mybatis介绍和mybatis快速入门

Posted 2022-09-15 kfsrex

1.mybatis介绍

mybatis是支持普通sql查询，存储过程和该机映射的持久层（把java对象存储到数据库中）框架。几乎消除jdbc代码和手动设置参数以及对结果集的检索封装。mybatis可以使用映射文件xml，接口dao来操作实体类bean。

2.mybatis快速入门

1.建立数据库表users

create database mybatis; use mybatis; CREATE TABLE users(id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20), age INT); INSERT INTO users(NAME, age) VALUES(‘Tom‘, 12); INSERT INTO users(NAME, age) VALUES(‘Jack‘, 11);

2.建立相应实体类Users

public class Users        private int id;        private String name;        private int age;        public Users()               super();               public Users(int id, String name, int age)               super();               this.id = id;               this.name = name;               this.age = age;               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 int getAge()               return age;               public void setAge(int age)               this.age = age;               @Override        public String toString()               return "Users [id=" + id + ", name=" + name + ", age=" + age + "]";

 

3.建立相应映射文件UsersMapper.xml

<?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"> <!-- namespace是命名空间，暂时原来区分id，被外面调用用，名字可以随意但后面和dao一起那么namespace要和dao全类名一致 --> <mapper namespace="Test">        <!--               select：sql查询语句的标签，               id：相当于方法名称，               parameterType：传入参数类型（输入类型），要写全类名               resultType：传出参数类型（输出类型），要写全类名         -->         <!-- 通过id查询 -->        <select id="selectById" parameterType="int"               resultType="com.zhiyou100.kfs.bean.Users">               select * from users where id=#id        </select> </mapper>

4.建立mybatis的配置文件，并注册UserMapper.xml映射文件

<?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">                             <!-- driver驱动 -->                             <property name="driver" value="com.mysql.jdbc.Driver" />                             <!--                                    url：数据库地址                                    username：数据库用户名                                    password：数据库密码                              -->                             <property name="url"                                    value="jdbc:mysql://localhost:3306/mybatis" />                             <property name="username" value="root" />                             <property name="password" value="123" />                      </dataSource>               </environment>        </environments>        <!-- 配置映射文件UserMapper.xml -->        <mappers>               <mapper resource="com/zhiyou100/kfs/mapper/UsersMapper.xml"/>        </mappers> </configuration>

 

5.在单元测试里测试

 

class TestMybatis        @Test        void test() throws Exception               //1.获取配置文件config.xml加入到io流中               InputStream inputStream = Resources.getResourceAsStream("config.xml");               //2.通过SqlSessionFatoryBuilder的builder创建sqlsessionfatory               SqlSessionFactory sqlSessionFatory = new SqlSessionFactoryBuilder().build(inputStream);               //3.通过sqlSessionFactory的openSession方法创建SqlSession               SqlSession sqlSession=sqlSessionFatory.openSession();               //4.调用sqlSession的selectOne来使用通过id查询一个用户               //第一个参数是映射文件的namespace.方法名，第二个参数是传入sql语句的参数，这里是id               Users user=sqlSession.selectOne("Test.selectById",1);               System.out.println(user);               //最后一个页是很重要的一个：关闭资源               sqlSession.close();