拦截器(interceptor)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。
HttpClient
请求拦截器
HttpRequestInterceptor接口表示请求拦截器。此接口包含一个称为进程的方法，需要编写代码块来拦截请求。
在客户端，此方法在将请求发送到服务器之前验证/处理请求，并且在服务器端，此方法在评估请求的主体之前执行。
创建请求拦截器
可以按照以下步骤创建请求拦截器。
第1步 - 创建HttpRequestInterceptor的对象
通过实现其抽象方法过程来创建HttpRequestInterceptor接口的对象。
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
通过将以上创建的拦截器添加到它来构建自定义的CloseableHttpClient对象，如下所示 -
//Creating a CloseableHttpClient object
CloseableHttpClient httpclient =
HttpClients.custom().addInterceptorFirst(requestInterceptor).build();
使用此对象，可以照常执行请求执行。
示例
以下示例演示了请求拦截器的用法。在此示例中，创建了一个HTTP GET请求对象，并添加了三个标头：sample-header，demoheader和test-header。
在拦截器processor()方法中，验证发送请求的头部; 如果这些标头中的任何一个是sample-header，我们尝试删除它并显示特定请求的标头列表。
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.kaops.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());
}
}
执行上面示例代码，得到以下结果:
Contains header sample-header, removing it..
demo-header
test-header
HTTP/1.1 200 OK
响应拦截器
HttpResponseInterceptor接口表示响应拦截器。该接口包含一个称为process()的方法。在此方法中，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，在客户端，此方法在评估响应主体之前执行。
创建响应拦截器
可以按照以下步骤创建响应拦截器 -
第1步 - 创建HttpResponseInterceptor的对象
通过实现其抽象方法过程来创建HttpResponseInterceptor接口的对象。
HttpResponseInterceptor responseInterceptor = new HttpResponseInterceptor() {
@Override
public void process(HttpResponse response, HttpContext context) throws HttpException, IOException {
//Method implementation . . . . . . . .
}
};
第2步 - 实例化CloseableHttpClient对象
通过向其添加上面创建的拦截器来构建自定义的CloseableHttpClient对象，如下所示 -
//Creating a CloseableHttpClient object
CloseableHttpClient httpclient =
HttpClients.custom().addInterceptorFirst(responseInterceptor).build();
使用此对象，可以照常执行请求执行。
示例
以下示例演示了响应拦截器的用法。在此示例中，向处理器中的响应添加了三个标头：sample-header，demo-header和test-header。
执行请求并获得响应后，使用getAllHeaders()方法打印响应的所有标头的名称。
在输出中，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.kaops.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());
}
}
}
执行上面示例代码，得到以下结果：
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
RestTemplate
实现org.springframework.http.client.ClientHttpRequestInterceptor接口,跟httpClient拦截器的原理类似，只是略有不同
public class RestTemplateIntercetor implements ClientHttpRequestInterceptor {
private static Logger logger = LoggerFactory.getLogger(RestTemplateIntercetor.class);
private static String NOTICE_MESSAGE_HOST = "www.zjzr.com.cn";
@Override
public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] bytes, ClientHttpRequestExecution clientHttpRequestExecution) throws IOException {
String authority = httpRequest.getURI().getAuthority();
if(NOTICE_MESSAGE_HOST.equals(authority)){
HttpHeaders headers = httpRequest.getHeaders();
boolean contains = headers.containsKey("token");
if(!contains){
logger.warn("您对www.zjzr.com.cn的访问没有认证标识token,有可能被网关拦截无权访问,请注意");
}
}
//继续执行请求
return clientHttpRequestExecution.execute(httpRequest,bytes);
}
}
配置文件
META-INFO/spring.factories
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.ruijie.springframework.core.configuration.HttpAutoConfiguration
设置自动化配置类 HttpAutoConfiguration
@Configuration
public class HttpAutoConfiguration {
@Bean
@ConditionalOnClass(HttpRequestInterceptor.class)
public HttpRequestInterceptor HttpClientRequestInterceptor(){
return new HttpClientRequestInterceptor();
}
@Bean
@ConditionalOnClass(ClientHttpRequestInterceptor.class)
public ClientHttpRequestInterceptor clientHttpRequestInterceptor(){
return new RestTemplateIntercetor();
}
@Bean
@ConditionalOnBean(ClientHttpRequestInterceptor.class)
public RestTemplate restTemplate(ClientHttpRequestInterceptor clientHttpRequestInterceptor){
RestTemplate restTemplate = new RestTemplate();
restTemplate.setInterceptors(Collections.singletonList(clientHttpRequestInterceptor));
return restTemplate;
}
@Autowired
private ConfigurableEnvironment configurableEnvironment;
@PostConstruct
public void init(){
String property = configurableEnvironment.getProperty("token");
HttpClientUtil.setToken(property);
}
}
这样 我们在使用HttpClientUtil或resttemplate的时候 ,拦截器就会生效，验证Token是否存在，并且给出相应提示或抛出异常.
