eu.webtoolkit.jwt
Class WTemplate

java.lang.Object
  eu.webtoolkit.jwt.WObject
      eu.webtoolkit.jwt.WWidget
          eu.webtoolkit.jwt.WWebWidget
              eu.webtoolkit.jwt.WInteractWidget
                  eu.webtoolkit.jwt.WTemplate

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 "$${".

There are currently two syntactic constructs defined.

A. Variable placeholders

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

• a widget, using bindWidget()
• a string value, using bindString() or bindInt()
• or in general, the result of resolveString() and resolveWidget() methods.

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

${var arg1=value1 arg2="A second value" arg3='A third 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. We are planning to add a syntax for conditional sections

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.

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

• Functions::tr() resolves a localized strings. This is convenient to create a language neutral template, which contains translated strings
• resolves the id of a bound widget. This is convenient to bind <label> elements to a form widget using its for attribute.

C. Conditional blocks

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

Conditions are set using setCondition().

Usage example

 WString userName = ...;
 
  WTemplate *t = new WTemplate();
  t.setTemplateText("
 How old are you, ${friend} ? ${age-input} 
");
 
  t.bindString("friend", userName, PlainText);
  t.bindWidget("age-input", ageEdit_ = new WLineEdit());
 

CSS

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

Constructor Summary

WTemplate()
Creates a template widget.

WTemplate(java.lang.CharSequence text)
Creates a template widget with given template.

WTemplate(java.lang.CharSequence text, WContainerWidget parent)
Creates a template widget with given template.

WTemplate(WContainerWidget parent)
Creates a template widget.

Method Summary

void	addFunction(java.lang.String name, eu.webtoolkit.jwt.WTemplate.Function function) Binds a function.
protected void	applyArguments(WWidget w, java.util.List<WString> args) Applies arguments to a resolved widget.
void	bindEmpty(java.lang.String varName) Binds an empty string to a variable.
void	bindInt(java.lang.String varName, int value) Binds an integer value to a variable.
void	bindString(java.lang.String varName, java.lang.CharSequence value) Binds a string value to a variable.
void	bindString(java.lang.String varName, java.lang.CharSequence value, TextFormat textFormat) Binds a string value to a variable.
void	bindWidget(java.lang.String varName, WWidget widget) Binds a widget to a variable.
void	clear() Erases all variable bindings.
boolean	conditionValue(java.lang.String name) Returns a condition value.
protected void	enableAjax() Progresses to an Ajax-enabled widget.
protected void	format(java.io.Writer result, java.lang.CharSequence s) Utility method to safely format an XHTML string.
protected void	format(java.io.Writer result, java.lang.CharSequence s, TextFormat textFormat) Utility method to safely format an XHTML string.
protected void	format(java.io.Writer result, java.lang.String s) Utility method to safely format an XHTML string.
protected void	format(java.io.Writer result, java.lang.String s, TextFormat textFormat) Utility method to safely format an XHTML string.
WString	getTemplateText() Returns the template.
void	handleUnresolvedVariable(java.lang.String varName, java.util.List<WString> args, java.io.Writer result) Handles a variable that could not be resolved.
boolean	hasInternalPathEncoding() Returns whether internal paths are enabled.
void	refresh() Refreshes the template.
protected void	renderTemplate(java.io.Writer result) Renders the template into the given result stream.
boolean	resolveFunction(java.lang.String name, java.util.List<WString> args, java.io.Writer result) Resolves a function call.
void	resolveString(java.lang.String varName, java.util.List<WString> args, java.io.Writer result) Resolves the string value for a variable name.
WWidget	resolveWidget(java.lang.String varName) Resolves a widget for a variable name.
void	setCondition(java.lang.String name, boolean value) Sets a condition.
void	setInternalPathEncoding(boolean enabled) Enables internal path anchors in the XHTML template.
void	setTemplateText(java.lang.CharSequence text) Sets the template text.
void	setTemplateText(java.lang.CharSequence text, TextFormat textFormat) Sets the template text.

