Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, QOS.ch. All rights reserved.
This program and the accompanying materials are dual-licensed under
either the terms of the Eclipse Public License v1.0 as published by
the Eclipse Foundation
  or (per the licensee's choosing)
under the terms of the GNU Lesser General Public License version 2.1
as published by the Free Software Foundation.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.classic.spi;

import ch.qos.logback.core.CoreConstants;

import java.util.List;

This class computes caller data returning the result in the form
of a StackTraceElement array.
Author:
Ceki Gülcü/**
 * This class computes caller data returning the result in the form
 * of a StackTraceElement array.
 *
 * @author Ceki Gülcü
 */
public class CallerData {

    
When caller information is not available this constant is used for file
name, method name, etc.
/**
     * When caller information is not available this constant is used for file
     * name, method name, etc.
     */
    public static final String NA = "?";

    // All logger call's in log4j-over-slf4j use the Category class
    private static final String LOG4J_CATEGORY = "org.apache.log4j.Category";
    private static final String SLF4J_BOUNDARY = "org.slf4j.Logger";

    
When caller information is not available this constant is used for the line
number.
/**
     * When caller information is not available this constant is used for the line
     * number.
     */
    public static final int LINE_NA = -1;

    public static final String CALLER_DATA_NA = "?#?:?" + CoreConstants.LINE_SEPARATOR;

    
This value is returned in case no caller data could be extracted.
/**
     * This value is returned in case no caller data could be extracted.
     */
    public static final StackTraceElement[] EMPTY_CALLER_DATA_ARRAY = new StackTraceElement[0];

    
Extract caller data information as an array based on a Throwable passed as
parameter
/**
     * Extract caller data information as an array based on a Throwable passed as
     * parameter
     */
    public static StackTraceElement[] extract(Throwable t, String fqnOfInvokingClass, final int maxDepth, List<String> frameworkPackageList) {
        if (t == null) {
            return null;
        }

        StackTraceElement[] steArray = t.getStackTrace();
        StackTraceElement[] callerDataArray;

        int found = LINE_NA;
        for (int i = 0; i < steArray.length; i++) {
            if (isInFrameworkSpace(steArray[i].getClassName(), fqnOfInvokingClass, frameworkPackageList)) {
                // the caller is assumed to be the next stack frame, hence the +1.
                found = i + 1;
            } else {
                if (found != LINE_NA) {
                    break;
                }
            }
        }

        // we failed to extract caller data
        if (found == LINE_NA) {
            return EMPTY_CALLER_DATA_ARRAY;
        }

        int availableDepth = steArray.length - found;
        int desiredDepth = maxDepth < (availableDepth) ? maxDepth : availableDepth;

        callerDataArray = new StackTraceElement[desiredDepth];
        for (int i = 0; i < desiredDepth; i++) {
            callerDataArray[i] = steArray[found + i];
        }
        return callerDataArray;
    }

    static boolean isInFrameworkSpace(String currentClass, String fqnOfInvokingClass, List<String> frameworkPackageList) {
        // the check for org.apache.log4j.Category class is intended to support
        // log4j-over-slf4j. it solves http://bugzilla.slf4j.org/show_bug.cgi?id=66
        if (currentClass.equals(fqnOfInvokingClass) || currentClass.equals(LOG4J_CATEGORY) || currentClass.startsWith(SLF4J_BOUNDARY)
                        || isInFrameworkSpaceList(currentClass, frameworkPackageList)) {
            return true;
        } else {
            return false;
        }
    }

    
Is currentClass present in the list of packages considered part of the logging framework?
/**
     * Is currentClass present in the list of packages considered part of the logging framework?
     */
    private static boolean isInFrameworkSpaceList(String currentClass, List<String> frameworkPackageList) {
        if (frameworkPackageList == null)
            return false;

        for (String s : frameworkPackageList) {
            if (currentClass.startsWith(s))
                return true;
        }
        return false;
    }

    
Returns a StackTraceElement where all string fields are set to NA and line number is set to LINE_NA. 
Returns:
StackTraceElement with values set to NA constants.
Since:
1.0.10/**
     * Returns a StackTraceElement where all string fields are set to {@link #NA} and line number is set to {@link #LINE_NA}.
     *
     * @return StackTraceElement with values set to NA constants.
     * @since 1.0.10
     */
    public static StackTraceElement naInstance() {
        return new StackTraceElement(NA, NA, NA, LINE_NA);
    }

}