如何使用MyBatis框架實(shí)現(xiàn)增刪改查（CRUD）操作

更新時(shí)間：2023年05月05日 08:18:39 作者：xiezhr

本文主要介紹了如何使用MyBatis框架實(shí)現(xiàn)增刪改查（CRUD）操作。首先介紹了MyBatis框架的基本概念和使用方法，然后分別介紹了如何使用MyBatis實(shí)現(xiàn)增刪改查操作。最后，通過一個(gè)簡單的示例演示了如何使用MyBatis框架實(shí)現(xiàn)CRUD操作。

mybatis 介紹

mybatis 本是apache的一個(gè)開源項(xiàng)目iBatis,
2010年這個(gè)項(xiàng)目由apache遷移到了googlecode，并且改名為MyBatis，2013年11月遷移到Github。
MyBatis 是一款優(yōu)秀的持久層框架，它支持定制化 SQL、存儲(chǔ)過程以及高級(jí)映射。
MyBatis 避免了幾乎所有的 JDBC 代碼和手動(dòng)設(shè)置參數(shù)以及獲取結(jié)果集。
MyBatis 可以使用簡單的 XML 或注解來配置和映射原生信息，將接口和 Java 的 POJOs(普通的 Java對象)映射成數(shù)據(jù)庫中的記錄

Mybatis官方文檔 :
http://www.mybatis.org/mybatis-3/zh/index.html

GitHub :https://github.com/mybatis/mybatis-3

代碼演示

所需環(huán)境

jdk1.8.0_91
mysql-5.7.29
apache-maven-3.6.3

創(chuàng)建數(shù)據(jù)庫

CREATE DATABASE `mybatis`;

USE `mybatis`;

DROP TABLE IF EXISTS `user`;

CREATE TABLE `user` (
`id` int(20) NOT NULL,
`name` varchar(30) DEFAULT NULL,
`pwd` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `user`(`id`,`name`,`pwd`) values (1,'張三','123456'),(2,'李四','abcdef'),(3,'王五','987654');

使用idea創(chuàng)建項(xiàng)目并導(dǎo)入導(dǎo)入mybatis所需jar包

<dependencies>
        <!--mysql驅(qū)動(dòng)-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.46</version>
        </dependency>
        <!--mybatis包-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--junit 測試包-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

編寫mybatis核心配置文件

該配置文件主要是配置連接mysql的基本信息及注冊mapper(具體配置參考官方文檔)

<?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.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&amp;characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/xiezhr/Dao/UserMapper.xml"></mapper>
    </mappers>
</configuration>

編寫mybatis工具類

查看官方文檔,我們這里要封裝一個(gè)工具類生成SqlSession對象，SqlSession用于后面的執(zhí)行sql

package com.xiezhr.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;

public class MysqlUtil {

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

    }

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


}

創(chuàng)建對應(yīng)數(shù)據(jù)庫表的實(shí)體類

各個(gè)屬性得命名必須與數(shù)據(jù)庫字段一一對應(yīng)，具體如下所示，數(shù)據(jù)庫對應(yīng)字段為id,name,pwd

package com.xiezhr.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

編寫Mapper接口

該接口對應(yīng)原來的dao,具體代碼如下

package com.xiezhr.dao;

import com.xiezhr.pojo.User;

import java.util.List;

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

編寫Mapper.xml 文件

由于我們使用了mybatis,所以這的xml文件相當(dāng)于我們原來dao得實(shí)現(xiàn)類daoimpl。namespace屬性對應(yīng)著接口，不能寫錯(cuò)，標(biāo)簽表示是個(gè)查詢語句。id 屬性對應(yīng)著接口的方法，result Type代表返回得類型，即對應(yīng)這pojo實(shí)體。具體代碼如下

<?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.xiezhr.dao.UserMapper">
    <select id="getUserList" resultType="com.xiezhr.pojo.User">
     select * from mybatis.user;
    </select>
</mapper>

到這一步我們第一個(gè)mybatis實(shí)現(xiàn)查詢就基本大功告成了，接下來就要編寫測試類測試我們寫得代碼

package com.xiezhr.dao;

import com.xiezhr.pojo.User;
import com.xiezhr.util.MysqlUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class TestUserDao {
    @Test
    public void selectUser(){
        SqlSession sqlSession = MysqlUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }

