Java开发小技巧(五):HttpClient工具类

大多数Java应用程序都会通过HTTP协议来调用接口访问各种网络资源,JDK也提供了相应的HTTP工具包,但是使用起来不够方便灵活,所以我们可以利用Apache的HttpClient来封装一个具有访问HTTP协议基本功能的高效工具类,为后续开发使用提供方便。

文章要点:

  • HttpClient使用流程
  • 工具类封装
  • 使用实例

HttpClient使用流程

1、导入Maven依赖

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<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、创建HttpClient实例

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

3、创建请求方法的实例

GET请求使用HttpGet,POST请求使用HttpPost,并传入请求的URL

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// POST请求
HttpPost post = new HttpPost(url);
// GET请求,URL中带请求参数
HttpGet get = new HttpGet(url);

4、添加请求参数

普通形式

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List<NameValuePair> list = new ArrayList<>();
list.add(new BasicNameValuePair("username", "admin"));
list.add(new BasicNameValuePair("password", "123456"));

// GET请求方式
// 由于GET请求的参数是拼装在URL后方,所以需要构建一个完整的URL,再创建HttpGet实例
URIBuilder uriBuilder = new URIBuilder("http://www.baidu.com");
uriBuilder.setParameters(list);
HttpGet get = new HttpGet(uriBuilder.build());

// POST请求方式
post.setEntity(new UrlEncodedFormEntity(list, Charsets.UTF_8));

JSON形式

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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、发送请求

调用HttpClient实例的execute方法发送请求,返回一个HttpResponse对象

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HttpResponse response = client.execute(post);

6、获取结果

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

7、释放连接

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post.releaseConnection();

工具类封装

HttpClient工具类代码(根据相应使用场景进行封装):

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public class HttpClientUtil {
// 发送GET请求
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();
}
}

// 发送POST请求(普通表单形式)
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);
}

// 发送POST请求(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);
}

// 发送POST请求
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();
}
}
}


使用实例

GET请求

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

POST请求

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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请求(JSON形式)

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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);

关于HttpClient的详细介绍看这里:HttpClient入门

本文为作者kMacro原创,转载请注明来源:https://zkhdev.github.io/2018/10/12/java-dev5/