mybatis入门之XML配置 idea版（含目录结构与sql语句）_idea中sql语句返回类型是int型,xml中的sql返回类型怎么写-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_43508555/article/details/113869317

本文详细介绍了如何在Maven项目中配置Mybatis，包括数据库连接、XML映射文件、Java接口、配置文件、单元测试和目录结构，适合初学者快速上手。

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mybatis入门之XML配置

maven目录结构

在这里插入图片描述

1、创建一个maven项目

如果你的maven项目加载不了依赖
方法炒鸡简单 —>：maven经常报错,改改你的setting.xml

2、配置pom文件

mysql依赖：数据库
mybatis依赖
junit依赖：用于单元测试
log4j：日志打印
build 在mybatis中必须写，因为在编译时加载不了src/main/java下的xml等文件


<dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
    </dependencies>


    <!--在mybatis当中，必须写-->
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.properties</include>
                    <include>**/*.yml</include>
                </includes>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.properties</include>
                    <include>**/*.yml</include>
                </includes>
            </resource>
        </resources>
    </build>

3、创建数据库及数据库表

CREATE DATABASE mybatis;
use mybatis;
CREATE TABLE IF NOT EXISTS user (
	id int(20) not null primary key,
    name VARCHAR(50) default NULL,
    pwd VARCHAR(50) default null 
)engine=innodb;

insert into user(id,name,pwd) values
(1,'贾立桐','123123'),
(2,'李四','123456'),
(3,'王麻子','111111');

4、java类和接口

4.1 User.java实体类

此处省略了有参构造及无参构造，getter and setter，toString，请自己添加
快捷键 Alt+insert

package com.tong.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;
    
    //有参构造及无参构造
    //getter and setter
    //toString
}

4.2、UserMapper.java 接口

package com.tong.dao;

import com.tong.pojo.User;

import java.util.List;

public interface UserMapper {

    List<User> getUserList();

    User getUserById(int id);

    int addUser(User user);

    int updateUser(User user);

    int deleteUser(int id);
}

4.3、UserMapper.xml 文件

mapper标签里的namespace 为对应的接口类的全限定名
resultType ：返回值类型，基本类型填名称，引用类型填全限定名称 （这里使用User而未使用com.tong.pojo.User的原因为在mybatis文件中配置了别名，请继续往后看）
parameterType：参数类型

<?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.tong.dao.UserMapper">

    <select id="getUserList" resultType="User">
        select * from user
    </select>

    <select id="getUserById" parameterType="int" resultType="User">
        select * from user where id = #{id}
    </select>

    <insert id="addUser" parameterType="User" >
        insert into user (id,name,pwd) values (#{id},#{name},#{pwd})
    </insert>

    <update id="updateUser" parameterType="User" >
        update user set name=#{name},pwd=#{pwd} where id = #{id}
    </update>

    <delete id="deleteUser" parameterType="int" >
        delete from user where id = #{id}
    </delete>
</mapper>

5、mybatis相关配置

5.1、db.properties文件

url后的mybatis为数据库名

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis
username=root
password=这里填你自己的密码

5.2、mybatis_config.xml文件

settings标签中配置了日志类型，此处选择为log4j
typeAliases 标签中配置了别名，可不使用全限定名，简化开发
environments 标签中配置mybatis环境，可创建多个环境environment ，在environments标签中的default来选中环境
dataSource 配置数据源
mappers 标签讲Mapper XML文件注册到Mybatis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>
    <properties resource="db.properties"/>
    
    <settings>
        <setting name="logImpl" value="LOG4J"/>
    </settings>
    <typeAliases>
        <package name="com.tong.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <package name="com.tong.dao"/>
    </mappers>
</configuration>

5.3、log4j.properties

log4j.rootLogger=DEBUG, Console

#Console
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%n

log4j.logger.java.sql.ResultSet=INFO
log4j.logger.org.apache=INFO
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

6、测试（5步）

6.1、MybatisUtils.java

读取配置文件
创建SqlSessionFactory工厂
使用工厂生产sqlSession对象

package com.tong.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 java.io.IOException;
import java.io.InputStream;

public class MybatisUtils {
    //创建一个工厂
    private static SqlSessionFactory sqlSessionFactory = null;
    static {
        try {
            InputStream in = Resources.getResourceAsStream("mybatis_config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //获取session
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

6.2、UserMapperTest.java

使用sqlSession创建DAO接口的代理对像
使用代理对象执行方法

package com.tong.dao;

import com.tong.pojo.User;
import com.tong.util.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.Before;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {
    private SqlSession session;
    private UserMapper userMapper;
    static Logger logger = Logger.getLogger(UserMapperTest.class);

    @Before
    public void init(){
        session = MybatisUtils.getSqlSession();
    }

    @Test
    public void getAll(){

        try {
            userMapper = session.getMapper(UserMapper.class);
            List<User> list = userMapper.getUserList();
            for (User user:list) {
                System.out.println(user);
            }
        }finally {
            session.close();
        }
    }

    @Test
    public void getUserByIdTest(){
        userMapper = session.getMapper(UserMapper.class);
        User user = userMapper.getUserById(1);
        System.out.println(user);
        session.close();
    }

    @Test
    public void adduser(){
        userMapper = session.getMapper(UserMapper.class);
        int res = userMapper.addUser(new User(4,"艾瑞克","987654"));
        if (res>0){
            System.out.println("插入成功");
        }
        session.commit();
        session.close();
    }

    @Test
    public void updateUser(){
        userMapper = session.getMapper(UserMapper.class);
        int res = userMapper.updateUser(new User(2,"李四儿","111222"));
        if (res>0){
            System.out.println("更新成功");
        }
        session.commit();
        session.close();
    }

    @Test
    public void deleteUser(){
        userMapper = session.getMapper(UserMapper.class);
        int res = userMapper.deleteUser(2);
        session.commit();
        session.close();
    }

    @Test
    public void Log4jTest(){
        logger.info("111");
        logger.debug("222");
        logger.error("333");
    }
}