mybatis快速入门案例详解
案例需求:通过mybatis查询数据库user表的所有记录,封装到User对象中,打印到控制台上
步骤分析:
1. 创建数据库及user表
2. 创建maven工程,导入依赖(MySQL驱动、mybatis、junit)
3. 编写User实体类
4. 编写UserMapper.xml映射配置文件(ORM思想)
5. 编写SqlMapConfig.xml核心配置文件
数据库环境配置
映射关系配置的引入(引入映射配置文件的路径)
6. 编写测试代码
6.1.加载核心配置文件
6.2.获取sqlSessionFactory工厂对象
6.3.获取sqlSession会话对象
6.4.执行sql
6.5.打印结果
6.6.释放资源
代码详解:
1. 创建数据库及user表
CREATE DATABASE `mybatis_db`; USE `mybatis_db`; CREATE TABLE `user` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `username` VARCHAR(32) NOT NULL COMMENT '用户名称', `birthday` DATETIME DEFAULT NULL COMMENT '生日', `sex` CHAR(1) DEFAULT NULL COMMENT '性别', `address` VARCHAR(256) DEFAULT NULL COMMENT '地址', PRIMARY KEY (`id`) ) ENGINE=INNODB DEFAULT CHARSET=utf8; -- insert.... INSERT INTO `user`(`id`,`username`,`birthday`,`sex`,`address`) VALUES (1,'子慕','2020-11-11 00:00:00','男','北京海淀'),(2,'应颠','2020-12-12 00:00:00','男','北京海淀');
2. 创建maven工程,导入依赖(MySQL驱动、mybatis、junit)
创建maven工程详见上篇文章
导入依赖包
<!--指定编码和版本--> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.encoding>UTF-8</maven.compiler.encoding> <java.version>1.11</java.version> <maven.compiler.source>1.11</maven.compiler.source> <maven.compiler.target>1.11</maven.compiler.target> </properties>
<!--mybatis坐标--> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.4</version> </dependency>
<!--mysql驱动坐标--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.6</version> <scope>runtime</scope> </dependency>
<!--单元测试坐标--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency>
3) 编写User实体
package com.lagou.dao; import java.util.Date; public class User { private Integer id; private String username; private Date birthday; private String sex; private String address; public User(Integer id, String username, Date birthday, String sex, String address) { this.id = id; this.username = username; this.birthday = birthday; this.sex = sex; this.address = address; } public User() { } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Override public String toString() { return "User{" + "id=" + id + ", username='" + username + '\'' + ", birthday=" + birthday + ", sex='" + sex + '\'' + ", address='" + address + '\'' + '}'; } }
4) 编写UserMapper映射文件
新建file文件,文件名称可以随便起,此处起名为UserMapper.xml。
编写配置文件:约束头 + 正文
<?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"> <!--正文--> <mapper namespace="UserMapper"> <!--namespace:命名空间,与id属性共同构成唯一标识 namespace.id 如user.fingAll--> <!--resultType:返回结果类型(自动映射封装):要封装的实体全路径--> <select id="findAll" resultType="com.lagou.dao.User"> select * from user -- 此处不写封号 </select> </mapper>
5) 编写MyBatis核心文件
新建file文件,文件名称可以随便起,此处起名为sqlMapConfig.xml(约定俗成的文件名称)。
编写配置文件:约束头 + 正文
<?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> <!--运行环境配置--> <environments default="development"> <!--使用MYSQL环境--> <environment id="development"> <!--当前的事务管理器是JDBC--> <transactionManager type="JDBC"></transactionManager> <!--数据源信息POOLED:使用mybatis的连接池--> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://mybatis_db"/> <property name="username" value="root"/> <property name="password" value="123456"/> </dataSource> </environment> </environments> <!--加载映射配置--> <mappers> <mapper resource="UserMapper.xml"></mapper>
</mappers> </configuration>
6) 编写测试类
package com.lagou.Test; import com.lagou.dao.User; 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 org.junit.Test; import java.io.IOException; import java.io.InputStream; import java.util.List; public class MytabisTest { /** * 快速入门测试方法 */ @Test public void mybatisQuickStart() throws IOException { //1.加载核心配置文件 InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml"); //2.获取SQLSessionFactory工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream); //3.获取SQLSession会话对象 SqlSession sqlSession = sqlSessionFactory.openSession(); //4.执行SQL 参数:statementid :namespace.id List<User> users = sqlSession.selectList("UserMapper.findAll"); //5.遍历打印结果 for (User user : users) { System.out.println(user); } //6.关闭资源 sqlSession.close(); } }
知识小结
1. 创建mybatis_db数据库和user表
2. 创建项目,导入依赖
3. 创建User实体类
4. 编写映射文件UserMapper.xml
5. 编写核心文件SqlMapConfig.xml
6. 编写测试类