Methods inherited from class eu.webtoolkit.jwt.WInteractWidget

clicked, doubleClicked, enterPressed, escapePressed, gestureChanged, gestureEnded, gestureStarted, isEnabled, keyPressed, keyWentDown, keyWentUp, load, mouseDragged, mouseMoved, mouseWentDown, mouseWentOut, mouseWentOver, mouseWentUp, mouseWheel, propagateSetEnabled, remove, setDraggable, setDraggable, setDraggable, setDraggable, touchEnded, touchMoved, touchStarted

Methods inherited from class eu.webtoolkit.jwt.WWebWidget

addStyleClass, callJavaScriptMember, childrenChanged, doJavaScript, domCanBeSaved, escapeText, escapeText, escapeText, escapeText, find, getAttributeValue, getChildren, getClearSides, getDecorationStyle, getFloatSide, getHeight, getId, getJavaScriptMember, getLineHeight, getMargin, getMaximumHeight, getMaximumWidth, getMinimumHeight, getMinimumWidth, getOffset, getPositionScheme, getStyleClass, getTabIndex, getToolTip, getVerticalAlignment, getVerticalAlignmentLength, getWidth, isDisabled, isHidden, isHiddenKeepsGeometry, isInline, isLoaded, isPopup, isRendered, isVisible, jsStringLiteral, jsStringLiteral, removeScript, removeStyleClass, resize, setAttributeValue, setClearSides, setDecorationStyle, setDisabled, setFloatSide, setHidden, setHiddenKeepsGeometry, setId, setInline, setJavaScriptMember, setLineHeight, setLoadLaterWhenInvisible, setMargin, setMaximumSize, setMinimumSize, setOffsets, setPopup, setPositionScheme, setSelectable, setStyleClass, setTabIndex, setToolTip, setVerticalAlignment, updateSignalConnection

Methods inherited from class eu.webtoolkit.jwt.WWidget

acceptDrops, acceptDrops, addCssRule, addCssRule, addStyleClass, animateHide, animateShow, boxBorder, boxPadding, containsExposed, disable, dropEvent, enable, getDrop, getJsRef, getParent, hide, htmlText, isLayoutSizeAware, layoutSizeChanged, positionAt, positionAt, removeStyleClass, resize, setClearSides, setHeight, setHidden, setLayoutSizeAware, setMargin, setMargin, setMargin, setMargin, setMargin, setOffsets, setOffsets, setOffsets, setOffsets, setOffsets, setToolTip, setVerticalAlignment, setWidth, show, stopAcceptDrops, toggleStyleClass, toggleStyleClass, tr

Methods inherited from class eu.webtoolkit.jwt.WObject

getObjectName, setObjectName

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

WTemplate

public WTemplate(WContainerWidget parent)

Creates a template widget.

WTemplate

public WTemplate()

Creates a template widget.

Calls this((WContainerWidget)null)

WTemplate

public WTemplate(java.lang.CharSequence text,
                 WContainerWidget parent)

Creates a template widget with given template.

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

WTemplate

public WTemplate(java.lang.CharSequence text)

Creates a template widget with given template.

Calls this(text, (WContainerWidget)null)

Method Detail

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)

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.

Depending on the textFormat, the value is validated according as for a WText.

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.

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)

bindEmpty

public void bindEmpty(java.lang.String varName)

Binds an empty string to a variable.

See Also:

bindString(String varName, CharSequence value, TextFormat textFormat)

addFunction

public void addFunction(java.lang.String name,
                        eu.webtoolkit.jwt.WTemplate.Function function)

Binds a function.

Functions are useful to automatically resolve placeholders.

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

${fun:bla}

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

 WTemplate *t = ...;
    t.addFunction("id", &WTemplate::Functions::id);
    t.addFunction("tr", &WTemplate::Functions::tr);
 

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)

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 (Widget *known = WTemplate::resolveWidget(varName)) {
        return known;
      } else {
        if (varName == "age-input") {
          WWidget *w = new WLineEdit(); // widget only created when used
          bind(varName, w);
          return 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, 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)

refresh

public void refresh()

Refreshes the template.

This rerenders the template.

Overrides:

refresh in class WWebWidget

renderTemplate

protected void renderTemplate(java.io.Writer result)
                       throws java.io.IOException

Renders the 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.

Throws:

java.io.IOException

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()