RestTemplate ConnectException Unreachable

Question

I don't understand this... I'm trying to catch a java.net.ConnectException in case my downstream API is offline. However Eclipse warns me that it's unreachable - suggesting the code cannot throw a ConnectException. However, it clearly can.

@RequestMapping("/product/{id}")
public JsonNode getProduct(@PathVariable("id") int productID, HttpServletResponse oHTTPResponse)
{
    RestTemplate oRESTTemplate = new RestTemplate();
    ObjectMapper oObjMapper = new ObjectMapper();

    JsonNode oResponseRoot = oObjMapper.createObjectNode();

    try
    {
        ResponseEntity<String> oHTTPResponseEntity = oRESTTemplate.getForEntity("http://localhost:9000/product/"+productID, String.class);
    }
    catch (ConnectException e)
    {
        System.out.println("ConnectException caught. Downstream dependency is offline");
    }
    catch (Exception e)
    {
        System.out.println("Other Exception caught: " + e.getMessage());
    }
}

The exception caught is:

Other Exception caught: I/O error on GET request for "http://localhost:9000/product/9": Connection refused: connect; nested exception is java.net.ConnectException: Connection refused: connect

My downstream returns a 404 if the productID is not found and clearly a ConnectException if the downstream is offline. All I want to do is pass relevant status codes back to the browser.

How do I do that?

In your catch block with "Exception" check the type of exception, looks like the ConnectException is wrapped inside another exception... — mrkernelpanic, Nov 01 '17 at 10:45

score 5 · Answer 1 · answered Sep 11 '18 at 08:14

5

Catch ResourceAccessException. It hides ConnectException in RestTemplate.

answered Sep 11 '18 at 08:14

ByeBye

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score 0 · Answer 2 · answered May 16 '20 at 00:56

The internal method chain of RestTemplate class handles all IOException (which is a superclass of ConnectException) and throws a new ResourceAccessException, therefore, RestTemplate methods only can catch exceptions of type ResourceAccessException or its hierarchy tree.

RestTemplate ConnectException Unreachable

2 Answers2