Class WTemplate

Direct Known Subclasses:
LostPasswordWidget, WNavigationBar, WTemplateFormView

public class WTemplate
extends WInteractWidget
A widget that renders an XHTML template.

The XHTML template may contain references to variables which replaced by strings are widgets.

Since the template text may be supplied by a WString, you can conveniently store the string in a message resource bundle, and make it localized by using WString#tr().

Placeholders (for variables and functions) are delimited by: ${...}. To use a literal "${", use "$${". Place holder names can contain '_', '-', '.' and alfanumeric characters.

Usage example:


 WString userName = ...;

 WTemplate t = new WTemplate();
 t.setTemplateText("<div> How old are you, ${friend} ? ${age-input} </div>");

 t.bindString("friend", userName, PlainText);
 t.bindWidget("age-input", ageEdit_ = new WLineEdit());

 

The ownership of the widgets bound to a WTemplate widget are transfered to the WTemplate widdget, and they are deleted when the WTemplate is deleted.

There are currently three syntactic constructs defined: variable place holders, functions and conditional blocks.

A. Variable placeholders

${var} defines a placeholder for the variable "var", and gets replaced with whatever is bound to that variable:

Optionally, additional arguments can be specified using the following syntax:

${var arg1="A value" arg2='A second value'}

The arguments can thus be simple simple strings or quoted strings (single or double quoted). These arguments are applied to a resolved widget in applyArguments() and currently supports only style classes.

You can bind widgets and values to variables using bindWidget(), bindString() or bindInt() or by reimplementing the resolveString() and resolveWidget() methods.

Note: The use of XML comments (<!-- ... -.) around variables that are bound to widgets will result in bad behaviour since the template parser is ignorant about these comments and the corresponding widgets will believe that they are rendered but aren't actually.

B. Functions

${fun:arg} defines a placeholder for applying a function "fun" to an argument "arg".

Optionally, additional arguments can be specified as with a variable placeholder.

WTemplate.Functions are resolved by resolveFunction(), and the default implementation considers functions bound with addFunction(). There are currently three functions that are generally useful:

  • Functions#tr : resolves a localized strings, this is convenient to create a language neutral template, which contains translated strings
  • Functions#id : resolves the id of a bound widget, this is convenient to bind <label> elements to a form widget using its for attribute.
  • Functions#block : recursively renders another string as macro block optional arguments substituted before processing template substitution.

For example, the following template uses the "tr" function to translate the age-label using the "age-label" internationalized key.


 WTemplate t = new WTemplate();
 t.setTemplateText("<div> ${tr:age-label} ${age-input} </div>");
 t.addFunction("tr", WTemplate.Functions.tr);
 t.bindWidget("age-input", ageEdit = new WLineEdit());

 

C. Conditional blocks

${<cond>} starts a conditional block with a condition name "cond", and must be closed by a balanced ${</cond>}.

For example:


 WTemplate t = new WTemplate();
 t.setTemplateText("<div> ${<if-register>} Register ... ${</if-register>}</div>");
 t.setCondition("if-register", true);

 

Conditions are set using setCondition().

CSS

This widget does not provide styling, and can be styled using inline or external CSS as appropriate.

  • Constructor Details

  • Method Details

    • remove

      public void remove()
      Description copied from class: WWidget
      Destructor.

      Deletes a widget and all children (recursively). If the widget is contained in another widget, it is removed first.

      Overrides:
      remove in class WInteractWidget
      See Also:
      WContainerWidget.removeWidget(WWidget widget)
    • getTemplateText

      public WString getTemplateText()
      Returns the template.

      See Also:
      setTemplateText(CharSequence text, TextFormat textFormat)
    • setTemplateText

      public void setTemplateText​(java.lang.CharSequence text, TextFormat textFormat)
      Sets the template text.

      The text must be proper XHTML, and this is checked unless the XHTML is resolved from a message resource bundle or TextFormat is TextFormat.XHTMLUnsafeText. This behavior is similar to a WText when configured with the TextFormat.XHTMLText textformat.

