log4javascript - open the same PopUpAppender so all the log is in one log window

Question

Can log4javascript reuse the same (the exact same) PopUpAppender ?

What do I mean by that : once you start logging the PopUpAppender will create a new window (usually with an 'windowId' something like *'log4javascriptConsoleWindow_1381843187828_742325019557029'*).

Now, the appender (PopUpAppender) is setup so : appender.setReopenWhenClosed( true ) - in this case even if the window is closed the next log message will open a new window for it. What do I want is to get back the previously closed window (the one with the strange windowId) so all my log messages are in one place.

In a couple of words - I want all my log messages in just 1 window.

One way to do that (I think) - is to modify the HTML that represents the PopUpAppender and modify the line that generates the windowId - in this way the same window will be created every time. So far so good - only that the array of 'LogEntry' is emptied. So before logging you might need to save them and then somehow insert them back (at the beggining) in the new window.

I'm willing to try this - I'm not sure that this is the right way - so if somebody has a better idea please share it with us (me).

Answer 1

I may add support for this in log4javascript 2.0. In the meantime, I suggest creating an appender object that wraps a PopUpAppender and stores all logging events that pass through so that they can be re-appended when the pop-up reopens.

function WrappedPopUpAppender(popUpAppender) {
    var appender = this;
    this.popUpAppender = popUpAppender;
    this.loggingEvents = [];
    this.closed = false;

    popUpAppender.addEventListener("unload", function() {
        appender.closed = true;
    });
}

WrappedPopUpAppender.prototype = new log4javascript.Appender();
WrappedPopUpAppender.prototype.append = function(loggingEvent) {
    this.loggingEvents.push(loggingEvent);
    if (this.closed) {
        for (var i = 0, evt; evt = this.loggingEvents[i++]; ) {
            this.popUpAppender.append(evt);
        }
        this.closed = false;
    } else {
        this.popUpAppender.append(loggingEvent);
    }
};

var popUpAppender = new log4javascript.PopUpAppender();
popUpAppender.setReopenWhenClosed(true);
var wrappedAppender = new WrappedPopUpAppender(popUpAppender);

var log = log4javascript.getLogger("main");
log.addAppender(wrappedAppender);

Answer 2

If you look inside log4javascript.js, you will see that PopUpAppender is configured to clear his list of logged events every time it is shown (line 4839 in the uncompressed version):

        while (queuedLoggingEvents.length > 0) {
            queuedLoggingEvents.shift().append();
        }

If you want the log entries to be kept even after the pop-up is closed and then re-opened, a quick fix would be to change the above code snippet to:

        for ( var i = 0; i < queuedLoggingEvents.length; i++ )
            queuedLoggingEvents[i].append();

The developers should ideally add this as an option in the PopUpAppender class, you can do so by adding these lines:

line 5254, inside PopUpAppender definition:

        var clearMessagesAfterOpening = this.defaults.clearMessagesAfterOpening;

line 5284, inside PopUpAppender definition:

        this.isClearMessagesAfterOpening = function()
        {
            return clearMessagesAfterOpening;
        };
        this.setClearMessagesAfterOpening = function( clearMessagesAfterOpeningParam )
        {
            // This property can be safely altered after logging has started
            clearMessagesAfterOpening = bool( clearMessagesAfterOpeningParam );
        };

line 5459, in PopUpAppender.prototype.defaults definition:

        clearMessagesAfterOpening : false,

Finally, change the initial code at line 4839 to take into account the newly added option:

        for ( var i = 0; i < queuedLoggingEvents.length; i++ )
            queuedLoggingEvents[i].append();
        if ( clearMessagesAfterOpening )
                queuedLoggingEvents.clear();

You can now control this behaviour by using PopUpAppender's "clearMessagesAfterOpening" option, which in the above code is false by default. Hope this helps! :)

Answer 3

@tim

i tried to do what you suggested, but somehow it bugged me all along :)

i now ended up in the following situation:

i have two options for my debugging (debugging with popup only):

1.: you can add an url param "debug=true" which initially opens the popupappender window and logs messages. 2.: you can also open/close the popupappender from a menu option.

the problem was: the popupappender opens cleaned up if closed/opened dynamically.

what i needed: the popupappender shall not re-open cleaned up, but re-open with all the old logging events.

the solution:

i added a second appender which always logs everything silently (or also appends to the popupappender if it is opened), and thus i can push all silently logged messages to the popupappender manually when it is re-opened by the ui.

the popupappender related stuff:

var popupAppender = new log4javascript.PopUpAppender(),
            layout = new log4javascript.PatternLayout('%d{yyyy MMM dd HH:mm:ss,SSS} %-5p %m');
        popupAppender.setLayout(layout);
        popupAppender.setThreshold(log4javascript.Level.TRACE);

... and later:

            toggleAppender: function () {
                var appender = log.getEffectiveAppenders();
                if (!appender.length || appender.length <= 1) {
                    // just to make sure...
                    log.addAppender(popupAppender);
                }
                if (!popupAppender.isVisible()) {
                    // got some "old" logging events?!
                    for (var index = 0; index < loggingEvents.length; index++) {
                        popupAppender.append(loggingEvents[index]);
                    }
                    popupAppender.show();
                } else {
                    popupAppender.hide();
                }
            },
            isPopupAppenderVisible: function () {
                return popupAppender.isVisible();
            },
            registerHeaderEventListener: function () {
                // just some angularing stuff for changing the "open"/"close" string
                var headerScope = angular.element('#headerBar').scope();
                popupAppender.addEventListener("unload", function() {
                    headerScope.popupAppenderIsVisible = false;
                });
                popupAppender.addEventListener("load", function() {
                    headerScope.popupAppenderIsVisible = true;
                });
            }

the custom appender related stuff:

function CustomAppender() {}
        CustomAppender.prototype = new log4javascript.PopUpAppender();
        CustomAppender.prototype.layout = new log4javascript.PatternLayout('%d{yyyy MMM dd HH:mm:ss,SSS} %-5p %m');
        CustomAppender.prototype.threshold = log4javascript.Level.TRACE;
        CustomAppender.prototype.toString = function () {
            return 'silent custom appender';
        };
        CustomAppender.prototype.append = function (loggingEvent) {
            if (loggingEvent.length > 1) {
                for (var index = 0; index < loggingEvent.length; index++) {
                    loggingEvents.push(loggingEvent[index]);
                    // update the popup appender if it is visible
                    if (popupAppender.isVisible()) {
                        popupAppender.append(loggingEvent[index]);
                    }
                }
            } else {
                loggingEvents.push(loggingEvent);
                // update the popup appender if it is visible
                if (popupAppender.isVisible()) {
                    popupAppender.append(loggingEvent);
                }
            }
        };

and some initialization:

log4javascript.CustomAppender = CustomAppender;

        var log = new log4javascript.getLogger('myLogger');

        log.setLevel(log4javascript.Level.TRACE);

        var customAppender = new log4javascript.CustomAppender();

        log.addAppender(customAppender);

        // the DEBUG var is true if the url wants it to be true
        if (DEBUG) {
            log.addAppender(popupAppender);
        }