javaweb

前言

跟着Boogipop大佬学java，这部分拖太久了，忙完下周的一个期末考试，趁其他考试还没来时赶紧学完这些开发的东西

参照Boogipop大佬的学习，学完Servlet和Listener和FIlter这部分就可以结束了

maven

M2_HOME E:\CTF学习笔记\Java\apache-maven-3.8.6-bin\apache-maven-3.8.6\bin
MAVEN_HOME E:\CTF学习笔记\Java\apache-maven-3.8.6-bin\apache-maven-3.8.6

在Path下添加%MAVEN_HOME%\bin

修改conf/setting.xml

<mirror>
  <id>aliyunmaven</id>
  <mirrorOf>*</mirrorOf>
  <name>阿里云公共仓库</name>
  <url>https://maven.aliyun.com/repository/public</url>
</mirror>

<localRepository>E:\CTF学习笔记\Java\apache-maven-3.8.6-bin\apache-maven-3.8.6\maven-repo</localRepository>

Servlet

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter writer = resp.getWriter();
        writer.println("hahahhahahahha");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    }
}

注册servlet

更新web.xml内容

<?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"
         metadata-complete="true">
    
    
</web-app>

<?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"
         metadata-complete="true">


    <!--注册servlet-->
    <servlet>
        <servlet-name>hello1</servlet-name>
        <servlet-class>HelloServlet</servlet-class>
    </servlet>
    <!--设置路由-->
    <servlet-mapping>
        <servlet-name>hello1</servlet-name>
        <url-pattern>/hello1</url-pattern>
    </servlet-mapping>
    
    <servlet-mapping>
        <servlet-name>hello1</servlet-name>
        <url-pattern>*.asd</url-pattern>    //自定义以.asd结尾，*前面不加/
    </servlet-mapping>
    
    <servlet>
        <servlet-name>error</servlet-name>
        <servlet-class>ErrorServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>error</servlet-name>
        <url-pattern>/*</url-pattern>          //优先级较低
    </servlet-mapping>
</web-app >

ServletContent

共享数据

public class GetServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        String user = (String)servletContext.getAttribute("user");
        resp.getWriter().println(user);


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter writer = resp.getWriter();
        writer.println("hahahhahahahha");
        ServletContext servletContext = this.getServletContext();
        servletContext.setAttribute("user","asdsadssad");
    }

直接访问GetServlet对应的路由，显示为null

要先访问HelloServlet对应的路由，再访问GetServlet对应的路由即可

getinitparam

web.xml中设置初始参数值

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    ServletContext servletContext = this.getServletContext();
    String user = (String)servletContext.getAttribute("user");
    resp.getWriter().println(user);

    String cmd1 = servletContext.getInitParameter("cmd");
    resp.getWriter().println(cmd1);


}

<?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"
         metadata-complete="true">

    <!--注册servlet-->
    <servlet>
        <servlet-name>hello1</servlet-name>
        <servlet-class>HelloServlet</servlet-class>
    </servlet>
    <!--设置路由-->
    <servlet-mapping>
        <servlet-name>hello1</servlet-name>
        <url-pattern>/hello1</url-pattern>
    </servlet-mapping>
    <context-param>
        <param-name>cmd</param-name>
        <param-value>jdbc:mysql://localhost:3306/test</param-value>
    </context-param>
</web-app >

getRequestDispatcher

请求转发

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class GetServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        String user = (String)servletContext.getAttribute("user");
        resp.getWriter().println(user);

        String cmd1 = servletContext.getInitParameter("cmd");
        resp.getWriter().println(cmd1);
        
        servletContext.getRequestDispatcher("/hello1").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

转发后，其他无效，只显示/hello1的页面

getResourceAsStream

resources目录下的和java目录下的都会被打包到classes目录下

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class ResourceServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        InputStream stream = this.getServletContext().getResourceAsStream("/WEB-INF/classes/cb.properties");
        Properties properties = new Properties();
        properties.load(stream);

        String username = properties.getProperty("username");
        resp.getWriter().println(username);


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

当properties文件不在resources目录下时，有可能无法导出

在pom.xml添加一段代码即可

<resources>
    <resource>
        <directory>src/main/resources</directory>
        <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
    </resource>
    <resource>
        <directory>src/main/java</directory>
        <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
        <filtering>true</filtering>
    </resource>
</resources>

response下载文件

关键在于响应的请求头Content-Disposition，内容为attachment;filename=

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class DownServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String path = "C:\\Users\\86136\\Pictures\\Saved Pictures\\yunchong.png";
        
        String filename = path.substring(path.lastIndexOf("\\")+1);
        
        resp.setHeader("Content-Disposition","attachment;filename="+filename);
        
        FileInputStream in = new FileInputStream(path);
        int len = 0;
        byte[] bytes = new byte[1024];

