Java HTTP编程

最新推荐文章于 2025-03-10 09:39:33 发布

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最新推荐文章于 2025-03-10 09:39:33 发布

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分类专栏： java核心技术笔记

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网页访问

网页是特殊的网络服务（HTTP，Hypertext Transfer Protocol）
– 在浏览器输入URL地址
– 浏览器将连接到远程服务器上（IP+80Port）
– 请求下载一个HTML文件下来，放在本地的临时文件夹中
– 在浏览器显示出来

HTTP

超文本传输协议（HyperText Transfer Protocol）
用于从万维网（www/World Wide Web）服务器传输超文本到本地浏览器的传输协议
资源文件采用HTML编写，以URL形式对外提供

HTML

超文本标记语言（HyperText Markup Language）
表单概念（form），网页上可以输入的地方
访问方式
– Get：从服务器获取资源到客户端
– Post：从客户端向服务器发送数据
– Put：上传文件
– Delete：删除文件
–Head：报文头部
–Options：询问支持的方法
–Trace：追踪路径
– Connect：用隧道协议连接代理

JAVA HTTP编程

Java HTTP 编程（java.net包）
支持模拟成浏览器的方式去访问网页
URL,代表一个资源
– http://www.zucc.edu.cn/index.html?a=1&b=2&c=3
–第一个代表什么协议、网站域名、目录资源文件名字、提供给资源文件的参数
URLConnection
– 获取资源的连接器
– 根据URL的openConnection（）方法获取URLConnection
–connet方法，建立和资源的联系通道
–getInputStream方法，获取资源的内容

//获取资源
public class URLConnectionGetTest
{
   public static void main(String[] args)
   {
      try
      {
         String urlName = "http://www.baidu.com";

         URL url = new URL(urlName);
         URLConnection connection = url.openConnection(); 
         connection.connect();  //建立好联系通道了

         // 打印http的头部信息

         Map<String, List<String>> headers = connection.getHeaderFields();
         for (Map.Entry<String, List<String>> entry : headers.entrySet())
         {
            String key = entry.getKey();
            for (String value : entry.getValue())
               System.out.println(key + ": " + value);
         }

         // 输出将要收到的内容属性信息

         System.out.println("----------");
         System.out.println("getContentType: " + connection.getContentType());
         System.out.println("getContentLength: " + connection.getContentLength());
         System.out.println("getContentEncoding: " + connection.getContentEncoding());
         System.out.println("getDate: " + connection.getDate());
         System.out.println("getExpiration: " + connection.getExpiration());
         System.out.println("getLastModifed: " + connection.getLastModified());
         System.out.println("----------");

         BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));

         // 输出收到的内容
         String line = "";
         while((line=br.readLine()) != null)
         {
        	 System.out.println(line);
         }
         br.close();
      }
      catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}


//发送数据到服务器
public class URLConnectionPostTest
{
   public static void main(String[] args) throws IOException
   {
      String urlString = "https://tools.usps.com/go/ZipLookupAction.action";
      Object userAgent = "HTTPie/0.9.2";
      Object redirects = "1";
      CookieHandler.setDefault(new CookieManager(null, CookiePolicy.ACCEPT_ALL));
      
      Map<String, String> params = new HashMap<String, String>();
      params.put("tAddress", "1 Market Street");   //定义参数
      params.put("tCity", "San Francisco");
      params.put("sState", "CA");
      String result = doPost(new URL(urlString), params, 
         userAgent == null ? null : userAgent.toString(), 
         redirects == null ? -1 : Integer.parseInt(redirects.toString()));
      System.out.println(result);
   }   

   public static String doPost(URL url, Map<String, String> nameValuePairs, String userAgent, int redirects)
         throws IOException
   {        
      HttpURLConnection connection = (HttpURLConnection) url.openConnection();
      if (userAgent != null)
         connection.setRequestProperty("User-Agent", userAgent);
      
      if (redirects >= 0)
         connection.setInstanceFollowRedirects(false);
      
      connection.setDoOutput(true);
      
      //输出请求的参数
      try (PrintWriter out = new PrintWriter(connection.getOutputStream()))
      {
         boolean first = true;
         for (Map.Entry<String, String> pair : nameValuePairs.entrySet())
         {
        	//参数必须这样拼接 a=1&b=2&c=3
            if (first) 
            {
            	first = false;
            }
            else
            {
            	out.print('&');
            }
            String name = pair.getKey();
            String value = pair.getValue();
            out.print(name);
            out.print('=');
            out.print(URLEncoder.encode(value, "UTF-8"));
         }
      }      
      String encoding = connection.getContentEncoding();
      if (encoding == null) 
      {
    	  encoding = "UTF-8";
      }
            
      if (redirects > 0)
      {
         int responseCode = connection.getResponseCode();
         System.out.println("responseCode: " + responseCode);
         if (responseCode == HttpURLConnection.HTTP_MOVED_PERM 
               || responseCode == HttpURLConnection.HTTP_MOVED_TEMP
               || responseCode == HttpURLConnection.HTTP_SEE_OTHER) 
         {
            String location = connection.getHeaderField("Location");
            if (location != null)
            {
               URL base = connection.getURL();
               connection.disconnect();
               return doPost(new URL(base, location), nameValuePairs, userAgent, redirects - 1);
            }
            
         }
      }
      else if (redirects == 0)
      {
         throw new IOException("Too many redirects");
      }
      
