1.4JavaEE——MyBatis入门程序

女爷i 2024-03-16 21:12 59阅读 0赞

**在MyBatis环境下实现一个入门程序来演示MyBatis框架的使用，该程序要求实现根据id查询用户信息的操作。**

1.  **数据准备**：在mybatis数据库中创建users表，并在users表中插入几条数据。

use mybatis;
    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,'张三',20),(null,'李四',18);

select * from users;  //查看users内容

![240eb562208542f6808bf59b1a224ee3.png][]

2、**创建POJO实体**：在项目的src/main/java目录下创建com.mac.pojo包，在com.mac.pojo包下创建User类，该类用于封装User对象的属性。

public class User {
            private int uid;
            private String uname;
            private int uage;
    
            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;
            }
        }

3、**创建映射文件UserMapper.xml**：在项目的src/main/resources目录下创建一个文件夹，在mapper文件夹下创建映射文件UserMapper.xml，该文件主要用于实现SQL语句和Java对象之间的映射，使SQL语句查询出来的关系型数据能够被封装成Java对象。

<mapper namespace="com.mac.pojo.User">
        
        <select id="findById" parameterType="int" resultType="com.mac.pojo.User">
            select *
            from users
            where uid = #{id}
      </select>
    </mapper>

![57dffe46898942d187219589d8552a96.png][]

4、**修改mybatis-config.xml配置文件**：在mybatis-config.xml映射文件中添加UserMapper.xml映射文件路径的配置，用于将UserMapper.xml映射文件加载到程序中。

<!– mapping文件路径配置-->
    
    <mappers>
    
        <mapper resource="mapper/UserMapper.xml"/>
    
    </mappers>

![323dfa20b5be4beb86a43d22e39cdf9f.png][]

<?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"/>
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="${mysql.driver}"/>
                    <property name="url" value="${mysql.url}"/>
                    <property name="username" value="root"/>
                    <property name="password" value="qazxcv001"/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
            <mapper resource="mapper/UserMapper.xml"/>
        </mappers>
    </configuration>

**这里username是mysql的用户名，我的用户名为root，password为mysql的登陆密码，我的密码为qazxcv001**

注:如果一个项目有多个映射文件，则mybatis-config.xml核心配置文件中需要在<mappers>元素下配置多个<mapper>元素指定映射文件的路径。

**5、编写测试类**：在项目的src/test/java目录下创建Test包，在Test包下创建UserTest类，该类主要用于程序测试。

public void userFindByIdTest(){
            String resources="mybatis-config.xml";
            Reader reader=null;
            try{
                reader= Resources.getResourceAsReader(resources);
            }catch (IOException e){
                e.printStackTrace();
            }
            SqlSessionFactory sqlMapper=new SqlSessionFactoryBuilder().build(reader);
            SqlSession session= sqlMapper.openSession();
            User user=session.selectOne("findById",1);
            System.out.println(user.getUname());
            session.close();
        }

![385b7357007e46ccb328e618dd5d77f6.png][]

package Test;
    
    import com.mac.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(){
            String resources="mybatis-config.xml";
            Reader reader=null;
            try{
                reader= Resources.getResourceAsReader(resources);
            }catch (IOException e){
                e.printStackTrace();
            }
            SqlSessionFactory sqlMapper=new SqlSessionFactoryBuilder().build(reader);
            SqlSession session= sqlMapper.openSession();
            User user=session.selectOne("findById",1);
            System.out.println(user.getUname());
            session.close();
        }
    }

**运行结果如下**

![e487cce446da4e7da0c0f3034b37e8b6.png][]

所有的项目如下：

![6720bcc4ba5a4d018cf4d6f2810b5f30.png][]

[240eb562208542f6808bf59b1a224ee3.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/7f5b2ab510384de29b94bdffdd0d81dd.png
[57dffe46898942d187219589d8552a96.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/909e940f5710440c8c856eeb3c1a879b.png
[323dfa20b5be4beb86a43d22e39cdf9f.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/e53faba2c9a243f9935e9f49858c03f4.png
[385b7357007e46ccb328e618dd5d77f6.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/d2667f0f80534d25bce56b9471df4db8.png
[e487cce446da4e7da0c0f3034b37e8b6.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/971fb2c2570540d6b7742a8fd702c55e.png
[6720bcc4ba5a4d018cf4d6f2810b5f30.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/e2e6c58052e7470db5b989ef4b0add29.png