        ServletOutputStream out = resp.getOutputStream();
        while ((len = in.read(bytes))!=0){
            out.write(bytes,0,len);
        }
        out.close();
        in.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

response 验证码

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;

public class ImageServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        //内存中生成
        BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g = (Graphics2D) image.getGraphics();


        g.setColor(Color.BLUE);
        g.fillRect(0,0,80,20);

        g.setColor(Color.BLACK);
        g.setFont(new Font(null,Font.BOLD,20));
        g.drawString("123456",0,20);


        resp.setContentType("image/jpg");
        resp.setHeader("Cache-Control","no-cache");

        ImageIO.write(image, "jpg", resp.getOutputStream());

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    }
}

response 重定向

设置跳转路径时，注意加上页面设置时的虚拟映射

//index.jsp

<%@page contentType="text/html; charset=utf-8" pageEncoding="UTF-8" %>
<html>
<body>
<h2>Hello World!</h2>

<form action="redirect" method="get">
    用户 <input type="text" name="username">
    密码 <input type="password" name="password">
    <input type="submit">
    <input type="search">
</form>
</body>
</html>

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class RedirectServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String username = req.getParameter("username");
        String password = req.getParameter("password");

        System.out.println(username+":"+password);

        resp.sendRedirect("/hello/success.jsp");    //要包含页面设置时的虚拟映射
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

request

req.getRequestDispatcher("success.jsp").forward(req,resp);请求路径已经在虚拟映射的路径下了，不用再写虚拟映射的路径，另外这里success.jsp加不加/是一样的

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;

public class RedirectServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String[] hobbys = req.getParameterValues("hobbys");


        System.out.println(hobbys);
        System.out.println(Arrays.toString(hobbys));
        System.out.println(username+":"+password);
        System.out.println(req.getContextPath());

//        resp.sendRedirect("/hello/success.jsp");
        req.getRequestDispatcher("success.jsp").forward(req,resp);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

一个cookie只能保存一个信息
一个web站点可以给浏览器发送多个cookie，最多存放20个cookie
cookie大小有限制4kb
300个cookie浏览器上限

删除cookie

不设置有效期
设置有效期为0

传递中文

URLEncoder.encode("啊啊啊","utf-8")
URLDecoder.decode(cookie.getValue(),"utf-8")

session

什么是session:

服务器会给浏览器创建一个session对象
一个session独占一个浏览器，只要浏览器没有关闭，这个session就存在
用户登陆之后，整个网站他都可以访问

session和cookie的区别

cookie是把用户的数据写到用户的浏览器中，可以保存多个cookie

session是把用户的数据写到用户独占的session中，服务器端保存（保存重要的信息，减少服务器资源的浪费）

session对象由服务器创建

session创建的逻辑实际上是

Cookie cookie = new cookie("JSESSIONID",id)
addCookie(cookie)

req.setCharacterEncoding("UTF-8");
resp.setCharacterEncoding("UTF-8");
resp.setContentType("text/plain;charset=utf-8");

PrintWriter writer = resp.getWriter();


HttpSession session = req.getSession();
session.setAttribute("name", "zeropeach");
String id = session.getId();
writer.println("session的id为"+id);

//判断是不是新创建的session，只有当session被销毁时才会重新自动生成
writer.println(session.isNew());



//获取session内容
HttpSession session = req.getSession();
Object name = session.getAttribute("name");
System.out.println(name.toString());


//销毁session
HttpSession session = req.getSession();
session.removeAttribute("name");
session.invalidate();

当有两个sessionid时，session不能共享对象，可以通过ServletContext（也叫ApplicationContext）

jsp原理

全称 Java Servlet Pages

说明也是一个java程序，是一个servlet

D:\idea_2022.3\.IntelliJIdea\system\tomcat\81de8c7e-5d87-4185-9841-7ba31aa3bac6\work\Catalina\localhost\hello\org\apache\jsp

jsp语法

热部署

要是exploded这个

然后改为这样既可

这样就不用每次重启tomcat，只需要刷新页面即可

基础语法

<%--
<%= 变量或表达式%>     用来输出

--%>
<%= new java.util.Date()%>

<%
    int sum=0;
    for (int i = 0; i <= 100; i++) {
        sum +=i;
    }
    out.println("<h1>sum"+sum+"</h1>");
%>


<%
    int y = 2;
%>

<%
    out.println(y);
%>



<%
    for (int i = 0; i < 5; i++) {
%>
<h1>wow</h1>
<%
    }
%>

因为本质就是java文件，所以能用java语法，作用域也是一样，于是可以配合HTML循环输出

jsp声明

<%! %> 声明全局变量和全局方法

<%!
    static {
        System.out.println("666");
    }
   private int m = 8848;
%>

使用声明后，后被写到java类的作用域下，与原方法同级

<%--注释--%>

jsp的注释不会在客户端的源代码中出现

在jsp中加入这一句，遇到错误就跳转到500.jsp

<%@ page errorPage="error/500.jsp" %>       //自定义错误页面

也可以修改web.xml，当遇到404时，就会跳到404.jsp

<error-page>
    <error-code>404</error-code>
    <location>/error/404.jsp</location>
</error-page>