      Changing the template text does not clear() bound widgets or values.

      See Also:
      clear()
    • setTemplateText

      public final void setTemplateText​(java.lang.CharSequence text)
      Sets the template text.

      Calls setTemplateText(text, TextFormat.XHTMLText)

    • setWidgetIdMode

      public void setWidgetIdMode​(WTemplate.WidgetIdMode mode)
      Sets how the varName should be reflected on bound widgets.

      To easily identify a widget in the browser, it may be convenient to reflect the varName to the widget's ID. This options allows you to choose from two methods.

      The default value is SetNoWidgetId which does not reflect the varName on the bound widget.

    • getWidgetIdMode

      public WTemplate.WidgetIdMode getWidgetIdMode()
      Returns how the varName is reflected on a bound widget.

      See Also:
      setWidgetIdMode(WTemplate.WidgetIdMode mode)
    • bindString

      public void bindString​(java.lang.String varName, java.lang.CharSequence value, TextFormat textFormat)
      Binds a string value to a variable.

      Each occurrence of the variable within the template will be substituted by its value.

      Note: Depending on the textFormat, the value is validated according as for a WText. The default (XHTMLText) filters "active" content, to avoid XSS-based security risks.

      See Also:
      bindWidget(String varName, WWidget widget), bindInt(String varName, int value), resolveString(String varName, List args, Writer result)
    • bindString

      public final void bindString​(java.lang.String varName, java.lang.CharSequence value)
      Binds a string value to a variable.

      Calls bindString(varName, value, TextFormat.XHTMLText)

    • bindInt

      public void bindInt​(java.lang.String varName, int value)
      Binds an integer value to a variable.

      See Also:
      bindString(String varName, CharSequence value, TextFormat textFormat)
    • bindWidget

      public void bindWidget​(java.lang.String varName, WWidget widget)
      Binds a widget to a variable.

      The corresponding variable reference within the template will be replaced with the widget (rendered as XHTML). Since a single widget may be instantiated only once in a template, the variable varName may occur at most once in the template, and the widget must not yet be bound to another variable.

      The widget is reparented to the WTemplate, so that it is deleted when the WTemplate is deleted.

      If a widget was already bound to the variable, it is deleted first. If previously a string or other value was bound to the variable, it is removed.

      You may also pass a null widget, which will resolve to an empty string.

      See Also:
      bindString(String varName, CharSequence value, TextFormat textFormat), resolveWidget(String varName)
    • takeWidget

      public WWidget takeWidget​(java.lang.String varName)
      Unbinds a widget.

      This removes a previously bound widget and unbinds the corresponding variable, effectively undoing the effect of bindWidget().

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    • bindEmpty

      public void bindEmpty​(java.lang.String varName)
      Binds an empty string to a variable.

      If a widget was bound to the variable, it is deleted first.

      See Also:
      bindString(String varName, CharSequence value, TextFormat textFormat)
    • addFunction

      public void addFunction​(java.lang.String name, WTemplate.Function function)
      Binds a function.

      WTemplate.Functions are useful to automatically resolve placeholders.

      The syntax for a function 'fun' applied to a single argument 'bla' is:

      ${fun:bla}

      There are three predefined functions, which can be bound using:

      
       WTemplate t = ...;
       t.addFunction("id", WTemplate.Functions.id);
       t.addFunction("tr", WTemplate.Functions.tr);
       t.addFunction("block", WTemplate.Functions.block);
      
       
    • setCondition

      public void setCondition​(java.lang.String name, boolean value)
      Sets a condition.

      This enables or disables the inclusion of a conditional block.

      The default value of all conditions is false.

    • conditionValue

      public boolean conditionValue​(java.lang.String name)
      Returns a condition value.

