001// *************************************************************************************************************************** 002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file * 003// * distributed with this work for additional information regarding copyright ownership. The ASF licenses this file * 004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance * 005// * with the License. You may obtain a copy of the License at * 006// * * 007// * http://www.apache.org/licenses/LICENSE-2.0 * 008// * * 009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an * 010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the * 011// * specific language governing permissions and limitations under the License. * 012// *************************************************************************************************************************** 013package org.apache.juneau.utils; 014 015import java.util.concurrent.*; 016 017/** 018 * An in-memory cache of stack traces. 019 * 020 * <p> 021 * Used for preventing duplication of stack traces in log files and replacing them with small hashes. 022 */ 023public class StackTraceDatabase { 024 025 private final ConcurrentHashMap<Integer,StackTraceInfo> db = new ConcurrentHashMap<>(); 026 private final String stopClass; 027 028 /** 029 * Constructor. 030 */ 031 public StackTraceDatabase() { 032 this.stopClass = null; 033 } 034 035 /** 036 * Constructor. 037 * 038 * @param stopClass When this class is encountered in a stack trace, stop calculating the hash. 039 */ 040 public StackTraceDatabase(Class<?> stopClass) { 041 this.stopClass = stopClass == null ? "" : stopClass.getName(); 042 } 043 044 /** 045 * Retrieves the stack trace information for the specified exception. 046 * 047 * @param e The exception. 048 * @param timeout The timeout in milliseconds to cache the hash for this stack trace. 049 * @return The stack trace info, never <jk>null</jk>. 050 */ 051 public StackTraceInfo getStackTraceInfo(Throwable e, int timeout) { 052 int hash = hash(e); 053 StackTraceInfo stc = db.get(hash); 054 if (stc != null && stc.timeout > System.currentTimeMillis()) { 055 stc.incrementAndClone(); 056 return stc.clone(); 057 } 058 synchronized (db) { 059 stc = new StackTraceInfo(timeout, hash); 060 db.put(hash, stc); 061 return stc.clone(); 062 } 063 } 064 065 private int hash(Throwable t) { 066 int i = 0; 067 while (t != null) { 068 for (StackTraceElement e : t.getStackTrace()) { 069 if (e.getClassName().equals(stopClass)) 070 break; 071 if (e.getClassName().indexOf('$') == -1) 072 i ^= e.hashCode(); 073 } 074 t = t.getCause(); 075 } 076 return i; 077 } 078 079 /** 080 * Clears out the stack trace cache. 081 */ 082 public void reset() { 083 db.clear(); 084 } 085}