拦截器是那些有助于阻止或改变请求或响应的拦截器.协议拦截器通常作用于特定标头或一组相关标头. HttpClient库为拦截器提供支持.
HttpRequestInterceptor 接口表示请求拦截器.此接口包含一个称为进程的方法，您需要编写代码块来拦截请求.
在客户端，此方法在发送请求之前验证/处理请求到服务器，在服务器端，这个方法在评估请求的主体之前执行.
你可以创建请按照以下步骤执行请求拦截器.
步骤1 - 创建HttpRequestInterceptor对象
创建对象通过实现其抽象方法过程来实现HttpRequestInterceptor接口.
HttpRequestInterceptor requestInterceptor = new HttpRequestInterceptor(){
@Override
public void process(HttpRequest request, HttpContext context) throws
HttpException, IOException {
//Method implementation . . . . .
};第2步 - 实例化CloseableHttpClient对象
构建自定义 CloseableHttpClient 通过向上面创建的拦截器添加对象，如下所示 :
//Creating a CloseableHttpClient object CloseableHttpClient httpclient = HttpClients.custom().addInterceptorFirst(requestInterceptor).build();
使用此对象，您可以照常执行请求.
以下示例演示了请求拦截器的用法.在这个例子中，我们创建了一个HTTP GET请求对象并添加了三个头文件:sample-header，demoheader和test-header.
在 processor()拦截器的方法，我们正在验证发送请求的标头;如果这些标题中的任何标题是 sample-header ，我们会尝试删除它并显示该特定请求的标题列表.
import java.io.IOException;
import org.apache.http.Header;
import org.apache.http.HttpException;
import org.apache.http.HttpRequest;
import org.apache.http.HttpRequestInterceptor;
import org.apache.http.HttpResponse;
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.message.BasicHeader;
import org.apache.http.protocol.HttpContext;
public class InterceptorsExample {
public static void main(String args[]) throws Exception{
//Creating an HttpRequestInterceptor
HttpRequestInterceptor requestInterceptor = new HttpRequestInterceptor() {
@Override
public void process(HttpRequest request, HttpContext context) throws
HttpException, IOException {
if(request.containsHeader("sample-header")) {
System.out.println("Contains header sample-header, removing it..");
request.removeHeaders("sample-header");
}
//Printing remaining list of headers
Header[] headers= request.getAllHeaders();
for (int i = 0; i<headers.length;i++) {
System.out.println(headers[i].getName());
}
}
};
//Creating a CloseableHttpClient object
CloseableHttpClient httpclient =
HttpClients.custom().addInterceptorFirst(requestInterceptor).build();
//Creating a request object
HttpGet httpget1 = new HttpGet("https://www.IT屋.com/");
//Setting the header to it
httpget1.setHeader(new BasicHeader("sample-header","My first header"));
httpget1.setHeader(new BasicHeader("demo-header","My second header"));
httpget1.setHeader(new BasicHeader("test-header","My third header"));
//Executing the request
HttpResponse httpresponse = httpclient.execute(httpget1);
//Printing the status line
System.out.println(httpresponse.getStatusLine());
}
}执行上述程序时，以下输出为生成&减去;
Contains header sample-header, removing it.. demo-header test-header HTTP/1.1 200 OK
HttpResponseInterceptor 接口代表响应拦截器.此接口包含一个称为 process()的方法.在此方法中，您需要编写代码块来拦截响应.
在服务器端，此方法在将响应发送到客户端之前验证/处理响应，并在客户端，此方法在评估响应主体之前执行.
您可以按照步骤创建响应拦截器给出以下 :
步骤1 - 创建HttpResponseInterceptor的对象
创建 HttpResponseInterceptor的对象通过实现其抽象方法接口进程.
HttpResponseInterceptor responseInterceptor = new HttpResponseInterceptor() {
@Override
public void process(HttpResponse response, HttpContext context) throws HttpException, IOException {
//Method implementation . . . . . . . .
}
};通过添加以上内容构建自定义 CloseableHttpClient 对象创建了拦截器，如下所示:
//Creating a CloseableHttpClient object CloseableHttpClient httpclient = HttpClients.custom().addInterceptorFirst(responseInterceptor).build();
使用此对象，您可以照常执行请求.
以下示例演示了响应拦截器的用法.在这个例子中，我们在处理器的响应中添加了三个标题:sample-header，demo-header和test-header.
执行请求并获得响应后，我们使用 getAllHeaders()方法打印响应的所有标题的名称.
在输出中，您可以观察列表中三个标题的名称.
import java.io.IOException;
import org.apache.http.Header;
import org.apache.http.HttpException;
import org.apache.http.HttpResponse;
import org.apache.http.HttpResponseInterceptor;
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.protocol.HttpContext;
public class ResponseInterceptorsExample {
public static void main(String args[]) throws Exception{
//Creating an HttpRequestInterceptor
HttpResponseInterceptor responseInterceptor = new HttpResponseInterceptor() {
@Override
public void process(HttpResponse response, HttpContext context) throws
HttpException, IOException {
System.out.println("Adding header sample_header, demo-header, test_header to the response");
response.setHeader("sample-header", "My first header");
response.setHeader("demo-header", "My second header");
response.setHeader("test-header", "My third header");
}
};
//Creating a CloseableHttpClient object
CloseableHttpClient httpclient = HttpClients.custom().addInterceptorFirst(responseInterceptor).build();
//Creating a request object
HttpGet httpget1 = new HttpGet("https://www.IT屋.com/");
//Executing the request
HttpResponse httpresponse = httpclient.execute(httpget1);
//Printing remaining list of headers
Header[] headers = httpresponse.getAllHeaders();
for (int i = 0; i<headers.length;i++) {
System.out.println(headers[i].getName());
}
}
}执行时，以上程序生成以下结果 :
On executing the above program generates the following output. Adding header sample_header, demo-header, test_header to the response Accept-Ranges Access-Control-Allow-Headers Access-Control-Allow-Origin Cache-Control Content-Type Date Expires Last-Modified Server Vary X-Cache sample-header demo-header test-header