    }
}

經(jīng)過測試后輸出測試結(jié)果

D:\Java\jdk1.8.0_91\bin\java.exe -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:D:\JetBrains\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar=54576:D:\JetBrains\IntelliJ IDEA 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\JetBrains\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar;D:\JetBrains\IntelliJ IDEA 2019.3.3\plugins\junit\lib\junit5-rt.jar;D:\JetBrains\IntelliJ IDEA 2019.3.3\plugins\junit\lib\junit-rt.jar;D:\Java\jdk1.8.0_91\jre\lib\charsets.jar;D:\Java\jdk1.8.0_91\jre\lib\deploy.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\access-bridge-64.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\cldrdata.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\dnsns.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\jaccess.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\jfxrt.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\localedata.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\nashorn.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\sunec.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\sunjce_provider.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\sunmscapi.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\sunpkcs11.jar;D:\Java\jdk1.8.0_91\jre\lib\ext\zipfs.jar;D:\Java\jdk1.8.0_91\jre\lib\javaws.jar;D:\Java\jdk1.8.0_91\jre\lib\jce.jar;D:\Java\jdk1.8.0_91\jre\lib\jfr.jar;D:\Java\jdk1.8.0_91\jre\lib\jfxswt.jar;D:\Java\jdk1.8.0_91\jre\lib\jsse.jar;D:\Java\jdk1.8.0_91\jre\lib\management-agent.jar;D:\Java\jdk1.8.0_91\jre\lib\plugin.jar;D:\Java\jdk1.8.0_91\jre\lib\resources.jar;D:\Java\jdk1.8.0_91\jre\lib\rt.jar;F:\workspace_idea\Mybatis-test\mybatis-01\target\test-classes;F:\workspace_idea\Mybatis-test\mybatis-01\target\classes;D:\maven\repository\mysql\mysql-connector-java\5.1.46\mysql-connector-java-5.1.46.jar;D:\maven\repository\org\mybatis\mybatis\3.5.2\mybatis-3.5.2.jar;D:\maven\repository\junit\junit\4.12\junit-4.12.jar;D:\maven\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar" com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 com.xiezhr.dao.TestUserDao,selectUser
Tue Apr 14 22:54:48 CST 2020 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
User{id=1, name='張三', pwd='322334'}
User{id=2, name='李四', pwd='123456'}
User{id=3, name='王五', pwd='123456'}

擴(kuò)展

根據(jù)id查詢用戶
1.在UserMapper接口中添加相應(yīng)的方法selectUserById(id)

public interface UserMapper {
    //根據(jù)ID查詢用戶
    User selectUserById(int id);
}

2.在UserMapper.xml 中添加相應(yīng)select 語句

<mapper namespace="com.xiezhr.dao.UserMapper">
    <select id="selectUserById" parameterType="int" resultType="com.xiezhr.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>
</mapper>

3.添加測試類

@Test
    public void selectUserByid(){
        SqlSession sqlSession = MysqlUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.selectUserById(1);
        System.out.println(user);
    }

測試通過

Wed Apr 15 23:08:00 CST 2020 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
User{id=1, name='張三', pwd='322334'}

根據(jù)用戶姓名密碼查詢用戶信息
1.在UserMapper接口中添加方法

public interface UserMapper {
    //根據(jù)用戶名密碼查詢用戶信息
    User selectUserByNP(@Param("name") String name,@Param("pwd") String pwd);
}

2.在UserMapper.xml 中添加select語句

<mapper namespace="com.xiezhr.dao.UserMapper">
    <select id="selectUserByNP" resultType="com.xiezhr.pojo.User">
        select * from mybatis.user where name=#{name} and pwd=#{pwd}
    </select>
</mapper>

3.添加測試類

    @Test
    public void selectUserByNP(){
        SqlSession sqlSession = MysqlUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.selectUserByNP("張三","322334");
        System.out.println(user);
    }

測試成功

Wed Apr 15 23:24:02 CST 2020 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
User{id=1, name='張三', pwd='322334'}

以上通過用戶名和密碼查詢用戶，傳參還可以通過萬能的map實(shí)現(xiàn)，具體代碼如下

1.向UserMapper接口中添加方法

public interface UserMapper {
    //根據(jù)用戶名和密碼查詢用戶信息
    User queryUserByNP(Map<String,Object> map);
}

2.向UserMapper.xml 中添加select語句，其中參數(shù)類型為map

<mapper namespace="com.xiezhr.dao.UserMapper">
    <select id="queryUserByNP" parameterType="map" resultType="com.xiezhr.pojo.User">
        select * from mybatis.user where name=#{name} and pwd=#{pwd}
    </select>
</mapper>

添加測試，在使用過程中，map的key對應(yīng)著UserMapper.xml中取值,map在put值時(shí)候沒有先后順序

 @Test
    public void queryUserByNp(){
        SqlSession sqlSession = MysqlUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name","張三");
        map.put("pwd","322334");
        User user = mapper.queryUserByNP(map);
        System.out.println(user);
    }

