MyBatis：实现MyBatis程序

Posted edda_huang

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一，MyBatis介绍

MyBatis是一个支持普通SQL查询，存储过程和高级映射的优秀持久层框架。MyBatis消除了几乎所有的JDBC代码和参数的手工设置以及对结果集的检索封装。MyBatis可以使用简单的XML或注解用于配置和原始映射，将接口和Java的POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录

二，MyBatis优点

不用再去写复杂的JDBC代码

  • 简单易学，不依赖第三方的程序或者框架。
  • 官网文档强大，开源，我们可以随时分析源码’；
  • 实现解耦，低耦合，高内聚
  • ORM；对象关系映射
  • 提供XML标签；

三， Mybatis程序

1，搭建实验环境，创建一个数据库

1-1，MySQL代码

CREATE DATABASE `mybatis` ;

USE mybatis;


DROP TABLE IF EXISTS user;


CREATE TABLE user (

id INT(20) NOT NULL,

name VARCHAR(30) DEFAULT NULL,

pwd VARCHAR(30) DEFAULT NULL,

PRIMARY KEY (id)

) ENGINE=INNODB DEFAULT CHARSET=utf8;


INSERT  INTO user(id,name,pwd)

VALUES (1,‘闪电侠‘,‘123‘),(2,‘蜘蛛侠‘,‘abc‘),(3,‘钢铁侠‘,‘520‘);

1-2，运行结果
技术图片

2，创建一个普通的Maven项目

2-1，创建Maven
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技术图片
2-2，编写pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>

<span class="hljs-tag">&lt;<span class="hljs-name">groupId</span>&gt;</span>com.Shandx<span class="hljs-tag">&lt;/<span class="hljs-name">groupId</span>&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">artifactId</span>&gt;</span>ssm-mybatis-study<span class="hljs-tag">&lt;/<span class="hljs-name">artifactId</span>&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">version</span>&gt;</span>1.0-SNAPSHOT<span class="hljs-tag">&lt;/<span class="hljs-name">version</span>&gt;</span>

<span class="hljs-tag">&lt;<span class="hljs-name">dependencies</span>&gt;</span>
    <span class="hljs-comment">&lt;!--单元测试--&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">dependency</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">groupId</span>&gt;</span>junit<span class="hljs-tag">&lt;/<span class="hljs-name">groupId</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">artifactId</span>&gt;</span>junit<span class="hljs-tag">&lt;/<span class="hljs-name">artifactId</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">version</span>&gt;</span>4.11<span class="hljs-tag">&lt;/<span class="hljs-name">version</span>&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">dependency</span>&gt;</span>

    <span class="hljs-comment">&lt;!--mybatis的包--&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">dependency</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">groupId</span>&gt;</span>org.mybatis<span class="hljs-tag">&lt;/<span class="hljs-name">groupId</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">artifactId</span>&gt;</span>mybatis<span class="hljs-tag">&lt;/<span class="hljs-name">artifactId</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">version</span>&gt;</span>3.5.1<span class="hljs-tag">&lt;/<span class="hljs-name">version</span>&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">dependency</span>&gt;</span>

    <span class="hljs-comment">&lt;!--连接数据库的驱动包--&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">dependency</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">groupId</span>&gt;</span>mysql<span class="hljs-tag">&lt;/<span class="hljs-name">groupId</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">artifactId</span>&gt;</span>mysql-connector-java<span class="hljs-tag">&lt;/<span class="hljs-name">artifactId</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">version</span>&gt;</span>5.1.47<span class="hljs-tag">&lt;/<span class="hljs-name">version</span>&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">dependency</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">dependencies</span>&gt;</span>

