MyBatis学习（二）——第一个MyBatis程序及配置

梦里梦外; 2022-12-28 09:27 145阅读 0赞

# MyBatis学习 #

### MyBatis程序 ###

*  MyBatis学习
 *  2.1、创建一个SQL表
 *  2.2、创建项目
 *  2.3、创建模块
 *  2.4、测试
 *  总流程
 *   *  各个部分代码：
     *   *  配置文件
         *  工具类
         *  mybatis配置文件
         *  实体类
         *  接口和Mapper.xml

# 2.1、创建一个SQL表 #

create database mybatis;
     use mybatis;
    create table user(
     	id int(20) 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");

![在这里插入图片描述][20201216150933569.png]  
![在这里插入图片描述][2020121615155642.png]  
![在这里插入图片描述][2020121615171598.png]  
![在这里插入图片描述][2020121615213019.png]

# 2.2、创建项目 #

*  新建一个Maven项目  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70]

Maven依赖

<dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.49</version>
            </dependency>
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.3</version>
            </dependency>
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.13</version>
                <scope>test</scope>
            </dependency>

# 2.3、创建模块 #

*  **编写mybatis核心配置文件**  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 1]

<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?userSSL=true&userUnicode=true&characterEncoding=utf-8"/>
                    <property name="username" value="root"/>
                    <property name="password" value="123456"/>
                </dataSource>
            </environment>
        </environments>
           
        <mappers>
            <mapper resource="com/my/dao/UserMapper.xml"/>
        </mappers>
    
    </configuration>

*  **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;
    
    //sqlSessionFactory  构建sqlSession
    public class MybatisUtils {
    
        private static SqlSessionFactory sqlSessionFactory;
        static {
            try{
                //使用mybatis第一步 获取sqlSessionFactory对象
                String resource = "mybatis-config.xml";
                InputStream inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
    /*    既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
         SqlSession 提供了在数据库执行  命令所需的所有方法。
        可以通过 SqlSession 实例来直接执行已映射的 SQL 语句*/
    
        public static SqlSession getSqlSession(){
            return sqlSessionFactory.openSession();
        }
    }

*  **编写代码**
 *  **实体类**

//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 void setId(int id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getPwd() {
            return pwd;
        }
    
        public void setPwd(String pwd) {
            this.pwd = pwd;
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", pwd='" + pwd + '\'' +
                    '}';
        }
    }

*  **Dao接口**

import com.my.pojo.User;
    
    import java.util.List;
    
    public interface UserDao {
        List<User> getUserList();
    
    }

*  **接口实现类由原来的dao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">
    
    <mapper namespace="com.my.dao.UserDao">
    
        
        <select id="getUserList" resultType="com.my.pojo.User">
        select * from mybatis.user
      </select>
    </mapper>

# 2.4、测试 #

![在这里插入图片描述][20201216180454900.png]

package com.my.dao;
    
    import com.my.pojo.User;
    import com.my.utils.MybatisUtils;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    
    import java.util.List;
    
    
    public class UserDaoTest {
        
        @Test
        public void test(){
        
    //第一步，获取sqlSession对象
            SqlSession sqlSession = MybatisUtils.getSqlSession();
            //方式一 执行sql getMapper
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            List<User> userList = userDao.getUserList();
    
            for (User user : userList) {
        
                System.out.println(user);
            }
    
            //关闭sqlSession
            sqlSession.close();
    
    
        }
    }

运行：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 2]

# 总流程 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 4]

## 各个部分代码： ##

### 配置文件 ###

<?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>org.example</groupId>
        <artifactId>MyBatis-Study</artifactId>
        <packaging>pom</packaging>
        <version>1.0-SNAPSHOT</version>
        <modules>
            <module>mybatis-01</module>
        </modules>
    
        
        <dependencies>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.49</version>
            </dependency>
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.3</version>
            </dependency>
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.13</version>
                <scope>test</scope>
            </dependency>
    
        </dependencies>
        
        <build>
            <resources>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.xml</include>
                        <include>**/*.properties</include>
                    </includes>
                </resource>
    
                <resource>
                    <directory>src/main/resources</directory>
                    <includes>
                        <include>**/*.xml</include>
                        <include>**/*.properties</include>
                    </includes>
                </resource>
            </resources>
        </build>
    
    
    </project>

### 工具类 ###

package com.my.utils;
    
    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;
    
    //sqlSessionFactory  构建sqlSession
    public class MybatisUtils {
        
        private static SqlSessionFactory sqlSessionFactory;
        static {
        
            try{
        
                //使用mybatis第一步 获取sqlSessionFactory对象
                String resource = "mybatis-config.xml";
                InputStream inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
        
                e.printStackTrace();
            }
        }
    /*    既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
         SqlSession 提供了在数据库执行  命令所需的所有方法。
        可以通过 SqlSession 实例来直接执行已映射的 SQL 语句*/
    
        public static SqlSession getSqlSession(){
        
            return sqlSessionFactory.openSession();
        }
    }

### mybatis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&userUnicode=true&characterEncoding=utf-8"/>
                    <property name="username" value="root"/>
                    <property name="password" value="123456"/>
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
            <mapper resource="com/my/dao/UserMapper.xml"/>
        </mappers>
    
    </configuration>

### 实体类 ###

package com.my.pojo;
    
    //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 void setId(int id) {
        
            this.id = id;
        }
    
        public String getName() {
        
            return name;
        }
    
        public void setName(String name) {
        
            this.name = name;
        }
    
        public String getPwd() {
        
            return pwd;
        }
    
        public void setPwd(String pwd) {
        
            this.pwd = pwd;
        }
    
        @Override
        public String toString() {
        
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", pwd='" + pwd + '\'' +
                    '}';
        }
    }

### 接口和Mapper.xml ###

package com.my.dao;
    
    import com.my.pojo.User;
    
    import java.util.List;
    
    public interface UserDao {
        
        List<User> getUserList();
    
    }

[20201216150933569.png]: /images/20221120/86965387442d4ec98d2742496d204614.png
[2020121615155642.png]: /images/20221120/8989cf3dd8174849ba78bdd12faab8ec.png
[2020121615171598.png]: /images/20221120/eab4de14b24f489ba18c7c7094a1da35.png
[2020121615213019.png]: /images/20221120/a743d2ab5ab241ff99aaeee9ee767b8c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70]: /images/20221120/4629933665ab4a0fb206b22571e06627.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 1]: /images/20221120/9467ef4498ac4f9da8d0fc9d79f5f7b6.png
[20201216180454900.png]: /images/20221120/f8053d792d644006b5baa2c5d5097983.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 2]: /images/20221120/e0d2d9aa52414cd68a0803948b60d259.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 3]: /images/20221120/c4c428907a994255b6316274833600f8.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 4]: /images/20221120/15eca6b040534d11bc0e1721017f90c7.png