前言
上一篇文章中我们讲了什么是持久化以及 Mybatis 的相关简介,今天就来看看如何创建一个 Mybatis 入门实例以及如何利用 Mybatis 进行 CRUD。
数据库准备
首先,我们来创建一个数据库,用于后序步骤的使用;
CREATE DATABASE test;
USE test;
接着创建一个表,用于存放数据;
CREATE TABLE user ( id int(20) NOT NULL AUTO_INCREMENT, name varchar(30) DEFAULT NULL, password varchar(30) DEFAULT NULL, PRIMARY KEY (id) );
向数据库中插入数据
INSERT INTO user (id, name, password) VALUES (1, '村雨遥', '123456'),(2, '张三', '1234567'),(3, '李四', '12345678');
1
创建 Maven 工程
对于如何创建 Maven 工程,可以参照我之前写的一篇文章:利用 IDEA 搭建一个 Maven 项目
接着在项目的 pom.xml 中添加 MyBatis、MySQL、Junit 的依赖;
<dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.5</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.49</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.13</version> <scope>test</scope> </dependency>
编写 MyBatis 实例
- 编写 MyBatis 核心配置文件,在
main/resources
文件下新建mybatis-config.xml
,配置数据库;
<?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/test?useSSL=false&useUnicode=true&characterEncoding=utf8"/> <property name="username" value="root"/> <property name="password" value="12345"/> </dataSource> </environment> </environments> <mappers> <mapper resource="UserMapper.xml"/> </mappers> </configuration>
- 编写 MyBatis 工具类;
package com.cunyu.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; /** * @author : cunyu * @version : 1.0 * @className : MyBatisUtils * @date : 2020/7/14 11:38 * @description : MyBatis 工具类 */ 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(); } } /** * @param * @return * @description 获取 SqlSession 连接 * @date 2020/7/14 11:46 * @author cunyu1943 * @version 1.0 */ public static SqlSession getSession() { return sqlSessionFactory.openSession(); } }
- 接下来创建实体类;
package com.cun.pojo; /** * @author : cunyu * @version : 1.0 * @className : User * @date : 2020/7/14 11:55 * @description : User 实体类 */ public class User { private int id; private String name; private String password; public User() { } public User(int id, String name, String password) { this.id = id; this.name = name; this.password = password; } 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 getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override public String toString() { return "User{" + "id=" + id + ", name='" + name + '\'' + ", password='" + password + '\'' + '}'; } }
- 编写 Mapper 接口;
package com.cunyu.dao; import com.cunyu.pojo.User; import java.util.List; /** * @InterfaceName : UserDao * @Author : cunyu * @Date : 2020/7/14 13:49 * @Version : 1.0 * @Description : User 接口 **/ public interface UserDao { List<User> getUser(); }
- 添加
UserMapper.xml
配置文件;
<?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"> <!--绑定对应Dao/Mapper接口--> <mapper namespace="com.cunyu.dao.UserDao"> <select id="getUser" resultType="com.cunyu.pojo.User"> select * from user </select> </mapper>
- 编写测试类,在
src/test/java/
目录下保持相同的目录结构,然后添加测试类进行测试;
package com.cunyu.dao; import com.cunyu.pojo.User; import com.cunyu.utils.MybatisUtils; import org.apache.ibatis.session.SqlSession; import org.junit.Test; import java.util.List; /** * @author : cunyu * @version : 1.0 * @className : UserDaoTest * @date : 2020/7/14 13:52 * @description : UserDao 接口测试 */ public class UserDaoTest { @Test public void test(){ // 获取 SqlSession 对象 SqlSession sqlSession = MybatisUtils.getSqlSession(); // 执行 SQL 语句 UserDao mapper = sqlSession.getMapper(UserDao.class); List<User> userList = mapper.getUser(); for (User user:userList ) { System.out.println(user); } // 关闭 SqlSession sqlSession.close(); } }
运行测试类,可以得出如下结果;
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查询操作 select
