第二弹：Mybatis实现CRUD的操作（Demo练习）

朱雀 2021-09-09 02:40 395阅读 0赞

> 今天通过练习，学会了结合Mybatis框架对数据库进行简单CEUD的操作，在此记录一下。

**什么是CRUD？ **

CRUD是指在做计算处理时的**增加(Create)**、**读取查询(Retrieve)**、**更新(Update)**和**删除(Delete)**几个单词的首字母简写。主要被用在描述软件系统中DataBase或者持久层的基本操作功能。

练习操作的表：stu

![20210719223933163.png][]

![20210719223955409.png][]

创建maven项目后，如下（用到的文件已经红色方框画出）

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDEwNzE0MA_size_16_color_FFFFFF_t_70][]

重要文件的内容如下：

**pom.xml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>com.lys</groupId>
        <artifactId>mybatis-demo1</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <name>demo</name>
        
        <url>http://www.example.com</url>
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <maven.compiler.source>1.8</maven.compiler.source>
            <maven.compiler.target>1.8</maven.compiler.target>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.11</version>
                <scope>test</scope>
            </dependency>
    
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.6</version>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                
                <version>8.0.17</version>
            </dependency>
        </dependencies>
    
        <build>
            <resources>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.properties </include>
                        <include>**/*.xml</include>
                    </includes>
                    <filtering>false</filtering>
                </resource>
            </resources>
        </build>
    
    </project>

**src\\main\\resources下的mybatis.xml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.cj.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/ems?useSSL=FALSE&serverTimezone=Asia/Shanghai"/>
                    <property name="username" value="root"/>
                    <property name="password" value="root"/>
                </dataSource>
            </environment>
        </environments>
        
        <mappers>
            
            <mapper resource="com/pojo/Dao/stuDao.xml"/>
        </mappers>
    </configuration>

**src\\main\\java\\com\\utils\\mybatisUtils.java**

package com.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 {
        private static SqlSessionFactory factory;
        static {
            //        定义主配置文件的名称，从类路径的跟开始(target/classes)
            String config = "mybatis.xml";
    //        读取文件
            InputStream in = null;
            try {
                in = Resources.getResourceAsStream(config);
            } catch (IOException e) {
                e.printStackTrace();
            }
    //        创建SqlSessionFactoryBuilder对象
            SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    //        创建SqlSessionFactory对象
             factory = builder.build(in);
    
        }
        public static SqlSession getSqlSession(){
            return factory.openSession();
        }
    }

**src\\main\\java\\com\\pojo\\Dao\\stuDao.java**

package com.pojo.Dao;
    
    import com.pojo.pp1.stu;
    
    import java.util.List;
    
    public interface stuDao {
        //    查询全部学生
        public List<stu> selectstu();
    
        //    用ID查询学生
        public stu findstuByID(int id);
    
        //    添加学生
        public int addstu(stu stu);
    
        //    删除学生信息
        public int deletestuById(int id);
    
        //    修改学生信息
        public int updatestu(stu stu);
    }

**src\\main\\java\\com\\pojo\\Dao\\stuDao.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.pojo.Dao.stuDao">
        <select id="selectstu" resultType="com.pojo.pp1.stu">
            select ID,name from stu
        </select>
        
        <select id="findstuByID" parameterType="int" resultType="com.pojo.pp1.stu">
            select ID,name from stu where id=#{id}
        </select>
        
        <insert id="addstu" parameterType="com.pojo.pp1.stu">
            insert into stu(ID,name) values (#{ID},#{name})
        </insert>
        
        <delete id="deletestuById" parameterType="int" >
            delete from stu where ID=#{id};
        </delete>
        
        <update id="updatestu" parameterType="com.pojo.pp1.stu">
            update stu set name=#{name} where ID=#{ID}
        </update>
    
    </mapper>

**src\\test\\java\\com\\pojo\\Dao\\stuDaoTest.java（测试文件）**

package com.pojo.Dao;
    
    import com.pojo.pp1.stu;
    import com.utils.mybatisUtils;
    import org.apache.ibatis.jdbc.SQL;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    
    import java.util.List;
    
    public class stuDaoTest {
        @Test
    //    查找全部写学生的信息
        public void selectstu() {
            SqlSession sqlSession = mybatisUtils.getSqlSession();
            stuDao stuDao = sqlSession.getMapper(com.pojo.Dao.stuDao.class);
            List<stu> stuList = stuDao.selectstu();
            for (stu stu : stuList) {
                System.out.println(stu);
            }
            sqlSession.close();
        }
        @Test
    //    通过ID查找学生
        public void findstuByID(){
            SqlSession sqlSession = mybatisUtils.getSqlSession();
            stuDao stuDao = sqlSession.getMapper(com.pojo.Dao.stuDao.class);
            stu s = stuDao.findstuByID(2);
            System.out.println(s);
        }
    //    插入学生信息
        @Test
        public void addstu() {
            SqlSession sqlSession = mybatisUtils.getSqlSession();
            stuDao stuDao = sqlSession.getMapper(com.pojo.Dao.stuDao.class);
            int a = stuDao.addstu(new stu(7, "李白"));
            if (a > 0) {
                System.out.println("添加学生成功！");
            }
            sqlSession.commit();
            sqlSession.close();
        }
    //    删除学生信息
        @Test
        public void deletestuById() {
            SqlSession sqlSession = mybatisUtils.getSqlSession();
            stuDao stuDao = sqlSession.getMapper(com.pojo.Dao.stuDao.class);
            int a = stuDao.deletestuById(2);
            if (a > 0) {
                System.out.println("删除学生信息成功！");
            }
            sqlSession.commit();
            sqlSession.close();
    
        }
    
        @Test
        public void updatestu() {
            SqlSession sqlSession = mybatisUtils.getSqlSession();
            stuDao stuDao = sqlSession.getMapper(com.pojo.Dao.stuDao.class);
            int a = stuDao.updatestu(new stu(1, "李新"));
            if (a > 0) {
                System.out.println("信息修改成功!");
            }
            sqlSession.commit();
            sqlSession.close();
        }
    }

--------------------

努力，加油干！！！！

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDEwNzE0MA_size_16_color_FFFFFF_t_70 1][]

[20210719223933163.png]: /images/20210813/d88dd1b9485744bb875a9541309ab5c5.png
[20210719223955409.png]: /images/20210813/5baa67eef6fe4751b37e31bcc1b667e1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDEwNzE0MA_size_16_color_FFFFFF_t_70]: /images/20210813/108d6a7e5f8f436b90f8acdcd4f3a106.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDEwNzE0MA_size_16_color_FFFFFF_t_70 1]: /images/20210813/d549db7a70ff4027bea1e65aea6b91f0.png