<span class="hljs-tag">&lt;<span class="hljs-name">build</span>&gt;</span>
    <span class="hljs-comment">&lt;!--希望maven在导出项目的时候,能够将我们的配置及资源导出--&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">resources</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">resource</span>&gt;</span>
            <span class="hljs-tag">&lt;<span class="hljs-name">directory</span>&gt;</span>src/main/java<span class="hljs-tag">&lt;/<span class="hljs-name">directory</span>&gt;</span>
            <span class="hljs-tag">&lt;<span class="hljs-name">includes</span>&gt;</span>
                <span class="hljs-tag">&lt;<span class="hljs-name">include</span>&gt;</span>**/*.properties<span class="hljs-tag">&lt;/<span class="hljs-name">include</span>&gt;</span>
                <span class="hljs-tag">&lt;<span class="hljs-name">include</span>&gt;</span>**/*.xml<span class="hljs-tag">&lt;/<span class="hljs-name">include</span>&gt;</span>
            <span class="hljs-tag">&lt;/<span class="hljs-name">includes</span>&gt;</span>
            <span class="hljs-tag">&lt;<span class="hljs-name">filtering</span>&gt;</span>false<span class="hljs-tag">&lt;/<span class="hljs-name">filtering</span>&gt;</span>
        <span class="hljs-tag">&lt;/<span class="hljs-name">resource</span>&gt;</span>
        <span class="hljs-tag">&lt;<span class="hljs-name">resource</span>&gt;</span>
            <span class="hljs-tag">&lt;<span class="hljs-name">directory</span>&gt;</span>src/main/resources<span class="hljs-tag">&lt;/<span class="hljs-name">directory</span>&gt;</span>
            <span class="hljs-tag">&lt;<span class="hljs-name">includes</span>&gt;</span>
                <span class="hljs-tag">&lt;<span class="hljs-name">include</span>&gt;</span>**/*.properties<span class="hljs-tag">&lt;/<span class="hljs-name">include</span>&gt;</span>
                <span class="hljs-tag">&lt;<span class="hljs-name">include</span>&gt;</span>**/*.xml<span class="hljs-tag">&lt;/<span class="hljs-name">include</span>&gt;</span>
            <span class="hljs-tag">&lt;/<span class="hljs-name">includes</span>&gt;</span>
            <span class="hljs-tag">&lt;<span class="hljs-name">filtering</span>&gt;</span>false<span class="hljs-tag">&lt;/<span class="hljs-name">filtering</span>&gt;</span>
        <span class="hljs-tag">&lt;/<span class="hljs-name">resource</span>&gt;</span>
    <span class="hljs-tag">&lt;/<span class="hljs-name">resources</span>&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">build</span>&gt;</span>



</project>

3，编写代码

3-1，创建pojo实体类

public class User {

<span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> id;
<span class="hljs-keyword">private</span> String name;
<span class="hljs-keyword">private</span> String pwd;

<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-title">User</span><span class="hljs-params">()</span> </span>{
}

<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-title">User</span><span class="hljs-params">(<span class="hljs-keyword">int</span> id, String name, String pwd)</span> </span>{
    <span class="hljs-keyword">this</span>.id = id;
    <span class="hljs-keyword">this</span>.name = name;
    <span class="hljs-keyword">this</span>.pwd = pwd;
}

<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getId</span><span class="hljs-params">()</span> </span>{
    <span class="hljs-keyword">return</span> id;
}

<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setId</span><span class="hljs-params">(<span class="hljs-keyword">int</span> id)</span> </span>{
    <span class="hljs-keyword">this</span>.id = id;
}

<span class="hljs-function"><span class="hljs-keyword">public</span> String <span class="hljs-title">getName</span><span class="hljs-params">()</span> </span>{
    <span class="hljs-keyword">return</span> name;
}

<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setName</span><span class="hljs-params">(String name)</span> </span>{
    <span class="hljs-keyword">this</span>.name = name;
}

<span class="hljs-function"><span class="hljs-keyword">public</span> String <span class="hljs-title">getPwd</span><span class="hljs-params">()</span> </span>{
    <span class="hljs-keyword">return</span> pwd;
}

<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setPwd</span><span class="hljs-params">(String password)</span> </span>{
    <span class="hljs-keyword">this</span>.pwd = password;
}

<span class="hljs-meta">@Override</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> String <span class="hljs-title">toString</span><span class="hljs-params">()</span> </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-string">"User{"</span> +
            <span class="hljs-string">"id="</span> + id +
            <span class="hljs-string">", name=‘"</span> + name + <span class="hljs-string">‘‘‘</span> +
            <span class="hljs-string">", pwd=‘"</span> +pwd + <span class="hljs-string">‘‘‘</span> +
            <span class="hljs-string">‘}‘</span>;
}



}

3-2，在resources下建一个mybatis-config.xml，编写mybatis配置文件
技术图片

<?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>
    <!--配置环境，这里可以有多套环境 default代表默认的是那一套-->
    <environments default="development">
        <!--配置一套环境 id .环境的名字-->
        <environment id="development">
            <!--transactionManager:事务管理，type:jdbc-->
            <transactionManager type="JDBC"/>
            <!--dataSource 数据源-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!--xml中不允许&符号直接出现，我们需要使用 &amp; 代替-->
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;charsetEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
</configuration>

