这两天在整理看httpclient，然后想自己用UrlConnection后台模拟实现Http请求，于是一个简单的小例子就新鲜出炉了（支持代理哦）：

public class SimpleHttpTest {

	public static String send(String urlStr, Map<String,String> map,String encoding){
		String body="";
		StringBuffer sbuf = new StringBuffer();
		if(map!=null){
			for (Entry<String,String> entry : map.entrySet()) {
				sbuf.append(entry.getKey()).append("=").append(entry.getValue()).append("&");
			}
			if(sbuf.length()>0){
				sbuf.deleteCharAt(sbuf.length()-1);
			}
		}
		 // 1、重新对请求报文进行 GBK 编码
        byte[] postData = null;
        try {
            postData = sbuf.toString().getBytes(encoding);
        } catch (UnsupportedEncodingException e) {
        	e.printStackTrace();
        }

        // 2、发送 HTTP(S) 请求
        OutputStream reqStream = null;
        InputStream resStream = null;
        URLConnection request = null;
        try {
            System.out.println("交易请求地址：" + urlStr);
            System.out.println("参数：" + sbuf.toString());
            
            //A、与服务器建立 HTTP(S) 连接
    		URL url = null;
            try {
            	Proxy proxy = new Proxy(java.net.Proxy.Type.HTTP,new InetSocketAddress("127.0.0.1", 8087));
                url = new URL(urlStr);
                request = url.openConnection(proxy);
                request.setDoInput(true);
                request.setDoOutput(true);
            } catch (MalformedURLException e) {
            	e.printStackTrace();
            } catch (IOException e) {
            	e.printStackTrace();
            }
            
            //B、指定报文头【Content-type】、【Content-length】 与 【Keep-alive】
            request.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
            request.setRequestProperty("Content-length", String.valueOf(postData.length));
            request.setRequestProperty("Keep-alive", "false");
            request.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
            
            //C、发送报文至服务器
            reqStream = request.getOutputStream();
            reqStream.write(postData);
            reqStream.close();
            
            //D、接收服务器返回结果
            ByteArrayOutputStream ms = null;
            resStream = request.getInputStream();
            ms = new ByteArrayOutputStream();
            byte[] buf = new byte[4096];
            int count;
            while ((count = resStream.read(buf, 0, buf.length)) > 0) {
                ms.write(buf, 0, count);
            }
            resStream.close();
            body = new String(ms.toByteArray(), encoding);
        } catch (UnknownHostException e) {
            System.err.println( "服务器不可达【" + e.getMessage() + "】");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (reqStream != null)
                	reqStream.close();
                if (resStream != null)
                	resStream.close();
            } catch (Exception ex) {
            }
        }

        System.out.println("交易响应结果：");
        System.out.println(body);
        return body;
	}
	
	public static void main(String[] args) {
		String url="http://php.weather.sina.com.cn/iframe/index/w_cl.php";
		Map<String, String> map = new HashMap<String, String>();
		map.put("code", "js");
		map.put("day", "0");
		map.put("city", "上海");
		map.put("dfc", "1");
		map.put("charset", "utf-8");
		send(url, map,"utf-8");
	}
}

结果如下：

交易请求地址：http://php.weather.sina.com.cn/iframe/index/w_cl.php
参数：dfc=1&charset=utf-8&day=0&code=js&city=上海
交易响应结果：
(function(){var w=[];w['上海']=[{s1:'阴',s2:'阴',f1:'yin',f2:'yin',t1:'17',t2:'14',p1:'≤3',p2:'≤3',d1:'东北风',d2:'东北风'}];var add={now:'2015-11-11 19:04:33',time:'1447239873',update:'北京时间11月11日17:10更新',error:'0',total:'1'};window.SWther={w:w,add:add};})();//0

代码中的步骤写的很明白了，如果你有心，还可以对该方法进行各种封装，方便使用。下篇我会分享一下httpclient是如何模拟后台来发送http请求的，还有配置ssl、代理、自定义header等等，敬请期待吧。