blocks|key|1860576|text|一旦Http响应/错误准备就绪，您就可以创建自己的侦听器，并使用传递回调用类的结果进行异步的HTTP调用。例如(有拼写错误)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1860577|创建一个接口，您的主类将实现该接口，并且您的Http客户端将利用...|1860578|public+interface+MyHttpListener+{
++public+httpComplete(MyHttpResults+results);
}|code-block|syntax|javascript|1860579|在你的主类中实现。|1860580|public+MyClass+implements+MyHttpListener+{

++public+void+processHttpRequests(){
++++++for(int+i=0;+i<10;+i%2B%2B){
++++++++//+instantiate+your+Http+Client+class+
++++++++HttpClient+client+=+new+HttpClient();

++++++++//+register+the+listener
++++++++client.addHttpListener(this);

++++++++//+execute+whatever+URL+you+want+and+you+are+notified+later+when+complete
++++++++client.executeRequest("http://whatever");
+++++}
++}

++public+httpRequestComplete(MyHttpResults+results)+{
++++//+do+something+with+the+results+++
++++results.getResponseCode();
++++results.getRawResponse();
++++results.whatever();
++}++|1860581|}|1860582|将方法添加到HttpClient以接受侦听器|1860583|public+class+MyHttpClient+{
++++List<MyHttpListener>+httpListenerList+=+new+ArrayList();+++

+++//+register+listeners
+++public+void+addHttpListener(MyHttpListener+listener){
+++++httpListenerList.add(listener);
+++}+++

+++//+this+is+the+method+that+processes+the+request
+++public+void+executeRequest(String+url)+{

+++++//+do+whatever+you+were+doing+previously+here+++

+++++//+optional+POJO+to+wrap+the+results+and/or+exceptions
+++++MyHttpResults+results+=+new+MyHttpResults();
+++++results.withResponseCode(response.getResponseCode());
+++++results.withResponse(responseAsString);
+++++results.withException(ex);
+++++results.withWhatever(whatever);

+++++//+notify+listeners
+++++notify(results);

+++}

++public+void+notify(MyHttpResults+results){
++++++//+notify+listeners
++++++for(MyHttpListener+listener+:+httpListenerList){
+++++++++listener.httpComplete(results);
++++++}
++}


+}|1860584|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|F|7|11|8|@]|9|@]|A|$G|H]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

You could create your own Listener and make your Http calls async with the results passed back to the calling class once the HTTP response/error is ready. For example (with typos):

Create an interface that your main class will implement and your Http Client will make use of...

<pre><code>public interface MyHttpListener {
 public httpComplete(MyHttpResults results);
}
</code></pre>

Implement in your main class.

<pre><code>public MyClass implements MyHttpListener {

 public void processHttpRequests(){
 for(int i=0; i&lt;10; i++){
 // instantiate your Http Client class 
 HttpClient client = new HttpClient();

 // register the listener
 client.addHttpListener(this);

 // execute whatever URL you want and you are notified later when complete
 client.executeRequest("http://whatever");
 }
 }

 public httpRequestComplete(MyHttpResults results) {
 // do something with the results 
 results.getResponseCode();
 results.getRawResponse();
 results.whatever();
 } 
</code></pre>

}

Add method to your HttpClient to accept listeners

<pre><code>public class MyHttpClient {
 List&lt;MyHttpListener&gt; httpListenerList = new ArrayList(); 

 // register listeners
 public void addHttpListener(MyHttpListener listener){
 httpListenerList.add(listener);
 } 

 // this is the method that processes the request
 public void executeRequest(String url) {

 // do whatever you were doing previously here 

 // optional POJO to wrap the results and/or exceptions
 MyHttpResults results = new MyHttpResults();
 results.withResponseCode(response.getResponseCode());
 results.withResponse(responseAsString);
 results.withException(ex);
 results.withWhatever(whatever);

 // notify listeners
 notify(results);

 }

 public void notify(MyHttpResults results){
 // notify listeners
 for(MyHttpListener listener : httpListenerList){
 listener.httpComplete(results);
 }
 }


 }
</code></pre>

blocks|key|1860597|text|如果使用Spring+Boot，可以尝试名为Feign的声明式REST客户端|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1860598|@FeignClient(url+=+"example.com",+fallback+=+YourTestFeignClient.YourTestFeignClientFallback.class)
public+interface+YourTestFeignClient+{

++++@RequestMapping(method+=+RequestMethod.POST,+value+=+"/example/path/to/resource/{id}")
++++YourTestResponse+requestExternalResource(@RequestParam("id")+Long+id,+SomeRequestDTO+requestDTO);