      See Also:
      setCondition(String name, boolean value)
    • getConditionsSet

      public java.util.Set<java.lang.String> getConditionsSet()
      Returns the set of conditions set to true.
    • resolveString

      public void resolveString​(java.lang.String varName, java.util.List<WString> args, java.io.Writer result) throws java.io.IOException
      Resolves the string value for a variable name.

      This is the main method used to resolve variables in the template text, during rendering.

      The default implementation considers first whether a string was bound using bindString(). If so, that string is returned. If not, it will attempt to resolve a widget with that variable name using resolveWidget(), and render it as XHTML. If that fails too, handleUnresolvedVariable() is called, passing the initial arguments.

      You may want to reimplement this method to provide on-demand loading of strings for your template.

      The result stream expects a UTF-8 encoded string value.

      Warning: When specializing this class, you need to make sure that you append proper XHTML to the result, without unsafe active contents. The format() methods may be used for this purpose.

      Throws:
      java.io.IOException
      See Also:
      renderTemplate(Writer result)
    • handleUnresolvedVariable

      public void handleUnresolvedVariable​(java.lang.String varName, java.util.List<WString> args, java.io.Writer result) throws java.io.IOException
      Handles a variable that could not be resolved.

      This method is called from resolveString() for variables that could not be resolved.

      The default implementation implementation writes "??" + varName + "??" to the result stream.

      The result stream expects a UTF-8 encoded string value.

      Warning: When specializing this class, you need to make sure that you append proper XHTML to the result, without unsafe active contents. The format() methods may be used for this purpose.

      Throws:
      java.io.IOException
      See Also:
      resolveString(String varName, List args, Writer result)
    • resolveWidget

      public WWidget resolveWidget​(java.lang.String varName)
      Resolves a widget for a variable name.

      The default implementation returns a widget that was bound using bindWidget().

      You may want to reimplement this method to create widgets on-demand. All widgets that are returned by this method are reparented to the WTemplate, so they will be deleted when the template is destroyed, but they are not deleted by clear() (unless bind was called on them as in the example below).

      This method is typically used for delayed binding of widgets. Usage example:

      
       if (WWidget known = super.resolveWidget(varName)) {
       return known;
       } else {
       if (varName == "age-input") {
       WWidget w = new WLineEdit(); // widget only created when used
       bindWidget(varName, w);
       return w;
       }
       }
      
       
    • getWidgets

      public java.util.List<WWidget> getWidgets()
    • varName

      public java.lang.String varName​(WWidget w)
    • resolveFunction

      public boolean resolveFunction​(java.lang.String name, java.util.List<WString> args, java.io.Writer result) throws java.io.IOException
      Resolves a function call.

      This resolves a function with name name, and one or more arguments args , and writes the result into the stream result. The method returns whether a function was matched and applied.

      The default implementation considers functions that were bound using addFunction().

      Throws:
      java.io.IOException
      See Also:
      addFunction(String name, WTemplate.Function function)
    • clear

      public void clear()
      Erases all variable bindings.

      Removes all strings and deletes all widgets that were previously bound using bindString() and bindWidget().

      This also resets all conditions set using setCondition(), but does not remove functions added with addFunction()

    • setInternalPathEncoding

      public void setInternalPathEncoding​(boolean enabled)
      Enables internal path anchors in the XHTML template.

      Anchors to internal paths are represented differently depending on the session implementation (plain HTML, Ajax or HTML5 history). By enabling this option, anchors which reference an internal path (by referring a URL of the form href="#/..." ), are re-encoded to link to the internal path.

      The default value is false.

      See Also:
      WAnchor.setRefInternalPath(String path)
    • hasInternalPathEncoding

      public boolean hasInternalPathEncoding()
      Returns whether internal paths are enabled.

      See Also:
      setInternalPathEncoding(boolean enabled)
    • setEncodeTemplateText

      public void setEncodeTemplateText​(boolean on)
      Configures when internal path encoding is done.

