java 学习笔记--mybatis 三剑客(mybatis)

Posted 2020-10-23 ransom

Java项目中使用Mybatis入门程序

 

wanna 关注

2017.03.23 14:33* 字数 270 阅读 1243评论 0喜欢 5

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。

欢迎访问本人博客：http://wangnan.tech

什么是 MyBatis ?

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。

MyBatis github

https://github.com/mybatis/mybatis-3

MyBatis 文档

http://mybatis.github.io/mybatis-3/zh/index.html

入门程序

想要使用 MyBatis 只需将 mybatis-x.x.x.jar 文件置于 classpath 中。
如果使用 Maven 构建项目，则需将下面的 dependency 置于 pom.xml 中：

    <dependency> 

        <groupId>org.mybatis</groupId>

        <artifactId>mybatis</artifactId> 

        <version>3.8.2</version> 

    </dependency>

我选择第二种，在Eclipse中新建一个maven项目

项目结构：

 

01.jpg

各文件介绍：

• pom文件：由于使用了mysql数据库，这里还依赖了一个mySQL驱动包
• 实体类User ：
• UserMapper接口：
• UserMapper接口的实现，userMapper.xml：
• 数据源配置 configuration.xml
• 测试类MyBatisTest：

     <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">  

      <modelVersion>4.0.0</modelVersion>  

      <groupId>Mybatis</groupId>  

      <artifactId>Mybatis</artifactId>  

      <version>0.0.1-SNAPSHOT</version>  

      <dependencies> 

        <dependency> 

          <groupId>org.mybatis</groupId>  

          <artifactId>mybatis</artifactId>  

          <version>3.2.8</version> 

        </dependency>  

        <dependency> 

          <groupId>mysql</groupId>  

          <artifactId>mysql-connector-java</artifactId>  

          <version>5.1.34</version> 

        </dependency> 

      </dependencies> 

     </project>

  package com.mybatis.domain;

    public class User {

         private String name;

         private Integer age;

         public String getName() {

            return name;

         }

         public void setName(String name) {

         this.name = name;

         }

         public Integer getAge() {

         return age;

         }

         public void setAge(Integer age) {

            this.age = age;

         }

    }

package com.mybatis.mapper; 

import com.mybatis.domain.User; 

public interface UserMapper { 

    public User findById(String Id); 

}

    <?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"> <!--相当于UserMapper接口的实现 namespace必须是UserMapper类路径-->

    <mapper namespace="com.mybatis.mapper.UserMapper"> 

        <!-- findById必须和接口中的方法名一样 返回一个User--> 

        <select id="findById" parameterType="String"

        resultType="com.mybatis.domain.User"> 

        select * from user where id=#{id} 

        </select> 

    </mapper>

    <?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> 

        <!--数据源配置 -->

        <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" />

                    <property name="username" value="root" /> 

                    <property name="password" value="123456" /> 

                </dataSource>

            </environment> 

        </environments> <mappers> 

            <!--userMapper.xml装载进来 --> 

            <mapper resource="userMapper.xml" /> 

        </mappers> 

    </configuration>

package com.mybatis.test;

import com.mybatis.domain.User;

import com.mybatis.mapper.UserMapper;

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;

public class MyBatisTest {

    /** * MyBatis SqlSessionFactory * SqlSessionFactory????SqlSession????????????SqlSession??????????commit?rollback?close???? * @return */ private static SqlSessionFactory getSessionFactory() {

        SqlSessionFactory sessionFactory = null;

        String resource = "configuration.xml";

        try {

            sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader(

                        resource));

        } catch (IOException e) {

            e.printStackTrace();

        }

        return sessionFactory;

    }

    public static void main(String[] args) {

        SqlSession sqlSession = getSessionFactory().openSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        User user = userMapper.findById("1");

        System.out.println(user.getName());

    }

}

数据库中插入条数据：
id=”1” name=”wn” age=”23”