org.springframework.util.function.ThrowingFunction Maven / Gradle / Ivy

/*
 * Copyright 2002-2022 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.util.function;

import java.util.function.BiFunction;
import java.util.function.Function;

/**
 * A {@link Function} that allows invocation of code that throws a checked
 * exception.
 *
 * @author Stephane Nicoll
 * @author Phillip Webb
 * @since 6.0
 * @param  the type of the input to the function
 * @param  the type of the result of the function
 */
@FunctionalInterface
public interface ThrowingFunction extends Function {

	/**
	 * Applies this function to the given argument, possibly throwing a checked
	 * exception.
	 * @param t the function argument
	 * @return the function result
	 * @throws Exception on error
	 */
	R applyWithException(T t) throws Exception;

	/**
	 * Default {@link Function#apply(Object)} that wraps any thrown checked
	 * exceptions (by default in a {@link RuntimeException}).
	 * @see java.util.function.Function#apply(java.lang.Object)
	 */
	@Override
	default R apply(T t) {
		return apply(t, RuntimeException::new);
	}

	/**
	 * Applies this function to the given argument, wrapping any thrown checked
	 * exceptions using the given {@code exceptionWrapper}.
	 * @param exceptionWrapper {@link BiFunction} that wraps the given message
	 * and checked exception into a runtime exception
	 * @return a result
	 */
	default R apply(T t, BiFunction exceptionWrapper) {
		try {
			return applyWithException(t);
		}
		catch (RuntimeException ex) {
			throw ex;
		}
		catch (Exception ex) {
			throw exceptionWrapper.apply(ex.getMessage(), ex);
		}
	}

	/**
	 * Return a new {@link ThrowingFunction} where the {@link #apply(Object)}
	 * method wraps any thrown checked exceptions using the given
	 * {@code exceptionWrapper}.
	 * @param exceptionWrapper {@link BiFunction} that wraps the given message
	 * and checked exception into a runtime exception
	 * @return the replacement {@link ThrowingFunction} instance
	 */
	default ThrowingFunction throwing(BiFunction exceptionWrapper) {
		return new ThrowingFunction<>() {

			@Override
			public R applyWithException(T t) throws Exception {
				return ThrowingFunction.this.applyWithException(t);
			}

			@Override
			public R apply(T t) {
				return apply(t, exceptionWrapper);
			}

		};
	}

	/**
	 * Lambda friendly convenience method that can be used to create a
	 * {@link ThrowingFunction} where the {@link #apply(Object)} method wraps
	 * any checked exception thrown by the supplied lambda expression or method
	 * reference.
	 * This method can be especially useful when working with method references.
	 * It allows you to easily convert a method that throws a checked exception
	 * into an instance compatible with a regular {@link Function}.
	 * 
For example:
	 * 
	 * stream.map(ThrowingFunction.of(Example::methodThatCanThrowCheckedException));
	 * 
	 * @param  the type of the input to the function
	 * @param  the type of the result of the function
	 * @param function the source function
	 * @return a new {@link ThrowingFunction} instance
	 */
	static  ThrowingFunction of(ThrowingFunction function) {
		return function;
	}

	/**
	 * Lambda friendly convenience method that can be used to create a
	 * {@link ThrowingFunction} where the {@link #apply(Object)} method wraps
	 * any thrown checked exceptions using the given {@code exceptionWrapper}.
	 * This method can be especially useful when working with method references.
	 * It allows you to easily convert a method that throws a checked exception
	 * into an instance compatible with a regular {@link Function}.
	 * 
For example:
	 * 
	 * stream.map(ThrowingFunction.of(Example::methodThatCanThrowCheckedException, IllegalStateException::new));
	 * 
	 * @param  the type of the input to the function
	 * @param  the type of the result of the function
	 * @param function the source function
	 * @param exceptionWrapper the exception wrapper to use
	 * @return a new {@link ThrowingFunction} instance
	 */
	static  ThrowingFunction of(ThrowingFunction function,
			BiFunction exceptionWrapper) {

		return function.throwing(exceptionWrapper);
	}

}