Module dk.cloudcreate.essentials.shared

Package dk.cloudcreate.essentials.shared.functional

Interface CheckedSupplier<R>

Type Parameters:

R - the return type

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface CheckedSupplier<R>

Variant of Supplier that behaves like Supplier, but which allows checked Exception's to be thrown from its get() method

See Also:

• safe(CheckedSupplier)
• safe(String, CheckedSupplier)

Method Summary

Modifier and Type	Method	Description
R	get()	This method performs the operation that may fail with a Checked Exception
static <R> Supplier<R>	safe(CheckedSupplier<R> supplierThatCanFailedWithACheckedException)	Wraps a CheckedSupplier (basically a lambda with no arguments that returns a result and which throws a Checked Exception) by returning a new Supplier instance The returned Supplier.get() method delegates directly to the get() and catches any thrown checked Exception's and rethrows them as a CheckedExceptionRethrownException Unless you provide a context-message (using safe(String, CheckedSupplier) then any caught checked Exception's message also becomes the CheckedExceptionRethrownException's message. Any RuntimeException's thrown aren't caught and the calling code will receive the original RuntimeException thrown. Usage example: Let's say we have a method called someOperation that cannot change, but which accepts a Supplier with the purpose of the calling the Supplier.get().
static <R> Supplier<R>	safe(String contextMessage, CheckedSupplier<R> supplierThatCanFailedWithACheckedException)	Wraps a CheckedSupplier (basically a lambda with no arguments that returns a result and which throws a Checked Exception) by returning a new Supplier instance The returned Supplier.get() method delegates directly to the get() and catches any thrown checked Exception's and rethrows them as a CheckedExceptionRethrownException Any RuntimeException's thrown aren't caught and the calling code will receive the original RuntimeException thrown. Usage example: Let's say we have a method called someOperation that cannot change, but which accepts a Supplier with the purpose of the calling the Supplier.get().

Method Details

safe

static <R> Supplier<R> safe(CheckedSupplier<R> supplierThatCanFailedWithACheckedException)

Wraps a CheckedSupplier (basically a lambda with no arguments that returns a result and which throws a Checked Exception) by returning a new Supplier instance
The returned Supplier.get() method delegates directly to the get() and catches any thrown checked Exception's and rethrows them as a CheckedExceptionRethrownException
Unless you provide a context-message (using safe(String, CheckedSupplier) then any caught checked Exception's message also becomes the CheckedExceptionRethrownException's message.
Any RuntimeException's thrown aren't caught and the calling code will receive the original RuntimeException thrown.

Usage example:
Let's say we have a method called someOperation that cannot change, but which accepts a Supplier with the purpose of the calling the Supplier.get().

 public void someOperation(Supplier<String> operation) {
      // ... Logic ...

      String value = operation.get();

      // ... More logic ---
 }
 

The problem will Supplier.get() occurs when Supplier calls any API that throws a checked Exception, e.g. the File API.
Since Supplier.get() doesn't define that it throws any Exception's we're forced to add a try/catch to handle the IOException for the code to compile:

  someOperation(() -> {
                      try {
                          // Logic that uses the File API
                          return "some-value";
                      } catch (IOException e) {
                          throw new RuntimeException(e);
                      }
                }));
 

This is where the CheckedSupplier comes to the aid as its get() methods defines that it throws a Checked Exception and its safe(CheckedSupplier) will return a new Supplier instance with a Supplier.get() method that ensures that the get() method is called and any checked Exception's thrown will be caught and rethrown as a CheckedExceptionRethrownException:

  someOperation(CheckedSupplier.safe(() -> {
                      // Logic that uses the File API that throws IOException
                      return "some-value";
                }));
 
 

Type Parameters:

R - the return type

Parameters:

supplierThatCanFailedWithACheckedException - the CheckedSupplier instance that will be wrapped as a Supplier

Returns:

a Supplier with a Supplier.get() method that ensures that the get() method is called when Supplier.get() and any checked Exception's thrown will be caught and rethrown as a CheckedExceptionRethrownException.
Any RuntimeException's thrown aren't caught and the calling code will receive the original RuntimeException thrown.

Throws:

CheckedExceptionRethrownException - in case the get() method throws a checked Exception

safe

static <R> Supplier<R> safe(String contextMessage,
 CheckedSupplier<R> supplierThatCanFailedWithACheckedException)

Wraps a CheckedSupplier (basically a lambda with no arguments that returns a result and which throws a Checked Exception) by returning a new Supplier instance
The returned Supplier.get() method delegates directly to the get() and catches any thrown checked Exception's and rethrows them as a CheckedExceptionRethrownException
Any RuntimeException's thrown aren't caught and the calling code will receive the original RuntimeException thrown.

Usage example:
Let's say we have a method called someOperation that cannot change, but which accepts a Supplier with the purpose of the calling the Supplier.get().

 public void someOperation(Supplier<String> operation) {
      // ... Logic ...

      String value = operation.get();

      // ... More logic ---
 }
 

The problem will Supplier.get() occurs when Supplier calls any API that throws a checked Exception, e.g. the File API.
Since Supplier.get() doesn't define that it throws any Exception's we're forced to add a try/catch to handle the IOException for the code to compile:

  someOperation(() -> {
                      try {
                          // Logic that uses the File API
                          return "some-value";
                      } catch (IOException e) {
                          throw new RuntimeException(e);
                      }
                }));
 

This is where the CheckedSupplier comes to the aid as its get() methods defines that it throws a Checked Exception and its safe(CheckedSupplier) will return a new Supplier instance with a Supplier.get() method that ensures that the get() method is called and any checked Exception's thrown will be caught and rethrown as a CheckedExceptionRethrownException:

  someOperation(CheckedSupplier.safe(msg("Processing file {}", fileName),
                () -> {
                      // Logic that uses the File API that throws IOException
                      return "some-value";
                }));
 
 

Type Parameters:

R - the return type

Parameters:

contextMessage - a string that the described the content for the CheckedSupplier and which will be used as message in any CheckedExceptionRethrownException thrown

supplierThatCanFailedWithACheckedException - the CheckedSupplier instance that will be wrapped as a Supplier

Returns:

a Supplier with a Supplier.get() method that ensures that the get() method is called when Supplier.get() and any checked Exception's thrown will be caught and rethrown as a CheckedExceptionRethrownException.
Any RuntimeException's thrown aren't caught and the calling code will receive the original RuntimeException thrown.

Throws:

CheckedExceptionRethrownException - in case the get() method throws a checked Exception

get

R get()
throws Exception

This method performs the operation that may fail with a Checked Exception

Returns:

the result of performing the operation

Throws:

Exception - this method can throw both checked Exception's as well as RuntimeException's