org.apache.commons.lang.exception.NestableDelegate Maven / Gradle / Ivy
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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.commons.lang.exception;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.Serializable;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
/**
* A shared implementation of the nestable exception functionality.
*
* The code is shared between
* {@link org.apache.commons.lang.exception.NestableError NestableError},
* {@link org.apache.commons.lang.exception.NestableException NestableException} and
* {@link org.apache.commons.lang.exception.NestableRuntimeException NestableRuntimeException}.
*
*
* @author Apache Software Foundation
* @author Rafal Krzewski
* @author Daniel L. Rall
* @author Kasper Nielsen
* @author Steven Caswell
* @author Sean C. Sullivan
* @since 1.0
* @version $Id: NestableDelegate.java 905636 2010-02-02 14:03:32Z niallp $
*/
public class NestableDelegate implements Serializable {
/**
* Required for serialization support.
*
* @see java.io.Serializable
*/
private static final long serialVersionUID = 1L;
/**
* Constructor error message.
*/
private transient static final String MUST_BE_THROWABLE =
"The Nestable implementation passed to the NestableDelegate(Nestable) "
+ "constructor must extend java.lang.Throwable";
/**
* Holds the reference to the exception or error that we're
* wrapping (which must be a {@link
* org.apache.commons.lang.exception.Nestable} implementation).
*/
private Throwable nestable = null;
/**
* Whether to print the stack trace top-down.
* This public flag may be set by calling code, typically in initialisation.
* This exists for backwards compatability, setting it to false will return
* the library to v1.0 behaviour (but will affect all users of the library
* in the classloader).
* @since 2.0
*/
public static boolean topDown = true;
/**
* Whether to trim the repeated stack trace.
* This public flag may be set by calling code, typically in initialisation.
* This exists for backwards compatability, setting it to false will return
* the library to v1.0 behaviour (but will affect all users of the library
* in the classloader).
* @since 2.0
*/
public static boolean trimStackFrames = true;
/**
* Whether to match subclasses via indexOf.
* This public flag may be set by calling code, typically in initialisation.
* This exists for backwards compatability, setting it to false will return
* the library to v2.0 behaviour (but will affect all users of the library
* in the classloader).
* @since 2.1
*/
public static boolean matchSubclasses = true;
/**
* Constructs a new NestableDelegate instance to manage the
* specified Nestable.
*
* @param nestable the Nestable implementation (must extend
* {@link java.lang.Throwable})
* @since 2.0
*/
public NestableDelegate(Nestable nestable) {
if (nestable instanceof Throwable) {
this.nestable = (Throwable) nestable;
} else {
throw new IllegalArgumentException(MUST_BE_THROWABLE);
}
}
/**
* Returns the error message of the Throwable in the chain of Throwables at the
* specified index, numbered from 0.
*
* @param index
* the index of the Throwable in the chain of Throwables
* @return the error message, or null if the Throwable at the specified index in the chain does not
* contain a message
* @throws IndexOutOfBoundsException
* if the index argument is negative or not less than the count of Throwables
* in the chain
* @since 2.0
*/
public String getMessage(int index) {
Throwable t = this.getThrowable(index);
if (Nestable.class.isInstance(t)) {
return ((Nestable) t).getMessage(0);
}
return t.getMessage();
}
/**
* Returns the full message contained by the Nestable and any nested Throwables.
*
* @param baseMsg
* the base message to use when creating the full message. Should be generally be called via
* nestableHelper.getMessage(super.getMessage()), where super is an
* instance of {@link java.lang.Throwable}.
* @return The concatenated message for this and all nested Throwables
* @since 2.0
*/
public String getMessage(String baseMsg) {
Throwable nestedCause = ExceptionUtils.getCause(this.nestable);
String causeMsg = nestedCause == null ? null : nestedCause.getMessage();
if (nestedCause == null || causeMsg == null) {
return baseMsg; // may be null, which is a valid result
}
if (baseMsg == null) {
return causeMsg;
}
return baseMsg + ": " + causeMsg;
}
/**
* Returns the error message of this and any nested Throwables in an array of Strings, one element
* for each message. Any Throwable not containing a message is represented in the array by a null.
* This has the effect of cause the length of the returned array to be equal to the result of the
* {@link #getThrowableCount()} operation.
*
* @return the error messages
* @since 2.0
*/
public String[] getMessages() {
Throwable[] throwables = this.getThrowables();
String[] msgs = new String[throwables.length];
for (int i = 0; i < throwables.length; i++) {
msgs[i] =
(Nestable.class.isInstance(throwables[i])
? ((Nestable) throwables[i]).getMessage(0)
: throwables[i].getMessage());
}
return msgs;
}
/**
* Returns the Throwable in the chain of
* Throwables at the specified index, numbered from 0.
*
* @param index the index, numbered from 0, of the Throwable in
* the chain of Throwables
* @return the Throwable
* @throws IndexOutOfBoundsException if the index argument is
* negative or not less than the count of Throwables in the
* chain
* @since 2.0
*/
public Throwable getThrowable(int index) {
if (index == 0) {
return this.nestable;
}
Throwable[] throwables = this.getThrowables();
return throwables[index];
}
/**
* Returns the number of Throwables contained in the
* Nestable contained by this delegate.
*
* @return the throwable count
* @since 2.0
*/
public int getThrowableCount() {
return ExceptionUtils.getThrowableCount(this.nestable);
}
/**
* Returns this delegate's Nestable and any nested
* Throwables in an array of Throwables, one
* element for each Throwable.
