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authorIlia Motornyi <elmot@vaadin.com>2015-12-03 14:59:05 +0000
committerVaadin Code Review <review@vaadin.com>2015-12-03 14:59:12 +0000
commit2af72ba9636bec70046394c41744f89ce4572e35 (patch)
treeccb3dc2d2239585f8c3f79eb5f131ff61ca9ce86 /documentation/application/application-errors.asciidoc
parent8aa5fabe89f2967e966a64842a608eceaf80d08f (diff)
downloadvaadin-framework-2af72ba9636bec70046394c41744f89ce4572e35.tar.gz
vaadin-framework-2af72ba9636bec70046394c41744f89ce4572e35.zip
Revert "Merge branch 'documentation'"7.6.0.beta2
This reverts commit f6874bde3d945c8b2d1b5c17ab50e2d0f1f8ff00. Change-Id: I67ee1c30ba3e3bcc3c43a1dd2e73a822791514bf
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----
-title: Handling Errors
-order: 6
-layout: page
----
-
-[[application.errors]]
-= Handling Errors
-
-[[application.errors.error-indicator]]
-== Error Indicator and Message
-
-All components have a built-in error indicator that is turned on if validating
-the component fails, and can be set explicitly with
-[methodname]#setComponentError()#. Usually, the error indicator is placed right
-of the component caption. The error indicator is part of the component caption,
-so its placement is usually managed by the layout in which the component is
-contained, but some components handle it themselves. Hovering the mouse pointer
-over the field displays the error message.
-
-
-[source, java]
-----
-textfield.setComponentError(new UserError("Bad value"));
-button.setComponentError(new UserError("Bad click"));
-----
-
-The result is shown in <<figure.application.errors.error-indicator>>.
-
-[[figure.application.errors.error-indicator]]
-.Error Indicator Active
-image::img/errorindicator-example2.png[]
-
-
-ifdef::web[]
-[[application.errors.systemmessages]]
-== Customizing System Messages
-
-System messages are notifications that indicate a major invalid state that
-usually requires restarting the application. Session timeout is perhaps the most
-typical such state.
-
-System messages are strings managed in the [classname]#SystemMessages# class.
-
-sessionExpired:: ((("session",
-"expiration")))
-((("session",
-"timeout")))
-The Vaadin session expired. A session expires if no server requests are made
-during the session timeout period. The session timeout can be configured with
-the [parameter]#session-timeout# parameter in [filename]#web.xml#, as described
-in
-<<dummy/../../../framework/application/application-environment#application.environment.web-xml,"Using
-a web.xml Deployment Descriptor">>.
-
-communicationError:: An unspecified communication problem between the Vaadin Client-Side Engine and
-the application server. The server may be unavailable or there is some other
-problem.
-
-authenticationError:: This error occurs if 401 (Unauthorized) response to a request is received from
-the server.
-
-internalError:: A serious internal problem, possibly indicating a bug in Vaadin Client-Side
-Engine or in some custom client-side code.
-
-outOfSync:: The client-side state is invalid with respect to server-side state.
-
-cookiesDisabled:: Informs the user that cookies are disabled in the browser and the application
-does not work without them.
-
-
-
-Each message has four properties: a short caption, the actual message, a URL to
-which to redirect after displaying the message, and property indicating whether
-the notification is enabled.
-
-Additional details may be written (in English) to the debug console window
-described in
-<<dummy/../../../framework/advanced/advanced-debug#advanced.debug,"Debug Mode
-and Window">>.
-
-You can override the default system messages by setting the
-[interfacename]#SystemMessagesProvider# in the [classname]#VaadinService#. You
-need to implement the [methodname]#getSystemMessages()# method, which should
-return a [classname]#SystemMessages# object. The easiest way to customize the
-messages is to use a [classname]#CustomizedSystemMessages# object.
-
-You can set the system message provider in the
-[methodname]#servletInitialized()# method of a custom servlet class, for example
-as follows:
-
-
-[source, java]
-----
-getService().setSystemMessagesProvider(
- new SystemMessagesProvider() {
- @Override
- public SystemMessages getSystemMessages(
- SystemMessagesInfo systemMessagesInfo) {
- CustomizedSystemMessages messages =
- new CustomizedSystemMessages();
- messages.setCommunicationErrorCaption("Comm Err");
- messages.setCommunicationErrorMessage("This is bad.");
- messages.setCommunicationErrorNotificationEnabled(true);
- messages.setCommunicationErrorURL("http://vaadin.com/");
- return messages;
- }
-});
-----
-
-See
-<<dummy/../../../framework/application/application-lifecycle#application.lifecycle.servlet-service,"Vaadin
-Servlet, Portlet, and Service">> for information about customizing Vaadin
-servlets.
-
-endif::web[]
-
-ifdef::web[]
-[[application.errors.unchecked-exceptions]]
-== Handling Uncaught Exceptions
-
-Handling events can result in exceptions either in the application logic or in
-the framework itself, but some of them may not be caught properly by the
-application. Any such exceptions are eventually caught by the framework. It
-delegates the exceptions to the [classname]#DefaultErrorHandler#, which displays
-the error as a component error, that is, with a small red "!" -sign (depending
-on the theme). If the user hovers the mouse pointer over it, the entire
-backtrace of the exception is shown in a large tooltip box, as illustrated in
-<<figure.application.errors.unchecked-exceptions>>.
-
-[[figure.application.errors.unchecked-exceptions]]
-.Uncaught Exception in Component Error Indicator
-image::img/errorindicator-exception.png[]
-
-You can customize the default error handling by implementing a custom
-[interfacename]#ErrorHandler# and enabling it with
-[methodname]#setErrorHandler()# in any of the components in the component
-hierarchy, including the [classname]#UI#, or in the [classname]#VaadinSession#
-object. You can either implement the [interfacename]#ErrorHandler# or extend the
-[classname]#DefaultErrorHandler#. In the following example, we modify the
-behavior of the default handler.
-
-
-[source, java]
-----
-// Here's some code that produces an uncaught exception
-final VerticalLayout layout = new VerticalLayout();
-final Button button = new Button("Click Me!",
- new Button.ClickListener() {
- public void buttonClick(ClickEvent event) {
- ((String)null).length(); // Null-pointer exception
- }
-});
-layout.addComponent(button);
-
-// Configure the error handler for the UI
-UI.getCurrent().setErrorHandler(new DefaultErrorHandler() {
- @Override
- public void error(com.vaadin.server.ErrorEvent event) {
- // Find the final cause
- String cause = "<b>The click failed because:</b><br/>";
- for (Throwable t = event.getThrowable(); t != null;
- t = t.getCause())
- if (t.getCause() == null) // We're at final cause
- cause += t.getClass().getName() + "<br/>";
-
- // Display the error message in a custom fashion
- layout.addComponent(new Label(cause, ContentMode.HTML));
-
- // Do the default error handling (optional)
- doDefault(event);
- }
-});
-----
-
-The above example also demonstrates how to dig up the final cause from the cause
-stack.
-
-When extending [classname]#DefaultErrorHandler#, you can call
-[methodname]#doDefault()# as was done above to run the default error handling,
-such as set the component error for the component where the exception was
-thrown. See the source code of the implementation for more details. You can call
-[methodname]#findAbstractComponent(event)# to find the component that caused the
-error. If the error is not associated with a component, it returns null.
-
-endif::web[]
-
-
-