org.sqlite.date.ExceptionUtils Maven / Gradle / Ivy
/*
* 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.sqlite.date;
/**
* Provides utilities for manipulating and examining Throwable objects.
*
* @since 1.0
*/
public class ExceptionUtils {
/**
* Throw a checked exception without adding the exception to the throws clause of the calling
* method. This method prevents throws clause pollution and reduces the clutter of "Caused by"
* exceptions in the stacktrace.
*
* The use of this technique may be controversial, but exceedingly useful to library
* developers.
* public int propagateExample { // note that there is no throws clause
* try {
* return invocation(); // throws IOException
* } catch (Exception e) {
* return ExceptionUtils.rethrow(e); // propagates a checked exception
* }
* }
*
*
*
This is an alternative to the more conservative approach of wrapping the checked exception
* in a RuntimeException:
* public int wrapExample { // note that there is no throws clause
* try {
* return invocation(); // throws IOException
* } catch (Error e) {
* throw e;
* } catch (RuntimeException e) {
* throw e; // wraps a checked exception
* } catch (Exception e) {
* throw new UndeclaredThrowableException(e); // wraps a checked exception
* }
* }
*
*
*
One downside to using this approach is that the java compiler will not allow invoking code
* to specify a checked exception in a catch clause unless there is some code path within the
* try block that has invoked a method declared with that checked exception. If the invoking
* site wishes to catch the shaded checked exception, it must either invoke the shaded code
* through a method re-declaring the desired checked exception, or catch Exception and use the
* instanceof operator. Either of these techniques are required when interacting with non-java
* jvm code such as Jython, Scala, or Groovy, since these languages do not consider any
* exceptions as checked.
*
* @since 3.5
* @see {{@link #wrapAndThrow(Throwable)}
* @param throwable The throwable to rethrow.
* @return R Never actually returns, this generic type matches any type which the calling site
* requires. "Returning" the results of this method, as done in the propagateExample above,
* will satisfy the java compiler requirement that all code paths return a value.
* @throws throwable
*/
public static R rethrow(Throwable throwable) {
// claim that the typeErasure invocation throws a RuntimeException
return ExceptionUtils.typeErasure(throwable);
}
/**
* Claim a Throwable is another Exception type using type erasure. This hides a checked
* exception from the java compiler, allowing a checked exception to be thrown without having
* the exception in the method's throw clause.
*/
@SuppressWarnings("unchecked")
private static R typeErasure(Throwable throwable) throws T {
throw (T) throwable;
}
}