      By default, the internal path encoding (if enabled) is done on the template text before placeholders are being resolved. In some rare situations, you may want to postpone the internal path encoding until after placeholders have been resolved, e.g. if a placeholder was used to provide the string for an anchor href.

      The default value is true

    • isEncodeTemplateText

      public boolean isEncodeTemplateText()
      Returns whether internal path encoding is done on the template text.

      See Also:
      setEncodeTemplateText(boolean on)
    • refresh

      public void refresh()
      Description copied from class: WWidget
      Refresh the widget.

      The refresh method is invoked when the locale is changed using WApplication#setLocale() or when the user hit the refresh button.

      The widget must actualize its contents in response.

      Note: This does *not* rerender the widget! Calling refresh() usually does not have any effect (unless you've reimplemented refresh() to attach to it an effect).

      Overrides:
      refresh in class WWebWidget
    • renderTemplate

      public void renderTemplate​(java.io.Writer result) throws java.io.IOException
      Renders the template into the given result stream.

      The default implementation will call renderTemplateText() with the getTemplateText().

      Throws:
      java.io.IOException
    • renderTemplateText

      public boolean renderTemplateText​(java.io.Writer result, java.lang.CharSequence templateText) throws java.io.IOException
      Renders a template into the given result stream.

      The default implementation will parse the template, and resolve variables by calling resolveString().

      You may want to reimplement this method to manage resources that are needed to load content on-demand (e.g. database objects), or support a custom template language.

      Return: true if rendered successfully. @see WTemplate#getErrorText()

      Throws:
      java.io.IOException
    • getErrorText

      public java.lang.String getErrorText()
      Renders the errors during renderring.

      See Also:
      renderTemplateText(Writer result, CharSequence templateText)
    • applyArguments

      protected void applyArguments​(WWidget w, java.util.List<WString> args)
      Applies arguments to a resolved widget.

      Currently only a class argument is handled, which adds one or more style classes to the widget w, using WWidget#addStyleClass().

    • format

      protected void format​(java.io.Writer result, java.lang.String s, TextFormat textFormat) throws java.io.IOException
      Utility method to safely format an XHTML string.

      The string is formatted according to the indicated textFormat. It is recommended to use this method when specializing resolveString() to avoid security risks.

      Throws:
      java.io.IOException
    • format

      protected final void format​(java.io.Writer result, java.lang.String s) throws java.io.IOException
      Utility method to safely format an XHTML string.

      Calls format(result, s, TextFormat.PlainText)

      Throws:
      java.io.IOException
    • format

      protected void format​(java.io.Writer result, java.lang.CharSequence s, TextFormat textFormat) throws java.io.IOException
      Utility method to safely format an XHTML string.

      The string is formatted according to the indicated textFormat. It is recommended to use this method when specializing resolveString() to avoid security risks.

      Throws:
      java.io.IOException
    • format

      protected final void format​(java.io.Writer result, java.lang.CharSequence s) throws java.io.IOException
      Utility method to safely format an XHTML string.

      Calls format(result, s, TextFormat.PlainText)

      Throws:
      java.io.IOException
    • enableAjax

      protected void enableAjax()
      Description copied from class: WWidget
      Progresses to an Ajax-enabled widget.

      This method is called when the progressive bootstrap method is used, and support for AJAX has been detected. The default behavior will upgrade the widget's event handling to use AJAX instead of full page reloads, and propagate the call to its children.

      You may want to reimplement this method if you want to make changes to widget when AJAX is enabled. You should always call the base implementation.

      Overrides:
      enableAjax in class WWebWidget
      See Also:
      WApplication.enableAjax()
    • reset

      protected void reset()
      Notifies the template that it has changed and must be rerendered.

      If you update a WTemplate with e.g bindWidget or setCondition, or change the template text, the template will automatically be rerendered.

      However, if you create a subclass of WTemplate and override resolveString or resolveWidget, you will have to notify the WTemplate if it has changed with a call to reset().