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Expect the Unexpected Kito D. Mann Principal Consultant.

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Presentation on theme: "Expect the Unexpected Kito D. Mann Principal Consultant."— Presentation transcript:

1 Expect the Unexpected Kito D. Mann Principal Consultant

2 Platinum Sponsor EXPECT THE UNEXPECTED Kito D. Mann Principal Consultant

3 Kito D. Mann @kito99 »Principal Consultant at Virtua »http://www.virtua.com »Training, consulting, architecture, mentoring, »JSF product development »Author, JavaServer Faces in Action »Founder, JSF Central »http://www.jsfcentral.com »Internationally recognized speaker »JavaOne, JavaZone, Devoxx, NFJS, TSSJS, etc. Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

4 Kito D. Mann @kito99 »JCP Member »JSF, WebBeans, JSF Portlet Bridge, Portlets Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

5 bad things happen Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

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8 “that should never happen” Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

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12 some bad things seem minor Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

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15 ex·cep·tion noun. something excepted; an instance or case not conforming to the general rule. Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

16 expect bad things Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

17 regardless of the what is happening, your application should be in a consistent state. Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

18 exception handling aphorisms Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

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20 don't eat exceptions Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

21 public void save() { try { getWidgetProvider().add(selectedWidget); } catch (DatabaseException e) { e.printStackTrace(); } display("Your widget has been created successfully."); setSelectedWidget(null); }

22 if you can recover from it, catch it and tell the user (if necessary) Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

23 public void save() throws DatabaseException { try { getWidgetProvider().add(selectedWidget); display("Your widget has been created successfully"); setSelectedWidget(null); } catch (DatabaseException e) { displayError("Sorry, a database error has occurred. Please try again later."); logger.log(Level.SEVERE, "Error accessing the database", e); }

24 if you cannot recover from it, don't catch it Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

25 public void save() throws DatabaseException { getWidgetProvider().add(selectedWidget); display("Your widget has been created successfully"); setSelectedWidget(null); }

26 demo Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

27 for any call, if something goes wrong, ensure consistency Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

28 try { session = openSession(); if (rule.isCachedModel() || BatchSessionUtil.isEnabled()) { Object staleObject = session.get(RuleImpl.class, rule.getPrimaryKeyObj()); if (staleObject != null) { session.evict(staleObject); } session.delete(rule); session.flush(); } catch (Exception e) { throw processException(e); } finally { closeSession(session); }

29 use a logging framework consistently Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

30 do not log an exception more than one time Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

31 demo Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

32 throw meaningful exceptions Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

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34 centralize exception handling Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

35 centralize exception handling »Logging »Notifications »Error page Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

36 web.xml … java.lang.Throwable /error.jsf Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

37 JSF 2 public class CustomExceptionHandler extends ExceptionHandlerWrapper { private static final Logger logger = Logger.getLogger(WidgetViewerBean.class.getName()); private ExceptionHandler wrapped; public CustomExceptionHandler(ExceptionHandler wrapped) { this.wrapped = wrapped; } Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

38 JSF 2 @Override public void handle() throws FacesException { Iterator i = getUnhandledExceptionQueuedEvents().iterator(); while (i.hasNext()) { ExceptionQueuedEvent event = i.next(); ExceptionQueuedEventContext context = (ExceptionQueuedEventContext) event.getSource(); Throwable t = context.getException(); try { logger.log(Level.SEVERE, "Serious error happened!", t); } finally { i.remove(); } getWrapped().handle(); } Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

39 JSF 2 @Override public ExceptionHandler getWrapped() { return this.wrapped; } Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

40 CDI – Apache DeltaSpike @ExceptionHandler public class MyHandlers { void logExceptions(@Handles @WebRequest CaughtException evt, Logger log) { log.error("Something bad happened!”, evt.getException()); } Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

41 Spring MVC @Controller public class SimpleController { @ExceptionHandler(IOException.class) public String handleIOException( IOException ex, HttpServletRequest request) { logger.error("A " + ex.getClass().getSimpleName() + " has occured in the application", ex); return "error"; } Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

42 Spring MVC public class SampleExceptionHandler extends SimpleMappingExceptionResolver { private static final Logger logger = LoggerFactory.getLogger(SampleExceptionHandler.class); @Override protected ModelAndView doResolveException( HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) { logger.error("A " + ex.getClass().getSimpleName() + " has occured in the application", ex); return super.doResolveException(request, response, handler, ex); } Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

43 handle browser exceptions Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

44 handle browser exceptions »in JavaScript code »returned from Ajax requests »while processing Ajax requests Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

45 demo Copyright (C) 2012-14 Virtua, Inc. All rights reserved.

46 Questions?

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