MyBatis的配置和简单使用

谁践踏了优雅 2023-10-01 20:28 20阅读 0赞

### 配置 ###

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pom.xml

<dependencies>
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.7</version>
            </dependency>
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
                <scope>test</scope>
            </dependency>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.3</version>
            </dependency>
            
            <dependency>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
                <version>1.2.17</version>
            </dependency>
        </dependencies>

mybatis-config.xml

<?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="jdbc.properties"></properties>
        <settings>
            
            <setting name="mapUnderscoreToCamelCase" value="true"/>
            
            <setting name="lazyLoadingEnabled" value="true"/>
        </settings>
        <typeAliases>
            
            
            
            
            <package name="com.atguigu.mybatis.pojo"/>
        </typeAliases>
        
        <environments default="mysql_test">
            
            <environment id="mysql_test">
                
                <transactionManager type="JDBC"/>
                
                <dataSource type="POOLED">
                    
                    <property name="driver" value="${jdbc.driver}"/>
                    
                    <property name="url" value="${jdbc.url}"/>
                    
                    <property name="username" value="${jdbc.username}"/>
                    
                    <property name="password" value="${jdbc.password}"/>
                </dataSource>
            </environment>
        </environments>
        
        <mappers>
            
            
            <package name="com.atguigu.mybatis.mapper"/>
        </mappers>
    </configuration>

jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
    jdbc.url=jdbc:mysql://localhost:3306/MyBatis
    jdbc.username=root
    jdbc.password=root

log4j.xml 配置打印sql

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
    <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
        <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
            <param name="Encoding" value="UTF-8"/>
            <layout class="org.apache.log4j.PatternLayout">
                <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n"/>
            </layout>
        </appender>
        
        <logger name="java.sql">
            <level value="debug"/>
        </logger>
        <logger name="org.apache.ibatis">
            <level value="info"/>
        </logger>
        <root>
            <level value="debug"/>
            <appender-ref ref="STDOUT"/>
        </root>
    </log4j:configuration>

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.atguigu.mybatis.mapper.UserMapper">
        
        <insert id="insertUser">
          insert into t_user values(null,'admin','123',23,'女','11222@qq.com')
        </insert>
    
        
        <select id="getAllUser" resultType="com.atguigu.mybatis.pojo.User">
            select * from t_user
        </select>
    </mapper>

UserMapper

public interface UserMapper {
        
       int insertUser();
    
       List<User> getAllUser();
    }

SqlSessionUtils

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 SqlSessionUtils {
        
        public static SqlSession getSqlSession() {
        
            SqlSession sqlSession = null;
            try {
        
                InputStream is = Resources.getResourceAsStream("mybatis-config.xml"); //创建SqlSessionFactoryBuilder对象
                SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
                // 创建SqlSession对象，此时通过SqlSession对象所操作的sql都会自动提交
                sqlSession = sqlSessionFactory.openSession(true);
            } catch (IOException e) {
        
                e.printStackTrace();
            }
            return sqlSession;
        }
    }

测试代码

@Test
        public void testMyBatis() throws IOException {
        
            SqlSession sqlSession = SqlSessionUtils.getSqlSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            // 调用UserMapper接口中的方法，就可以根据UserMapper的全类名匹配元素文件，通过调用的方法名匹配 映射文件中的SQL标签，并执行标签中的SQL语句
            List<User> result = userMapper.getAllUser();
            System.out.println(result);
            // sqlSession.commit(); 手动提交
        }

运行结果  
![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bCn5LiK5pyJ5Yac_size_20_color_FFFFFF_t_70_g_se_x_16 1]

### xxxxMapper.xml获取参数值的两种方式 ###

1.  若mapper接口中的方法参数为实体类对象时  
    $\{\} ：拼接字符串，需要加单引号  
    \#\{\} ：占位符

<insert id="insertUser">
          insert into t_user values(null,#{username},#{password},#{age},#{sex},#{email})
        </insert>

调用

@Test
        public void testMyBatis() throws IOException {
        
            SqlSession sqlSession = SqlSessionUtils.getSqlSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            // 调用UserMapper接口中的方法，就可以根据UserMapper的全类名匹配元素文件，通过调用的方法名匹配 映射文件中的SQL标签，并执行标签中的SQL语句
            int result = userMapper.insertUser(new User(-1, "admin", "123456", 18, "女", "111@qq.com"));
            System.out.println(result);
        }

![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bCn5LiK5pyJ5Yac_size_20_color_FFFFFF_t_70_g_se_x_16 2]

1.  使用@Param标识参数

可以通过@Param注解标识mapper接口中的方法参数

<select id="getUserByLogin" resultType="User">
       
       select * from t_user where username = '${param1}' and password = #{param2}
    </select>

测试

![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bCn5LiK5pyJ5Yac_size_20_color_FFFFFF_t_70_g_se_x_16 3]  
注：传入一个指定key的map集合也可以，在xxxxMapper.xml通过用map集合的key也可以获取到参数。

[watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bCn5LiK5pyJ5Yac_size_20_color_FFFFFF_t_70_g_se_x_16]: https://img-blog.csdnimg.cn/1a4c05a8bc794c3ea4fe57fa8071f662.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA5bCn5LiK5pyJ5Yac,size_20,color_FFFFFF,t_70,g_se,x_16
[watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bCn5LiK5pyJ5Yac_size_20_color_FFFFFF_t_70_g_se_x_16 1]: https://img-blog.csdnimg.cn/298ede2c8d0348afac04667c00b7138e.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA5bCn5LiK5pyJ5Yac,size_20,color_FFFFFF,t_70,g_se,x_16
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[watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bCn5LiK5pyJ5Yac_size_20_color_FFFFFF_t_70_g_se_x_16 3]: https://img-blog.csdnimg.cn/39032cf3ac324492ac4979f00fae0fd0.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA5bCn5LiK5pyJ5Yac,size_20,color_FFFFFF,t_70,g_se,x_16