java/org/apache/tomcat/util/ExceptionUtils.java

/*
 * 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.tomcat.util;

import java.lang.reflect.InvocationTargetException;


/**
 * Utilities for handling Throwables and Exceptions.
 */
public class ExceptionUtils {

    /**
     * Checks whether the supplied Throwable is one that needs to be
     * rethrown and swallows all others.
     * @param t the Throwable to check
     */
    public static void handleThrowable(Throwable t) {
        if (t instanceof ThreadDeath) {
            throw (ThreadDeath) t;
        }
        if (t instanceof StackOverflowError) {
            // Swallow silently - it should be recoverable
            return;
        }
        if (t instanceof VirtualMachineError) {
            throw (VirtualMachineError) t;
        }
        // All other instances of Throwable will be silently swallowed
    }

    /**
     * Checks whether the supplied Throwable is an instance of
     * <code>InvocationTargetException</code> and returns the throwable that is
     * wrapped by it, if there is any.
     *
     * @param t the Throwable to check
     * @return <code>t</code> or <code>t.getCause()</code>
     */
    public static Throwable unwrapInvocationTargetException(Throwable t) {
        if (t instanceof InvocationTargetException && t.getCause() != null) {
            return t.getCause();
        }
        return t;
    }


    /**
     * NO-OP method provided to enable simple pre-loading of this class. Since
     * the class is used extensively in error handling, it is prudent to
     * pre-load it to avoid any failure to load this class masking the true
     * problem during error handling.
     */
    public static void preload() {
        // NO-OP
    }
}