    
    
//        System.out.println("t1()。。。");
//    }

    @Test
    public void addMonster(){
    
    
        for (int i=0;i<3;i++){
    
    
            Monster monster = new Monster();
            monster.setAge(10+i);
            monster.setBirthday(new Date());
            monster.setEmail("[email protected]");
            monster.setGender(1);
            monster.setName("松鼠精"+i);
            monster.setSalary(1000+i*10);
//            id不用设置
            monsterMapper.addMonster(monster);
            System.out.println("添加对象-"+monster);
        }
        //如果是增删改，需要提交事务
        if (sqlSession!=null){
    
    
            sqlSession.commit();
            sqlSession.close();
        }
        System.out.println("保存成功···");
    }

    @Test
    public void delMonster(){
    
    
        monsterMapper.delMonster(2);

        //如果是增删改，需要提交事务
        if (sqlSession!=null){
    
    
            sqlSession.commit();
            sqlSession.close();
        }
        System.out.println("删除成功···");
    }

    @Test
    public void updateMonster(){
    
    
        Monster monster = new Monster();
        monster.setAge(200);
        monster.setBirthday(new Date());
        monster.setEmail("[email protected]");
        monster.setGender(2);
        monster.setName("狐狸精");
        monster.setSalary(9234.89);
        monster.setId(4);
        monsterMapper.updateMonster(monster);
        if (sqlSession != null) {
    
    
            sqlSession.commit();
            sqlSession.close();
        }
        System.out.println("修改 ok");
    }

    @Test
    public void getMonsterById(){
    
    
//        Monster monster = new Monster();
        Monster monster=monsterMapper.getMonsterById(6);
        System.out.println("monster="+monster);


        if (sqlSession != null) {
    
    
            sqlSession.commit();
            sqlSession.close();
        }
        System.out.println("查询 ok");
    }

    @Test
    public void findAllMonster(){
    
     //查询全部结果
        List<Monster> allMonster = monsterMapper.findAllMonster();
        for (Monster monster :allMonster) {
    
    
            System.out.println(monster);
        }

        if (sqlSession != null) {
    
    
            sqlSession.close();
        }
        System.out.println("查询 ok");

    }
}

2. Clases de herramientas Utils requeridas

Herramientas :MyBatisUtils.java

package com.linghu.util;

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 javax.annotation.Resource;
import java.io.IOException;
import java.io.InputStream;

/**
 * @author 令狐荣豪
 * @version 1.0
 * 这是一个工具类，可以得到Sqlsession会话，这个会话提供了执行SQL命令的方法CRUD
 */
public class MyBatisUtils {
    
    
    private static SqlSessionFactory sqlSessionFactory;

    static {
    
    //静态代码块-初始化sqlSessionFactory对象
        try {
    
    
            /**
             * 指定资源文件
             */
            String resource="mybatis-config.xml";
            //指定资源文件流
            InputStream inputStream = Resources.getResourceAsStream(resource);
            //获取SqlSession实例
            sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
    }

    /**
     * 返回一个SQLSession会话，这个会话提供了执行SQL命令的方法CRUD
     * @return
     */
    public static SqlSession getSqlSession(){
    
    
        return sqlSessionFactory.openSession();
    }
}

3. Dependencias básicas de Pom

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.linghu</groupId>
    <artifactId>Linghu_Mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <modules>
<!--        这里可以看到父项目下有哪些子项目-->
        <module>mybatisqucikstart</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <!-- 导入依赖 -->
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

<!--    配置resources-->
<!--    配置目的：将src/main/java目录和子目录和src/main/resources目录和子目录的
资源文件xml和properties在build项目时，导出到对应的target目录下
-->
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.properties</include>
                </includes>
            </resource>
        </resources>
    </build>

</project>

4. Operación de creación de tablas de bases de datos

CREATE DATABASE `mybatis`
CREATE TABLE `monster` (
	`id` INT NOT NULL AUTO_INCREMENT, 
    `age` INT NOT NULL, 
    `birthday` DATE DEFAULT NULL, 
    `email` VARCHAR(255) NOT NULL , 
    `gender` TINYINT NOT NULL, 
    `name` VARCHAR(255) NOT NULL, 
    `salary` DOUBLE NOT NULL,
	PRIMARY KEY (`id`)
) CHARSET=utf8