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Java学习-MyBatis学习(一)

news 来源：原创 2024/9/29 7:31:49

MyBatis

MyBatis历史

MyBatis本是apache的一个开源项目iBatis，2010年这个项目由apache software foundation迁移到了google code，并且改名为MyBatis。2013年11月迁移到Github。
iBATIS一词来源于“internet”和“abatis”的组合，是一个基于Java的持久层框架。iBATIS提供的持久层框架包括SQL Maps和Data Access Objects（DAOs）

MyBatis特性

支持定制化SQL，存储过程及高级映射的优秀持久层框架
避免了几乎所有的JDBC代码和手动设置参数以及获取结果集
使用简单的XML和注解用于配置和原始映射，将接口和Java的POJO映射到数据库中记录
是一个半自动化的ORM(Object Relation Mapping)框架

MyBatis-Maven配置

<dependencies><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.7</version></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.23</version></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version></dependency></dependencies>

在这里插入图片描述

MyBatis的核心配置文件

建议名称mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!-- 配置连接数据库环境 --><environments default="development"><environment id="development"><transactionManager type="JDBC"/>        <!-- 使用原始JDBC的方式管理事务，代码提交时需要手动提交--><dataSource type="POOLED"><property name="driver" value="com.mysql.cj.jdbc.Driver"/><property name="url" value="jdbc:mysql://192.168.29.201:3306/mybatis"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><!-- 引入映射文件 --><mappers><mapper resource="mappers/UserMapper.xml"/></mappers>
</configuration>

<!-- log4j.xml配置文件-- >
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/"><appender name="STDOUT" class="org.apache.log4j.ConsoleAppender"><param name="Encoding" value="UTF-8"/><layout class="org.apache.log4j.PatternLayout"><param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS}
%m (%F:%L) \n"/></layout></appender><logger name="java.sql"><level value="debug"/></logger><logger name="org.apache.ibatis"><level value="info"/></logger><root><level value="debug"/><appender-ref ref="STDOUT"/></root>
</log4j:configuration>

创建mapper接口

# 创建数据库和表
mysql> create database mybatis;
Query OK, 1 row affected (0.00 sec)
mysql> use mybatis;
Database changed
mysql> create table t_user(id int primary key auto_increment,username varchar(20),password varchar(20),age int,sex char,email varchar(20));
Query OK, 0 rows affected (0.01 sec)

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.lotus.mybatis.mapper.UserMapper"><!--int insertUser();--><insert id="insertUser">insert into t_user values(null,'edison','123456',23,'男','edison@qq.com')</insert><!--int updateUser();--><update id="updateUser">update t_user set username = 'dizzy' where id = 3</update><!--int deleteUser();--><delete id="deleteUser">delete from t_user where id = 3</delete><!-- getUserById --><!--查询功能标签必须设置resultType或resultMapresultType：设置默认的映射关系resultMap：设置自定义的映射关系--><select id="getUserById" resultType="com.lotus.mybatis.pojo.User">select * from t_user where id = 4</select><!-- List<User> getAllUser(); --><select id="getAllUser" resultType="com.lotus.mybatis.pojo.User">select * from t_user</select>
</mapper>

package com.lotus.mybatis.mapper;/*** MyBatis面向接口编程的两个一致* ①映射文件的namespace要和Mapper接口全类名一致* ②映射文件中SQL语句的id要和mapper中的方法名一致*/
public interface UserMapper {/*** 添加用户信息*/int insertUser();/*** 删除用户*/int deleteUser();/*** 修改用户*/int updateUser();/*** 查询数据*/User getUserById();/*** 查询所有用户信息*/List<User> getAllUser();
}
package com.lotus.mybatis.pojo;
public class User {private Integer id;private String username;private String password;private Integer age;private String sex;private String email;public User() {}public User(Integer id, String username, String password, Integer age, String sex, String email) {this.id = id;this.username = username;this.password = password;this.age = age;this.sex = sex;this.email = email;}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 getPassword() {return password;}public void setPassword(String password) {this.password = password;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}@Overridepublic String toString() {return "User{" +"id=" + id +", username='" + username + '\'' +", password='" + password + '\'' +", age=" + age +", sex='" + sex + '\'' +", email='" + email + '\'' +'}';}
}

创建MyBatis映射文件

ORM对象映射关系
- 对象：Java实体类对象
- 关系：关系型数据库
- 映射：二者之间的对应关系
映射文件命名规则
- 表所对应的实体类名+Mapper.xml-----如表t_user,映射的实体类为User,
MyBatis可以面向接口操作数据，要保证两个一致
SqlSession：代表Java程序和数据库之前的会话
SqlSessionFactory：生产SqlSession的工厂
工厂模式：创建某一个对象，使用的过程基本固定，那么我们就可以创建这个对象的相关代码封装到一个“工厂类”中，以后使用这个工厂类生产我们需要的对象

//SqlSession默认不自动提交事务，需要自动提交事务,使用openSession(true)自动提交事务public class MyBatisTest {@Testpublic void testMyBatis() throws IOException {//加载核心配置文件InputStream is = Resources.getResourceAsStream("mybatis-config.xml");//获取SqlSessionFactoryBuilderSqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();//SqlSessionFactorySqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);//获取SqlSessionSqlSession sqlSession = sqlSessionFactory.openSession();//获取Mapper接口对象UserMapper mapper = sqlSession.getMapper(UserMapper.class);//测试功能int res = mapper.insertUser();//提交事务sqlSession.commit();System.out.println(res);}@Testpublic void testCRUD() throws IOException {//加载核心配置文件InputStream is = Resources.getResourceAsStream("mybatis-config.xml");//获取SqlSessionFactoryBuilderSqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();//SqlSessionFactorySqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);//获取SqlSessionSqlSession sqlSession = sqlSessionFactory.openSession(true);//获取Mapper接口对象UserMapper mapper = sqlSession.getMapper(UserMapper.class);//int res = mapper.updateUser();//int res = mapper.deleteUser();/*User user = mapper.getUserById();System.out.println(user);*///System.out.println(res);List<User> users = mapper.getAllUser();users.forEach(user-> System.out.println(user));}
}