用Idea搭建一个Mybatis项目

清疚 2022-12-11 15:11 201阅读 0赞

# 什么是 MyBatis？ #

MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

# 官方文档 #

https://mybatis.org/mybatis-3/zh/index.html  
最好的官方文档之一，一篇文档读懂，根本不用看其他任何教程

# 环境 #

window10  
IntelliJ Idea（2020.2）  
JDK 8  
MySql server

# 新建项目 #

### 打开idea，file -> new -> Project -> maven ###

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### 点击next，下一步设置项目名和组织名 ###

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项目名（name）随意，GroupId一般是域名的倒写，一般和你的包结构一致  
其实随便填就行

### 点击Finish，项目新建成功 ###

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图片仅供参考，我是在项目中创建了子Module，不必模仿，用你们新建的项目就够了

### 数据库中创建测试用的表 ###

DROP TABLE IF EXISTS `user`;
    CREATE TABLE `user` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `name` varchar(32) NOT NULL COMMENT '用户名称',,
      `pwd` varchar(256) DEFAULT NULL COMMENT '地址',
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8;
     
    -- ----------------------------
    -- Records of user
    -- ----------------------------
    INSERT INTO `user` VALUES ('1', '王五',‘123’);
    INSERT INTO `user` VALUES ('10', '张三', '123');
    INSERT INTO `user` VALUES ('16', '张小明', ‘123’);
    INSERT INTO `user` VALUES ('22', '陈小明', ‘123’);
    INSERT INTO `user` VALUES ('24', '张三丰', ‘123’);
    INSERT INTO `user` VALUES ('25', '陈小明', ‘123’);
    INSERT INTO `user` VALUES ('26', '王五', ‘123’);

### 项目中创建表对应的实体类 ###

新建package名叫model  
新建class User

package com.term.model;
    
    import java.io.Serializable;
    
    public class User implements Serializable { 
        private int id;
        private String name;
        private String pwd;
    
        public User() { 
        }
    
        public User(int id, String name, String pwd) { 
            this.id = id;
            this.name = name;
            this.pwd = pwd;
        }
    
        public int getId() { 
            return id;
        }
    
        public void setId(int id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public String getPwd() { 
            return pwd;
        }
    
        public void setPwd(String pwd) { 
            this.pwd = pwd;
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", pwd='" + pwd + '\'' +
                    '}';
        }
    }

### 创建mapper接口 ###

新建package名叫dao  
新建interface名叫UserDao

package com.term.dao;
    
    import com.term.model.User;
    
    import java.util.List;
    import java.util.Map;
    
    public interface UserDao { 
        List<User> getAllUsers();
        int updateUser(User user);
        int addUser(User user);
        int deleteUser(int id);
        User getOneUser(Map<String, Object> map);
        List<User> getUsersByNameLike(String name);
    
    }

以上内容和普通的JDBC一致  
接下来引入Mybatis  
打开项目的pom文件，导入Mybatis依赖

<?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.term</groupId>
        <artifactId>MybatisStudy</artifactId>
        <packaging>pom</packaging>
        <version>1.0-SNAPSHOT</version>
        <dependencies>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.47</version>
            </dependency>
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.2</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
            </dependency>
        </dependencies>
        <build>
            <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>
    </project>

如上所示，我导入了mybatis 3.5.2 jar包，和mybatis所依赖的Junit、mysql  
中的内容时配置文件扫描，以免编译器不加载配置文件

### 创建Mybatis核心配置文件 ###

在项目的resources文件夹中创建mybatis-config.xml  
别问我为什么叫这个名字，其实想叫什么叫什么，只是因为官方文档叫这个名字，所有大家都喜欢用这个名字，显得比较专业

<?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&characterEncoding=utf8&autoReconnect=true"/>
                    <property name="username" value="root"/>
                    <property name="password" value="root"/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
            <mapper resource="com/term/dao/UserMapper.xml"/>
        </mappers>
    </configuration>

