HttpClient工具類

前言

大多數Java應用程序都會通過HTTP協議來調用接口訪問各種網絡資源，JDK也提供了相應的HTTP工具包，但是使用起來不夠方便靈活，所以我們可以利用Apache的HttpClient來封裝一個具有訪問HTTP協議基本功能的高效工具類，為后續開發使用提供方便。

文章要點：

• HttpClient使用流程
• 工具類封裝
• 使用實例

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HttpClient使用流程

1、導入Maven依賴

<dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.5</version> </dependency> <dependency> <groupId>commons-codec</groupId> <artifactId>commons-codec</artifactId> <version>1.11</version> </dependency> <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.8.5</version> </dependency> 

2、創建HttpClient實例

HttpClient client = HttpClientBuilder.create().build();

3、創建請求方法的實例

GET請求使用HttpGet，POST請求使用HttpPost，並傳入請求的URL

// POST請求 HttpPost post = new HttpPost(url); // GET請求，URL中帶請求參數 HttpGet get = new HttpGet(url); 

4、添加請求參數

普通形式

List<NameValuePair> list = new ArrayList<>(); list.add(new BasicNameValuePair("username", "admin")); list.add(new BasicNameValuePair("password", "123456")); // GET請求方式 // 由於GET請求的參數是拼裝在URL后方，所以需要構建一個完整的URL，再創建HttpGet實例 URIBuilder uriBuilder = new URIBuilder("http://www.baidu.com"); uriBuilder.setParameters(list); HttpGet get = new HttpGet(uriBuilder.build()); // POST請求方式 post.setEntity(new UrlEncodedFormEntity(list, Charsets.UTF_8)); 

JSON形式

Map<String,String> map = new HashMap<>(); map.put("username", "admin"); map.put("password", "123456"); Gson gson = new Gson(); String json = gson.toJson(map, new TypeToken<Map<String, String>>() {}.getType()); post.setEntity(new StringEntity(json, Charsets.UTF_8)); post.addHeader("Content-Type", "application/json"); 

5、發送請求

調用HttpClient實例的execute方法發送請求，返回一個HttpResponse對象

HttpResponse response = client.execute(post);

6、獲取結果

String result = EntityUtils.toString(response.getEntity());

7、釋放連接

post.releaseConnection();

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工具類封裝

HttpClient工具類代碼（根據相應使用場景進行封裝）：

public class HttpClientUtil { // 發送GET請求 public static String getRequest(String path, List<NameValuePair> parametersBody) throws RestApiException, URISyntaxException { URIBuilder uriBuilder = new URIBuilder(path); uriBuilder.setParameters(parametersBody); HttpGet get = new HttpGet(uriBuilder.build()); HttpClient client = HttpClientBuilder.create().build(); try { HttpResponse response = client.execute(get); int code = response.getStatusLine().getStatusCode(); if (code >= 400) throw new RuntimeException((new StringBuilder()).append("Could not access protected resource. Server returned http code: ").append(code).toString()); return EntityUtils.toString(response.getEntity()); } catch (ClientProtocolException e) { throw new RestApiException("postRequest -- Client protocol exception!", e); } catch (IOException e) { throw new RestApiException("postRequest -- IO error!", e); } finally { get.releaseConnection(); } } // 發送POST請求（普通表單形式） public static String postForm(String path, List<NameValuePair> parametersBody) throws RestApiException { HttpEntity entity = new UrlEncodedFormEntity(parametersBody, Charsets.UTF_8); return postRequest(path, "application/x-www-form-urlencoded", entity); } // 發送POST請求（JSON形式） public static String postJSON(String path, String json) throws RestApiException { StringEntity entity = new StringEntity(json, Charsets.UTF_8); return postRequest(path, "application/json", entity); } // 發送POST請求 public static String postRequest(String path, String mediaType, HttpEntity entity) throws RestApiException { logger.debug("[postRequest] resourceUrl: {}", path); HttpPost post = new HttpPost(path); post.addHeader("Content-Type", mediaType); post.addHeader("Accept", "application/json"); post.setEntity(entity); try { HttpClient client = HttpClientBuilder.create().build(); HttpResponse response = client.execute(post); int code = response.getStatusLine().getStatusCode(); if (code >= 400) throw new RestApiException(EntityUtils.toString(response.getEntity())); return EntityUtils.toString(response.getEntity()); } catch (ClientProtocolException e) { throw new RestApiException("postRequest -- Client protocol exception!", e); } catch (IOException e) { throw new RestApiException("postRequest -- IO error!", e); } finally { post.releaseConnection(); } } } 

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使用實例

GET請求

List<NameValuePair> parametersBody = new ArrayList(); parametersBody.add(new BasicNameValuePair("userId", "admin")); String result = HttpClientUtil.getRequest("http://www.test.com/user",parametersBody); 

POST請求

List<NameValuePair> parametersBody = new ArrayList(); parametersBody.add(new BasicNameValuePair("username", "admin")); parametersBody.add(new BasicNameValuePair("password", "123456")); String result = HttpClientUtil.postForm("http://www.test.com/login",parametersBody); 

POST請求（JSON形式）

Map<String,String> map = new HashMap<>(); map.put("username", "admin"); map.put("password", "123456"); Gson gson = new Gson(); String json = gson.toJson(map, new TypeToken<Map<String, String>>() {}.getType()); String result = HttpClientUtil.postJSON("http://www.test.com/login", json); 

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關於HttpClient的詳細介紹看這里：HttpClient入門

本文為作者kMacro原創，轉載請注明來源：https://zkhdev.github.io/2018/10/12/java_dev5/。