Web应用实战：Servlet与JSP实现功能与安全-优快云博客

本文链接：https://blog.youkuaiyun.com/grace_dragon/article/details/125398468

JAVA WEB结课作业

1. 编写一个Servlet，实现统计网站被访问次数的功能。

ShowTimesServlet类

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

public class ShowTimesServlet extends HttpServlet {
   
    private static final long serialVersionUID = 1L;

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

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
   
        ServletContext context = req.getServletContext();
        Integer times = (Integer) context.getAttribute("times");
        if (times == null) {
   
            times = new Integer(1);
        } else {
   
            times = new Integer(times.intValue() + 1);
        }

        resp.setContentType("text/html;charset=GB2312");
        PrintWriter out = resp.getWriter();
        out.println("<html><head><title>");
        out.println("页面访问统计");
        out.println("</title></head><body>");
        out.println("当前页面被访问了");
        out.println("<font color = red size=20>" + times +"</font>次");
        context.setAttribute("times", times);
    }
}

web.xml 的配置信息

<?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">
    <servlet>
        <servlet-name>ShowTimesServlet</servlet-name>
        <servlet-class>ShowTimesServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ShowTimesServlet</servlet-name>
        <url-pattern>/ShowTimesServlet</url-pattern>
    </servlet-mapping>
</web-app>

结果展示

在这里插入图片描述

2. 请编写一段程序，使程序能够读取该Servlet的配置信息，从中获得参数名为encoding对应的参数值，并输出到页面上。

TestServlet

import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.io.PrintWriter;

public class TestServlet extends HttpServlet {
   
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
   
        PrintWriter out = resp.getWriter();
        ServletConfig config = this.getServletConfig();
        String param = config.getInitParameter("encoding");
        out.println("encoding=" + param);
    }

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

web.xml的配置信息

<?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">
    <servlet>
        <servlet-name>TestServlet</servlet-name>
        <servlet-class>TestServlet</servlet-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>TestServlet</servlet-name>
        <url-pattern>/TestServlet</url-pattern>
    </servlet-mapping>
</web-app>

结果展示

在这里插入图片描述

3. 编写一个类，该类使用HttpServletRequest对象的getHeader(“referer”)方法实现下载资源防盗链的功能。

DownManagerServlet

import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringReader;

public class DownManagerServlet extends HttpServlet {
   
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
   
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter out = resp.getWriter();
        String referer = req.getHeader("referer");
        String sitPart = "http://" + req.getServerName();
        if (referer != null && referer.startsWith(sitPart)) {
   
            out.println("dealing download ... ");
        } else {
   
            RequestDispatcher rd = req.getRequestDispatcher("/download.html");
            rd.forward(req, resp);
        }
    }

}

download.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Insert title here</title>
</head>
<body>
    <a href="DownManagerServlet">download</a>
</body>
</html>

web.xml的配置信息

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee

JAVA WEB作业

JAVA WEB结课作业

1. 编写一个Servlet，实现统计网站被访问次数的功能。

结果展示

2. 请编写一段程序，使程序能够读取该Servlet的配置信息，从中获得参数名为encoding对应的参数值，并输出到页面上。

结果展示

3. 编写一个类，该类使用HttpServletRequest对象的getHeader(“referer”)方法实现下载资源防盗链的功能。