Mybatis - 简单使用_mybatis [ca-优快云博客

本文链接：https://blog.youkuaiyun.com/DarinWang/article/details/107646168

本文详细介绍了一个基于Maven项目、MySQL数据库和Java8的MyBatis使用案例，包括项目结构、依赖包、数据库创建、配置文件设置、XML映射文件编写以及Java代码实现，展示了如何通过MyBatis进行数据查询。

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Mybatis 使用

开发环境: maven 项目, mysql 数据库, java 8.

项目结构

project:
	pom.xml
	src:
		main:
			java:
				ca.wd4.learn:
					entity:
						User.java
					mapper:
						UserMapper.java
					UserMapperTest.java
			resources:
				mapper:
					UserMapper.xml
				mybatis-config.xml

导包

<!--mybatis-->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.5</version>
</dependency>

<!--mysql-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.21</version>
</dependency>

建库建表

库名: student

表名: user

建表语句

create table `user` (
	`id` int(11) not null,
  `username` varchar(255) default null,
  `password` varchar(255) default null,
  primary key (`id`)
);

Mybatis 配置文件

mybatis-config.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>

    <typeAliases>
        <package name="ca.wd4.learn.entity"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/student"/>
                <property name="username" value="root"/>
                <property name="password" value=""/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>
</configuration>

mapper/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="ca.wd4.learn.mapper.UserMapper">
    <select id="findAll" resultType="User">
        select * from user
    </select>
    <select id="findUserById" resultType="user">
        select * from user where id = #{id}
    </select>
</mapper>

Java

User.java

package ca.wd4.learn.entity;

import lombok.Data;

import java.io.Serializable;

@Data // lombok
public class User implements Serializable {
    private int id;
    private String username;
    private String password;
}

UserMapper.java

package ca.wd4.learn.mapper;

import ca.wd4.learn.entity.User;
import org.apache.ibatis.annotations.Mapper;

import java.util.List;

@Mapper
public interface UserMapper {
    public List<User> findAll();
    public User findUserById(int id);
}

UserMapperTest.java

package ca.wd4.learn;

import ca.wd4.learn.entity.User;
import ca.wd4.learn.mapper.UserMapper;
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.Reader;
import java.util.List;

public class UserMapperTest {
    public static void main(String[] args) {
        try {
            Reader resourceAsReader = Resources.getResourceAsReader("mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsReader);
            resourceAsReader.close();

            SqlSession sqlSession = sqlSessionFactory.openSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            List<User> selectAll = userMapper.findAll();
            System.out.println(selectAll.toString());
            User one = userMapper.findUserById(1);
            System.out.println(one);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}