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With inspiration from other libraries
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package org.apache.commons.lang3;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.lang.reflect.UndeclaredThrowableException;
/** This class provides utility functions, and classes for working with the
* {@code java.util.function} package, or more generally, with Java 8
* lambdas.
* More specifically, it attempts to address the fact that lambdas are supposed
* not to throw Exceptions, at least not checked Exceptions, aka instances of
* {@link Exception}. This enforces the use of constructs like
*
* Consumer<java.lang.reflect.Method> consumer = (m) -> {
* try {
* m.invoke(o, args);
* } catch (Throwable t) {
* throw Functions.rethrow(t);
* }
* };
*
* By replacing a {@link java.util.function.Consumer Consumer<O>} with a
* {@link FailableConsumer FailableConsumer<O,? extends Throwable>}, this can be
* written like follows:
*
* Functions.accept((m) -> m.invoke(o,args));
*
* Obviously, the second version is much more concise and the spirit of
* Lambda expressions is met better than the second version.
*/
public class Functions {
@FunctionalInterface
public interface FailableRunnable {
/**
* Runs the function.
* @throws T if the function fails
*/
void run() throws T;
}
@FunctionalInterface
public interface FailableCallable {
/**
* Calls the callable.
* @return The value returned from the callable
* @throws T if the callable fails
*/
O call() throws T;
}
@FunctionalInterface
public interface FailableConsumer {
/**
* Accepts the consumer.
* @param pObject the parameter for the consumable to accept
* @throws T if the consumer fails
*/
void accept(O pObject) throws T;
}
@FunctionalInterface
public interface FailableBiConsumer {
/**
* Accepts the consumer.
* @param pObject1 the first parameter for the consumable to accept
* @param pObject2 the second parameter for the consumable to accept
* @throws T if the consumer fails
*/
void accept(O1 pObject1, O2 pObject2) throws T;
}
@FunctionalInterface
public interface FailableFunction {
/**
* Apply the function.
* @param pInput the input for the function
* @return the result of the function
* @throws T if the function fails
*/
O apply(I pInput) throws T;
}
@FunctionalInterface
public interface FailableBiFunction {
/**
* Apply the function.
* @param pInput1 the first input for the function
* @param pInput2 the second input for the function
* @return the result of the function
* @throws T if the function fails
*/
O apply(I1 pInput1, I2 pInput2) throws T;
}
@FunctionalInterface
public interface FailablePredicate {
/**
* Test the predicate.
* @param pObject the object to test the predicate on
* @return the predicate's evaluation
* @throws T if the predicate fails
*/
boolean test(O pObject) throws T;
}
@FunctionalInterface
public interface FailableBiPredicate {
/**
* Test the predicate.
* @param pObject1 the first object to test the predicate on
* @param pObject2 the second object to test the predicate on
* @return the predicate's evaluation
* @throws T if the predicate fails
*/
boolean test(O1 pObject1, O2 pObject2) throws T;
}
/**
* Runs a runnable and rethrows any exception as a {@link RuntimeException}.
* @param pRunnable The runnable to run
* @param the type of checked exception the runnable may throw
*/
public static void run(FailableRunnable pRunnable) {
try {
pRunnable.run();
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* Calls a callable and rethrows any exception as a {@link RuntimeException}.
* @param pCallable the callable to call
* @param the return type of the callable
* @param the type of checked exception the callable may throw
* @return the value returned from the callable
*/
public static O call(FailableCallable pCallable) {
try {
return pCallable.call();
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* Consumes a consumer and rethrows any exception as a {@link RuntimeException}.
* @param pConsumer the consumer to consume
* @param pObject the object to consume by pConsumer
* @param the type the consumer accepts
* @param the type of checked exception the consumer may throw
*/
public static void accept(FailableConsumer pConsumer, O pObject) {
try {
pConsumer.accept(pObject);
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* Consumes a consumer and rethrows any exception as a {@link RuntimeException}.
* @param pConsumer the consumer to consume
* @param pObject1 the first object to consume by pConsumer
* @param pObject2 the second object to consume by pConsumer
* @param the type of the first argument the consumer accepts
* @param the type of the second argument the consumer accepts
* @param the type of checked exception the consumer may throw
*/
public static void accept(FailableBiConsumer pConsumer, O1 pObject1, O2 pObject2) {
try {
pConsumer.accept(pObject1, pObject2);
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* Applies a function and rethrows any exception as a {@link RuntimeException}.
* @param pFunction the function to apply
* @param pInput the input to apply pFunction on
* @param the type of the argument the function accepts
* @param the return type of the function
* @param the type of checked exception the function may throw
* @return the value returned from the function
*/
public static O apply(FailableFunction pFunction, I pInput) {
try {
return pFunction.apply(pInput);
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* Applies a function and rethrows any exception as a {@link RuntimeException}.
