USE mybatisdemo

CREATE TABLE users(
    uid INT PRIMARY KEY AUTO_INCREMENT,
    uname VARCHAR(20) NOT NULL,
    uage INT NOT NULL
);
INSERT INTO users(uid,uname,uage) VALUES(NULL,'張##',25),(NULL,'李##',23),(NULL,'王##',23);

IDEA 創(chuàng)建 maven工程

完成之后如下圖所示：

在 src - main - java 下新建 package，名字為 com.mybatisdemo.pojo

在 com.mybatisdemo.pojo 中新建類 User.java

package com.mybatisdemo.pojo;

public class User {
    private int uid;             //用戶id
    private String uname;       //用戶姓名
    private int uage;            //用戶年齡
    public int getUid() {
        return uid;
    }
    public void setUid(int uid) {
        this.uid = uid;
    public String getUname() {
        return uname;
    public void setUname(String uname) {
        this.uname = uname;
    public int getUage() {
        return uage;
    public void setUage(int uage) {
        this.uage = uage;
}

在 resources 下新建文件夾 mapper

在 mapper 下建文件 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為映射的根節(jié)點-->
<!-- mapper為映射的根節(jié)點，namespace指定Dao接口的完整類名
mybatis會依據(jù)這個接口動態(tài)創(chuàng)建一個實現(xiàn)類去實現(xiàn)這個接口，
而這個實現(xiàn)類是一個Mapper對象-->
<mapper namespace="com.mybatisdemo.pojo.User">
    <!--id ="接口中的方法名"
　　parameterType="傳入的參數(shù)類型"
　　resultType = "返回實體類對象，使用包.類名"-->
    <select id="findById" parameterType="int"
            resultType="com.mybatisdemo.pojo.User">
         select * from users where uid = #{id}
    </select>
</mapper>

在 resources 下新建 db.properties

mysql.driver=com.mysql.cj.jdbc.Driver
mysql.url=jdbc:mysql://127.0.0.1:3306/mybatisdemo?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
mysql.username=root
mysql.password=123456

在 resources 下新建 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>
    <!-- 環(huán)境配置 -->
    <!-- 加載類路徑下的屬性文件 -->
    <properties resource="db.properties"/>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <!-- 數(shù)據(jù)庫連接相關(guān)配置 ,db.properties文件中的內(nèi)容-->
            <dataSource type="POOLED">
                <property name="driver" value="${mysql.driver}"/>
                <property name="url" value="${mysql.url}"/>
                <property name="username" value="${mysql.username}"/>
                <property name="password" value="${mysql.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- mapping文件路徑配置 -->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>

</configuration>

test - java - 下建 package, 名字為Test

test - java - Test 下建立文件 UserTest.java

package Test;

import com.mybatisdemo.pojo.User;
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 org.junit.Test;
import java.io.IOException;
import java.io.Reader;
public class UserTest {
    @Test
    public void userFindByIdTest() {
        //讀取文件名
        String resources = "mybatis-config.xml";
        //創(chuàng)建流
        Reader reader = null;
        try {
            //讀取mybatis-config.xml文件內(nèi)容到reader對象中
            reader = Resources.getResourceAsReader(resources);
        } catch (IOException e) {
            e.printStackTrace();
        }
        //初始化mybatis數(shù)據(jù)庫,創(chuàng)建SqlSessionFactory類的實例
        SqlSessionFactory sqlMapper = new
                SqlSessionFactoryBuilder().build(reader);
        //創(chuàng)建SqlSession實例
        SqlSession session = sqlMapper.openSession();
        //傳入?yún)?shù)查詢，返回結(jié)果
        User user = session.selectOne("findById", 1);
        //輸出結(jié)果
        System.out.println(user.getUname());
        //關(guān)閉session
        session.close();
    }
}

修改 pom.xml 文件

<?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.mybatisdemo</groupId>
    <artifactId>mybatis_demo01</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <!--               <scope>test</scope>-->
            <scope>compile</scope>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

最終的文件：