用MyBatis進行數據庫的增刪改查

前提是MyBatis環境部署好了，參考地址：

https://www.cnblogs.com/package-java/p/10316536.html

為了方便演示，我提前在數據庫插入了數據方便查詢

1. 創建新的數據庫`tedu_ums`；
 
    CREATE DATABASE tedu_ums;
 
2. 在新數據庫中創建數據表`t_user`，表中至少包含id, username, password, age, phone, email這6個屬性；  
 
    USE tedu_ums;
 
    CREATE TABLE t_user (
        id INT AUTO_INCREMENT,
        username VARCHAR(20) UNIQUE NOT NULL,
        password VARCHAR(20) NOT NULL,
        age INT,
        phone VARCHAR(20),
        email VARCHAR(50),
        PRIMARY KEY(id)
    ) DEFAULT CHARSET=utf8;
 
3. 添加不少於10條數據；
 
    INSERT INTO t_user  
        (username, password, age, phone, email)  
    VALUES  
        ('root', '1234', 18, '13800138001', '[e-mail]'),
        ('admin', '4567', 19, '13800138002', '[e-mail]'),
        ('jack', '1234', 20, '13800138003', '[e-mail]'),
        ('tom', '1234', 22, '13800138010', '[e-mail]'),
        ('jerry', '1234', 25, '13800138011', '[e-mail]'),
        ('rose', '1234', 21, '13800138004', '[e-mail]'),
        ('mike', '1234', 22, '13800138005', '[e-mail]'),
        ('lily', '1234', 23, '13800138006', '[e-mail]'),
        ('lucy', '1234', 24, '13800138007', '[e-mail]'),
        ('mary', '1234', 25, '13800138008', '[e-mail]'),
        ('alex', '1234', 26, '13800138009', '[e-mail]');
 
4. 查詢所有數據；
 
    SELECT id,username,password,age,phone,email FROM t_user;   

 

一、創建實體類

每張數據表都應該有1個對應的實體類，所以，創建`cn.tedu.mybatis.entity.User`類，屬性的數量與類型請參考數據表的設計：
 

package cn.tedu.mybatis.entity;

public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;
    private String phone;
    private String email;
    public Integer getId() {
        return id;
    }
    public void setId(Integer 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;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password=" + password + ", age=" + age + ", phone="
                + phone + ", email=" + email + "]";
    }
    

}

 

二、創建接口，聲明抽象方法

 
創建`cn.tedu.mybatis.mapper.UserMapper`接口，並在接口中聲明“插入用戶數據”的抽象方法：
 

package cn.tedu.mybatis.mapper;

import cn.tedu.mybatis.entity.User;

public interface UserMapper {
    Integer addnew(User user);//增
    User findById(Integer id);//查
    Integer updatenew(User user);//改
    Integer deletenew(Integer id);//刪

}

 

 

關於抽象方法，在MyBatis中，執行的操作如果是增、刪、改，返回值均使用`Integer`，表示受影響的行數；方法的名稱可以自定義，只要不違反Java的命名規則即可，另外，不允許在接口中使用重載機制；參數也可以自定義，如果執行的是增加操作，參數應該是與數據表對應的實體類的類型。

 