* @param pFunction the function to apply
* @param pInput1 the first input to apply pFunction on
* @param pInput2 the second input to apply pFunction on
* @param the type of the first argument the function accepts
* @param the type of the second argument the function accepts
* @param the return type of the function
* @param the type of checked exception the function may throw
* @return the value returned from the function
*/
public static O apply(FailableBiFunction pFunction, I1 pInput1, I2 pInput2) {
try {
return pFunction.apply(pInput1, pInput2);
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* Tests a predicate and rethrows any exception as a {@link RuntimeException}.
* @param pPredicate the predicate to test
* @param pObject the input to test by pPredicate
* @param the type of argument the predicate tests
* @param the type of checked exception the predicate may throw
* @return the boolean value returned by the predicate
*/
public static boolean test(FailablePredicate pPredicate, O pObject) {
try {
return pPredicate.test(pObject);
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* Tests a predicate and rethrows any exception as a {@link RuntimeException}.
* @param pPredicate the predicate to test
* @param pObject1 the first input to test by pPredicate
* @param pObject2 the second input to test by pPredicate
* @param the type of the first argument the predicate tests
* @param the type of the second argument the predicate tests
* @param the type of checked exception the predicate may throw
* @return the boolean value returned by the predicate
*/
public static boolean test(FailableBiPredicate pPredicate, O1 pObject1, O2 pObject2) {
try {
return pPredicate.test(pObject1, pObject2);
} catch (Throwable t) {
throw rethrow(t);
}
}
/**
* A simple try-with-resources implementation, that can be used, if your
* objects do not implement the {@link AutoCloseable} interface. The method
* executes the {@code pAction}. The method guarantees, that all
* the {@code pResources} are being executed, in the given order, afterwards,
* and regardless of success, or failure. If either the original action, or
* any of the resource action fails, then the first failure (aka
* {@link Throwable} is rethrown. Example use:
*
* final FileInputStream fis = new FileInputStream("my.file");
* Functions.tryWithResources(useInputStream(fis), null, () -> fis.close());
*
* @param pAction The action to execute. This object will always
* be invoked.
* @param pErrorHandler An optional error handler, which will be invoked finally,
* if any error occurred. The error handler will receive the first
* error, aka {@link Throwable}.
* @param pResources The resource actions to execute. All resource
* actions will be invoked, in the given order. A resource action is an
* instance of {@link FailableRunnable}, which will be executed.
* @see #tryWithResources(FailableRunnable, FailableRunnable...)
*/
@SafeVarargs
public static void tryWithResources(FailableRunnable pAction,
FailableConsumer pErrorHandler,
FailableRunnable... pResources) {
final FailableConsumer errorHandler;
if (pErrorHandler == null) {
errorHandler = (t) -> rethrow(t);
} else {
errorHandler = pErrorHandler;
}
if (pResources != null) {
for (FailableRunnable runnable : pResources) {
if (runnable == null) {
throw new NullPointerException("A resource action must not be null.");
}
}
}
Throwable th = null;
try {
pAction.run();
} catch (Throwable t) {
th = t;
}
if (pResources != null) {
for (FailableRunnable runnable : pResources) {
try {
runnable.run();
} catch (Throwable t) {
if (th == null) {
th = t;
}
}
}
}
if (th != null) {
try {
errorHandler.accept(th);
} catch (Throwable t) {
throw rethrow(t);
}
}
}
/**
* A simple try-with-resources implementation, that can be used, if your
* objects do not implement the {@link AutoCloseable} interface. The method
* executes the {@code pAction}. The method guarantees, that all
* the {@code pResources} are being executed, in the given order, afterwards,
* and regardless of success, or failure. If either the original action, or
* any of the resource action fails, then the first failure (aka
* {@link Throwable} is rethrown. Example use:
*
* final FileInputStream fis = new FileInputStream("my.file");
* Functions.tryWithResources(useInputStream(fis), () -> fis.close());
*
* @param pAction The action to execute. This object will always
* be invoked.
* @param pResources The resource actions to execute. All resource
* actions will be invoked, in the given order. A resource action is an
* instance of {@link FailableRunnable}, which will be executed.
* @see #tryWithResources(FailableRunnable, FailableConsumer, FailableRunnable...)
*/
@SafeVarargs
public static void tryWithResources(FailableRunnable pAction,
FailableRunnable... pResources) {
tryWithResources(pAction, null, pResources);
}
/**
* Rethrow a {@link Throwable} as an unchecked exception.
* @param pThrowable The throwable to rethrow
* @return Never returns anything, this method never terminates normally
*/
public static RuntimeException rethrow(Throwable pThrowable) {
if (pThrowable == null) {
throw new NullPointerException("The Throwable must not be null.");
} else {
if (pThrowable instanceof RuntimeException) {
throw (RuntimeException) pThrowable;
} else if (pThrowable instanceof Error) {
throw (Error) pThrowable;
} else if (pThrowable instanceof IOException) {
throw new UncheckedIOException((IOException) pThrowable);
} else {
throw new UndeclaredThrowableException(pThrowable);
}
}
}
}