除了本文推薦的幾種方式，強烈推薦 OkHttp

目前JAVA實現HTTP請求的方法用的最多的有兩種：一種是通過HTTPClient這種第三方的開源框架去實現。HTTPClient對HTTP的封裝性比較不錯，通過它基本上能夠滿足我們大部分的需求。

HttpClient3.1 是 org.apache.commons.httpclient下操作遠程 url的工具包，雖然已不再更新，但實現工作中使用httpClient3.1的代碼還是很多，HttpClient4.5是org.apache.http.client下操作遠程 url的工具包，最新的；

另一種則是通過HttpURLConnection去實現，HttpURLConnection是JAVA的標準類，是JAVA比較原生的一種實現方式。

自己在工作中三種方式都用到過，總結一下分享給大家，也方便自己以后使用，話不多說上代碼。

第一種方式：java原生HttpURLConnection

package com.powerX.httpClient;import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL;public class HttpClient {public static String doGet(String httpurl) {HttpURLConnection connection = null;InputStream is = null;BufferedReader br = null;String result = null;// 返回結果字符串try {// 創建遠程url連接對象URL url = new URL(httpurl);// 通過遠程url連接對象打開一個連接，強轉成httpURLConnection類connection = (HttpURLConnection) url.openConnection();// 設置連接方式：getconnection.setRequestMethod("GET");// 設置連接主機服務器的超時時間：15000毫秒connection.setConnectTimeout(15000);// 設置讀取遠程返回的數據時間：60000毫秒connection.setReadTimeout(60000);// 發送請求connection.connect();// 通過connection連接，獲取輸入流if (connection.getResponseCode() == 200) {is = connection.getInputStream();// 封裝輸入流is，并指定字符集br = new BufferedReader(new InputStreamReader(is, "UTF-8"));// 存放數據StringBuffer sbf = new StringBuffer();String temp = null;while ((temp = br.readLine()) != null) {sbf.append(temp);sbf.append("\r\n");}result = sbf.toString();}} catch (MalformedURLException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 關閉資源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}connection.disconnect();// 關閉遠程連接}return result;}public static String doPost(String httpUrl, String param) {HttpURLConnection connection = null;InputStream is = null;OutputStream os = null;BufferedReader br = null;String result = null;try {URL url = new URL(httpUrl);// 通過遠程url連接對象打開連接connection = (HttpURLConnection) url.openConnection();// 設置連接請求方式connection.setRequestMethod("POST");// 設置連接主機服務器超時時間：15000毫秒connection.setConnectTimeout(15000);// 設置讀取主機服務器返回數據超時時間：60000毫秒connection.setReadTimeout(60000);// 默認值為：false，當向遠程服務器傳送數據/寫數據時，需要設置為trueconnection.setDoOutput(true);// 默認值為：true，當前向遠程服務讀取數據時，設置為true，該參數可有可無connection.setDoInput(true);// 設置傳入參數的格式:請求參數應該是 name1=value1&name2=value2 的形式。connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");// 設置鑒權信息：Authorization: Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0connection.setRequestProperty("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");// 通過連接對象獲取一個輸出流os = connection.getOutputStream();// 通過輸出流對象將參數寫出去/傳輸出去,它是通過字節數組寫出的os.write(param.getBytes());// 通過連接對象獲取一個輸入流，向遠程讀取if (connection.getResponseCode() == 200) {is = connection.getInputStream();// 對輸入流對象進行包裝:charset根據工作項目組的要求來設置br = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String temp = null;// 循環遍歷一行一行讀取數據while ((temp = br.readLine()) != null) {sbf.append(temp);sbf.append("\r\n");}result = sbf.toString();}} catch (MalformedURLException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 關閉資源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != os) {try {os.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}// 斷開與遠程地址url的連接connection.disconnect();}return result;} }

