Mybatis的初始化

ゝ一纸荒年。 2023-10-03 13:22 8阅读 0赞

## 一、添加jar包 ##

<dependencies>
    
        
        <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>8.0.22</version>
        </dependency>
    
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.11</version>
          <scope>test</scope>
        </dependency>
        
        <dependency>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
          <version>3.5.2</version>
        </dependency>

这是用了Maven构建工具来添加jar包

## 二、配置Mybatis-config.xml ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc_size_16_color_FFFFFF_t_70][]

内容如下

<?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.cj.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/Book?useSSL=false&serverTimezone=UTC&useUnicode=true&characterEncoding=UTF-8&allowPublicKeyRetrieval=true"/>
                    <property name="username" value="root"/>
                    <property name="password" value="密码"/>
                </dataSource>
            </environment>
        </environments>
    
        <mappers>
            <mapper resource="com/gy/dao/UserMapper.xml"/>
            <mapper resource="com/gy/dao/PageMapper.xml"/>
            <mapper resource="com/gy/dao/StudentMapper.xml"/>
        </mappers>
    </configuration>

## 三、编写MybatisUtils工具类 ##

package com.gy.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;
    
    public class MybatisUtils {
       static SqlSessionFactory  sqlSessionFactory =null;
        static {
            try {
                String resource = "mybatis-config.xml";//resources目录下的文件可以直接访问。
                InputStream inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
        public static SqlSession getSqlSession(){
            return sqlSessionFactory.openSession();
        }
    }

依据为官网帮助文档

![20210812095257100.png][]

sqlSessionFactoryBuilder应该为局部变量，而SqlSessionFactory应该为静态变量。

## 四、开始编写代码并使用 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc_size_16_color_FFFFFF_t_70 1][]

### （1）UserMapper为接口只需要写返回类型和方法名即可 ###

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

### （2）编写对应的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 namespace="com.gy.dao.UserMapper">
    
        
    
    
        <select id="getUserList" resultType="com.gy.pojo.User">
            select * from mybatis.user;
        </select>
        
        <select id="getUserOne" resultType="com.gy.pojo.User">
            select * from mybatis.user where id=2;
        </select>
    
    
    </mapper>

### （3）还有就是要在Maven的pom.xml添加如下代码(第一篇文章有说) ###

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

### （4）使用并测试 ###

package com.gy.dao;
    
    import com.gy.pojo.User;
    import com.gy.utils.MybatisUtils;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    
    import java.util.List;
    
    public class UserDaoTest {
        @Test
        public void test(){
    
            //不需要手动关闭流了 不管如何都会关闭try()中的流对象
            // 获取sqlSession对象
            try(SqlSession sqlSession = MybatisUtils.getSqlSession()){
                //获取mapper接口对象
                UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
                //直接执行mapper接口中写好的方法getUserList()即可
                List<User> userList = userMapper.getUserList();
                for (User user : userList) {
                    System.out.println(user);
                }
                //直接执行mapper接口中写好的方法getUserOne()即可
                User userOne = userMapper.getUserOne();
                System.out.println(userOne);
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc_size_16_color_FFFFFF_t_70 2][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20210812094700365.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc=,size_16,color_FFFFFF,t_70
[20210812095257100.png]: https://img-blog.csdnimg.cn/20210812095257100.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20210812095748427.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20210812100726522.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDc3NDc=,size_16,color_FFFFFF,t_70