Resttemplate обработка ошибок

The code of exchange is below:

public <T> ResponseEntity<T> exchange(String url, HttpMethod method,
            HttpEntity<?> requestEntity, Class<T> responseType, Object... uriVariables) throws RestClientException

Exception RestClientException has HttpClientErrorException and HttpStatusCodeException exception.

So in RestTemplete there may occure HttpClientErrorException and HttpStatusCodeException exception.
In exception object you can get exact error message using this way: exception.getResponseBodyAsString()

Here is the example code:

public Object callToRestService(HttpMethod httpMethod, String url, Object requestObject, Class<?> responseObject) {

        printLog( "Url : " + url);
        printLog( "callToRestService Request : " + new GsonBuilder().setPrettyPrinting().create().toJson(requestObject));

        try {

            RestTemplate restTemplate = new RestTemplate();
            restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
            restTemplate.getMessageConverters().add(new StringHttpMessageConverter());


            HttpHeaders requestHeaders = new HttpHeaders();
            requestHeaders.setContentType(MediaType.APPLICATION_JSON);

            HttpEntity<Object> entity = new HttpEntity<>(requestObject, requestHeaders);

            long start = System.currentTimeMillis();

            ResponseEntity<?> responseEntity = restTemplate.exchange(url, httpMethod, entity, responseObject);

            printLog( "callToRestService Status : " + responseEntity.getStatusCodeValue());


            printLog( "callToRestService Body : " + new GsonBuilder().setPrettyPrinting().create().toJson(responseEntity.getBody()));

            long elapsedTime = System.currentTimeMillis() - start;
            printLog( "callToRestService Execution time: " + elapsedTime + " Milliseconds)");

            if (responseEntity.getStatusCodeValue() == 200 && responseEntity.getBody() != null) {
                return responseEntity.getBody();
            }

        } catch (HttpClientErrorException exception) {
            printLog( "callToRestService Error :" + exception.getResponseBodyAsString());
            //Handle exception here
        }catch (HttpStatusCodeException exception) {
            printLog( "callToRestService Error :" + exception.getResponseBodyAsString());
            //Handle exception here
        }
        return null;
    }

Here is the code description:

In this method you have to pass request and response class. This method will automatically parse response as requested object.

First of All you have to add message converter.

restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
            restTemplate.getMessageConverters().add(new StringHttpMessageConverter());

Then you have to add requestHeader.
Here is the code:

HttpHeaders requestHeaders = new HttpHeaders();
            requestHeaders.setContentType(MediaType.APPLICATION_JSON);

            HttpEntity<Object> entity = new HttpEntity<>(requestObject, requestHeaders);

Finally, you have to call exchange method:

ResponseEntity<?> responseEntity = restTemplate.exchange(url, httpMethod, entity, responseObject);

For prety printing i used Gson library.
here is the gradle : compile 'com.google.code.gson:gson:2.4'

You can just call the bellow code to get response:

ResponseObject response=new RestExample().callToRestService(HttpMethod.POST,"URL_HERE",new RequestObject(),ResponseObject.class);

Here is the full working code:

import com.google.gson.GsonBuilder;
import org.springframework.http.*;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.client.HttpClientErrorException;
import org.springframework.web.client.HttpStatusCodeException;
import org.springframework.web.client.RestTemplate;


public class RestExample {

    public RestExample() {

    }

    public Object callToRestService(HttpMethod httpMethod, String url, Object requestObject, Class<?> responseObject) {

        printLog( "Url : " + url);
        printLog( "callToRestService Request : " + new GsonBuilder().setPrettyPrinting().create().toJson(requestObject));

        try {

            RestTemplate restTemplate = new RestTemplate();
            restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
            restTemplate.getMessageConverters().add(new StringHttpMessageConverter());


            HttpHeaders requestHeaders = new HttpHeaders();
            requestHeaders.setContentType(MediaType.APPLICATION_JSON);

            HttpEntity<Object> entity = new HttpEntity<>(requestObject, requestHeaders);

            long start = System.currentTimeMillis();

            ResponseEntity<?> responseEntity = restTemplate.exchange(url, httpMethod, entity, responseObject);

            printLog( "callToRestService Status : " + responseEntity.getStatusCodeValue());


            printLog( "callToRestService Body : " + new GsonBuilder().setPrettyPrinting().create().toJson(responseEntity.getBody()));

            long elapsedTime = System.currentTimeMillis() - start;
            printLog( "callToRestService Execution time: " + elapsedTime + " Milliseconds)");

            if (responseEntity.getStatusCodeValue() == 200 && responseEntity.getBody() != null) {
                return responseEntity.getBody();
            }