简单解释一下，这是mybatis最简单的配置，  
environments便签是环境配置，如上主要是dataSource连接数据库的参数，以及transactionManager决定数据库事务处理方式  
mappers标签用来指定mapper.xml，如上  
意思就是我待会会在com/term/dao中创建一个Mapper.xml实现数据库具体操作  
如果不配置这各标签，那么mapper将不生效  
就这些

### MybatisUtils ###

写一个全局的工具类，静态返回初始化好的SqlSession对象：

package com.term.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;
    
    /** * 初始化sqlSessionFactory，并返回sqlSession */
    public class MybatisUtils { 
    	//SqlSessionFactory 对象最好是全局的单例变量
        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();
            }
        }
    	//每个请求初始化一个SqlSession，调用这个方法
        public static SqlSession getSqlSession() { 
            return sqlSessionFactory.openSession();
        }
        //得到支持自动提交的SqlSession对象
        public static SqlSession getAutoCommitSqlSession(){ 
            return sqlSessionFactory.openSession(true);
        }
    }

### 创建mapper.xml ###

刚才我们写了一个UserDao接口，并定义了一些数据库操作方法，mybatis要求我们使用xml文件的方式去实现这个接口

<?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.term.dao.UserDao">
        
        <select id="getAllUsers" resultType="com.term.model.User">
            
            select * from user
        </select>
        <update id="updateUser" parameterType="com.term.model.User">
            
            update user set name=#{ name},pwd=#{ pwd} where id=#{ id}
        </update>
        <insert id="addUser" parameterType="com.term.model.User">
            insert into user (id,name,pwd) values (#{ id},#{ name},#{ pwd})
        </insert>
        <delete id="deleteUser" parameterType="int">
            delete from user where id=#{ id}
        </delete>
    
        <select id="getOneUser" parameterType="map" resultType="com.term.model.User">
            select * from user where id=#{ id}
        </select>
        <select id="getUsersByNameLike" parameterType="String" resultType="com.term.model.User">
            select * from user where name like #{ name}
        </select>
    </mapper>

好了，写完了

### 使用JUNIT测试 ###

package com.term.dao;
    
    import com.term.model.User;
    import com.term.utils.MybatisUtils;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    /** * Mybatis 增删改查Junit */
    public class UserDaoTest { 
        @Test
        public void testGetAllUser() { 
            final SqlSession sqlSession = MybatisUtils.getSqlSession();
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            List<User> users = userDao.getAllUsers();
            for (User user : users) { 
                System.out.println(user);
            }
    
    
            sqlSession.close();
        }
    
        @Test
        public void testAddUser() { 
            final SqlSession sqlSession = MybatisUtils.getSqlSession();
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            userDao.addUser(new User(1, "li", "zhang3"));
    
            sqlSession.commit();
            sqlSession.close();
        }
    
        @Test
        public void testUpdateUser() { 
            final SqlSession sqlSession = MybatisUtils.getSqlSession();
            final UserDao userDao = sqlSession.getMapper(UserDao.class);
            userDao.updateUser(new User(2, "lisi", "lisq"));
    
            //增删改需要提交事务
            sqlSession.commit();
            sqlSession.close();
        }
    
        @Test
        public void testDelUser(){ 
            final SqlSession sqlSession = MybatisUtils.getSqlSession();
            final UserDao userDao = sqlSession.getMapper(UserDao.class);
            userDao.deleteUser(1);
    
            //增删改需要提交事务
            sqlSession.commit();
            sqlSession.close();
        }
    
        @Test
        public void testGetOneUser(){ 
            final SqlSession sqlSession = MybatisUtils.getSqlSession();
            final UserDao userDao = sqlSession.getMapper(UserDao.class);
            Map<String, Object> map = new HashMap<>();
            map.put("id", 2);
    
            System.out.println(userDao.getOneUser(map));
            sqlSession.close();
        }
    
        @Test
        public void testGetUsersByNameLike(){ 
            final SqlSession sqlSession = MybatisUtils.getSqlSession();
            final UserDao userDao = sqlSession.getMapper(UserDao.class);
            List<User> users = userDao.getUsersByNameLike("%l%");
            for (User user : users)
                System.out.println(user);
            sqlSession.close();
        }
    }

感谢大家收看

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