++++@Component
++++public+static+class+YourTestFeignClientFallback+implements+YourTestFeignClient+{

++++++++@Override
++++++++public+YourTestResponse+requestExternalResource(Long+id,+SomeRequestDTO+requestDTO)+{
++++++++++++YourTestResponse+testResponse+=+new+YourTestResponse();
++++++++++++testResponse.setMessage("Service+unavailable");
++++++++++++return+testResponse;
++++++++}

++++}
}|code-block|syntax|javascript|1860599|在这里，您需要做的就是在代码中注入YourTestFeignClient并在其上调用requestExternalResource方法。这将使用从SomeRequestDTO获取的JSON+body调用POST+example.com/example/path/to/resource/34。如果请求失败，将调用YourTestFeignClientFallback内部的回退方法，然后返回一些默认数据。|style|CODE|1860600|entityMap|0|LINK|mutability|MUTABLE|url|http://cloud.spring.io/spring-cloud-netflix/spring-cloud-netflix.html#spring-cloud-feign^0|M|5|0|0|0|H|J|16|N|21|E|2T|18|4C|R|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@$A|10|B|11|K|L]|$A|12|B|13|K|L]|$A|14|B|15|K|L]|$A|16|B|17|K|L]|$A|18|B|19|K|L]]|9|@]|C|$]]|$1|M|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

If you use Spring Boot you can try a declarative REST client called <a href="http://cloud.spring.io/spring-cloud-netflix/spring-cloud-netflix.html#spring-cloud-feign" rel="nofollow noreferrer">Feign</a>:

<pre><code>@FeignClient(url = "example.com", fallback = YourTestFeignClient.YourTestFeignClientFallback.class)
public interface YourTestFeignClient {

 @RequestMapping(method = RequestMethod.POST, value = "/example/path/to/resource/{id}")
 YourTestResponse requestExternalResource(@RequestParam("id") Long id, SomeRequestDTO requestDTO);

 @Component
 public static class YourTestFeignClientFallback implements YourTestFeignClient {

 @Override
 public YourTestResponse requestExternalResource(Long id, SomeRequestDTO requestDTO) {
 YourTestResponse testResponse = new YourTestResponse();
 testResponse.setMessage("Service unavailable");
 return testResponse;
 }

 }
}
</code></pre>

All you need to do here is to inject <code>YourTestFeignClient</code> in your code and invoke method <code>requestExternalResource</code> on it. This will call <code>POST example.com/example/path/to/resource/34</code>with JSON body taken from <code>SomeRequestDTO</code>. In case a request fails a fallback method inside <code>YourTestFeignClientFallback</code> will get called, which then returns some default data.

I'm making a REST call to an external system from Java. If there are any connection interruptions like if the external system goes offline, I need a listener to detect that and perform corresponding actions. Kindly let me know if I can achieve this in Java. Preferably in Java 8.

Currently i'm not getting any exception if I get into any such situation. I having the below code currently

<pre><code> Client client = ClientBuilder.newClient();
 WebTarget target = client.target(HOSTNAME);
 Invocation.Builder requestBuilder;

 requestBuilder = target.path(URL).request(MediaType.APPLICATION_JSON)
 .header(HEADER_AUTHORIZATION, AUTH_TOKEN); 
 Response response = null;
 if (HTTP_POST.equalsIgnoreCase(method)) {
 try{
 response = requestBuilder.post(Entity.entity(message, MediaType.APPLICATION_JSON_TYPE));
 }catch(Exception ex ){
 ex.printStackTrace();
 }
 } else if (HTTP_GET.equalsIgnoreCase(method)) {
 response = requestBuilder.get();
 } 

 String executeMessage = null;
 if(response != null){
 if (response.getStatus() == 200) {
 executeMessage = response.readEntity(String.class); 
 return new JSONObject(executeMessage);
 } else {
 executeMessage = response.readEntity(String.class);
 final JSONObject status = new JSONObject();
 status.put(STATUS_CODE, response.getStatus());
 status.put(STATUS_INFO, response.getStatusInfo());
 status.put("response", executeMessage);
 final JSONObject error = new JSONObject();
 error.put(ERROR, status);
 return error;
 }
 }
</code></pre>

Detect HTTP interruption in Java

Spring Boot

JSON

Java

我正在从Java向外部系统发出REST调用。如果有任何连接中断，比如外部系统脱机，我需要一个侦听器来检测并执行相应的操作。如果我可以用Java实现这一点，请让我知道。最好是在Java 8中。目前，如果我遇到这样的情况，我不会得到任何异常。我现在有以下代码    Client client = ClientBuilder...

问在Java中检测HTTP中断
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