Property file based builder pattern in java

Question

I have a property file which has the details of Elasticsearch hostname, port number, and the scheme.

The Elasticsearch RestCleint API provides constructors to instantiate a client object with the hostname and also with hostname, port number and scheme.

There are cases when an application is deployed to AWS it has only a URL which can be used as the hostname. The same application, when deployed in the different environment, will have all 3 properties.

Therefore, I have created a class which does some if else and tried to instantiate the RestClient basing on the availability. The code looks very ugly. I want to use a Builder kind of Pattern which handles this elegantly. But, I am unable to get an idea to implement it. I would like to request a help.

This is how my current implementation looks like.

public class ElasticSearchContext
{
private RestClient restClient;

public RestClient getContext() throws Exception
{
  if (PropertyFileReader.getInstance().containsKey("elasticsearchHostName") && 
      PropertyFileReader.getInstance().containsKey("elasticsearchPortNumber") && 
      PropertyFileReader.getInstance().containsKey("elasticsearchScheme"))
    {

      restClient = RestClient.builder(new HttpHost(PropertyFileReader.getInstance().getProperty("elasticsearchHostName"),
                                                   Integer.parseInt(PropertyFileReader.getInstance().getProperty("elasticsearchPortNumber")),
                                                   PropertyFileReader.getInstance().getProperty("elasticsearchScheme"))).build();

    }
  else if (PropertyFileReader.getInstance().containsKey("elasticsearchHostName") && 
           !PropertyFileReader.getInstance().containsKey("elasticsearchPortNumber") || 
           PropertyFileReader.getInstance().containsKey("elasticsearchScheme"))
    {
      restClient = RestClient.builder(new HttpHost(PropertyFileReader.getInstance().getProperty("elasticsearchHostName"))).build();
    }
  else
    {
      throw new Exception("Hostname is mandatory");
    }

  return restClient;

    }
}

This is how my properties look like.

elasticsearchHostName=localhost
elasticsearchPortNumber=9200
elasticsearchScheme=http

Answer 1

I found the answer to this. This is a typical scenario of a Runtime Exception. For example, we are running a command in Linux say ls -l|grep "pattern" . In this case, Linux will not throw an exception. It just shows up the usage guide. Similarly, the user does not know until he executes the code. If I throw an exception it can neither be handled by the code or by in any other way. Rather than throwing an exception, we should help the user showing usage guide or some information which helps him understand why the code crashed.