*
* @return the Throwables
* @since 2.0
*/
public Throwable[] getThrowables() {
return ExceptionUtils.getThrowables(this.nestable);
}
/**
* Returns the index, numbered from 0, of the first Throwable
* that matches the specified type, or a subclass, in the chain of Throwables
* with an index greater than or equal to the specified index.
* The method returns -1 if the specified type is not found in the chain.
*
* NOTE: From v2.1, we have clarified the Nestable interface
* such that this method matches subclasses.
* If you want to NOT match subclasses, please use
* {@link ExceptionUtils#indexOfThrowable(Throwable, Class, int)}
* (which is avaiable in all versions of lang).
* An alternative is to use the public static flag {@link #matchSubclasses}
* on NestableDelegate, however this is not recommended.
*
* @param type the type to find, subclasses match, null returns -1
* @param fromIndex the index, numbered from 0, of the starting position in
* the chain to be searched
* @return index of the first occurrence of the type in the chain, or -1 if
* the type is not found
* @throws IndexOutOfBoundsException if the fromIndex argument
* is negative or not less than the count of Throwables in the
* chain
* @since 2.0
*/
public int indexOfThrowable(Class type, int fromIndex) {
if (type == null) {
return -1;
}
if (fromIndex < 0) {
throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex);
}
Throwable[] throwables = ExceptionUtils.getThrowables(this.nestable);
if (fromIndex >= throwables.length) {
throw new IndexOutOfBoundsException("The start index was out of bounds: "
+ fromIndex + " >= " + throwables.length);
}
if (matchSubclasses) {
for (int i = fromIndex; i < throwables.length; i++) {
if (type.isAssignableFrom(throwables[i].getClass())) {
return i;
}
}
} else {
for (int i = fromIndex; i < throwables.length; i++) {
if (type.equals(throwables[i].getClass())) {
return i;
}
}
}
return -1;
}
/**
* Prints the stack trace of this exception the the standar error
* stream.
*/
public void printStackTrace() {
printStackTrace(System.err);
}
/**
* Prints the stack trace of this exception to the specified
* stream.
*
* @param out PrintStream to use for output.
* @see #printStackTrace(PrintWriter)
*/
public void printStackTrace(PrintStream out) {
synchronized (out) {
PrintWriter pw = new PrintWriter(out, false);
printStackTrace(pw);
// Flush the PrintWriter before it's GC'ed.
pw.flush();
}
}
/**
* Prints the stack trace of this exception to the specified
* writer. If the Throwable class has a getCause
* method (i.e. running on jre1.4 or higher), this method just
* uses Throwable's printStackTrace() method. Otherwise, generates
* the stack-trace, by taking into account the 'topDown' and
* 'trimStackFrames' parameters. The topDown and trimStackFrames
* are set to 'true' by default (produces jre1.4-like stack trace).
*
* @param out PrintWriter to use for output.
*/
public void printStackTrace(PrintWriter out) {
Throwable throwable = this.nestable;
// if running on jre1.4 or higher, use default printStackTrace
if (ExceptionUtils.isThrowableNested()) {
if (throwable instanceof Nestable) {
((Nestable)throwable).printPartialStackTrace(out);
} else {
throwable.printStackTrace(out);
}
return;
}
// generating the nested stack trace
List stacks = new ArrayList();
while (throwable != null) {
String[] st = getStackFrames(throwable);
stacks.add(st);
throwable = ExceptionUtils.getCause(throwable);
}
// If NOT topDown, reverse the stack
String separatorLine = "Caused by: ";
if (!topDown) {
separatorLine = "Rethrown as: ";
Collections.reverse(stacks);
}
// Remove the repeated lines in the stack
if (trimStackFrames) {
trimStackFrames(stacks);
}
synchronized (out) {
for (Iterator iter=stacks.iterator(); iter.hasNext();) {
String[] st = (String[]) iter.next();
for (int i=0, len=st.length; i < len; i++) {
out.println(st[i]);
}
if (iter.hasNext()) {
out.print(separatorLine);
}
}
}
}
/**
* Captures the stack trace associated with the specified
* Throwable object, decomposing it into a list of
* stack frames.
*
* @param t The Throwable.
* @return An array of strings describing each stack frame.
* @since 2.0
*/
protected String[] getStackFrames(Throwable t) {
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw, true);
// Avoid infinite loop between decompose() and printStackTrace().
if (t instanceof Nestable) {
((Nestable) t).printPartialStackTrace(pw);
} else {
t.printStackTrace(pw);
}
return ExceptionUtils.getStackFrames(sw.getBuffer().toString());
}
/**
* Trims the stack frames. The first set is left untouched. The rest
* of the frames are truncated from the bottom by comparing with
* one just on top.
*
* @param stacks The list containing String[] elements
* @since 2.0
*/
protected void trimStackFrames(List stacks) {
for (int size=stacks.size(), i=size-1; i > 0; i--) {
String[] curr = (String[]) stacks.get(i);
String[] next = (String[]) stacks.get(i-1);
List currList = new ArrayList(Arrays.asList(curr));
List nextList = new ArrayList(Arrays.asList(next));
ExceptionUtils.removeCommonFrames(currList, nextList);
int trimmed = curr.length - currList.size();
if (trimmed > 0) {
currList.add("\t... "+trimmed+" more");
stacks.set(
i,
currList.toArray(new String[currList.size()])
);
}
}
}
}