第二種方式：apache HttpClient3.1

package com.powerX.httpClient;import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.UnsupportedEncodingException; import java.util.Iterator; import java.util.Map; import java.util.Map.Entry; import java.util.Set;import org.apache.commons.httpclient.DefaultHttpMethodRetryHandler; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.HttpStatus; import org.apache.commons.httpclient.NameValuePair; import org.apache.commons.httpclient.methods.GetMethod; import org.apache.commons.httpclient.methods.PostMethod; import org.apache.commons.httpclient.params.HttpMethodParams;public class HttpClient3 {public static String doGet(String url) {// 輸入流InputStream is = null;BufferedReader br = null;String result = null;// 創建httpClient實例HttpClient httpClient = new HttpClient();// 設置http連接主機服務超時時間：15000毫秒// 先獲取連接管理器對象，再獲取參數對象,再進行參數的賦值httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);// 創建一個Get方法實例對象GetMethod getMethod = new GetMethod(url);// 設置get請求超時為60000毫秒getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);// 設置請求重試機制，默認重試次數：3次，參數設置為true，重試機制可用，false相反getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, true));try {// 執行Get方法int statusCode = httpClient.executeMethod(getMethod);// 判斷返回碼if (statusCode != HttpStatus.SC_OK) {// 如果狀態碼返回的不是ok,說明失敗了,打印錯誤信息System.err.println("Method faild: " + getMethod.getStatusLine());} else {// 通過getMethod實例，獲取遠程的一個輸入流is = getMethod.getResponseBodyAsStream();// 包裝輸入流br = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();// 讀取封裝的輸入流String temp = null;while ((temp = br.readLine()) != null) {sbf.append(temp).append("\r\n");}result = sbf.toString();}} catch (IOException e) {e.printStackTrace();} finally {// 關閉資源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}// 釋放連接getMethod.releaseConnection();}return result;}public static String doPost(String url, Map<String, Object> paramMap) {// 獲取輸入流InputStream is = null;BufferedReader br = null;String result = null;// 創建httpClient實例對象HttpClient httpClient = new HttpClient();// 設置httpClient連接主機服務器超時時間：15000毫秒httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);// 創建post請求方法實例對象PostMethod postMethod = new PostMethod(url);// 設置post請求超時時間postMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);NameValuePair[] nvp = null;// 判斷參數map集合paramMap是否為空if (null != paramMap && paramMap.size() > 0) {// 不為空// 創建鍵值參數對象數組，大小為參數的個數nvp = new NameValuePair[paramMap.size()];// 循環遍歷參數集合mapSet<Entry<String, Object>> entrySet = paramMap.entrySet();// 獲取迭代器Iterator<Entry<String, Object>> iterator = entrySet.iterator();int index = 0;while (iterator.hasNext()) {Entry<String, Object> mapEntry = iterator.next();// 從mapEntry中獲取key和value創建鍵值對象存放到數組中try {nvp[index] = new NameValuePair(mapEntry.getKey(),new String(mapEntry.getValue().toString().getBytes("UTF-8"), "UTF-8"));} catch (UnsupportedEncodingException e) {e.printStackTrace();}index++;}}// 判斷nvp數組是否為空if (null != nvp && nvp.length > 0) {// 將參數存放到requestBody對象中postMethod.setRequestBody(nvp);}// 執行POST方法try {int statusCode = httpClient.executeMethod(postMethod);// 判斷是否成功if (statusCode != HttpStatus.SC_OK) {System.err.println("Method faild: " + postMethod.getStatusLine());}// 獲取遠程返回的數據is = postMethod.getResponseBodyAsStream();// 封裝輸入流br = new BufferedReader(new InputStreamReader(is, "UTF-8"));StringBuffer sbf = new StringBuffer();String temp = null;while ((temp = br.readLine()) != null) {sbf.append(temp).append("\r\n");}result = sbf.toString();} catch (IOException e) {e.printStackTrace();} finally {// 關閉資源if (null != br) {try {br.close();} catch (IOException e) {e.printStackTrace();}}if (null != is) {try {is.close();} catch (IOException e) {e.printStackTrace();}}// 釋放連接postMethod.releaseConnection();}return result;} }

