/*
* Copyright 2007 Google Inc.
*
* Licensed 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 com.google.gwt.dev.util.log;
import com.google.gwt.core.ext.TreeLogger;
import com.google.gwt.core.ext.UnableToCompleteException;
import java.util.HashSet;
/**
* Abstract base class for TreeLoggers.
*/
public abstract class AbstractTreeLogger extends TreeLogger {
private static class UncommittedBranchData {
public final Throwable caught;
public final String message;
public final TreeLogger.Type type;
private final HelpInfo helpInfo;
public UncommittedBranchData(Type type, String message, Throwable caught,
HelpInfo helpInfo) {
this.caught = caught;
this.message = message;
this.type = type;
this.helpInfo = helpInfo;
}
}
// This message is package-protected so that the unit test can access it.
static final String OUT_OF_MEMORY_MSG = "Out of memory; to increase the "
+ "amount of memory, use the -Xmx flag at startup (java -Xmx128M ...)";
// This message is package-protected so that the unit test can access it.
static final String STACK_OVERFLOW_MSG = "Stack overflow; to increase the "
+ "stack size, use the -Xss flag at startup (java -Xss1M ...)";
public static String getStackTraceAsString(Throwable e) {
// Show the exception info for anything other than "UnableToComplete".
if (e == null || e instanceof UnableToCompleteException) {
return null;
}
// For each cause, print the requested number of entries of its stack
// trace, being careful to avoid getting stuck in an infinite loop.
//
StringBuffer message = new StringBuffer();
Throwable currentCause = e;
String causedBy = "";
HashSet<Throwable> seenCauses = new HashSet<Throwable>();
while (currentCause != null && !seenCauses.contains(currentCause)) {
seenCauses.add(currentCause);
message.append(causedBy);
causedBy = "\nCaused by: "; // after 1st, all say "caused by"
message.append(currentCause.getClass().getName());
message.append(": " + currentCause.getMessage());
StackTraceElement[] stackElems = currentCause.getStackTrace();
if (stackElems != null) {
for (int i = 0; i < stackElems.length; ++i) {
message.append("\n\tat ");
message.append(stackElems[i].toString());
}
}
currentCause = currentCause.getCause();
}
return message.toString();
}
protected static String getExceptionName(Throwable e) {
if (e == null || e instanceof UnableToCompleteException) {
return null;
}
return e.getClass().getSimpleName();
}
protected TreeLogger.Type logLevel = TreeLogger.ALL;
protected AbstractTreeLogger parent;
private int indexWithinMyParent;
private int nextChildIndex;
private final Object nextChildIndexLock = new Object();
private UncommittedBranchData uncommitted;
/**
* The constructor used when creating a top-level logger.
*/
protected AbstractTreeLogger() {
}
/**
* Implements branching behavior that supports lazy logging for low-priority
* branched loggers.
*/
@Override
public final synchronized TreeLogger branch(TreeLogger.Type type, String msg,
Throwable caught, HelpInfo helpInfo) {
if (msg == null) {
msg = "(Null branch message)";
}
// Compute at which index the new child will be placed.
//
int childIndex = allocateNextChildIndex();
// The derived class creates the child logger.
AbstractTreeLogger childLogger = doBranch();
// Set up the child logger.
//
// Unsynchronized operations on childLogger are safe since no other
// thread could have a reference to it yet.
childLogger.logLevel = logLevel;
// Take a snapshot of the index that the branched child should have.
//
childLogger.indexWithinMyParent = childIndex;
// Have the child hang onto this (its parent logger).
//
childLogger.parent = this;
// We can avoid committing this branch entry until and unless some
// child (or grandchild) tries to log something that is loggable,
// in which case there will be cascading commits of the parent branches.
//
childLogger.uncommitted = new UncommittedBranchData(type, msg, caught,
helpInfo);
// This logic is intertwined with log(). If a log message is associated
// with a special error condition, then we turn it into a branch,
// so this method can be called directly from log(). It is of course
// also possible for someone to call branch() directly. In either case, we
// (1) turn the original message into an ERROR and
// (2) drop an extra log message that explains how to recover
String specialErrorMessage = causedBySpecialError(caught);
if (specialErrorMessage != null) {
type = TreeLogger.ERROR;
childLogger.log(type, specialErrorMessage, null);
}
// Decide whether we want to log the branch message eagerly or lazily.
//
if (isLoggable(type)) {
// We can commit this branch entry eagerly since it is a-priori loggable.
// Commit the parent logger if necessary before continuing.
