代码记事本

在这里记录所有重复使用的代码

“计算机科学是一门让你学会如何思考的科学，而不是一门让你学会如何编程的科学。”

课程-KuangStudy

JDBC

Mysql的配置

8.0以上数据库需要加时区设置

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jdbc.username=root
jdbc.password=root
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai

JavaWeb

web.xml4.0配置
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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
</web-app>

Maven

解决资源导出问题和xml乱码

pom.xml

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<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>
<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

Mybatis

Mybatis配置文件 官方

mybatis-config.xml

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="org/mybatis/example/BlogMapper.xml"/>
  </mappers>
</configuration>
Mybatis配置文件 Joker
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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- 核心配置文件 -->
<configuration>
    <settings>
        <!-- 标准的日志工厂实现 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
        <!-- 显式的开启缓存 -->
        <setting name="cacheEnabled" value="true"/>
    </settings>

    <!-- 给实体类型起别名 -->
    <typeAliases>
        <package name="com.joker_yue.pojo"/>
    </typeAliases>

    <!-- 可以配置多套环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 配置mapper的位置 -->
    <mappers>
        <mapper class="com.joker_yue.dao.UserMapper"/>
    </mappers>

</configuration>
Mybatis配置文件 Properties

mybatis-config.xml

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- 核心配置文件 -->
<configuration>
    <!-- 引入外部配置文件 -->
    <properties resource="db.properties">
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    </properties>

    <settings>
        <!-- 标准的日志工厂实现 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
        <!-- 显式的开启缓存 -->
        <setting name="cacheEnabled" value="true"/>
    </settings>

    <!-- 给实体类型起别名 -->
    <typeAliases>
        <package name="com.joker_yue.pojo"/>
    </typeAliases>

    <!-- 可以配置多套环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 配置mapper的位置 -->
    <mappers>
        <mapper class="com.joker_yue.dao.UserMapper"/>
    </mappers>

</configuration>

db.properties

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jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8
Mybatis的Mapper文件

UserMapper.xml

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.joker_yue.mapper.UserMapper">
    
</mapper>
Mybatis的SqlSessionFactory工厂

MybatisUtils.java

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package com.joker_yue.utils.utils;

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;
import java.io.InputStream;

/**
 * 工具类
 * sqlSessionFactory的作用是构建sqlSession
 *
 * @author Joker
 * @version 1.0
 * @date 2023/7/19 19:48
 */
public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory = null;

    static {
        try {
            String resource = "mybatis-config.xml";         // 准备mybatis的配置
            InputStream inputStream = Resources.getResourceAsStream(resource);    // 读取mybatis的配置
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);    // 根据读取到的配置构建sqlSessionFactory
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    // 既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
    // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession(true); // true 表示自动提交事务
    }
}

注意事项

  • 每写好一个Mapper的xml文件，应当立即去mybatis-config.xml文件中注册

Spring

Spring默认配置 官方

applicationContext.xml

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- services -->

    <bean id="petStore" class="org.springframework.samples.jpetstore.services.PetStoreServiceImpl">
        <property name="accountDao" ref="accountDao"/>
        <property name="itemDao" ref="itemDao"/>
        <!-- additional collaborators and configuration for this bean go here -->
    </bean>

    <!-- more bean definitions for services go here -->

</beans>
Spring注解支持

applicationContext.xml

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd">

    <context:annotation-config/>

</beans>

SpringMVC

SpringMVC通用配置

web.xml

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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

  <!-- 1.  配置DispatcherServlet，这是SpringMVC的核心：请求分发器，前端控制器   -->
  <servlet>
    <servlet-name>springmvc</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <!--  DispatcherServlet 要绑定SpringMVC的配置文件    -->
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:springmvc-servlet.xml</param-value>
    </init-param>
    <!--   启动级别，为1时跟随服务器启动   -->
    <load-on-startup>1</load-on-startup>
  </servlet>

  <!-- 注意：
   / 匹配所有的请求（不包括.jsp)
   /* 匹配所有的请求(包括.jsp)
   一般写/就行
   -->
  <servlet-mapping>
    <servlet-name>springmvc</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

</web-app>

springmvc-servlet.xml

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        https://www.springframework.org/schema/mvc/spring-mvc.xsd">


    <!--   自动扫描包   -->
    <context:component-scan base-package="com.joker_yue.controller"/>

    <!--   让SpringMVC不处理静态资源 例如css,js,mp3,mp4等  -->
    <mvc:default-servlet-handler/>

    <!--
        支持MVC注解驱动
            在Spring中一般采用@RequestMapping注解来完成映射关系
            原来必须向上下文注册DefaultAnnotationHandlerMapping和一个AnnotationMethodHandlerAdapter实例
            这两个示例分别在类级别和方法级别处理
            而现在使用annotation-driven配置就可以帮助我们自动完成上述两个示例的注入
     -->
    <mvc:annotation-driven/>

    <!--   视图解析器   -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver">
        <!-- 前缀 -->
        <property name="prefix" value="/WEB-INF/jsp/" />
        <!-- 后缀 -->
        <property name="suffix" value=".jsp" />
    </bean>


