使用java程序发送post请求给servlet

我们需要完成的工作其实很简单，就是将一个文件流以post的方式发送到服务器或者也可以是客户端。

java发送请求是通过HttpURLConnection来实现的：

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
public class SendPostRequest {
	static String sessionId = "";
	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub
		URL url = new URL("http://localhost:8080/GetRequest/");
		HttpURLConnection connection = (HttpURLConnection) url.openConnection();
		connection.setDoOutput(true);
		// Read from the connection. Default is true.
		connection.setDoInput(true);
		// Set the post method. Default is GET
		connection.setRequestMethod("POST");
		// Post cannot use caches
		// Post 请求不能使用缓存
		connection.setUseCaches(false);
		// This method takes effects to
		// every instances of this class.
		// URLConnection.setFollowRedirects是static函数，作用于所有的URLConnection对象。
		// connection.setFollowRedirects(true);
		// This methods only
		// takes effacts to this
		// instance.
		// URLConnection.setInstanceFollowRedirects是成员函数，仅作用于当前函数
		connection.setInstanceFollowRedirects(false);
		// Set the content type to urlencoded,
		// because we will write
		// some URL-encoded content to the
		// connection. Settings above must be set before connect!
		// 配置本次连接的Content-type，配置为application/x-www-form-urlencoded的
		// 意思是正文是urlencoded编码过的form参数，下面我们可以看到我们对正文内容使用URLEncoder.encode
		// 进行编码
		connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
		// 连接，从postUrl.openConnection()至此的配置必须要在connect之前完成，
		// 要注意的是connection.getOutputStream会隐含的进行connect。
		connection.connect();
		Long sendTime = System.currentTimeMillis();
		DataOutputStream out = new DataOutputStream(connection.getOutputStream());
		// 要传的参数
		String content = URLEncoder.encode("username", "UTF-8") + "=" + URLEncoder.encode("XXX", "UTF-8");
		content += "&" + URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode("XXXX", "UTF-8");
		content += "&" + URLEncoder.encode("sendTime", "UTF-8") + "=" + URLEncoder.encode(sendTime.toString(), "UTF-8");
		//读海量文件
		StringBuilder postStrBuf = new StringBuilder();
		for (int i = 0; i < 1; i++) {
			File file = new File("E:/toodou_work/yuliang.csv");
			BufferedReader reader = null;
			String postStr = null;
			reader = new BufferedReader(new FileReader(file));
			while ((postStr = reader.readLine()) != null) {
				postStrBuf.append(postStr);
			}
		}
		content = content + "&" + URLEncoder.encode("file", "UTF-8") + "=" + URLEncoder.encode(postStrBuf.toString(), "UTF-8");
		// DataOutputStream.writeBytes将字符串中的16位的unicode字符以8位的字符形式写道流里面
		out.writeBytes(content);
		out.flush();
		out.close(); // flush and close
		//Get Session ID
		String key = "";
		if (connection != null) {
			for (int i = 1; (key = connection.getHeaderFieldKey(i)) != null; i++) {
				if (key.equalsIgnoreCase("set-cookie")) {
					sessionId = connection.getHeaderField(key);
					sessionId = sessionId.substring(0, sessionId.indexOf(";"));
				}
			}
		}
		connection.disconnect();
	}
}

接受post请求的一端，为了便于大家理解，就作为服务器吧，上面的代码则作为客户端好了。服务器这边我们需要写一个servlet，这个servlet是服务器启动，就立即启动的，这个是在web.xml文件里配置，我想大家是会的。服务器端的代码如下所示：

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Servlet implementation class GetRequestServlet
 */
public class GetRequestServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	//private static final Logger log = Logger.getLogger(GetRequestServlet.class);
	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public GetRequestServlet() {
		super();
		// TODO Auto-generated constructor stub
	}
	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String file = request.getParameter("file");
		String sendTimeStr = request.getParameter("sendTime");
		long sendTime = Long.valueOf(sendTimeStr);
		response.setContentType("text/html;charset=utf-8");
		System.out.println(file);
		System.out.println("当前从发送到接受所用时间为：" + (System.currentTimeMillis() - sendTime));
		//PrintWriter out = response.getWriter();
		//out.println("hello world!" + file);
	}
	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
}

大家运行会发现，如果读取的文件不大，是可以将读取的文件流输送到服务器的，但是一旦文件变大，就会出错。这一方面可能是post后缀的内容大小是被限定的吧，我是这么想的，如果有错误请纠正。