根据各属性来查询用户
在 UserDao 中添加对应方法:
/** * @param name 用户名 * @return 对应用户名的用户对象 * @description 根据用户名获取用户 * @date 2020/7/14 14:52 * @author cunyu1943 * @version 1.0 */ User getUserByName(String name); /** * @param password 密码 * @return 对应密码的用户对象 * @description 根据用户密码获取用户对象 * @date 2020/7/14 14:57 * @author cunyu1943 * @version 1.0 */ User getUserByPassword(String password);
- 接着在
UserMapper.xml
中添加Select
语句。其中各属性含义如下:
- id:对应接口中的 方法名;
- resultType:SQL 语句执行的返回值;
- parameterType:参数类型;
<select id="getUserById" resultType="com.cunyu.pojo.User"> select * from user where id=#{id} </select> <select id="getUserByName" resultType="com.cunyu.pojo.User"> select * from user where name=#{name} </select> <select id="getUserByPassword" resultType="com.cunyu.pojo.User"> select * from user where password=#{password} </select>
- 在测试类中测试即可;
@Test public void testGetUserById() { // 执行 SQL 语句 UserDao mapper = sqlSession.getMapper(UserDao.class); User user = mapper.getUserById(2); System.out.println(user); // 关闭 SqlSession sqlSession.close(); } @Test public void testGetUserByName() { UserDao mapper = sqlSession.getMapper(UserDao.class); User user = mapper.getUserByName("村雨遥"); System.out.println(user); sqlSession.close(); } @Test public void testGetUserByPassword(){ UserDao mapper = sqlSession.getMapper(UserDao.class); User user=mapper.getUserByPassword("123456"); System.out.println(user); sqlSession.close(); }
插入操作 insert
- 首先在
UserDao
接口中添加对应方法
/** * @description 添加用户 * @param user 待添加的用户对象 * @return * @date 2020/7/14 15:50 * @author cunyu1943 * @version 1.0 */ int addUser(User user);
在 UserMapper.xml 中添加 Insert 语句;
<insert id="addUser" parameterType="com.cunyu.pojo.User">
insert into user(id, name, password) values (#{id},#{name},#{password})
</insert>
测试方法中测试;
@Test public void testAddUser() { UserDao mapper = sqlSession.getMapper(UserDao.class); User user = new User(5, "小雨", "6543210"); int i = mapper.addUser(user); System.out.println(i); // 提交事务到数据库 sqlSession.commit(); System.out.println("添加用户成功"); sqlSession.close(); }
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修改操作 update
- 在
UserDao
添加对应接口;
/** * @description 根据 id 修改用户 * @param user 待修改的用户对象 * @return * @date 2020/7/14 16:04 * @author cunyu1943 * @version 1.0 */ int updateUser(User user);
在 UserMapper.xml 中添加 update 语句;
<update id="updateUser" parameterType="com.cunyu.pojo.User">
update user set name=#{name},password=#{password} where id=#{id}
</update>
测试类中测试;
@Test public void testUpdateUser(){ // 获取 SqlSession 对象 SqlSession sqlSession = MybatisUtils.getSqlSession(); UserDao mapper = sqlSession.getMapper(UserDao.class); User user = mapper.getUserById(1); user.setPassword("7891011"); int i = mapper.updateUser(user); sqlSession.commit(); System.out.println("更新数据成功"); sqlSession.close(); }
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删除操作 delete
- 在
userDao
中添加接口;
/** * @description 删除用户 * @param user 待删除的用户 * @return * @date 2020/7/14 16:21 * @author cunyu1943 * @version 1.0 */ int deleteUserById(User user);
在 UserMapper.xml 中添加 delete 语句;
<delete id="deleteUserById" parameterType="com.cunyu.pojo.User">
delete from user where id=#{id}
</delete>
在测试类中测试;
@Test public void testDeleteUser(){ // 获取 SqlSession 对象 SqlSession sqlSession = MybatisUtils.getSqlSession(); UserDao mapper = sqlSession.getMapper(UserDao.class); User user = mapper.getUserById(5); int i = mapper.deleteUserById(user); sqlSession.commit(); System.out.println("删除数据成功"); sqlSession.close(); }
最后
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