模糊查詢實(shí)現(xiàn)
1.在Java代碼中添加sql通配符

string wildcardname = “%smi%”;
list<name> names = mapper.selectlike(wildcardname);
<select id=”selectlike”>
select * from foo where bar like #{value}
</select>

2.在sql語句中拼接通配符，會(huì)引起sql注入

string wildcardname = “smi”;
list<name> names = mapper.selectlike(wildcardname);
<select id=”selectlike”>
    select * from foo where bar like "%"#{value}"%"
</select>

接下來我們分別來實(shí)現(xiàn)insert、update、delete

insert

在之前編寫的UserMapper 接口中添加增加方法

public interface UserMapper {
    //添加一條用戶信息
    int addUser(User user);
}

2.在UserMapper.xml 中寫insert 語句

<insert id="addUser" parameterType="com.xiezhr.pojo.User">
        insert into mybatis.user values(#{id},#{name},#{pwd})
</insert>

添加測試類
insert、update、delete 一定要提交事務(wù)，千萬千萬不能忘記了

@Test
    public void addUser(){
        SqlSession sqlSession = MysqlUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = new User(4, "大頭兒子", "123456");
        mapper.addUser(user);
        sqlSession.commit();  //增刪改一定要提交事務(wù)
        sqlSession.close();
    }

update

在之前編寫的UserMapper 接口中添加update方法

public interface UserMapper {
    //修改一條記錄
    int updateUserById(int id);
}

2.在UserMapper.xml 中寫insert 語句

<update id="updateUserById" parameterType="int">
        update mybatis.user set name='小頭爸爸' where id=#{id}
</update>

添加測試類
insert、update、delete 一定要提交事務(wù)，千萬千萬不能忘記了

    @Test
    public void updateUserById(){
        SqlSession sqlSession = MysqlUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.updateUserById(4);
        sqlSession.commit();  //增刪改一定要提交事務(wù)
        sqlSession.close();
    }

delete

在之前編寫的UserMapper 接口中添加delete方法

public interface UserMapper {
    //根據(jù)ID刪除一條記錄
    int deleteUserById(int id);
}
}

2.在UserMapper.xml 中寫insert 語句

<delete id="deleteUserById" parameterType="int">
        delete from mybatis.user where id=#{id}
</delete>

添加測試類
insert、update、delete 一定要提交事務(wù)，千萬千萬不能忘記了

    @Test
    public void deletUserById(){
        SqlSession sqlSession = MysqlUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.deleteUserById(4);
        sqlSession.commit();  //增刪改一定要提交事務(wù)
        sqlSession.close();
    }

注意

所有的insert、update、delete 必須要提交事務(wù)
接口中所有的普通參數(shù)盡量寫上@Param 參數(shù)，尤其是多個(gè)參數(shù)的時(shí)候一定要寫上
有些時(shí)候由于業(yè)務(wù)需要需要可通過map傳值
為了規(guī)范在sql配置文件中即本例的UserMapper.xml 中select inset delete update 盡量寫上Parameter參數(shù)和resultType

可能出現(xiàn)問題說明：Maven靜態(tài)資源過濾問題

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

在靜態(tài)資源的過濾中，基本的元素有三種：

directory：指定資源所在的目錄，這個(gè)目錄的路徑是相對于pom.xml文件；
includes：指定要包含哪些文件，其中包括inlcude子節(jié)點(diǎn)來指定匹配的模式；
excludes：指定要排除哪些文件，其中包括exclude子節(jié)點(diǎn)來指定匹配的模式；
filtering：指定哪些文件需要過濾，這個(gè)過濾的目的是為了替換其中的占位符${}，其中的占位符屬性在pom.xml文件中的中指定；

MyBatis是一款優(yōu)秀的持久層框架，它可以幫助我們簡化數(shù)據(jù)庫操作的代碼。本文介紹了MyBatis框架的基本概念和使用方法，以及如何使用MyBatis實(shí)現(xiàn)增刪改查操作。在使用MyBatis進(jìn)行開發(fā)時(shí)，需要注意一些細(xì)節(jié)問題，比如如何處理事務(wù)、如何使用Mapper接口等。此外，MyBatis還提供了一些高級(jí)特性，比如動(dòng)態(tài)SQL、緩存等，可以幫助我們更加靈活地進(jìn)行數(shù)據(jù)庫操作。MyBatis是一款非常優(yōu)秀的持久層框架，值得我們深入學(xué)習(xí)和使用。

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