      //接下来获取html 内容
      StringBuilder response = new StringBuilder();
      try (Scanner in = new Scanner(connection.getInputStream(), encoding))
      {
         while (in.hasNextLine())
         {
            response.append(in.nextLine());
            response.append("\n");
         }         
      }
      catch (IOException e)
      {
         InputStream err = connection.getErrorStream();
         if (err == null) throw e;
         try (Scanner in = new Scanner(err))
         {
            response.append(in.nextLine());
            response.append("\n");
         }
      }

      return response.toString();
   }
}

HttpClient 的HTTP编程

JDK HTTP Client （JDK自带，从9开始）
– JDK11正式发布
– java.net.http包
– 取代URLConnection
–支持HTTP1.1和HTTP/2
– 实现大部分HTTP方法
– 主要类 - HttpClient - HttpRequest（提交参数给服务器） - HttpResponse（服务器反馈给我的信息）


	
public static void doGet() {
		try{
			HttpClient client = HttpClient.newHttpClient();
			HttpRequest request = HttpRequest.newBuilder(URI.create("http://www.baidu.com")).build();
			HttpResponse response = client.send(request, HttpResponse.BodyHandlers.ofString());
			System.out.println(response.body());
		}
		catch(Exception e) {
			e.printStackTrace();
		}
	}
}


public static void doPost() {
		try {
			HttpClient client = HttpClient.newBuilder().build();
			HttpRequest request = HttpRequest.newBuilder()
					.uri(URI.create("https://tools.usps.com/go/ZipLookupAction.action"))
					//.header("Content-Type","application/x-www-form-urlencoded")
					.header("User-Agent", "HTTPie/0.9.2")
					.header("Content-Type","application/x-www-form-urlencoded;charset=utf-8")
					//.method("POST", HttpRequest.BodyPublishers.ofString("tAddress=1 Market Street&tCity=San Francisco&sState=CA"))
					//.version(Version.HTTP_1_1)
					.POST(HttpRequest.BodyPublishers.ofString("tAddress=" 
					    + URLEncoder.encode("1 Market Street", "UTF-8") 
					    + "&tCity=" + URLEncoder.encode("San Francisco", "UTF-8") + "&sState=CA"))
					//.POST(HttpRequest.BodyPublishers.ofString("tAddress=" + URLEncoder.encode("1 Market Street", "UTF-8") + "&tCity=" + URLEncoder.encode("San Francisco", "UTF-8") + "&sState=CA"))
					.build();
			HttpResponse response = client.send(request, HttpResponse.BodyHandlers.ofString());
			System.out.println(response.statusCode());
			System.out.println(response.headers());
			System.out.println(response.body().toString());

		}
		catch(Exception e) {
			e.printStackTrace();
		}
	}

Apache HttpComponents 的HttpClient（Apache出品）
– 从HttpClien进化而来
– 是一个集成的Java HTTP 工具包
– 实现所有HTTO方法：get/post/put/delete
– 支持自动转向
–支持https协议
–支持代理服务器等

public class HttpComponentsGetTest {

    public final static void main(String[] args) throws Exception {
    	
    	CloseableHttpClient httpClient = HttpClients.createDefault();
        RequestConfig requestConfig = RequestConfig.custom()
                .setConnectTimeout(5000)   //设置连接超时时间
                .setConnectionRequestTimeout(5000) // 设置请求超时时间
                .setSocketTimeout(5000)
                .setRedirectsEnabled(true)//默认允许自动重定向
                .build();
        
        HttpGet httpGet = new HttpGet("http://www.baidu.com");
        httpGet.setConfig(requestConfig);
        String srtResult = "";
        try {
            HttpResponse httpResponse = httpClient.execute(httpGet);
            if(httpResponse.getStatusLine().getStatusCode() == 200){  //200代表网页访问成功
                srtResult = EntityUtils.toString(httpResponse.getEntity(), "UTF-8");//获得返回的结果                
                System.out.println(srtResult);
            }else
            {
                //异常处理
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                httpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
public class HttpComponentsPostTest {

    public final static void main(String[] args) throws Exception {
    	
    	//获取可关闭的 httpCilent
        //CloseableHttpClient httpClient = HttpClients.createDefault();
    	CloseableHttpClient httpClient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();
    	//配置超时时间
        RequestConfig requestConfig = RequestConfig.custom().
                setConnectTimeout(10000).setConnectionRequestTimeout(10000)
                .setSocketTimeout(10000).setRedirectsEnabled(false).build();
         
        HttpPost httpPost = new HttpPost("https://tools.usps.com/go/ZipLookupAction.action");
        //设置超时时间
        httpPost.setConfig(requestConfig);
        
        //装配post请求参数
        List<BasicNameValuePair> list = new ArrayList<BasicNameValuePair>(); 
        list.add(new BasicNameValuePair("tAddress", URLEncoder.encode("1 Market Street", "UTF-8")));  //请求参数
        list.add(new BasicNameValuePair("tCity", URLEncoder.encode("San Francisco", "UTF-8"))); //请求参数
        list.add(new BasicNameValuePair("sState", "CA")); //请求参数
        try {
            UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list,"UTF-8"); 
            //设置post求情参数
            httpPost.setEntity(entity);
            httpPost.setHeader("User-Agent", "HTTPie/0.9.2");
            //httpPost.setHeader("Content-Type","application/form-data");
            HttpResponse httpResponse = httpClient.execute(httpPost);
            String strResult = "";
            if(httpResponse != null){ 
                System.out.println(httpResponse.getStatusLine().getStatusCode());
                if (httpResponse.getStatusLine().getStatusCode() == 200) {
                    strResult = EntityUtils.toString(httpResponse.getEntity());
                }
                else {
                    strResult = "Error Response: " + httpResponse.getStatusLine().toString();
                } 
            }else{
                 
            }
            System.out.println(strResult);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                if(httpClient != null){
                    httpClient.close(); //释放资源
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}