FunctionalCheckedExceptionWrappers.java
/*
* *********************************************************************************************************************
*
* TheseFoolishThings: Miscellaneous utilities
* http://tidalwave.it/projects/thesefoolishthings
*
* Copyright (C) 2009 - 2021 by Tidalwave s.a.s. (http://tidalwave.it)
*
* *********************************************************************************************************************
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*
* *********************************************************************************************************************
*
* git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
* git clone https://github.com/tidalwave-it/thesefoolishthings-src
*
* *********************************************************************************************************************
*/
package it.tidalwave.util;
import javax.annotation.Nonnull;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.io.IOException;
import java.io.UncheckedIOException;
import lombok.NoArgsConstructor;
import static lombok.AccessLevel.PRIVATE;
/***********************************************************************************************************************
*
* A collections of utility methods for simplifying the syntax of lambda expressions with APIs that don't accept
* checked exceptions (such as {@link java.util.stream.Stream}): they provide wrapped functions that have no checked
* exception in the signature and whose implementation delegates to the original function wrapping an eventual checked
* exception into a {@link RuntimeException}. For instance, given the following method that could not be used as a
* {@link java.util.stream.Stream#filter(Predicate)} argument:
*
* <pre>
* private boolean matchEven (final int number)
* throws Exception
* {
* if (number == 13)
* {
* throw new Exception("13!");
* }
*
* return number % 2 == 0;
* }
* </pre>
*
* working code can be written as:
*
* <pre>
* try
* {
* List<Integer> numbers = IntStream.rangeClosed(1, 20)
* .mapToObj(Integer::valueOf)
* .filter(_p(this::matchEven)) // note the wrapper here
* .collect(Collectors.toList());
* ...
* }
* catch (RuntimeException e)
* {
* ...
* }
* </pre>
*
* Any checked exception is wrapped by a {@code RuntimeException}, but {@link IOException} is wrapped by a
* {@link UncheckedIOException}.
*
* @author Fabrizio Giudici
* @it.tidalwave.javadoc.draft
* @since 3.2-ALPHA-1
*
**********************************************************************************************************************/
@NoArgsConstructor(access = PRIVATE)
public final class FunctionalCheckedExceptionWrappers
{
/*******************************************************************************************************************
*
* A variant of {@link Function} that might throw an {@link Exception}. This interface must not be directly used,
* it's defined to let the compiler infer functional equivalence.
*
* @param <T> the type of the function argument
* @param <R> the type of the function return value
* @hidden
*
******************************************************************************************************************/
@FunctionalInterface
public static interface FunctionWithException<T, R>
{
public R apply (T t)
throws Exception;
}
/*******************************************************************************************************************
*
* A variant of {@link Consumer} that might throw an {@link Exception}. This interface must not be directly used,
* it's defined to let the compiler infer functional equivalence.
*
* @param <T> the type of the {@code Consumer} argument
* @hidden
*
******************************************************************************************************************/
@FunctionalInterface
public static interface ConsumerWithException<T>
{
public void accept (T t)
throws Exception;
}
/*******************************************************************************************************************
*
* A variant of {@link Supplier} that might throw an {@link Exception}. This interface must not be directly used,
* it's defined to let the compiler infer functional equivalence.
*
* @param <T> the type of the {@code Supplier} argument
* @hidden
*
******************************************************************************************************************/
@FunctionalInterface
public static interface SupplierWithException<T>
{
public T get ()
throws Exception;
}
/*******************************************************************************************************************
*
* A variant of {@link Predicate} that might throw an {@link Exception}. This interface must not be directly used,
* it's defined to let the compiler infer functional equivalence.
*
* @param <T> the type of the {@code Predicate} argument
* @hidden
*
******************************************************************************************************************/
@FunctionalInterface
public static interface PredicateWithException<T>
{
public boolean test (T t)
throws Exception;
}
/*******************************************************************************************************************
*
* A variant of {@link Runnable} that might throw an {@link Exception}. This interface must not be directly used,
* it's defined to let the compiler infer functional equivalence.
*
* @hidden
*
******************************************************************************************************************/
@FunctionalInterface
public static interface RunnableWithException
{
public void run()
throws Exception;
}
/*******************************************************************************************************************
*
* A wrapper for a {@link Function} that catches exceptions and wraps them into {@link RuntimeException}s.
*
* @param function the {@code Function} to wrap.
* @param <T> the type of the function argument
* @param <R> the type of the function return value
* @return the wrapped {@code Function}
*
******************************************************************************************************************/
@Nonnull
public static <T, R> Function<T, R> _f (@Nonnull final FunctionWithException<T, R> function)
{
return t ->
{
try
{
return function.apply(t);
}
catch (Exception e)
{
throw wrappedException(e);
}
};
}
/*******************************************************************************************************************
*
* A wrapper for a {@link Consumer} that catches exceptions and wraps them into {@link RuntimeException}s.
*
* @param consumer the {@code Consumer} to wrap.
* @param <T> the type of the {@code Consumer} argument
* @return the wrapped {@code Consumer}
*
******************************************************************************************************************/
@Nonnull
public static <T> Consumer<T> _c (@Nonnull final ConsumerWithException<T> consumer)
{
return t ->
{
try
{
consumer.accept(t);
}
catch (Exception e)
{
throw wrappedException(e);
}
};
}
/*******************************************************************************************************************
*
* A wrapper for a {@link Supplier} that catches exceptions and wraps them into {@link RuntimeException}s.
*
* @param supplier the {@code Supplier} to wrap.
* @param <T> the type of the {@code Supplier} argument
* @return the wrapped {@code Supplier}
*
******************************************************************************************************************/
@Nonnull
public static <T> Supplier<T> _s (@Nonnull final SupplierWithException<T> supplier)
{
return () ->
{
try
{
return supplier.get();
}
catch (Exception e)
{
throw wrappedException(e);
}
};
}
/*******************************************************************************************************************
*
* A wrapper for a {@link Predicate} that catches exceptions and wraps them into {@link RuntimeException}s.
*
* @param predicate the {@code Predicate} to wrap.
* @param <T> the type of the {@code Predicate} argument
* @return the wrapped {@code Predicate}
*
******************************************************************************************************************/
@Nonnull
public static <T> Predicate<T> _p (@Nonnull final PredicateWithException<T> predicate)
{
return t ->
{
try
{
return predicate.test(t);
}
catch (Exception e)
{
throw wrappedException(e);
}
};
}
/*******************************************************************************************************************
*
* A wrapper for an equivalent of {@link Runnable} that catches exceptions and wraps them into
* {@link RuntimeException}s.
*
* @param runnable the {@code Runnable} to wrap.
* @return the wrapped {@code Predicate}
* @since 3.2-ALPHA-12
*
******************************************************************************************************************/
@Nonnull
public static Runnable _r (@Nonnull final RunnableWithException runnable)
{
return () ->
{
try
{
runnable.run();
}
catch (Exception e)
{
throw wrappedException(e);
}
};
}
/*******************************************************************************************************************
*
* Wraps a throwable with a {@link RuntimeException}. Unchecked exceptions are not wrapped; {@link IOException}
* is wrapped with {@link UncheckedIOException}.
*
* @param e the exception to wrap
* @return the wrapped exception
*
******************************************************************************************************************/
@Nonnull
public static RuntimeException wrappedException (@Nonnull final Throwable e)
{
if (e instanceof RuntimeException)
{
return (RuntimeException)e;
}
if (e instanceof IOException)
{
return new UncheckedIOException((IOException)e);
}
return new RuntimeException(e);
}
}