Utility method for converting an exception into a string. - Java java.lang

Java examples for java.lang:Exception StackTrace

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Description

Utility method for converting an exception into a string.

Demo Code

/*/* w w  w . ja  va 2s . c om*/
 *
 *  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.
 *
 */
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Method;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;
import java.lang.reflect.InvocationTargetException;

public class Main{
    /**
     * List of no-arg methods that are known to return a wrapped throwable
     **/
    private static final String[] unwrapMethods = { "getRootCause",
            "getTargetException", "getTargetError", "getException",
            "getCausedByException", "getLinkedException" };
    /**
     * Utility method for converting an exception into a string. This
     * method unwinds all wrapped exceptions
     * @param t The throwable exception
     * @return The printable exception
     */
    public static String exceptionToString(Throwable t) {
        StringWriter sw = new StringWriter();
        PrintWriter out = new PrintWriter(sw);

        //print out the exception stack.
        printExceptionStack(t, out, 0);
        return sw.toString();
    }
    /**
     * Recursively prints out a stack of wrapped exceptions.
     */
    protected static void printExceptionStack(Throwable th,
            PrintWriter out, int depth) {
        //only print the stack depth if the depth is greater than 0
        boolean printStackDepth = depth > 0;

        Throwable wrappedException = ExceptionUtil.wrappedException(th);
        if (wrappedException != null) {
            printStackDepth = true;
            printExceptionStack(wrappedException, out, depth + 1);
        }

        if (printStackDepth) {
            out.write("[" + depth + "]");
        }

        th.printStackTrace(out);
    }
    /**
     * return the stack trace in a String
     */
    public static String toString(Throwable t) {
        StringWriter strWrt = new StringWriter();
        t.printStackTrace(new PrintWriter(strWrt));

        return strWrt.toString();
    }
    public static Throwable wrappedException(Throwable t) {
        // handle these statically since they are core to Java
        if (t instanceof InvocationTargetException) {
            return ((InvocationTargetException) t).getTargetException();
        }

        return getRootCauseWithReflection(t);
    }
    private static Throwable getRootCauseWithReflection(Throwable t) {
        for (int i = 0; i < unwrapMethods.length; i++) {
            Method m = null;

            try {
                m = t.getClass()
                        .getMethod(unwrapMethods[i], (Class[]) null);
                return (Throwable) m.invoke(t, (Object[]) null);
            } catch (Exception nsme) {
                // ignore
            }
        }

        return null;
    }
}

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