URLConnection实例

URLConnection 用于发请求与其他服务器建立连接

URLConnection 发请求多线程下载资源

package it.net;

import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.*;
/**
 * Description:
 * URL 多线程下载资源
 * 网站: <a href="http://www.crazyit.org">疯狂Java联盟</a><br>
 * Copyright (C), 2001-2018, Yeeku.H.Lee<br>
 * This program is protected by copyright laws.<br>
 * Program Name:<br>
 * Date:<br>
 * @author Yeeku.H.Lee [email protected]
 * @version 1.0
 */
public class DownUtil
{
	// 定义下载资源的路径
	private String path;
	// 指定所下载的文件的保存位置
	private String targetFile;
	// 定义需要使用多少线程下载资源
	private int threadNum;
	// 定义下载的线程对象
	private DownThread[] threads;
	// 定义下载的文件的总大小
	private int fileSize;

	public DownUtil(String path, String targetFile, int threadNum)
	{
		this.path = path;
		this.threadNum = threadNum;
		// 初始化threads数组
		threads = new DownThread[threadNum];
		this.targetFile = targetFile;
	}

	public void download() throws Exception
	{
		URL url = new URL(path);
		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
		//设置请求头
		conn.setConnectTimeout(5 * 1000);
		conn.setRequestMethod("GET");
		conn.setRequestProperty(
			"Accept",
			"image/gif, image/jpeg, image/pjpeg, image/pjpeg, "
			+ "application/x-shockwave-flash, application/xaml+xml, "
			+ "application/vnd.ms-xpsdocument, application/x-ms-xbap, "
			+ "application/x-ms-application, application/vnd.ms-excel, "
			+ "application/vnd.ms-powerpoint, application/msword, */*");
		conn.setRequestProperty("Accept-Language", "zh-CN");
		conn.setRequestProperty("Charset", "UTF-8");
		conn.setRequestProperty("Connection", "Keep-Alive");

		// 获取响应头信息的方法，会自动调用connect()方法。

		fileSize = conn.getContentLength();
		System.out.println(fileSize);
		conn.disconnect();
		int currentPartSize = fileSize / threadNum + 1;
		RandomAccessFile file = new RandomAccessFile(targetFile, "rw");
		// 设置本地文件的大小
		file.setLength(fileSize);
		file.close();
		for (int i = 0; i < threadNum; i++)
		{
			// 计算每条线程的下载的开始位置
			int startPos = i * currentPartSize;
			// 每个线程使用一个RandomAccessFile进行下载
			RandomAccessFile currentPart = new RandomAccessFile(targetFile,
				"rw");
			// 定位该线程的下载位置
			currentPart.seek(startPos);
			// 创建下载线程
			threads[i] = new DownThread(startPos, currentPartSize,
				currentPart);
			// 启动下载线程
			threads[i].start();
		}
	}

	// 获取下载的完成百分比
	public double getCompleteRate()
	{
		// 统计多条线程已经下载的总大小
		int sumSize = 0;
		for (int i = 0; i < threadNum; i++)
		{
			sumSize += threads[i].length;
		}
		// 返回已经完成的百分比
		return sumSize * 1.0 / fileSize;
	}

	private class DownThread extends Thread
	{
		// 当前线程的下载位置
		private int startPos;
		// 定义当前线程负责下载的文件大小
		private int currentPartSize;
		// 当前线程需要下载的文件块
		private RandomAccessFile currentPart;
		// 定义已经该线程已下载的字节数
		public int length;

		public DownThread(int startPos, int currentPartSize,
			RandomAccessFile currentPart)
		{
			this.startPos = startPos;
			this.currentPartSize = currentPartSize;
			this.currentPart = currentPart;
		}

		@Override
		public void run()
		{
			try
			{
				URL url = new URL(path);
				HttpURLConnection conn = (HttpURLConnection)url
					.openConnection();
				conn.setConnectTimeout(5 * 1000);
				conn.setRequestMethod("GET");
				conn.setRequestProperty(
					"Accept",
					"image/gif, image/jpeg, image/pjpeg, image/pjpeg, "
					+ "application/x-shockwave-flash, application/xaml+xml, "
					+ "application/vnd.ms-xpsdocument, application/x-ms-xbap, "
					+ "application/x-ms-application, application/vnd.ms-excel, "
					+ "application/vnd.ms-powerpoint, application/msword, */*");
				conn.setRequestProperty("Accept-Language", "zh-CN");
				conn.setRequestProperty("Charset", "UTF-8");
				InputStream inStream = conn.getInputStream();
				// 跳过startPos个字节，表明该线程只下载自己负责哪部分文件。
				inStream.skip(this.startPos);
				byte[] buffer = new byte[1024];
				int hasRead = 0;
				// 读取网络数据，并写入本地文件
				while (length < currentPartSize
					&& (hasRead = inStream.read(buffer)) != -1)
				{
					currentPart.write(buffer, 0, hasRead);
					// 累计该线程下载的总大小
					length += hasRead;
				}
				currentPart.close();
				inStream.close();
			}
			catch (Exception e)
			{
				e.printStackTrace();
			}
		}
	}
}

