Java中有关HttpClient知识

什么是HTTP协议

以下博主写的十分清楚，认真阅读即可。在这里感谢大佬的总结(●’◡’●)

https://www.jianshu.com/p/7c8b4576e4bb

简述几条最基本使用
1.通过TCP套接字,客户端向Web服务器发送一个文本的请求报文,一个请求报文由请求行,请求头部,空行和请求体4个部分构成。
2.在接收到请求之后,服务器经过解释之后,会返回个一个HTTP响应。HTTP响应是由四部分构成:状态行 响应头 空行 响应体。

以下是几个比较常用到的请求头，大家可以参照引用博主的详情信息打捞基础！
Accept：可接收的响应内容类型
Accept-Charset：可接收的字符集
Accept-Encoding：可接受的响应内容的编码方式 （http协议在传输时的加密方式，如果你的相应总是莫名其妙的乱码，你要对这个地方格外注意）
Content-Type：请求体的MIME类型

具体的代码

一些java中HttpClient的知识已在代码中体现，详情可以仔细阅读代码。

/**
	 * post请求(用于key-value格式的参数)
	 * @param url 请求连接
	 * @param maps 请求数据的集合
	 * @throws Exception
	 */
	public static void postClient(String url , Map<String,String> maps) throws Exception{
		CloseableHttpClient  httpClient = HttpClients.createDefault();	//创建一个可以关闭的Http链接
		HttpPost post = new HttpPost(url);		//这里使用Post方式提交
		//以下是post提交的时候所包含的请求头
		post.addHeader("Authorization", "basic {"+token+"}"); //token为认证所需，对接不同接口形式不同可能不需要
		post.addHeader("Content-Type", "text/xml; charset=utf-8");
		post.addHeader("Accept","application/xml");
		
		//以下是请求时所要post提交的数据
		ArrayList<NameValuePair> resbodyValue = new ArrayList<NameValuePair>();
		for(Map.Entry<String, String> entry : maps.entrySet()){
			String key = entry.getKey();
			String value = entry.getValue();
			resbodyValue.add(new BasicNameValuePair(key,value));
		}
		//post提交时有许多Entity，e.g:StringEntity,BasicHttpEntity,ByteArrayEntity等
		
		post.setEntity(new UrlEncodedFormEntity(resbodyValue,"UTF-8"));	
		
		CloseableHttpResponse response = httpClient.execute(post);//发送请求
		int status = response.getStatusLine().getStatusCode(); // 获取相应状态码 
		BufferedReader in = null;  
		if(status == 200){	//请求成功
         	in = new BufferedReader(new InputStreamReader(response.getEntity()  
                     .getContent(),"utf-8"));
             StringBuffer sb = new StringBuffer("");  
             String line = "";  
             String NL = System.getProperty("line.separator");  
             while ((line = in.readLine()) != null) {  
                 sb.append(line + NL);  
             }
             
             in.close();  
         }
        else{	
         	System.out.println("状态码：" + status);
         }
	}
	
	/**
	 * post请求（用于请求json格式的参数）
	 * @param url
	 * @param params
	 * @return
	 */
	public static String doPost(String url,String params) throws Exception {
		
		String code = (appId+"&"+appKey);
		
		String token = Base64Utils.encode(code.getBytes());
		
		CloseableHttpClient httpclient = HttpClients.createDefault();
		HttpPost httpPost = new HttpPost(url);// 创建httpPost   
    	httpPost.setHeader("Accept", "text/json"); 
    	httpPost.setHeader("Content-Type", "application/json;charset=UTF-8");
    	httpPost.setHeader("Accept-Language", "zh-cn");
    	httpPost.setHeader("Authorization", "Basic "+token);
    	String charSet = "UTF-8";
    	StringEntity entity = new StringEntity(params, charSet);
    	httpPost.setEntity(entity);    
    	
        CloseableHttpResponse response = null;
        
        try {
        	
        	response = httpclient.execute(httpPost);
            StatusLine status = response.getStatusLine();
            int state = status.getStatusCode();
            if (state == HttpStatus.SC_OK) {
            	HttpEntity responseEntity = response.getEntity();
            	String jsonString = EntityUtils.toString(responseEntity);
            	String str = new String(jsonString.getBytes("ISO-8859-1"),"UTF-8");
            	return str;
            }else{
				 logger.error("请求返回:"+state+"("+url+")");
				 System.out.println("请求返回:"+state+"("+url+")");
			}
        }
        finally {
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            try {
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
        }
        return null;
	}
	

Get请求相对于刚才Post请求就简单的很多，毕竟是有了Post的请求的基础了嘛，详见代码：

/**
	 * get请求
	 * @return
	 */
	public static String doGet(String url) {
		String token = Base64Utils.encode((appId+"&"+appKey).getBytes());
        try {
        	HttpClient client = new DefaultHttpClient();
            //发送get请求
            HttpGet request = new HttpGet(url);
            request.setHeader("Accept", "text/json"); 
            request.setHeader("Content-Type", "application/json;charset=UTF-8");
            request.setHeader("Accept-Language", "zh-cn");
            request.setHeader("Authorization", "Basic "+token);
            
            HttpResponse response = client.execute(request);
 
            System.out.println(response);
            /**请求发送成功，并得到响应**/
            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                /**读取服务器返回过来的json字符串数据**/
                String strResult = EntityUtils.toString(response.getEntity());
                
                return strResult;
            }
        } 
        catch (IOException e) {
        	e.printStackTrace();
        }
        
        return null;
	}

通过Poxy的方式进行的Http请求，这个一般适用于翻译的**等功能，需要不断的切换IP的场景

 /**
     * 
     * @param ipBean 存放ip的实体
     * @param params 以Key-value的形式进行
     * @return
     */
    public String ProxyTranlate(IPBean ipBean,List<NameValuePair> params){
    	String translateLang = "";

        IPBean ip = IpUtils.getIP();
    	Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(ip.getIp(), ip.getPort())); //设置代理IP的地址和端口
        try {
            URLConnection httpCon = new URL(PATH).openConnection(proxy);
            httpCon.setConnectTimeout(5000);
            httpCon.setReadTimeout(5000);
            httpCon.setDoOutput(true);
            httpCon.setDoInput(true);
            httpCon.setRequestProperty("User-Agent",USER_AGENT);
            //httpCon.setRequestProperty("accept-encoding","gzip");
            httpCon.setRequestProperty("accept-language","zh-CN,zh;q=0.9");
            //httpCon.setRequestProperty("content-type","application/json; charset=UTF-8");
            OutputStream os = httpCon.getOutputStream(); //获取响应流并解析
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os,"UTF-8"));
            writer.write(getQuery(params));
            writer.flush();
            writer.close();
            os.close();
            InputStream in = httpCon.getInputStream();  //带资源的try-catch语句。自动关闭
			InputStream buffer = new BufferedInputStream(in);
			// 将InputStream串链到一个Reader
			Reader reader = new InputStreamReader(buffer, "UTF-8");
			int c;
			while ((c = reader.read()) != -1) {
				translateLang += (char) c;
			}
			reader.close();
			buffer.close();
			in.close();
			System.out.println(ip);
            return translateLang;
        } catch (IOException e) {
        	if(e.getMessage().indexOf("proxy")==-1){
        		e.printStackTrace();
            	IpUtils.removeIp(ip);
            	return "error";
        	}else{
        		e.printStackTrace();
        		return "404";
        	}
        }
    }

文章仅供参考，旨为学习参考，如果有什么不对的地方请大家多多指教，必当及时更正！