Mybatis 快速入门(XML方式)第一天

导读

架构原理图

说明

mybatis配置文件

SqlMapConfig.xml，此文件为mybatis的全局配置文件，配置了mybatis的运行环境等信息
XXXMapper.xml，此文件作为mybatis的sql映射文件，文件中配置了操作数据库的CRUD语句。需要在SqlMapConfig.xml中加载

SqlSessionFactory

通过mybatis环境等配置信息构造SqlSessionFactory，既会话工厂

跟底层源码查看创建SqlSessionFactory流程

注：底层如何获取标签值，请自行研究(剧透：for循环遍历XML获取标签中的值，然后放入Map)！~

SqlSession

通过会员工厂创建SqlSession即会话，程序通过SqlSession会话接口对数据库进行CRUD操作。

Executor执行器

　　mybatis底层自定义了Executor执行器接口来具体操作数据库，Executor接口有两个实现，一个是基本执行器(默认)，一个缓存执行器，SqlSession底层是通过executor接口操作数据库

Mapped Statement

　　他是mybatis一个底层封装对象，包装了mybatis配置信息及XXXMapper.xml映射文件等。XXXMapper.xml文件中一个个select/insert/update/delete标签对应一个Mapped Statement对象。

原始JDBC代码

　　原始JDBC和mybatis操作数据库数据，与上面架构图流程相对应。

 public class JDBCTest {
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
    Connection connection </span>= <span style="color: #0000ff;">null</span><span style="color: #000000;">;
    PreparedStatement preparedStatement </span>= <span style="color: #0000ff;">null</span><span style="color: #000000;">;
    ResultSet resultSet </span>= <span style="color: #0000ff;">null</span><span style="color: #000000;">;

    </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 加载数据库驱动</span>
        Class.forName("com.mysql.jdbc.Driver"<span style="color: #000000;">);

        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 通过驱动管理类获取数据库链接connection = DriverManager</span>
        connection =<span style="color: #000000;"> DriverManager.getConnection(
                          </span>"jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8"<span style="color: #000000;">,
                         </span>"root"<span style="color: #000000;">, 
                          </span>"root"<span style="color: #000000;">
                          );

        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 定义sql语句 ?表示占位符</span>
        String sql = "select * from user where username = ?"<span style="color: #000000;">;
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 获取预处理 statement</span>
        preparedStatement =<span style="color: #000000;"> connection.prepareStatement(sql);
        
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 设置参数，第一个参数为 sql 语句中参数的序号（从 1 开始），第二个参数为设置的</span>
        preparedStatement.setString(1, "王五"<span style="color: #000000;">);
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 向数据库发出 sql 执行查询，查询出结果集</span>
        resultSet =<span style="color: #000000;"> preparedStatement.executeQuery();
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 遍历查询结果集</span>
        <span style="color: #0000ff;">while</span><span style="color: #000000;"> (resultSet.next()) {
            System.out.println(
                              resultSet.getString(</span>"id"<span style="color: #000000;">) 
                              </span>+ " " +<span style="color: #000000;"> 
                              resultSet.getString(</span>"username"<span style="color: #000000;">)
                 );
        }
    } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (Exception e) {
        e.printStackTrace();
    } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 释放资源</span>
        <span style="color: #0000ff;">if</span> (resultSet != <span style="color: #0000ff;">null</span><span style="color: #000000;">) {
            </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                resultSet.close();
            } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (SQLException e) {
                e.printStackTrace();
            }
        }
        </span><span style="color: #0000ff;">if</span> (preparedStatement != <span style="color: #0000ff;">null</span><span style="color: #000000;">) {
            </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                preparedStatement.close();
            } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (SQLException e) {
                e.printStackTrace();
            }
        }
        </span><span style="color: #0000ff;">if</span> (connection != <span style="color: #0000ff;">null</span><span style="color: #000000;">) {
            </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                connection.close();
            } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (SQLException e) {
                </span><span style="color: #008000;">//</span><span style="color: #008000;"> TODO Auto-generated catch block e.printStackTrace();</span>

