什麼是httpclient

1.    

1.1.   什麼是httpclient

HTTP 協議多是如今 Internet 上使用得最多、最重要的協議了，愈來愈多的 Java 應用程序須要直接經過 HTTP 協議來訪問網絡資源。雖然在 JDK 的 java net包中已經提供了訪問 HTTP 協議的基本功能，可是對於大部分應用程序來講，JDK 庫自己提供的功能還不夠豐富和靈活。HttpClient 是 Apache Jakarta Common 下的子項目，用來提供高效的、最新的、功能豐富的支持 HTTP 協議的客戶端編程工具包，而且它支持 HTTP 協議最新的版本和建議。
下載地址：

http://hc.apache.org/

 

1.2.   功能介紹

如下列出的是 HttpClient 提供的主要的功能，要知道更多詳細的功能能夠參見 HttpClient 的主頁。

（1）實現了全部 HTTP 的方法（GET,POST,PUT,HEAD 等）

（2）支持自動轉向

（3）支持 HTTPS 協議

（4）支持代理服務器等

1.3.   導入依賴

1.4.   執行GET請求

public class DoGET {

    public static void main(String[] args) throws Exception {

        // 建立Httpclient對象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        // 建立http GET請求
        HttpGet httpGet = new HttpGet("http://www.baidu.com/");

        CloseableHttpResponse response = null;
        try {
            // 執行請求
            response = httpclient.execute(httpGet);
            // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println("內容長度：" + content.length());
//                FileUtils.writeStringToFile(new File("C:\\baidu.html"), content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }

    }

}

 

1.5.   執行GET帶參數

public class DoGETParam {

    public static void main(String[] args) throws Exception {

        // 建立Httpclient對象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        // 定義請求的參數
        URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build();

        System.out.println(uri);

        // 建立http GET請求
        HttpGet httpGet = new HttpGet(uri);

        CloseableHttpResponse response = null;
        try {
            // 執行請求
            response = httpclient.execute(httpGet);
            // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println(content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }

    }

}

 

1.6.   執行post請求

public class DoPOST {

    public static void main(String[] args) throws Exception {

        // 建立Httpclient對象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        // 建立http POST請求
        HttpPost httpPost = new HttpPost("http://www.oschina.net/");

        CloseableHttpResponse response = null;
        try {
            // 執行請求
            response = httpclient.execute(httpPost);
            // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println(content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }

    }

}

 

1.7.   帶參數的post請求

public class DoPOSTParam {

    public static void main(String[] args) throws Exception {

        // 建立Httpclient對象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        // 建立http POST請求
        HttpPost httpPost = new HttpPost("http://www.oschina.net/search");

        // 設置2個post參數，一個是scope、一個是q
        List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
        parameters.add(new BasicNameValuePair("scope", "project"));
        parameters.add(new BasicNameValuePair("q", "java"));
        // 構造一個form表單式的實體
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters);
        // 將請求實體設置到httpPost對象中
        httpPost.setEntity(formEntity);

        CloseableHttpResponse response = null;
        try {
            // 執行請求
            response = httpclient.execute(httpPost);
            // 判斷返回狀態是否爲200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println(content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }

    }

}

 

1.8.   封裝HttpClient通用工具類

public class HttpClientUtil {

	public static String doGet(String url, Map<String, String> param) {

		// 建立Httpclient對象
		CloseableHttpClient httpclient = HttpClients.createDefault();

		String resultString = "";
		CloseableHttpResponse response = null;
		try {
			// 建立uri
			URIBuilder builder = new URIBuilder(url);
			if (param != null) {
				for (String key : param.keySet()) {
					builder.addParameter(key, param.get(key));
				}
			}
			URI uri = builder.build();

			// 建立http GET請求
			HttpGet httpGet = new HttpGet(uri);

			// 執行請求
			response = httpclient.execute(httpGet);
			// 判斷返回狀態是否爲200
			if (response.getStatusLine().getStatusCode() == 200) {
				resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (response != null) {
					response.close();
				}
				httpclient.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return resultString;
	}

	public static String doGet(String url) {
		return doGet(url, null);
	}

	public static String doPost(String url, Map<String, String> param) {
		// 建立Httpclient對象
		CloseableHttpClient httpClient = HttpClients.createDefault();
		CloseableHttpResponse response = null;
		String resultString = "";
		try {
			// 建立Http Post請求
			HttpPost httpPost = new HttpPost(url);
			// 建立參數列表
			if (param != null) {
				List<NameValuePair> paramList = new ArrayList<>();
				for (String key : param.keySet()) {
					paramList.add(new BasicNameValuePair(key, param.get(key)));
				}
				// 模擬表單
				UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
				httpPost.setEntity(entity);
			}
			// 執行http請求
			response = httpClient.execute(httpPost);
			resultString = EntityUtils.toString(response.getEntity(), "utf-8");
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				response.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}

		return resultString;
	}

	public static String doPost(String url) {
		return doPost(url, null);
	}
}

 

本文爲博主原創文章，轉載請註明出處！

https://my.oschina.net/u/3375733/blog/