Java 中的某些链接运行 HTTPUrlConnection 下载缓慢

Question

我是编程新手。我正在尝试为 Android 编写一个应用程序，它在 HTML 中下载带有 Links 的列表，并使用给定的 Links 下载这些 [=21] 的内容=]秒。我会Post下载器的代码和日志。我的问题是：为什么有些 Link 需要大约 5 秒，而有些需要长达 5 分钟？这不可能是网站的原因，因为当我在 Chrome 或其他浏览器中打开 Link 时，页面会立即加载。你们能帮帮我吗？

package com.example.newsreader;

import android.util.Log;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MyRunnable implements Runnable {

    String result = "";
    String urlSource="";

    public MyRunnable(String urlSource){
        this.urlSource = urlSource;
    }

    @Override
    public void run() {
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    result = "";
                    URL url = new URL(urlSource);
                    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
                    urlConnection.setRequestMethod("GET");
                    InputStream inputStream = urlConnection.getInputStream();
                    InputStreamReader inputStreamReader = new InputStreamReader(inputStream);

                    int data = inputStreamReader.read();

                    while (data !=-1) {
                        char current = (char) data;
                        result += current;
                        data = inputStreamReader.read();
                    }

                    inputStream.close();

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        t1.start();
        try{
            t1.join();
        } catch (Exception e){
            e.printStackTrace();
        }
    }

    public String getResult(){
        return result;
    }
}

日志数据： Times for Each Link to finish

Answer 1

您正在逐条读取数据，效率不高。相反，您应该创建 char 缓冲区并按小块读取数据。

也不要连接很多字符串，使用 StringBuilder，它使用的内存更少。

 public class MyRunnable implements Runnable {

    private final StringBuilder result = new StringBuilder();
    String urlSource="";
    private final char[] buffer = new char[512]; //allocating buffer

    public MyRunnable(String urlSource){
        this.urlSource = urlSource;
    }

    @Override
    public void run() {
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    result.setLength(0); //clearing StringBuilder
                    URL url = new URL(urlSource);
                    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
                    urlConnection.setRequestMethod("GET");
                    InputStream inputStream = urlConnection.getInputStream();
                    InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
                    
                    // now reading not by 1 char, but by 512 for once
                    int i;
                    while ((i = inputStreamReader.read(buffer)) != -1) {
                       result.append(buffer, 0, i);
                    }

                    inputStreamReader.close(); //close reader instead of InputStream

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        t1.start();
        try{
            t1.join();
        } catch (Exception e){
            e.printStackTrace();
        }
    }

    public String getResult(){
        return result.toString(); //converting StringBuilder to String
    }
}

并且使用BufferedInputStream，它也提高了速度。

InputStreamReader inputStreamReader = new InputStreamReader(new BufferedInputStream(inputStream));

使用“https://www.google.com”进行的一些测试：

Simple run
time: 838 ms
run with char buffer
time: 264 ms
Run with char buffer and BufferedInputStream
time: 130 ms

Java 中的某些链接运行 HTTPUrlConnection 下载缓慢

Slow Download of some Links running HTTPUrlConnection in Java

java

android

httpurlconnection

runnable

Java 中的某些链接 运行 HTTPUrlConnection 下载缓慢

Slow Download of some Links running HTTPUrlConnection in Java

java

android

httpurlconnection

runnable

Java 中的某些链接运行 HTTPUrlConnection 下载缓慢