模拟get post请求

package it.net;
import java.io.*;
import java.net.*;
import java.util.*;
/**
 * Description:
 * 网站: <a href="http://www.crazyit.org">疯狂Java联盟</a><br>
 * Copyright (C), 2001-2018, Yeeku.H.Lee<br>
 * This program is protected by copyright laws.<br>
 * Program Name:<br>
 * Date:<br>
 * @author Yeeku.H.Lee [email protected]
 * @version 1.0
 */
public class GetPostTest
{
	/**
	 * 向指定URL发送GET方法的请求
	 * @param url 发送请求的URL
	 * @param param 请求参数，格式满足name1=value1&name2=value2的形式。
	 * @return URL所代表远程资源的响应
	 */
	public static String sendGet(String url , String param)
	{
		String result = "";
		String urlName = url + "?" + param;
		try
		{
			URL realUrl = new URL(urlName);
			// 打开和URL之间的连接
			URLConnection conn = realUrl.openConnection();
			// 设置通用的请求属性
			conn.setRequestProperty("accept", "*/*");
			conn.setRequestProperty("connection", "Keep-Alive");
			conn.setRequestProperty("user-agent"
				, "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
			// 建立实际的连接
			conn.connect();
			// 获取所有响应头字段
			Map<String, List<String>> map = conn.getHeaderFields();
			// 遍历所有的响应头字段
			for (String key : map.keySet())
			{
				System.out.println(key + "--->" + map.get(key));
			}
			try(
				// 定义BufferedReader输入流来读取URL的响应
				BufferedReader in = new BufferedReader(
					new InputStreamReader(conn.getInputStream() , "utf-8")))
			{
				String line;
				while ((line = in.readLine())!= null)
				{
					result += "\n" + line;
				}
			}
		}
		catch(Exception e)
		{
			System.out.println("发送GET请求出现异常！" + e);
			e.printStackTrace();
		}
		return result;
	}
	/**
	 * 向指定URL发送POST方法的请求
	 * @param url 发送请求的URL
	 * @param param 请求参数，格式应该满足name1=value1&name2=value2的形式。
	 * @return URL所代表远程资源的响应
	 */
	public static String sendPost(String url , String param)
	{
		String result = "";
		try
		{
			URL realUrl = new URL(url);
			// 打开和URL之间的连接
			URLConnection conn = realUrl.openConnection();
			// 设置通用的请求属性
			conn.setRequestProperty("accept", "*/*");
			conn.setRequestProperty("connection", "Keep-Alive");
			conn.setRequestProperty("user-agent",
			"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
			// 发送POST请求必须设置如下两行
			conn.setDoOutput(true);
			conn.setDoInput(true);
			try(
				// 获取URLConnection对象对应的输出流
				PrintWriter out = new PrintWriter(conn.getOutputStream()))
			{
				// 发送请求参数
				out.print(param);
				// flush输出流的缓冲
				out.flush();
			}
			try(
				// 定义BufferedReader输入流来读取URL的响应
				BufferedReader in = new BufferedReader(new InputStreamReader
					(conn.getInputStream() , "utf-8")))
			{
				String line;
				while ((line = in.readLine())!= null)
				{
					result += "\n" + line;
				}
			}
		}
		catch(Exception e)
		{
			System.out.println("发送POST请求出现异常！" + e);
			e.printStackTrace();
		}
		return result;
	}
	// 提供主方法，测试发送GET请求和POST请求
	public static void main(String args[])
	{
		// 发送GET请求
		String s = GetPostTest.sendGet("http://localhost:8888/abc/a.jsp"
			, null);
		System.out.println(s);
		// 发送POST请求
		String s1 = GetPostTest.sendPost("http://localhost:8888/abc/login.jsp"
			, "name=crazyit.org&pass=leegang");
		System.out.println(s1);
	}
}