Helpful Routines

This project contains some useful helper classes which are handy in any projects.

Table of Contents

1. TryCatch
2. MdcThreadHelper

1. TryCatch

Imagine, you are processing a stream of values and a streaming operation threw a checked exception. You will be forced to enclose those operation calls in a try-catch block, only to re-throw as unchecked exception (RuntimeException). TryCatch.wrap() methods help in reducing this verbose code in an elegant way.

Before

List<String> fileData = files.stream()
    .map(f -> try { 
            return FileUtils.readFileToString(f, "UTF-8"); 
        } catch(IOException io) {
            throw new RuntimeException(io);
        }   
    )
    .collect(Collectors.toList())

After

List<String> fileData = files.stream()
    .map(TryCatch.wrap(f -> FileUtils.readFileToString(f, "UTF-8")))
    .collect(Collectors.toList())

Similarly, there are overloaded TryCatch.wrap() methods for Suppliers and Consumers as well. Check them out.

2. MdcThreadHelper

Suppose, you have a vanilla tracing mechanism where you use MDC of a logging framework to trace calls. Since, MDCs are associated with a calling thread, anytime, we spawn additional threads for processing, those additional threads will loose the tracing info. In such situations, we must transfer the tracing information from calling thread to other spawned threads. This helper class exactly does that.

Before

CompletableFuture<PersonData> personDataCall = CompletableFuture.supplyAsynch(() -> getPersonData(key));
CompletableFuture<PersonTaxData> personTaxDataCall = CompletableFuture.supplyAsynch(() -> getPersonTaxData(key));

CompletableFuture.allOf(personDataCall, personTaxDataCall).join();

After

CompletableFuture<PersonData> personDataCall = CompletableFuture.supplyAsynch(MdcThreadHelper.tracedSupplier(() -> getPersonData(key)));
CompletableFuture<PersonTaxData> personTaxDataCall = CompletableFuture.supplyAsynch(MdcThreadHelper.tracedSupplier(() -> getPersonTaxData(key)));

CompletableFuture.allOf(personDataCall, personTaxDataCall).join();

Similarly, MdcThreadHelper has methods for Callable and Runnable calls. Check them out.