页面内容合二为一
<%@include file=""%>         //文件包含



页面内容拼接，实际还是多个页面
<jsp:include page="500.jsp" />

jsp 内置对象

<%
    pageContext.setAttribute("name1","1");   //保存的数据只在一个页面中有效
    request.setAttribute("name2","2");    //只在一次请求中有效，请求转发会携带这个数据
    session.setAttribute("name3","3");    //只在一次会话中有效，从打开浏览器到关闭浏览器
    application.setAttribute("name4","4");   //在服务器中有效 ，从打开服务器到关闭服务器
%>

<%
    String name1 = (String) pageContext.getAttribute("name1");
    String name2 = (String) pageContext.getAttribute("name2");
    String name3 = (String) pageContext.getAttribute("name3");
    String name4 = (String) pageContext.getAttribute("name4");
    String name5 = (String) pageContext.getAttribute("name5");
%>

<h3>${name1}</h3>
<h3>${name2}</h3>
<h3>${name3}</h3>
<h3>${name4}</h3>
<%=name5%>

双亲委派机制（与作用域进行类比）

想要重写一个类，但加载时会在类加载器中不断地往上找，在最上面加载器中找到的话，只会使用根加载器的，不会使用你重写的

作用域

指定作用域

<%pageContext.setAttribute("name","123",3);%>

//都是请求转发

<%
    pageContext.forward("/hello/hello.jsp");
    request.getRequestDispatcher("/hello/hello.jsp").forward(request,response);
%>

MVC框架

Model

增删改查

view

controller

Filter

导入的包不要错 javax.servlet.Filter

import javax.servlet.*;
import java.io.IOException;

public class TestFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("初始化");
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/plain;charset=utf-8");


        System.out.println("执行前");
        chain.doFilter(request,response);
        System.out.println("执行后");

    }

    @Override
    public void destroy() {
        System.out.println("销毁");
    }
}

web.xml

<filter>
    <filter-name>filter</filter-name>
    <filter-class>TestFilter</filter-class>
</filter>


<!--相对路径，不用包含映射-->
<filter-mapping>
    <filter-name>filter</filter-name>
    <url-pattern>/hello.jsp</url-pattern>
</filter-mapping>

Listener

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class OnlineListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent se) {
        ServletContext context = se.getSession().getServletContext();
        System.out.println(se.getSession().getId());

        Integer count = (Integer) context.getAttribute("OnlineCount");

        if (count==null){
            count = new Integer(1);
        }
        else {
            int i = count.intValue();
            count = new Integer(i+1);
        }

        context.setAttribute("OnlineCount",count);


    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        ServletContext context = se.getSession().getServletContext();

        Integer count = (Integer) context.getAttribute("OnlineCount");

        if (count==null){
            count = new Integer(0);
        }
        else {
            int i = count.intValue();
            count = new Integer(i-1);
        }

        context.setAttribute("OnlineCount",count);
    }
}

web.xml

<listener>
    <listener-class>OnlineListener</listener-class>
</listener>

Filter权限管理案例

写的时候注意跳转的地方，我在写的时候写出个一直重定向的错误。。。

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class SysFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse resp = (HttpServletResponse) response;

        Object userSession = req.getSession().getAttribute("USER_SESSION");
        if (userSession==null){
            resp.sendRedirect("/hello/sys/error.jsp");
        }


        chain.doFilter(req,resp);
    }

    @Override
    public void destroy() {

    }
}

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String username = req.getParameter("username");

        if (username.equals("admin")){
            req.getSession().setAttribute("USER_SESSION",req.getSession().getId());
            resp.sendRedirect("/hello/success.jsp");
        }
        else {
            resp.sendRedirect("/hello/sys/error.jsp");
        }


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LogoutServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Object userSession = req.getSession().getAttribute("USER_SESSION");

        if (userSession!=null){
            req.getSession().removeAttribute("USER_SESSION");
            resp.sendRedirect("/hello/sys/login.jsp");
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

<servlet>
    <servlet-name>login</servlet-name>
    <servlet-class>LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>login</servlet-name>
    <url-pattern>/sys/login</url-pattern>
</servlet-mapping>
<servlet>
    <servlet-name>logout</servlet-name>
    <servlet-class>LogoutServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>logout</servlet-name>
    <url-pattern>/sys/logout</url-pattern>
</servlet-mapping>
<filter>
    <filter-name>log</filter-name>
    <filter-class>SysFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>log</filter-name>
    <url-pattern>/success.jsp</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>log</filter-name>
    <url-pattern>/sys/logout.jsp</url-pattern>
</filter-mapping>

javaweb

https://zer0peach.github.io/2023/12/10/javaweb/

作者

Zer0peach

发布于

2023年12月10日

许可协议

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javaweb

javaweb

前言

maven

Servlet

注册servlet

ServletContent

getinitparam

getRequestDispatcher

getResourceAsStream

response下载文件

response 验证码

response 重定向

request

cookie (客户端携带)

session

jsp原理

jsp语法

热部署

基础语法

jsp声明

jsp 内置对象

双亲委派机制 （与作用域进行类比）

作用域

MVC框架

Filter

Listener

Filter权限管理案例

双亲委派机制（与作用域进行类比）