                }
}
}
}
}

Mybatis 入门基础

表结构

表数据

Mybatis环境搭建

添加依赖

pom.xml

 <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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.cyb</groupId>
    <artifactId>mybatis</artifactId>
    <packaging>war</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>mybatis Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <dependencies>
        <!-- mybatis依赖 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <!-- mysql依赖 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.20</version>
        </dependency>
    <span style="color: #008000;">&lt;!--</span><span style="color: #008000;"> 单元测试 </span><span style="color: #008000;">--&gt;</span>
    <span style="color: #0000ff;">&lt;</span><span style="color: #800000;">dependency</span><span style="color: #0000ff;">&gt;</span>
        <span style="color: #0000ff;">&lt;</span><span style="color: #800000;">groupId</span><span style="color: #0000ff;">&gt;</span>junit<span style="color: #0000ff;">&lt;/</span><span style="color: #800000;">groupId</span><span style="color: #0000ff;">&gt;</span>
        <span style="color: #0000ff;">&lt;</span><span style="color: #800000;">artifactId</span><span style="color: #0000ff;">&gt;</span>junit<span style="color: #0000ff;">&lt;/</span><span style="color: #800000;">artifactId</span><span style="color: #0000ff;">&gt;</span>
        <span style="color: #0000ff;">&lt;</span><span style="color: #800000;">version</span><span style="color: #0000ff;">&gt;</span>4.12<span style="color: #0000ff;">&lt;/</span><span style="color: #800000;">version</span><span style="color: #0000ff;">&gt;</span>
    <span style="color: #0000ff;">&lt;/</span><span style="color: #800000;">dependency</span><span style="color: #0000ff;">&gt;</span>
<span style="color: #0000ff;">&lt;/</span><span style="color: #800000;">dependencies</span><span style="color: #0000ff;">&gt;</span>
<span style="color: #0000ff;">&lt;</span><span style="color: #800000;">build</span><span style="color: #0000ff;">&gt;</span>
    <span style="color: #0000ff;">&lt;</span><span style="color: #800000;">finalName</span><span style="color: #0000ff;">&gt;</span>mybatis<span style="color: #0000ff;">&lt;/</span><span style="color: #800000;">finalName</span><span style="color: #0000ff;">&gt;</span>
<span style="color: #0000ff;">&lt;/</span><span style="color: #800000;">build</span><span style="color: #0000ff;">&gt;</span>

</project>

SqlMapConfig.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>
    <!-- 引入外部配置文件 -->
    <properties resource="db.properties"></properties>
    <!-- 数据库链接相关 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="${db.driver}" />
                <property name="url" value="${db.url}" />
                <property name="username" value="${db.username}" />
                <property name="password" value="${db.password}" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 添加映射文件 -->
        <mapper resource="UserMapper.xml" />
    </mappers>
</configuration>

db.properties

 db.driver=com.mysql.jdbc.Driver
db.url=jdbc:mysql://127.0.0.1:3306/cyb
db.username=root
db.password=root

UserMapper.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">
<!-- namespace:为了分类管理映射文件中的MappedStatement -->
<mapper namespace="test">
<select id="queryUserById" parameterType="int" resultType="com.cyb.mybatis.demo.User">
        select * from user where id = #{id} 
    </select>
</mapper>

User.java

 package com.cyb.mybatis.demo;
import java.util.Date;
public class User {
private int id;
private String username;
private Date birthday;
private int sex;
private String address;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public int getSex() {
return sex;
}
public void setSex(int sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", birthday=" + birthday + ", sex=" + sex + ", address="
+ address + "]";
}
}

MybatisDemo.java

 package com.cyb.mybatis.demo;
import java.io.InputStream;
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 org.junit.Before;
import org.junit.Test;
public class MybatisDemo {
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> SqlSessionFactory sqlSessionFactory;

@Before
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> init() <span style="color: #0000ff;">throws</span><span style="color: #000000;"> Exception {
    </span><span style="color: #008000;">//</span><span style="color: #008000;">指定全局配置文件路径</span>
    String resource = "SqlMapConfig.xml"<span style="color: #000000;">;
    </span><span style="color: #008000;">//</span><span style="color: #008000;">加载资源文件(包括全局文件和映射文件)</span>
    InputStream inputStream =<span style="color: #000000;"> Resources.getResourceAsStream(resource);
    </span><span style="color: #008000;">//</span><span style="color: #008000;">使用构建者模式创建SqlSessionFactory</span>
    sqlSessionFactory = <span style="color: #0000ff;">new</span><span style="color: #000000;"> SqlSessionFactoryBuilder().build(inputStream);
}

@Test
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> testSelect() {
    </span><span style="color: #008000;">//</span><span style="color: #008000;">由SqlSessionFactory工厂去创建SqlSession(会话)</span>
    SqlSession sqlSession =<span style="color: #000000;"> sqlSessionFactory.openSession();
    </span><span style="color: #008000;">//</span><span style="color: #008000;">调用SqlSession接口，去实现数据库的CRUD</span>
    User user = sqlSession.selectOne("test.queryUserById", 1<span style="color: #000000;">);
    System.out.println(user);
    </span><span style="color: #008000;">//</span><span style="color: #008000;">释放资源</span>

        sqlSession.close();
}
}

Mybatis 快速入门(XML方式)第一天

导读

架构原理图

说明

mybatis配置文件

SqlSessionFactory

***跟底层源码查看创建SqlSessionFactory流程***

SqlSession

Executor执行器

Mapped Statement

原始JDBC代码

Mybatis 入门基础

表结构

表数据

Mybatis环境搭建

添加依赖

SqlMapConfig.xml

UserMapper.xml

User.java

MybatisDemo.java

项目结构

测试

功能实现

根据用户id查询一个用户信息

根据用户名称模糊查询用户信息列表

添加用户

更新用户

删除用户

前端开发

后端开发

移动端开发

数据库

服务器运维

人工智能

区块链

游戏开发

网站运营

大数据/云计算

软件工程

软件/开发工具使用

资讯

跟底层源码查看创建SqlSessionFactory流程