Jweb之Content-Length

最新推荐文章于 2025-06-02 11:59:16 发布

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#Content-Length #JWeb

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本文探讨了HTTP响应头中的Content-Length字段在JWeb中的作用，它用于指示消息实体的传输长度。通过设置不同Content-Length值的测试，发现当Content-Length小于等于实际body长度时，数据能正常显示；而当Content-Length大于body长度，会导致浏览器解析时出现卡顿。

消息头的响应头中有字段Content-Length

作用是描述HTTP消息实体的传输长度
浏览器通过Content-Length可以得知本次传输何时结束

下面根据已知响应体长度设置不同的Content-Length来观察具体表现

一.前端代码展示:

<%--
  Created by IntelliJ IDEA.
  User: WHW
  Date: 2019/7/23
  Time: 18:27
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
    <b>已知:</b><br/>
    消息体为:"ABCDEFGHIJKLMN"<br/>
    bodyLength=14<br/>
    <b>设置Content-Length:</b>
    <fieldset>
      <a href="http://localhost:8080/rr/cls?value=13">13</a>
    </fieldset>
    <fieldset>
      <a href="http://localhost:8080/rr/cls?value=14">14</a>
    </fieldset>
    <fieldset>
      <a href="http://localhost:8080/rr/cls?value=15">15</a>
    </fieldset>
  </body>
</html>

二.Servlet代码展示

package controller;

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

/**
 * @Author weihuanwen
 * @Date 2019/7/25 8:05
 * @Version 1.0
 */
@WebServlet(urlPatterns = "/cls")
public class ContentLengthServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取前端设置的Content-Length
        String valueStr = req.getParameter("value");
        int contentLength = Integer.parseInt(valueStr);
        //设置Content-Length
        resp.setContentLength(contentLength);
        //设置响应消息体
        resp.getWriter().write("ABCDEFGHIJKLMN");
    }

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