Http学习之使用HttpURLConnection发送post和get请求

最常用的Http请求无非是get和post，get请求可以获取静态页面，也可以把参数放在URL字串后面，传递给servlet，post与get的不同之处在于post的参数不是放在URL字串里面，而是放在http请求的正文内。
在Java中可以使用HttpURLConnection发起这两种请求，了解此类，对于了解soap，和编写servlet的自动测试代码都有很大的帮助。
下面的代码简单描述了如何使用HttpURLConnection发起这两种请求，以及传递参数的方法：

public???class??HttpInvoker??{

????public?static?final?String?GET_URL?=?"http://localhost:8080/welcome1";

????public?static?final?String?POST_URL?=?"http://localhost:8080/welcome1";

????public?static?void?readContentFromGet()?throws?IOException?{
????????//?拼凑get请求的URL字串，使用URLEncoder.encode对特殊和不可见字符进行编码
????????String?getURL?=?GET_URL?+?"?username="
????????????????+?URLEncoder.encode("fat?man",?"utf-8");
????????URL?getUrl?=?new?URL(getURL);
????????//?根据拼凑的URL，打开连接，URL.openConnection函数会根据URL的类型，
????????//?返回不同的URLConnection子类的对象，这里URL是一个http，因此实际返回的是HttpURLConnection
????????HttpURLConnection?connection?=?(HttpURLConnection)?getUrl
????????????????.openConnection();
????????//?进行连接，但是实际上get?request要在下一句的connection.getInputStream()函数中才会真正发到
????????//?服务器
????????connection.connect();
????????//?取得输入流，并使用Reader读取
????????BufferedReader?reader?=?new?BufferedReader(new?InputStreamReader(
????????????????connection.getInputStream()));
????????System.out.println("=============================");
????????System.out.println("Contents?of?get?request");
????????System.out.println("=============================");
????????String?lines;
????????while?((lines?=?reader.readLine())?!=?null)?{
????????????System.out.println(lines);
????????}
????????reader.close();
????????//?断开连接
????????connection.disconnect();
????????System.out.println("=============================");
????????System.out.println("Contents?of?get?request?ends");
????????System.out.println("=============================");
????}

????public?static?void?readContentFromPost()?throws?IOException?{
????????//?Post请求的url，与get不同的是不需要带参数
????????URL?postUrl?=?new?URL(POST_URL);
????????//?打开连接
????????HttpURLConnection?connection?=?(HttpURLConnection)?postUrl
????????????????.openConnection();
????????//?Output?to?the?connection.?Default?is
????????//?false,?set?to?true?because?post
????????//?method?must?write?something?to?the
????????//?connection
????????//?设置是否向connection输出，因为这个是post请求，参数要放在
????????//?http正文内，因此需要设为true
????????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(true);
????????//?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();
????????DataOutputStream?out?=?new?DataOutputStream(connection
????????????????.getOutputStream());
????????//?The?URL-encoded?contend
????????//?正文，正文内容其实跟get的URL中'?'后的参数字符串一致
????????String?content?=?"firstname="?+?URLEncoder.encode("一个大肥人",?"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
????????BufferedReader?reader?=?new?BufferedReader(new?InputStreamReader(
????????????????connection.getInputStream()));
????????String?line;
????????System.out.println("=============================");
????????System.out.println("Contents?of?post?request");
????????System.out.println("=============================");
????????while?((line?=?reader.readLine())?!=?null)?{
????????????System.out.println(line);
????????}
????????System.out.println("=============================");
????????System.out.println("Contents?of?post?request?ends");
????????System.out.println("=============================");
????????reader.close();
????????connection.disconnect();
????}

????/**
?????*?@param?args
?????*/
????public?static?void?main(String[]?args)?{
????????//?TODO?Auto-generated?method?stub
????????try?{
????????????readContentFromGet();
????????????readContentFromPost();
????????}?catch?(IOException?e)?{
????????????//?TODO?Auto-generated?catch?block
????????????e.printStackTrace();
????????}
????}

}

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转自：http://toughpatient5.diandian.com/post/2011-07-06/19241336

http://java.chinaitlab.com/net/831820.html

http://dusiguxia.blog.163.com/blog/static/5562931620119193430501/

http://androidyo.iteye.com/blog/624015