MyBatis框架——单表查询

Mybatis单表查询，示例

1、创建数据库

/*
Navicat MySQL Data Transfer

Source Server         : localhost
Source Server Version : 50620
Source Host           : 127.0.0.1:3306
Source Database       : mybatis

Target Server Type    : MYSQL
Target Server Version : 50620
File Encoding         : 65001

Date: 2020-03-22 14:02:25
*/

;

-- ----------------------------
-- Table structure for t_user
-- ----------------------------
DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user` (
  `id` ) NOT NULL AUTO_INCREMENT,
  `username` ) DEFAULT NULL,
  `password` ) DEFAULT NULL,
  `age` ) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of t_user
-- ----------------------------
');
');

2、创建实体类

package com.sunjian.entity;

/**
 * @author sunjian
 * @date 2020/3/22 9:59
 */
public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;

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

    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;
    }
}

3、编写repository接口

package com.sunjian.repository;

import com.sunjian.entity.User;

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

/**
 * @author sunjian
 * @date 2020/3/22 10:44
 */
public interface UserRepository {
    public User findUserById(Integer id);
    public User findUserByName(String name);
    public User findUserByIdAndName(int id, String name);
    public User findUserByUser(User user);

    public String findUsernameById(Integer id);

    public List<User> findAll();

    public void addUser(User user);

    public void deleteUser(Integer id);

    public void updateUser(User user);
}

4、编写mapper.xml文件

<?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.sunjian.repository.UserRepository">
    <select id="findUserById" parameterType="java.lang.Integer" resultType="com.sunjian.entity.User">
        select * from t_user where id = #{id}
    </select>

    <select id="findAll" resultType="com.sunjian.entity.User">
        select * from t_user
    </select>

    <insert id="addUser" parameterType="com.sunjian.entity.User">
        insert into t_user(username, password, age)values(#{username}, #{password}, #{age})
    </insert>

    <delete id="deleteUser" parameterType="java.lang.Integer">
        delete from t_user where id = #{id}
    </delete>

    <update id="updateUser" parameterType="com.sunjian.entity.User">
        update t_user set username = #{username}, password = #{password}, age = #{age} where id = #{id}
    </update>

    <select id="findUserByName" parameterType="String" resultType="com.sunjian.entity.User">
        select * from t_user where username = #{username}
    </select>

    <select id="findUserByIdAndName" resultType="com.sunjian.entity.User">
        select * from t_user where id = #{param1} and username = #{param2}
    </select>

    <select id="findUserByUser" parameterType="com.sunjian.entity.User" resultType="com.sunjian.entity.User">
        select * from t_user where id = #{id} and username = #{username}
    </select>

    <select id="findUsernameById" parameterType="java.lang.Integer" resultType="java.lang.String">
        select username from t_user where id = #{id}
    </select>
</mapper>

5、编写config.xml文件，将mapper.xml注册到config.xml文件中

<?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>
    <!-- 配置 MyBatis 数据源 -->
    <environments default="development">
        <environment id="development">
            <!-- JDBC事务管理 -->
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <!-- 注册 -->
        <mapper resource="com/sunjian/repository/UserRepository.xml"></mapper>
    </mappers>

</configuration>

6、编写测试类

package com.sunjian.test;

import com.sunjian.entity.User;
import com.sunjian.repository.UserRepository;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

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

/**
 * @author sunjian
 * @date 2020/3/22 10:20
 */
public class Test {
    public static void main(String[] args) {// Mapper 代理实现自定义接口
        InputStream inputStream = User.class.getClassLoader().getResourceAsStream("config.xml");
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        // 获取接口的处理对象
        UserRepository userRepository = sqlSession.getMapper(UserRepository.class);

        // 增加
//        User u = new User();
//        u.setUsername("王五2");
//        u.setPassword("123456");
//        u.setAge(19);
//        userRepository.addUser(u);
//        sqlSession.commit();

        // 删除
//        userRepository.deleteUser(3);
//        sqlSession.commit();

        // 修改
//        User u2 = userRepository.findUserById(1);
//        if(u2 != null){
//            u2.setUsername("张三1");
//            u2.setPassword("1234567");
//            u2.setAge(88);
//            userRepository.updateUser(u2);
//            sqlSession.commit();
//        }

        // 根据id查
//        User user = userRepository.findUserById(2);
//        System.out.println(user);

        // 查所有
//        List<User> list = userRepository.findAll();        //        for(User u1: list){
//            System.out.println(u1);
//        }

        // 根据username查
        User u3 = userRepository.findUserByName("张三");
        System.out.println(u3);

        // 根据id和username查
        User u4 = userRepository.findUserByIdAndName(2, "张三");
        System.out.println(u4);

        // 根据User查
        User u5 = new User();
        u5.setId(2);
        u5.setUsername("张三");
        u5 = userRepository.findUserByUser(u5);
        System.out.println(u5);

        // 根据id查username
        String username = userRepository.findUsernameById(2);
        System.out.println(username);
    }

}

pom.xml

<?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.sunjian</groupId>
    <artifactId>mybatisPrac</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
    </dependencies>

    <build>
        <!-- 允许程序读取src/main/java目录下的xml文件 -->
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
        </resources>

    </build>

</project>

OK.