</beans>
解决jackson时，JSON乱码

spingmvc-servlet.xml

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<!-- 解决JSON乱码 -->
<mvc:annotation-driven>
    <mvc:message-converters register-defaults="true">
        <bean class="org.springframework.http.converter.StringHttpMessageConverter">
            <constructor-arg value="UTF-8"/>
        </bean>
        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
            </property>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>
commons-io文件上传

springmvc-servlet.xml

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<!--  文件上传配置 -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!-- 请求的编码格式，必须和jsp的pageEncoding属性一致，以便正确读取表单中的内容，默认为ISO-8859-1  -->
    <property name="defaultEncoding" value="UTF-8"/>
    <!-- 文件上传大小限制，单位为字节 (10MB=10485760) -->
    <property name="maxUploadSize" value="10485760"/>
    <!-- 缓冲 -->
    <property name="maxInMemorySize" value="40960"/>
</bean>

SSM

image-20230730201713975

mybatis-config.xml Mybatis核心配置文件
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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- 核心配置文件 -->
<configuration>
    <!-- 日志 -->
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <!-- 给实体类型起别名 -->
    <typeAliases>
        <package name="com.joker_yue.pojo"/>
    </typeAliases>

    <!-- 配置mapper的位置 -->
    <mappers>
        <mapper class="com.joker_yue.dao.BookMapper"/>
    </mappers>

</configuration>
web.xml 注册核心分发器，设置乱码过滤，Session自动超时
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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">


    <!--  DispatcherServlet 核心Servlet  -->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:applicationContext.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <!--   乱码过滤   -->
    <filter>
        <filter-name>encodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>encodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <!--   Session自动超时   -->
    <session-config>
        <session-timeout>15</session-timeout>
    </session-config>
    
</web-app>
applicationContext.xml
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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd">

    
    <!-- 整合包放在这里 -->
    <import resource="classpath:spring-dao.xml"/>
    <import resource="classpath:spring-service.xml"/>
    <import resource="classpath:spring-mvc.xml"/>

</beans>
spring-dao.xml
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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

    <!--   1. 关联数据库配置文件    -->
    <context:property-placeholder location="classpath:db.properties"/>

    <!--   2. 连接池
      dbcp： 半自动化操作
      c3p0： 自动化操作，自动加载配置文件并自动设置到对象中
      druid、hikari
      -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="${jdbc.driver}"/>
        <property name="jdbcUrl" value="${jdbc.url}"/>
        <property name="user" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>

        <!--  c3p0的一些私有属性   -->
        <property name="maxPoolSize" value="30"/>
        <property name="minPoolSize" value="10"/>
        <!--   关闭连接后不自动commit   -->
        <property name="autoCommitOnClose" value="false"/>
        <!--   获取连接超时时间   -->
        <property name="checkoutTimeout" value="10000"/>
        <!--   当获取连接失败重试次数   -->
        <property name="acquireRetryAttempts" value="2"/>
    </bean>

    <!--   3. sqlSessionFactory   -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!--   绑定Mybatis的配置文件   -->
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
    </bean>


    <!--  4. 配置dao接口扫描包，动态的实现了Dao接口可以注入到spring容器中    -->
    <bean id="mapperScanner" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <!-- 注入sqlSessionFactory -->
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
        <!-- 要扫描的包 -->
        <property name="basePackage" value="com.joker_yue.dao"/>
    </bean>
</beans>
spring-service.xml
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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

    <!--  1. 扫描service下的包    -->
    <context:component-scan base-package="com.joker_yue.service"/>


    <!--   2. 将所有业务类注入到spring，可以通过配置或者注解实现   -->
    <bean id="bookServiceImpl" class="com.joker_yue.service.BookServiceImpl">
        <property name="bookMapper" ref="bookMapper"/>
    </bean>

    <!--   3. 声明式事务配置       -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <!-- 注入数据源 -->
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <!--   4. AOP横切事务       -->


</beans>
spring-mvc.xml
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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/mvc
       https://www.springframework.org/schema/mvc/spring-mvc.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

    <!--   1. 注解驱动   -->
    <mvc:annotation-driven/>
    <!--   2. 静态资源过滤   -->
    <mvc:default-servlet-handler/>
    <!--   3. 扫描包：Controller   -->
    <context:component-scan base-package="com.joker_yue.controller"/>
    <!--   4. 视图解析器   -->
    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <!-- <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/> -->
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>
</beans>

设计模式

动态代理

ProxyInvocationHandler.java

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import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

/**
 * @author Joker
 * @version 1.0
 * @date 2023/7/26 16:31
 */

// 一会通过这个类自动生成代理类
public class ProxyInvocationHandler implements InvocationHandler {

    /*
      InvocationHandler handler = new MyInvocationHandler(...);
     Class<?> proxyClass = Proxy.getProxyClass(Foo.class.getClassLoader(), Foo.class);
     Foo f = (Foo) proxyClass.getConstructor(InvocationHandler.class).
                     newInstance(handler);
     */

    // 被代理的接口
    private Object target;

    public void setTarget(Object target) {
        this.target = target;
    }

    // 生成得到代理类
    public Object getProxy( ) {
        return Proxy.newProxyInstance(this.getClass().getClassLoader(),
                target.getClass().getInterfaces(), this);
    }

    // 处理代理示例，并返回结果
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // 动态代理的本质，就是使用反射机制实现
        Object result = method.invoke(target, args);

        return result;
    }

}