三、配置接口所在的包並配置配置XML文件的位置與數據源

1、在MyBatis中，通過`MapperScannerConfigurer`類掃描持久層接口的，所以，應該在`spring-dao.xml`文件中進行配置：
 2、MyBatis通過`SqlSessionFactoryBean`獲取數據源，並且掃描配置了SQL語句的XML文件，最終由MyBatis框架來執行SQL語句，所以，需要在`spring-dao.xml`中配置`SqlSessionFactoryBean`：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:jee="http://www.springframework.org/schema/jee"
    xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:util="http://www.springframework.org/schema/util"
    xmlns:jpa="http://www.springframework.org/schema/data/jpa"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">
    <!-- 加載數據庫的配置文件 -->
    <util:properties id="dbConfig" location="classpath:db.properties"></util:properties>
<!--     配置數據源 -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
<property name="url" value="#{dbConfig.url}"></property>
<property name="driverClassName" value="#{dbConfig.driver}"></property>
<property name="username" value="#{dbConfig.username}"></property>
<property name="password" value="#{dbConfig.password}"></property>
<property name="initialSize" value="#{dbConfig.initialSize}"></property>
<property name="maxActive" value="#{dbConfig.maxActive}"></property>
</bean>
<!-- 掃描持久層接口 -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<!-- 配置接口文件所在的包 -->
<property name="basePackage" value="cn.tedu.mybatis.mapper"></property>
</bean>
<!-- 或取數據源 -->
<bean class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"></property>
<property name="mapperLocations" value="classpath:mappers/*.xml"></property>
</bean>


</beans>

 

四、在XML中配置接口方法對應的SQL語句

在`src/main/resources`下創建名為`mappers`文件夾，創建名為UserMapper.xml的文件

根節點必須是`<mapper>`，且根節點的`namespace`表示對應的接口文件，然后，添加子節點，以對應接口中的抽象方法：

<?xml version="1.0" encoding="UTF-8" ?>  
<!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"      
 "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<!-- 根節點必須是mapper -->
<!-- namespace對應的接口文件 -->
<mapper namespace="cn.tedu.mybatis.mapper.UserMapper">
    <!-- 根據執行的操作類型選擇節點 -->
    <!-- id:對應的抽象方法的方法名 -->
    <!-- 值：#{}括號里面的是User的屬性名 -->
    <insert id="addnew">
        INSERT INTO t_user(
        username,password,age,phone,email
        ) value(
        #{username},#{password},#{age},#{phone},#{email}
        )
    </insert>
    <select id="findById" resultType="cn.tedu.mybatis.entity.User">
        SELECT id,username,password,age,phone,email FROM t_user WHERE id=#{id}
    </select>
    <insert id="addnewone">
        INSERT INTO t_user(
        username,password,age,phone,email
        ) value(
        #{username},#{password},#{age},#{phone},#{email}
        )
    </insert>
    <update id="updatenew">
        UPDATE t_user SET
        username=#{username},
        password=#{password},
        age = #{age},
        phone = #{phone},
        email=#{email}
        WHERE
        id=#{id}
    </update>
    <delete id="deletenew">
        DELETE FROM t_user WHERE age=#{age}
    </delete>
</mapper>

五、在測試類中測試

package web;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import cn.tedu.mybatis.entity.User;
import cn.tedu.mybatis.mapper.UserMapper;

public class TestDemo01 {
    AbstractApplicationContext ac;
    UserMapper mapper;
    @Before
    public void doBefore() {
        ac = new ClassPathXmlApplicationContext("spring-dao.xml");
        mapper = ac.getBean("userMapper",UserMapper.class);//根據id或取對象
    }
    @After
    public void doafter() {
        ac.close();
    }
/*    測試插入*/
    @Test
    public void add() {
        User user = new User();
        user.setUsername("學海無崖");
        user.setPassword("12345600");
        Integer row = mapper.addnew(user);
        System.out.println("row:"+row);
    }
/*    測試查詢*/
    @Test
    public void findById() {
        Integer id=8;
        User user = mapper.findById(id);
        System.out.println(user);
    }
/*    測試修改*/
    @Test
    public void updatenew() {
        User user = new User();
        user.setUsername("小珠佩琦");
        user.setPassword("5548");
        user.setAge(18);
        user.setEmail("[e-mail]");
        user.setPhone("448484");
        user.setId(6);
        Integer num = mapper.updatenew(user);
        System.out.println("num:"+num);
    }
/*    測試刪除*/
    @Test
    public void deletenew() {
        Integer age = 60;
        Integer row = mapper.deletenew(age);
        System.out.println("row:"+row);
    }

}