SSM框架-MyBatis学习日记1

1.搭建试验数据库

CREATE DATABASE `MyBatis`;

USE `MyBatis`;

CREATE TABLE `user`(
`id` INT(20) NOT NULL PRIMARY KEY,
`name` VARCHAR(30) DEFAULT NULL,
`pwd` VARCHAR(30) DEFAULT NULL
)ENGINE=INNODB DEFAULT CHARSET=utf8;

INSERT INTO `user`(`id`,`name`,`pwd`)VALUES
(1,'张三','123456'),
(2,'李四','1234567'),
(3,'王五','12345678');

2、导入MyBatis相关 jar 包

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.2</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.47</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.11</version>
        <scope>test</scope>
    </dependency>
</dependencies>

3、编写MyBatis工具类

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 {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        //使用MyBatis第一步 获取SqlSessionFactory对象
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    public static SqlSession getSqlSession(){
        return  sqlSessionFactory.openSession();
    }
}

4、编写MyBatis核心配置文件

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=utf8&amp;serverTimezone=GMT"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/kuang/dao/userMapper.xml"/>
    </mappers>
</configuration>

5、创建实体类

//idea快速生成get/set方法快捷键：alt+insert

//实体类
public class User {
    private int id;
    private String name;
    private String pwd;

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getPwd() {
        return pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

5、编写Mapper接口类

public interface UserDao {
    List<User> getUserList();
}

6、编写Mapper.xml配置文件

接口实现类由原来的UserDaoImpl转换为一个Mapper配置文件

<?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">
<!--namespace绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.kuang.dao.UserDao">
    <select id="getUserList" resultType="com.kuang.pojo.User">

        select * from user
    </select>
</mapper>

7、修改Maven配置（静态过滤器问题）

<resources>
   <resource>
       <directory>src/main/java</directory>
       <includes>
           <include>**/*.properties</include>
           <include>**/*.xml</include>
       </includes>
       <filtering>false</filtering>
   </resource>
   <resource>
       <directory>src/main/resources</directory>
       <includes>
           <include>**/*.properties</include>
           <include>**/*.xml</include>
       </includes>
       <filtering>false</filtering>
   </resource>
</resources>

8、编写测试代码

public class UserDaoTest {
    @Test
    public void test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        try {
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            List<User> userList = userDao.getUserList();

            //这是一个循环，相当于从userList里面取出每个元素user；在{}里可以直接使用user，即每次取出的值。
            for (User user:userList){
                System.out.println(user);
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }finally {
            //关闭sqlSession
            sqlSession.close();
        }

    }
}

9、总结

首先按照Mybatis的文档要求，我们应该首先配置工具类（MyBatisUtils），接着因为工具类需要调用mybatis-config.xml所以在resource文件夹下进行配置。

接着因为需要在mybatis-config.xml中配置mapper文件，所以我们需要对UserMapper.xml进行配置。

UserMapper.xml需要调用一个Dao接口（以及里面的方法）与实体类，所以对UserDao与User类进行编写。

最后在配置Maven过滤器之后，即可通过junit进行测试。

文件路径如下：