        } catch (HttpClientErrorException exception) {
            printLog( "callToRestService Error :" + exception.getResponseBodyAsString());
            //Handle exception here
        }catch (HttpStatusCodeException exception) {
            printLog( "callToRestService Error :" + exception.getResponseBodyAsString());
            //Handle exception here
        }
        return null;
    }

    private void printLog(String message){
        System.out.println(message);
    }
}

Thanks

In an earlier article, I wrote about making HTTP requests using the RestTemplate class in a Spring Boot application.

In this short article, you’ll learn how to handle the errors thrown by the RestTemplate, during the execution of an HTTP request.

Default error handling

By default, if there is an error during the execution of the request or the server returns a non-successful HTTP status code (4xx or 5xx), RestTemplate will throw one of the following exceptions:

• HttpClientErrorException — For HTTP status code 4xx
• HttpServerErrorException — For HTTP status code 5xx
• UnknownHttpStatusCodeException — In case of an unknown HTTP status code

All these exceptions extend a base class called RestClientResponseException that contains actual HTTP response data.

Error handling using try...catch

The simplest way to add a custom error handler is to use a try-catch block to catch the HttpStatusCodeException exception. From the HttpStatusCodeException instance, you can then get the response status code, body, and headers, as shown below:

try {
    // request url
    String url = "https://reqres.in/api/unknown/23";

    // create an instance of RestTemplate
    RestTemplate restTemplate = new RestTemplate();

    // make an HTTP GET request
    ResponseEntity<String> response = restTemplate.getForEntity(url, String.class);
    
} catch (HttpStatusCodeException ex) {
    // raw http status code e.g `404`
    System.out.println(ex.getRawStatusCode());
    
    // http status code e.g. `404 NOT_FOUND`
    System.out.println(ex.getStatusCode().toString());
    
    // get response body
    System.out.println(ex.getResponseBodyAsString());
    
    // get http headers
    HttpHeaders headers = ex.getResponseHeaders();
    System.out.println(headers.get("Content-Type"));
    System.out.println(headers.get("Server"));
}

Implementing a custom error handler

Sometimes, a try-catch block is not enough to handle errors as it is not scalable when the number of HTTP requests increases.

You may want to create a reusable custom error handler by implementing the ResponseErrorHandler interface as follows:

MyErrorHandler.java

package com.attacomsian.runner;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.web.client.DefaultResponseErrorHandler;
import org.springframework.web.client.ResponseErrorHandler;

import java.io.IOException;

public class MyErrorHandler implements ResponseErrorHandler {

    @Override
    public boolean hasError(ClientHttpResponse response) throws IOException {
        return new DefaultResponseErrorHandler().hasError(response);
    }

    @Override
    public void handleError(ClientHttpResponse response) throws IOException {

        if (response.getStatusCode().series() == HttpStatus.Series.SERVER_ERROR) {
            // handle 5xx errors
            // raw http status code e.g `500`
            System.out.println(response.getRawStatusCode());

            // http status code e.g. `500 INTERNAL_SERVER_ERROR`
            System.out.println(response.getStatusCode());

        } else if (response.getStatusCode().series() == HttpStatus.Series.CLIENT_ERROR) {
            // handle 4xx errors
            // raw http status code e.g `404`
            System.out.println(response.getRawStatusCode());

            // http status code e.g. `404 NOT_FOUND`
            System.out.println(response.getStatusCode());

            // get response body
            System.out.println(response.getBody());

            // get http headers
            HttpHeaders headers = response.getHeaders();
            System.out.println(headers.get("Content-Type"));
            System.out.println(headers.get("Server"));
        }
    }
}

You can now create an instance of MyErrorHandler and pass it to the RestTemplate class:

// request url
String url = "https://reqres.in/api/unknown/23";

// create an instance of RestTemplate
RestTemplate restTemplate = new RestTemplate();

// set custom error handler
restTemplate.setErrorHandler(new MyErrorHandler());

// make an HTTP GET request
ResponseEntity<String> response = restTemplate.getForEntity(url, String.class);

Check out the Making HTTP Requests using RestTemplate in Spring Boot guide for more RestTemplate examples.

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