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Today, I will talk to you about how to set request timeout and exception handling in WebClient. Many people may not know much about it. In order to make you understand better, the editor has summarized the following for you. I hope you can get something according to this article.

What to do when an exception occurs in a WebClient request. In order to explain exception handling, we need to create an exception first, so let's first introduce to you: request the setting of the timeout.

I. setting the timeout period of the request

To simulate a timeout exception, we first need to know what the normal configuration channel for the timeout length is. As shown in the following code:

ChannelOption.CONNECT_TIMEOUT_MILLIS is used to set the connection timeout (in milliseconds)

ReadTimeoutHandler (5000, TimeUnit.MILLISECONDS) is used to set the read data timeout (in milliseconds)

WriteTimeoutHandler (5000, TimeUnit.MILLISECONDS) is used to set the write data timeout (in milliseconds)

/ / initialize a WebClientprivate WebClient getWebClient () {TcpClient tcpClient = TcpClient .create () .option (ChannelOption.CONNECT_TIMEOUT_MILLIS, 5000) .doOnConnected (connection-> {connection.addHandlerLast (new ReadTimeoutHandler (5000, TimeUnit.MILLISECONDS)); connection.addHandlerLast (new WriteTimeoutHandler (5000, TimeUnit.MILLISECONDS));}) Return WebClient.builder () .baseUrl ("http://jsonplaceholder.typicode.com") .clientConnector (new ReactorClientHttpConnector (HttpClient.from (tcpClient) .build ();}

When we set the connection timeout to 5 (milliseconds), the connection will definitely time out. Send a random request, and a ConnectTimeoutException will be thrown after the timeout.

When we set the length of time to read the data supermarket to 5 (milliseconds), the data read operation will definitely time out. Send a random request, and a ReadTimeoutException will be thrown after the timeout.

Second, handle specific exceptions

Let's take ConnectTimeoutException as an example to handle exceptions.

/ / create an exception and set the timeout to 5 milliseconds .option (ChannelOption.CONNECT_TIMEOUT_MILLIS, 5)

Then execute the following GET request, and the baseurl of the above WebClient is: "http://jsonplaceholder.typicode.com", a website that provides free HTTP server-side testing.

@ Testpublic void testSimple () throws Exception {Mono mono = getWebClient () .get () / send GET request .uri ("/ posts/1") / / Service request path Based on baseurl .response () / / get response body .bodyToMono (String.class) / / response data type conversion / / exception handling .doOnError (ConnectTimeoutException.class, err-> {System.out.println ("error:" + err.getMessage () }); System.out.println (mono.block ());}

The doOnError above is the exception handling method we introduced in this section, which is used to handle ConnectTimeoutException. The output is as follows:

From the output: one: the exception was handled because the System.out printed log was seen. Second, the exception is still thrown and no return value is obtained.

3. The default return value is given for the request exception.

From the code in the second section and the console output, you can see that the HTTP client request did not get a return value, but continued to throw the exception. What if our current requirement is to give the client a return value regardless of whether the request succeeds or fails? In other words, we need to give the default return value when an exception occurs in the request.

@ Testpublic void testReturn () throws Exception {Mono mono = getWebClient () .get () / send GET request .uri ("/ posts/1") / / Service request path Get the response body .bodyToMono (String.class) / / response data type conversion .doonError (ConnectTimeoutException.class, err-> {System.out.println ("error occurred:" + err.getMessage ()) based on baseurl. }) .onErrorReturn ("an exception occurred in the request, please check!") ; System.out.println (mono.block ());}

Use onErrorReturn (); to give the default return value of the request, and the output is as follows:

You can see that the request test case succeeded in pass because we gave the default return value for exception handling and did not continue to throw the exception.

IV. Classification exception handling

The above exception handling method can only handle a specified exception: ConnectTimeoutException. What if we want exception handling to be relatively generic? Some partners may want to intercept the abnormal parent class Exception, which is also a way.

.doOnError (Exception.class, err-> {System.out.println ("error occurs:" + err.getMessage ());})

Let's take a look at a more friendly way to handle HTTP response exceptions. In general, exceptions can be divided into two types:

One is the client input or access exception, for example: the accessed resource does not exist 404, does not have permission to access the resource 403, the input data does not conform to the format and so on. This exception is usually caused by a user accessing a resource that should not be accessed, or entering data that should not be entered. It is usually expressed in the range of 400-499 by HTTP status code.

The other is server internal error, such as 500 service internal error, 502 gateway error and so on. This exception usually has nothing to do with the user, but is caused by the IT infrastructure or programming.

So we only need to handle the above two types of exceptions. As shown in the following code:

E.is4xxClientError () represents the exception of the 400-499 status code segment.

E.is5xxClientError () represents the exception of the 500-599 status code segment

Public void testSimple2 () throws Exception {Mono mono = getWebClient () .get () / send GET request .uri ("/ postss/1") / / Service request path Get the response body .onStatus (e-> e.is4xxClientError (), resp-> {System.out.println ("client input error:" + resp.statusCode () .value () + "+ resp.statusCode () .getReasonPhrase () based on baseurl .response () / /. Return Mono.error (new RuntimeException ("request failed");}) .onStatus (e-> e.is5xxServerError (), resp-> {System.out.println ("Server side error:" + resp.statusCode () .value () + "+ resp.statusCode () .getReasonPhrase () Return Mono.error (new RuntimeException ("server exception");}) .bodyToMono (String.class); / / response data type conversion System.out.println (mono.block ());}

Now we change the request address from the correct "/ posts/1" to the wrong "/ postss/1", so when we visit the server, the resource does not exist on the server. The output of exception handling is as follows:

After reading the above, do you have any further understanding of how to set request timeout and exception handling in WebClient? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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