MyBatis學習總結

阿新 • • 發佈：2020-10-11

1 什麼是mybatis?

MyBatis 是一款優秀的持久層框架
MyBatis 避免了幾乎所有的 JDBC 程式碼和手動設定引數以及獲取結果集的過程
MyBatis 可以使用簡單的 XML 或註解來配置和對映原生資訊，將介面和 Java 的實體類【Plain Old Java Objects,普通的 Java物件】對映成資料庫中的記錄。
Mybatis官方文件 : http://www.mybatis.org/mybatis-3/zh/index.html

2 mybatis的第一個程式

2.1搭建環境

2.1.1 專案結構

2.1.2 pom檔案新增依賴

 <dependencies 
>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        <!--MySQL驅動-->
        <dependency>
            <groupId 
>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId 
>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--日誌-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <!--實體類偷懶-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.10</version>
        </dependency>
    </dependencies>

<build>
        <!--引入配置檔案-->
        <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>
    </build>

2.1.3編寫MyBatis核心配置檔案

2.1.3.1mybatis-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>

    <!--引入外部檔案-->
    <properties resource="db.properties">
<!--        <property name="username" value="root"/>-->
    </properties>
    <settings>
        <!--標準日誌工廠-->
        <!--        <setting name="logImpl" value="STDOUT_LOGGING"/>-->
        <setting name="logImpl" value="LOG4J"/>

    </settings>
    <!--實體類起別名-->
    <typeAliases>
        <package name="bean"/>
        <!--        <typeAlias type="com.bean.User" alias="User"></typeAlias>-->
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 使用相對於類路徑的資源引用 -->
    <mappers>
        <mapper resource="dao/UserMapper.xml"/>
    </mappers>
</configuration>

2.1.3.2db.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&useSSL=true&useUnicode=true&characterEncoding=UTF-8
username=root
password=123456

2.1.3.3 log4j-properties

#將等級為DEBUG的日誌資訊輸出到console和file這兩個目的地，console和file的定義在下面的程式碼
log4j.rootLogger=DEBUG,console,file

#控制檯輸出的相關設定
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=[%c]-%m%n

#檔案輸出的相關設定
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./log/log.log
log4j.appender.file.MaxFileSize=10mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yy-MM-dd}][%c]%m%n

#日誌輸出級別
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

2.1.4編寫MyBatis工具類 MyBatisUtils.java

package util;

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;

/**
 * @author MoooJL
 * @data 2020/9/22-20:42
 */
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;

    static {

        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

2.2 編寫程式碼

2.2.1 建立實體類

public class User {
   
   private int id;  //id
   private String name;   //姓名
   private String pwd;   //密碼
   
   //構造,有參,無參
   //set/get
   //toString()
   
}

2.2.3 編寫mapper介面類

public interface UserMapper {
   //查詢全部使用者
   List<User> selectUser();
   //根據id查詢使用者
   User selectUserById(int id);
    //新增一個使用者
    int addUser(User user);
    //修改一個使用者
    int updateUser(User user);
    //根據id刪除使用者
    int deleteUser(int id);
}

2.2.4 在UserMapper.xml檔案插入相關SQL語句附模糊查詢格式

<?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="dao.UserMapper">
    <select id="selectUser" resultType="user">
    select * from mybatis.user
  </select>
    <select id="selectUserById" resultType="user" parameterType="int">
        select * from mybatis.user where id=#{id}
    </select>
    <insert id="addUser" parameterType="user">
        insert into mybatis.user (name,password) values(#{name},#{password})
    </insert>
    <update id="updateUser" parameterType="user">
        update mybatis.user set name=#{name} ,password=#{password} where id=#{id}
    </update>
    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id=#{id}
    </delete>
</mapper>

<select id=”selectlike”>
    select * from user where bar like "%"#{value}"%"
</select>

2.2.5 編寫測試程式碼

@Test
public void tsetSelectUserById() {
   SqlSession session = MybatisUtils.getSession();  //獲取SqlSession連線
   UserMapper mapper = session.getMapper(UserMapper.class);
   User user = mapper.selectUserById(1);
   System.out.println(user);
   session.close();
}

@Test
public void testAddUser() {
   SqlSession session = MybatisUtils.getSession();
   UserMapper mapper = session.getMapper(UserMapper.class);
   User user = new User(5,"王五","zxcvbn");
   int i = mapper.addUser(user);
   System.out.println(i);
   session.commit(); //提交事務,重點!不寫的話不會提交到資料庫
   session.close();
}

@Test
public void testUpdateUser() {
   SqlSession session = MybatisUtils.getSession();
   UserMapper mapper = session.getMapper(UserMapper.class);
   User user = mapper.selectUserById(1);
   user.setPwd("asdfgh");
   int i = mapper.updateUser(user);
   System.out.println(i);
   session.commit(); //提交事務,重點!不寫的話不會提交到資料庫
   session.close();
}

@Test
public void testDeleteUser() {
   SqlSession session = MybatisUtils.getSession();
   UserMapper mapper = session.getMapper(UserMapper.class);
   int i = mapper.deleteUser(5);
   System.out.println(i);
   session.commit(); //提交事務,重點!不寫的話不會提交到資料庫
   session.close();
}