//
childLogger.commitMyBranchEntryInMyParentLogger();
}
return childLogger;
}
public final int getBranchedIndex() {
return indexWithinMyParent;
}
public final synchronized TreeLogger.Type getMaxDetail() {
return logLevel;
}
public final AbstractTreeLogger getParentLogger() {
return parent;
}
@Override
public final synchronized boolean isLoggable(TreeLogger.Type type) {
return !type.isLowerPriorityThan(logLevel);
}
/**
* Immediately logs or ignores the specified messages, based on the specified
* message type and this logger's settings. If the message is loggable, then
* parent branches may be lazily created before the log can take place.
*/
@Override
public final synchronized void log(TreeLogger.Type type, String msg,
Throwable caught, HelpInfo helpInfo) {
if (msg == null) {
msg = "(Null log message)";
}
// If this log message is caused by out of memory or stack overflow, we
// provide a little extra help by creating a child log message.
if (causedBySpecialError(caught) != null) {
branch(TreeLogger.ERROR, msg, caught);
return;
}
int childIndex = allocateNextChildIndex();
if (isLoggable(type)) {
commitMyBranchEntryInMyParentLogger();
doLog(childIndex, type, msg, caught, helpInfo);
}
}
/**
* @param type the log type representing the most detailed level of logging
* that the caller is interested in, or <code>null</code> to choose
* the default level.
*/
public final synchronized void setMaxDetail(TreeLogger.Type type) {
if (type == null) {
type = TreeLogger.INFO;
}
logLevel = type;
}
@Override
public String toString() {
return getLoggerId();
}
protected int allocateNextChildIndex() {
synchronized (nextChildIndexLock) {
// postincrement because we want indices to start at 0
return nextChildIndex++;
}
}
/**
* Commits the branch after ensuring that the parent logger (if there is one)
* has been committed first.
*/
protected synchronized void commitMyBranchEntryInMyParentLogger() {
// (Only the root logger doesn't have a parent.)
//
if (parent != null) {
if (uncommitted != null) {
// Commit the parent first.
//
parent.commitMyBranchEntryInMyParentLogger();
// Let the subclass do its thing to commit this branch.
//
parent.doCommitBranch(this, uncommitted.type, uncommitted.message,
uncommitted.caught, uncommitted.helpInfo);
// Release the uncommitted state.
//
uncommitted = null;
}
}
}
/**
* Derived classes should override this method to return a branched logger.
*/
protected abstract AbstractTreeLogger doBranch();
/**
* @deprecated This method has been deprecated; override
* {@link #doCommitBranch(AbstractTreeLogger, com.google.gwt.core.ext.TreeLogger.Type, String, Throwable, com.google.gwt.core.ext.TreeLogger.HelpInfo)}
* instead.
*
* @param childBeingCommitted
* @param type
* @param msg
* @param caught
*/
@Deprecated
protected final void doCommitBranch(AbstractTreeLogger childBeingCommitted,
TreeLogger.Type type, String msg, Throwable caught) {
}
/**
* Derived classes should override this method to actually commit the
* specified message associated with this the root of this branch.
*/
protected abstract void doCommitBranch(
AbstractTreeLogger childBeingCommitted, TreeLogger.Type type, String msg,
Throwable caught, HelpInfo helpInfo);
/**
* @deprecated This method has been deprecated; override
* {@link #branch(com.google.gwt.core.ext.TreeLogger.Type, String, Throwable, com.google.gwt.core.ext.TreeLogger.HelpInfo)
* instead.
*
* @param indexOfLogEntryWithinParentLogger
* @param type
* @param msg
* @param caught
*/
@Deprecated
protected final void doLog(int indexOfLogEntryWithinParentLogger,
TreeLogger.Type type, String msg, Throwable caught) {
}
/**
* Derived classes should override this method to actually write a log
* message. Note that {@link #isLoggable(TreeLogger.Type)} will have already
* been called.
*/
protected abstract void doLog(int indexOfLogEntryWithinParentLogger,
TreeLogger.Type type, String msg, Throwable caught, HelpInfo helpInfo);
/**
* Scans <code>t</code> and its causes for {@link OutOfMemoryError} or
* {@link StackOverflowError}.
*
* @param t a possibly null {@link Throwable}
* @return true if {@link OutOfMemoryError} or {@link StackOverflowError}
* appears anywhere in the cause list or if <code>t</code> is an
* {@link OutOfMemoryError} or {@link StackOverflowError.
*/
private String causedBySpecialError(Throwable t) {
while (t != null) {
if (t instanceof OutOfMemoryError) {
return OUT_OF_MEMORY_MSG;
} else if (t instanceof StackOverflowError) {
return STACK_OVERFLOW_MSG;
}
t = t.getCause();
}
return null;
}
private String getLoggerId() {
if (parent != null) {
if (parent.parent == null) {
// Top-level
return parent.getLoggerId() + getBranchedIndex();
} else {
// Nested
return parent.getLoggerId() + "." + getBranchedIndex();
}
} else {
// The root
return "#";
}
}
}