第三種方式：apache httpClient4.5

package com.powerX.httpClient;import java.io.IOException; import java.io.UnsupportedEncodingException; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Set;import org.apache.http.HttpEntity; import org.apache.http.NameValuePair; import org.apache.http.client.ClientProtocolException; import org.apache.http.client.config.RequestConfig; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpPost; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils;public class HttpClient4 {public static String doGet(String url) {CloseableHttpClient httpClient = null;CloseableHttpResponse response = null;String result = "";try {// 通過址默認配置創建一個httpClient實例httpClient = HttpClients.createDefault();// 創建httpGet遠程連接實例HttpGet httpGet = new HttpGet(url);// 設置請求頭信息，鑒權httpGet.setHeader("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");// 設置配置請求參數RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 連接主機服務超時時間.setConnectionRequestTimeout(35000)// 請求超時時間.setSocketTimeout(60000)// 數據讀取超時時間.build();// 為httpGet實例設置配置httpGet.setConfig(requestConfig);// 執行get請求得到返回對象response = httpClient.execute(httpGet);// 通過返回對象獲取返回數據HttpEntity entity = response.getEntity();// 通過EntityUtils中的toString方法將結果轉換為字符串result = EntityUtils.toString(entity);} catch (ClientProtocolException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 關閉資源if (null != response) {try {response.close();} catch (IOException e) {e.printStackTrace();}}if (null != httpClient) {try {httpClient.close();} catch (IOException e) {e.printStackTrace();}}}return result;}public static String doPost(String url, Map<String, Object> paramMap) {CloseableHttpClient httpClient = null;CloseableHttpResponse httpResponse = null;String result = "";// 創建httpClient實例httpClient = HttpClients.createDefault();// 創建httpPost遠程連接實例HttpPost httpPost = new HttpPost(url);// 配置請求參數實例RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 設置連接主機服務超時時間.setConnectionRequestTimeout(35000)// 設置連接請求超時時間.setSocketTimeout(60000)// 設置讀取數據連接超時時間.build();// 為httpPost實例設置配置httpPost.setConfig(requestConfig);// 設置請求頭httpPost.addHeader("Content-Type", "application/x-www-form-urlencoded");// 封裝post請求參數if (null != paramMap && paramMap.size() > 0) {List<NameValuePair> nvps = new ArrayList<NameValuePair>();// 通過map集成entrySet方法獲取entitySet<Entry<String, Object>> entrySet = paramMap.entrySet();// 循環遍歷，獲取迭代器Iterator<Entry<String, Object>> iterator = entrySet.iterator();while (iterator.hasNext()) {Entry<String, Object> mapEntry = iterator.next();nvps.add(new BasicNameValuePair(mapEntry.getKey(), mapEntry.getValue().toString()));}// 為httpPost設置封裝好的請求參數try {httpPost.setEntity(new UrlEncodedFormEntity(nvps, "UTF-8"));} catch (UnsupportedEncodingException e) {e.printStackTrace();}}try {// httpClient對象執行post請求,并返回響應參數對象httpResponse = httpClient.execute(httpPost);// 從響應對象中獲取響應內容HttpEntity entity = httpResponse.getEntity();result = EntityUtils.toString(entity);} catch (ClientProtocolException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {// 關閉資源if (null != httpResponse) {try {httpResponse.close();} catch (IOException e) {e.printStackTrace();}}if (null != httpClient) {try {httpClient.close();} catch (IOException e) {e.printStackTrace();}}}return result;} }

有時候我們在使用post請求時，可能傳入的參數是json或者其他格式，此時我們則需要更改請求頭及參數的設置信息，以httpClient4.5為例，更改下面兩列配置：

httpPost.setEntity(new StringEntity("你的json串")); httpPost.addHeader("Content-Type", "application/json")。

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