Mybatis快速入门
步骤：
- 1.加入mybatis的依赖
- 2.添加Mybatis的配置文件
- 3.场景介绍
- 4.编写实体类丶mapper接口及mapper.xml文件
- 5.编写测试代码
demo:
public class TUser { private Integer id; private String userName; private String realName; private Byte sex; private String mobile; private String email; private String note; private Integer positionId; 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 String getRealName() { return realName; } public void setRealName(String realName) { this.realName = realName; } public Byte getSex() { return sex; } public void setSex(Byte sex) { this.sex = sex; } public String getMobile() { return mobile; } public void setMobile(String mobile) { this.mobile = mobile; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public String getNote() { return note; } public void setNote(String note) { this.note = note; } public Integer getPositionId() { return positionId; } public void setPositionId(Integer positionId) { this.positionId = positionId; } }public interface TUserMapper { TUser selectByPrimaryKey(Integer id); }TUserMapper.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" ><mapper namespace="com.enjoylearning.mybatis.mapper.TUserMapper"> <select id="selectByPrimaryKey" resultType="com.enjoylearning.mybatis.entity.TUser" parameterType="java.lang.Integer"> select id, user_name , real_name , sex, mobile, email, note, position_id positionId from t_user where id = #{id} </select></mapper>mybatis-config.xml:
<?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> <properties resource="db.properties" /> <settings> <!-- 全局开关--> <!-- 设置自动驼峰转换--> <setting name="mapUnderscoreToCamelCase" value="true" /> <!-- 开启懒加载--> <setting name="lazyLoadingEnabled" value="false"/> </settings> <!--别名定义 --> <typeAliases> <package name="com.enjoylearning.mybatis.entity"/></typeAliases> <!--配置environment环境 --> <environments default="development"> <!-- 环境配置1，每个SqlSessionFactory对应一个环境 --> <environment id="development"> <transactionManager type="JDBC" /> <dataSource type="UNPOOLED"> <property name="driver" value="${jdbc_driver}" /> <property name="url" value="${jdbc_url}" /> <property name="username" value="${jdbc_username}" /> <property name="password" value="${jdbc_password}" /> </dataSource> </environment> </environments> <!-- 映射文件，mapper的配置文件 --><!-- <mappers> 直接映射到相应的mapper文件 <mapper resource="sqlmapper/TUserMapper.xml" /> </mappers> --> <mappers> <mapper class="com.enjoylearning.mybatis.mapper.TUserMapper" /> </mappers></configuration>db.properties:
jdbc_driver=com.mysql.jdbc.Driverjdbc_url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&allowMultiQueries=truejdbc_username=rootjdbc_password=qq997921测试类：
public class MybatisQuickStart {private SqlSessionFactory sqlSessionFactory;@Test// 快速入门public void quickStart() throws IOException { //-------------第一阶段------------- // 1.读取mybatis配置文件创SqlSessionFactory String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); inputStream.close(); //-------------第二阶段------------- // 2.获取sqlSession SqlSession sqlSession = sqlSessionFactory.openSession(); // 3.获取对应mapper TUserMapper mapper = sqlSession.getMapper(TUserMapper.class); //-------------第三阶段------------- // 4.执行查询语句并返回结果 TUser user = mapper.selectByPrimaryKey(1); System.out.println(user.toString());}}
Mybatis两种编程模型
1.封装了iBatis编程模型,使用sqlSession对外提供数据库的访问
比如使用sqlSession直接访问数据库,代码如：
User user1 = session.selectOne("com.XX.XX.XXMapper.selectOneByKey","1");2.使用mapper接口编程,就可以访问数据库
UserMapper userMapper = session.getMapper(UserMapper.class);User user = userMapper.selectByPrimaryKey(1);对比两种模型
第一种缺点:代码里面会很多硬编码,硬编码不好维护,代码不优雅,并且selectOne方法名称没有业务含义.
优先选择mapper接口编程。
Mybatis核心流程三大阶段
缕清思路也就是Mybatis核心流程之后，我们就开始写代码了，详见下节~~