MyBatis入门（图文）

Love The Way You Lie 2023-07-23 03:51 35阅读 0赞

## MyBatis入门 ##

最近入门了mybatis，怕以后忘记，做个入门笔记

**mybatis的环境搭建**  
第一步：创建maven工程并导入坐标

pom.xml

<?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>MybatisTest</artifactId>
        <version>1.0-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <dependencies>
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.4</version>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.48</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
            </dependency>
            <dependency>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
                <version>1.2.17</version>
            </dependency>
        </dependencies>
    
    </project>

第二步：创建实体类和dao的接口

**注意：实体类的列名应与实体类的成员变量一致**  
User.java

package com.itheima.test;
    
    import java.io.Serializable;
    import java.util.Date;
    
    public class User implements Serializable { 
        private Integer id;
        private String username;
        private Date birthday;
        private String sex;
        private String address;
    
        public Integer getId() { 
            return id;
        }
    
        public void setId(Integer id) { 
            this.id = id;
        }
    
        public String getUsername() { 
            return username;
        }
    
        public void setUsername(String username) { 
            this.username = username;
        }
    
        public Date getBirthday() { 
            return birthday;
        }
    
        public void setBirthday(Date birthday) { 
            this.birthday = birthday;
        }
    
        public String getSex() { 
            return sex;
        }
    
        public void setSex(String sex) { 
            this.sex = sex;
        }
    
        public String getAddress() { 
            return address;
        }
    
        public void setAddress(String address) { 
            this.address = address;
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", birthday=" + birthday +
                    ", sex='" + sex + '\'' +
                    ", address='" + address + '\'' +
                    '}';
        }
    }

IUserDao.java

package com.itheima.dao;
    
    import com.itheima.test.User;
    
    import java.util.List;
    
    public interface IUserDao { 
        /* * 查询所有操作 * @return * * */
        List<User> findAll();
    }

第三步：创建mybatis的主配置文件 SqlMapConifg.xml

SqlMapConifg.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>
        
        <environments default="mysql">
            
            <environment id="mysql">
                
                <transactionManager type="JDBC"></transactionManager>
                
                <dataSource type="POOLED">
                    
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/xscj?useSSL=false"/>
                    <property name="username" value="root"/>
                    <property name="password" value="520China"/>
                </dataSource>
            </environment>
        </environments>
        
        <mappers>
            <mapper resource="com/itheima/dao/IUserDao.xml"/>
        </mappers>
    </configuration>

第四步：创建映射配置文件 IUserDao.xml

IUserDao.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.itheima.dao.IUserDao">
        
        <select id="findAll" resultType="com.itheima.test.User" >
            select * from user
        </select>
    </mapper>

**注意事项：**

1.  mybatis的映射配置文件位置要与dao接口包结构相同
2.  映射配置文件mapper标签的spacename属性的取值必须是dao接口的全限定类名
3.  映射配置文件的操作配置（select），id的取值必须是dao接口的方法名

**mybatis入门案例**

1.在resources下写一个配置文件 log4j.properties，如下：

#Set root category priority to INFO and its only appender to CONSOLE.
    #Log4j.rootCategory=INFO,CONSOLE debug info warn error fatal
    log4j.rootCategory=debug,CONSOLE,LOGFILE
    
    #Set the enterprise logger category to FATAL and its only appender to CONSOLE.
    log4j.logger.org.apache.axis.enterprise=FATAL,CONSOLE
    
    #CONSOLE is set to be a ConsoleAppender using A PatternLayout.
    log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
    log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
    log4j.appender.CONSOLE.layout.ConversionPattern=%d{ ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
    
    #LOGFILE is set to be a File appender using a PatternLayout.
    log4j.appender.LOGFILE=org.apache.log4j.FileAppender
    log4j.appender.LOGFILE.File=d:\axis.log
    log4j.appender.LOGFILE.Append=true
    log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
    log4j.appender.LOGFILE.layout.ConversionPattern=%d{ ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

2.在test下写个测试类 MyBatisTest.java 如下：

package com.itheima.test;
    
    import com.itheima.dao.IUserDao;
    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;
    import java.util.List;
    
    public class MyBatisTest { 
        /* * 入门 * */
        public static void main(String[] arg) throws IOException { 
            //1.读取配置文件
            InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
            //2.创建SqlSessionFactory工厂
            SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
            SqlSessionFactory factory = builder.build(in);
            //3.使用工厂生产SqlSession对象
            SqlSession session = factory.openSession();
            //4.使用SQLSession创建dao接口的代理对象
            IUserDao userDao = session.getMapper(IUserDao.class);
            //5.使用代理对象执行方法
            List<User> users = userDao.findAll();
            for(User user:users){ 
                System.out.println(user);
            }
            //6.释放资源
            session.close();
            in.close();
        }
    }

运行结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzUyMDY3MA_size_16_color_FFFFFF_t_70]  
与数据库一样  
![在这里插入图片描述][20200407003327237.png]  
自此就入门完成了。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzUyMDY3MA_size_16_color_FFFFFF_t_70]: /images/20230528/ad0aa0bbc05c4170b5b187aed3bbd197.png
[20200407003327237.png]: /images/20230528/72651e46500a4cebb65444aaca9cdf92.png