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

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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.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
+    }
+}