3-3，创建工具类

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;

//mybatis的工具类，重复的代码的提纯

public class MyBatisUtils {


<span class="hljs-comment">//类变量不需要设置默认值；</span>
<span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> <span class="hljs-type">SqlSessionFactory</span> sqlSessionFactory;

<span class="hljs-keyword">static</span> {
    <span class="hljs-comment">//在maven中，所有的资源文件一般都放在resources目录下，我们可以直接拿到。</span>
    <span class="hljs-keyword">try</span> {
        <span class="hljs-type">String</span> resource = <span class="hljs-string">"mybatis-config.xml"</span>;
        <span class="hljs-type">InputStream</span> inputStream = <span class="hljs-type">Resources</span>.getResourceAsStream(resource);
        sqlSessionFactory = new <span class="hljs-type">SqlSessionFactoryBuilder</span>().build(inputStream);
    } <span class="hljs-keyword">catch</span> (<span class="hljs-type">IOException</span> e) {
        e.printStackTrace();
    }
}

<span class="hljs-comment">//设置SqlSessionFactory公共的方法</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-type">SqlSessionFactory</span> getSqlSessionFactory(){
    <span class="hljs-keyword">return</span> sqlSessionFactory;
}



}

3-4，映射文件的接口

import com.shandx.pojo.User;
import java.util.List;

public interface UserMapper {


<span class="hljs-comment">//获取全部的用户</span>
<span class="hljs-function">List&lt;User&gt; <span class="hljs-title">selectUser</span><span class="hljs-params">()</span></span>;



}

3-5，编写对应的mapper映射文件

<?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标签的namespace对应Mapper接口的类-->

<mapper namespace="com.Shandx.dao.UserMapper">

<!--select标签的id对应映射接口的方法名字  resultType:返回结果的类型  中间就编写sql语句-->

<select id="selectUser" resultType="com.Shandx.pojo.User">

select * from user

</select>


</mapper>

3-6，在mybatis配置文件中绑定编写映射文件

<?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>
    <!--配置环境，这里可以有多套环境 default代表默认的是那一套-->
    <environments default="development">
        <!--配置一套环境 id .环境的名字-->
        <environment id="development">
            <!--transactionManager:事务管理，type:jdbc-->
            <transactionManager type="JDBC"/>
            <!--dataSource 数据源-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!--xml中不允许&符号直接出现，我们需要使用 &amp; 代替-->
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;charsetEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

<span class="hljs-comment">&lt;!--关联映射文件--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">mappers</span>&gt;</span>
    <span class="hljs-tag">&lt;<span class="hljs-name">mapper</span> <span class="hljs-attr">resource</span>=<span class="hljs-string">"com/kuang/dao/userMapper.xml"</span>/&gt;</span>
<span class="hljs-tag">&lt;/<span class="hljs-name">mappers</span>&gt;</span>



</configuration>

4，测试一下

在maven的test文件夹下编写对应的测试类

import com.Shandx.dao.UserMapper;
import com.Shandx.pojo.User;
import com.Shandx.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;

import java.util.List;


public class UserMapperTest {

@Test

public void selectUser(){


    <span class="hljs-comment">//1.拿到sqlSessionFactory对象</span>
    <span class="hljs-type">SqlSessionFactory</span> sqlSessionFactory = <span class="hljs-type">MyBatisUtils</span>.getSqlSessionFactory();
    <span class="hljs-comment">//2.通过sqlSessionFactory对象openSession()创建一个sqlSession。</span>
    <span class="hljs-type">SqlSession</span> sqlSession = sqlSessionFactory.openSession();
    <span class="hljs-comment">//3.通过sqlSession获得mapper对象 ， 参数为映射文件对应的接口类的class对象</span>
    <span class="hljs-type">UserMapper</span> mapper = sqlSession.getMapper(<span class="hljs-type">UserMapper</span>.<span class="hljs-keyword">class</span>);
    <span class="hljs-comment">//4.通过mapper对象来执行操作；</span>
    <span class="hljs-type">List</span>&lt;<span class="hljs-type">User</span>&gt; users = mapper.selectUser();

    <span class="hljs-comment">//获得结果集</span>
    <span class="hljs-keyword">for</span> (<span class="hljs-type">User</span> user : users) {
        <span class="hljs-type">System</span>.out.<span class="hljs-built_in">println</span>(user);
    }
    
}



}

5，结果展示

技术图片

四，项目结构

技术图片



























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