gwt@jazoon08 - part 4/6 - attention to detail

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# 4

attention to detail.

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your Porsche may drive better but ...

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create delightfull experiences ...

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annoying.

ajax stuff you can’t bookmarkbroken back buttonserror type 11page that crashes during submit, what now?

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history.[ for dummies ]

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LISTEN TO HISTORY EVENTS

public class Example implements EntryPoint, HistoryListener {

public void onModuleLoad() {

History.addHistoryListener(this);

}

public void onHistoryChanged(String historyToken) { ... }

}

CREATE HISTORY EVENTS

History.newItem(“profile”); = http://localhost:8080/example#profile

History.newItem(“search”); = http://localhost:8080/example#search

History.newItem(“edit”); = http://localhost:8080/example#edit

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history.[ demystified ]

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BEHIND THE SCENES

browser history does not only effect top level pages browser history also works for iFrames History maintains a stack of applied tokens these tokens can be used to map to specific application state

background timer which check each ¼ of a second if $wnd.location has changed, if so it triggers the History listener (onHistoryChanged)

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error handling.[ best practices ]

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CATCH UNCAUGHT EXCEPTIONS

catch exceptions at the top-level just before they escape to the browser useful for event callbacks, timers, rpc… which are hard to try / catch

GWT.setUncaughtExceptionHandler(new GWT.UncaughtExceptionHandler() { public void onUncaughtException(Throwable e) {         Window.alert(“You thought you could get away didn’t you !!!");         }     });    

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STANDARDIZE EXCEPTION HANDLING

public abstract class ApplicationAsyncCallback<T> implements AsyncCallback<T> {

public final void onSuccess(T object) { onSuccessInternal(object);

}

public final void onFailure(Throwable throwable) { onFailureInternal(throwable);

Window.alert(“KABOEMMMM”); }

protected void onSuccessInternal(T object) {}

protected void onFailureInternal(Throwable throwable) {} }

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LOG, LOG, LOG, LOG EVERYWHERE (1/4)

Log.debug(“Some log message”);

public class Log {

private static final Logger logger = GWT.isScript() ? new com.FireBugLogger() : new HostedModeLogger();

public static void debug(String message) { log(DEBUG, message); }

protected static void log(Level level, String message) { if (enabled && level.getWeight() <= getMaxLevel().getWeight()) { switch (level) { case ERROR: logger.error(message); break; case WARN: logger.warn(message); break; case INFO: logger.info(message); break; case DEBUG: logger.debug(message); break;

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LOG, LOG, LOG, LOG EVERYWHERE (2/4)

// request log level at runtime http://localhost:8080/x.html?log.level=error public static native String getLoglevel() /*-{

var level; var args = $wnd.location.search; var startLang = args.indexOf("log.level"); if (startLang >= 0) { var value = args.substring(startLang); var begin = value.indexOf("=") + 1; var end = value.indexOf("&"); if (end == -1) { end = value.length; } level = value.substring(begin, end); } return level; }-*/;

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LOG, LOG, LOG, LOG EVERYWHERE (3/4)

public class FireBugLogger implements Logger {

private boolean fireBugInstalled = false;

protected FireBugLogger() { checkIfFireBugInstalled(); }

protected native void checkIfFireBugInstalled() /*-{ this.@com.FireBugLogger::fireBugInstalled = (typeof console != 'undefined'); }-*/;

public native void debug(String message) /*-{ if (this.@com.FireBugLogger::fireBugInstalled) console.debug(message); }-*/;

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LOG, LOG, LOG, LOG EVERYWHERE (4/4)

public class HostedModeLogger implements Logger {

public void debug(String message) { log(toMessageWithLineInformation("DEBUG", message)); }

public void log(String message) { GWT.log(message, null); }

private String toMessageWithLineInformation(String logLevel, String message) { StackTraceElement line = new Throwable().getStackTrace()[4]; return (logLevel + " " + toLine(line) + ": " + message); }

private String toLine(StackTraceElement line) { return line.getClassName() + "(" + line.getLineNumber() + ")"; }

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what’s wrong with the log example?

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AUTOMATED USER ACCEPTANCE TESTS WITH SELENIUM

your code

Label firstnameLabel = new Label(); label.ensureDebugId(“firstnameLabel”); // if not enabled does nothing

enable debug mode – go Selenium gooooo…..

<inherits name=“com.google.gwt.user.Debug”/> // DOM.setElementProperty(…)

under the hood – UIObject

private static DebugIdImpl debugIdImpl = GWT.create(DebugIdImpl.class);

public static void ensureDebugId(Element elem, String id) { debugIdImpl.ensureDebugId(elem, id); }

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