如何用 Java 读取和下载网页

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问题描述

如何读取和下载网页？

解决方案

以下示例展示如何读取和下载网址 net.URL 类的 URL() 构造器。

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.net.URL;

public class Main {
   public static void main(String[] args) throws Exception {
      URL url = new URL("http://www.google.com");
      BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
      BufferedWriter writer = new BufferedWriter(new FileWriter("data.html"));
      String line;
      
      while ((line = reader.readLine()) != null) {
         System.out.println(line);
         writer.write(line);
         writer.newLine();
      }
      reader.close();
      writer.close();
   }
}

结果

上述代码示例将产生以下结果。

Welcome to Java Tutorial
	Here we have plenty of examples for you!
	
   Come and Explore Java!

以下是读取和下载网页的另一个示例。

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class NewClass {
   public static void main(String[] args) {
      URL url;
      InputStream is = null;
      BufferedReader br;
      String line;
      try {
         url = new URL("https://tutorialspoint.com/javaexamples/net_singleuser.htm");
         is = url.openStream();  // throws an IOException
         br = new BufferedReader(new InputStreamReader(is));
         
         while ((line = br.readLine()) != null) {
            System.out.println(line);
         } 
      } catch (MalformedURLException mue) {
         mue.printStackTrace();
      } catch (IOException ioe) {
         ioe.printStackTrace();
      } 
      finally {
         try {
            if (is != null) is.close();
         } catch (IOException ioe) {} 
      } 
   }
}

结果

上述代码示例将产生以下结果。

<!DOCTYPE html>
<!--[if IE 8]><html class="ie ie8"> <![endif]-->
<!--[if IE 9]><html class="ie ie9"> <![endif]-->
<!--[if gt IE 9]><!-->	<html> <!--<![endif]-->
<head>
<!-- Basic -->
<meta charset="utf-8">
<title>Java Examples - Socket to a single client</title>
<meta name="description" content="Java Examples Socket to a single client : A beginner's tutorial containing complete knowledge of Java Syntax Object Oriented Language, Methods, Overriding, Inheritance, Polymorphism, Interfaces, Packages, Collections, Networking, Multithreading, Generics, Multimedia, Serialization, GUI." />
<meta name="keywords" content="Java, Tutorials, Learning, Beginners, Basics, Object Oriented Language, Methods, Overriding, Inheritance, Polymorphism, Interfaces, Packages, Collections, Networking, Multithreading, Generics, Multimedia, Serialization, GUI." />
<base href="https://tutorialspoint.com/" />
<link rel="shortcut icon" href="/favicon.ico" type="image/x-icon" />
<meta name="viewport" content="width=device-width,initial-scale=1.0,user-scalable=yes">
<meta property="og:locale" content="en_US" />
<meta property="og:type" content="website" />
<meta property="fb:app_id" content="471319149685276" />
<meta property="og:site_name" content="www.tutorialspoint.com" />
<meta name="robots" content="index, follow"/>
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="black">
<meta name="author" content="tutorialspoint.com">
<script type="text/javascript" src="/theme/js/script-min-v4.js"></script>
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