mybatis入门到熟练（一）

一、创建一个空的maven项目

使用idea创建一个空的maven项目，引入依赖

<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.18</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.4.4</version>
    </dependency>
</dependencies>

二、配置mybatis

先来一个总体的结构。有点不好看，就是为了熟悉mybatis。

再看一下我们的数据库

1.在resource目录下增加mybatis-config.xml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>

    <properties>
        <property name="jdbc.driver" value="com.mysql.cj.jdbc.Driver" />
        <property name="jdbc.user" value="你的账号" />
        <property name="jdbc.pass" value="你的密码" />
        <property name="jdbc.url" value="你的url" />
    </properties>

    <!--便于后面解析对象-->
    <typeAliases>
        <package name="com.test" />
    </typeAliases>

    <!-- Continue going here -->
    <environments default="dev">
        <environment id="dev">
            <transactionManager type="JDBC"> </transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}" />
                <property name="url" value="${jdbc.url}" />
                <property name="username" value="${jdbc.user}" />
                <property name="password" value="${jdbc.pass}" />
            </dataSource>
        </environment>
    </environments>
    
    <!-- 告诉mybatis去这里找你的mapper ，这里不写会报错找不到mapper-->
    <mappers>
        <mapper resource="BlogMapper.xml" />
    </mappers>

</configuration>

2.在resource目录下增加BlogMapper.xml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 namespace="com.test.Tutorial">

    <select id="selectBlog" resultType="com.test.Blog">
        select * from Blog where id = #{id}
    </select>

    <insert id="insertBlog" parameterType="Blog">
        insert into Blog (id,title) values (#{id},#{title})
    </insert>

    <update id="updateBlog" parameterType="Blog">
        UPDATE Blog SET title=#{title} WHERE id=#{id}
    </update>

    <delete id="deleteBlog" parameterType="Integer">
        DELETE FROM BLOG WHERE id=#{id}
    </delete>

</mapper>

三、具体Java代码

实体类

package com.test;

/**
 * @author lichenhui
 * @version 1.0
 * @ClassName Blog
 * @date 2021/5/8 10:59
 */
public class Blog {
    int id;
    String title;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @Override
    public String toString() {
        return "Blog{" +
                "id=" + id +
                ", title='" + title + '\'' +
                '}';
    }
}

具体演示类
建议增删改查一个一个的测试，测试其中的一个注释掉其他的

package com.test;

import ......

/**
 * @author lichenhui11
 * @version 1.0
 * @ClassName Tutorial
 * @date 2021/5/8 11:11
 */
public class Tutorial {
    public static void main(String[] args) {
        SqlSession sqlSession = null;
        int row;
        try {
            InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

            // 查询数据库内容
            sqlSession = sqlSessionFactory.openSession();
            Blog blog = sqlSession.selectOne("com.test.Tutorial.selectBlog",1);
            System.out.println(blog);

            Blog b = new Blog();
            // 插入数据库内容
            b.setTitle("b");
            b.setId(2);
            row = sqlSession.insert("com.test.Tutorial.insertBlog",b);
            System.out.println(row);
            sqlSession.commit();

             //更新数据库内容
            b.setId(2);
            b.setTitle("c");
            row = sqlSession.update("com.test.Tutorial.updateBlog",b);
            System.out.println(row);
            sqlSession.commit();


            //删除数据库内容
            row = sqlSession.delete("com.test.Tutorial.deleteBlog",2);
            System.out.println(row);
            sqlSession.commit();

        } catch (IOException e) {
            e.printStackTrace();
            assert false;
            sqlSession.rollback();
        }finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }

}

结论：
基于xml的方式，对数据库进行增删改查

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