mybatis入门篇（一）：通过SqlSession.selectList进行数据查询

你的名字 2022-10-02 00:52 22阅读 0赞

[2019独角兽企业重金招聘Python工程师标准>>> ][2019_Python_] ![hot3.png][]

作为一个java菜鸟，早就从慕课网中学到一些基本的mybatis的用法，但是一直不成体系，懵懵懂懂，既然正式入了java这个坑，就打算好好学学，所以买了本《MyBatis从入门到精通》，在此记录下学习的点滴，便于日后温习。

强调一下：这些代码是我根据书籍编写的代码并亲自运行测试的，严格意义上说，这些并非我个人原创

数据库版本：Server version: 8.0.15 MySQL Community Server - GPL 数据准备：

![c3c23dacce55b6feb6092214b0f9dfbdfba.jpg][]

先写一个最简单的查询 1、新建一个空白的maven项目，引入相关依赖包

<dependencies>
        
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.0</version>
        </dependency>
        
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.15</version>
        </dependency>
    </dependencies>

2、在resources中添加mybatis的配置文件mybatis-config.xml 这里选用最基本的jdbc事务管理器，不用数据库连接池。此处因为mysql的版本原因，要禁用SSL。同时配置数据库实体的位置和mapper文件路径。

<?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="com.forest.owl.entity"/>
        </typeAliases>
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC">
                    <property name="" value=""/>
                </transactionManager>
                <dataSource type="UNPOOLED">
                    <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/forest?useSSL=false"/>
                    <property name="username" value="root"/>
                    <property name="password" value="root"/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
            <mapper resource="mapper/UserMapper.xml" />
        </mappers>
    </configuration>

2、编辑数据库实体User

import java.util.Date;
    public class User {
        private int id;
        private String account;
        private String passwd;
        private String nickname;
        private String phone;
        private String email;
        private Date createTime;
        private Date updateTime;
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getAccount() {
            return account;
        }
        public void setAccount(String account) {
            this.account = account;
        }
        public String getPasswd() {
            return passwd;
        }
        public void setPasswd(String passwd) {
            this.passwd = passwd;
        }
        public String getNickname() {
            return nickname;
        }
        public void setNickname(String nickname) {
            this.nickname = nickname;
        }
        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;
        }
        public Date getCreateTime() {
            return createTime;
        }
        public void setCreateTime(Date createTime) {
            this.createTime = createTime;
        }
        public Date getUpdateTime() {
            return updateTime;
        }
        public void setUpdateTime(Date updateTime) {
            this.updateTime = updateTime;
        }
    }

3、在resources中添加mapper文件夹，在该文件夹中添加UserMapper.xml文件 mapper文件的命名空间是必须的，这里是随便命名，暂且还不清楚该属性的具体作用。

<!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="mapper">
        <select id="selectUsers" resultType="com.forest.owl.entity.User">
            SELECT id, account, passwd, nickname, phone, email, create_time as createTime, update_time as updateTime
            FROM user
        </select>
    </mapper>

4、编写测试类

import com.forest.owl.entity.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.BeforeClass;
    import org.junit.Test;
    import java.io.IOException;
    import java.io.Reader;
    import java.util.List;
    public class TestUserMapper {
        private static SqlSessionFactory sqlSessionFactory;
        @BeforeClass
        public static void init(){
            try {
                Reader reader = Resources.getResourceAsReader("mybatis.config.xml");
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        @Test
        public void TestMybatis(){
            SqlSession sqlSession = sqlSessionFactory.openSession();
            List<User> userList = sqlSession.selectList("selectUsers");
            System.out.println(userList.size());
            System.out.println(userList.get(0).getNickname());
            System.out.println(userList.get(0).getCreateTime());
        }
    }

测试结果：

![189c493f6b015de120df8e38192f848594c.jpg][]

转载于:https://my.oschina.net/u/4108765/blog/3059535

[2019_Python_]: https://my.oschina.net/u/2663968/blog/3061697
[hot3.png]: /images/20220113/43df393638ab480996754d66816ee4a1.png
[c3c23dacce55b6feb6092214b0f9dfbdfba.jpg]: /images/20220113/f29ca230a0b2427f841d4f57e225d8ee.png
[189c493f6b015de120df8e38192f848594c.jpg]: /images/20220113/d91909152bd4467b9e4ff84fbcaabc42.png