建议使用响应处理程序处理HTTP响应.在本章中，我们将讨论如何创建响应处理程序以及如何使用它们来处理响应.
如果使用响应处理程序，将自动释放所有HTTP连接.
HttpClient API在包<中提供了一个名为 ResponseHandler 的接口b> org.apache.http.client.为了创建响应处理程序，实现此接口
并覆盖其 handleResponse()方法.
每个响应都有一个状态代码，如果状态代码在200到300之间，则表示该操作已成功接收，理解和接受.因此，在我们的示例中，我们将使用此类状态代码处理响应的实体.
按照步骤操作下面给出使用响应处理程序执行请求.
createDefault() HttpClients 类的方法返回类 CloseableHttpClient 的对象，它是 HttpClient 接口的基本实现.使用此方法创建一个HttpClient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
使用以下代码行实现上面创建的响应处理程序对象&minus ;
ResponseHandler<String> responseHandler = new MyResponseHandler();
HttpGet 类表示HTTP GET请求使用URI检索给定服务器的信息.
通过实例化HttpGet类并将表示URI作为参数的字符串传递给其构造函数来创建HttpGet请求.
ResponseHandler<String> responseHandler = new MyResponseHandler();
CloseableHttpClient 类具有 execute()方法的变体，它接受两个对象 ResponseHandler 和HttpUriRequest，并返回一个响应对象.
String httpResponse = httpclient.execute(httpget, responseHandler);
以下示例演示了响应处理程序的用法.
import java.io.IOException;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
class MyResponseHandler implements ResponseHandler<String>{
public String handleResponse(final HttpResponse response) throws IOException{
//Get the status of the response
int status = response.getStatusLine().getStatusCode();
if (status >= 200 && status < 300) {
HttpEntity entity = response.getEntity();
if(entity == null) {
return "";
} else {
return EntityUtils.toString(entity);
}
} else {
return ""+status;
}
}
}
public class ResponseHandlerExample {
public static void main(String args[]) throws Exception{
//Create an HttpClient object
CloseableHttpClient httpclient = HttpClients.createDefault();
//instantiate the response handler
ResponseHandler<String> responseHandler = new MyResponseHandler();
//Create an HttpGet object
HttpGet httpget = new HttpGet("http://www.IT屋.com/");
//Execute the Get request by passing the response handler object and HttpGet object
String httpresponse = httpclient.execute(httpget, responseHandler);
System.out.println(httpresponse);
}
}以上程序生成以下输出 :
<!DOCTYPE html>
<!--[if IE 8]><html class = "ie ie8"> <![endif]-->
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<html lang = "en-US"> <!--<![endif]-->
<head>
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<meta charset = "utf-8">
<meta http-equiv = "X-UA-Compatible" content = "IE = edge">
<meta name = "viewport" content = "width = device-width,initial-scale = 1.0,userscalable = yes">
<link href = "https://img01.yuandaxia.cn/Content/img/tutorials/apache_httpclient/mui-rem.min.css"
rel = "stylesheet" type = "text/css" />
<link rel = "stylesheet" href = "/questions/css/home.css?v = 3" />
<script src = "/questions/js/jquery.min.js"></script>
<script src = "/questions/js/fontawesome.js"></script>
<script src = "https://cdn.muicss.com/mui-0.9.39/js/mui.min.js"></script>
</head>
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