javax.faces.component
Class UIData

java.lang.Object
  javax.faces.component.UIComponent
      javax.faces.component.UIComponentBase
          javax.faces.component.UIData

All Implemented Interfaces:

NamingContainer, StateHolder

@JSFComponent(defaultRendererType="javax.faces.Table")
public class UIData
extends UIComponentBase
implements NamingContainer

Represents an abstraction of a component which has multiple "rows" of data.

The children of this component are expected to be UIColumn components.

Note that the same set of child components are reused to implement each row of the table in turn during such phases as apply-request-values and render-response. Altering any of the members of these components therefore affects the attribute for every row, except for the following members:

• submittedValue
• value (where no EL binding is used)
• valid

This reuse of the child components also means that it is not possible to save a reference to a component during table processing, then access it later and expect it to still represent the same row of the table.

Implementation Notes

Each of the UIColumn children of this component has a few component children of its own to render the contents of the table cell. However there can be a very large number of rows in a table, so it isn't efficient for the UIColumn and all its child objects to be duplicated for each row in the table. Instead the "flyweight" pattern is used where a serialized state is held for each row. When setRowIndex is invoked, the UIColumn objects and their children serialize their current state then reinitialise themselves from the appropriate saved state. This allows a single set of real objects to represent multiple objects which have the same types but potentially different internal state. When a row is selected for the first time, its state is set to a clean "initial" state. Transient components (including any read-only component) do not save their state; they are just reinitialised as required. The state saved/restored when changing rows is not the complete component state, just the fields that are expected to vary between rows: "submittedValue", "value", "isValid".

Note that a table is a "naming container", so that components within the table have their ids prefixed with the id of the table. Actually, when setRowIndex has been called on a table with id of "zzz" the table pretends to its children that its ID is "zzz_n" where n is the row index. This means that renderers for child components which call component.getClientId automatically get ids of form "zzz_n:childId" thus ensuring that components in different rows of the table get different ids.

When decoding a submitted page, this class iterates over all its possible rowIndex values, restoring the appropriate serialized row state then calling processDecodes on the child components. Because the child components (or their renderers) use getClientId to get the request key to look for parameter data, and because this object pretends to have a different id per row ("zzz_n") a single child component can decode data from each table row in turn without being aware that it is within a table. The table's data model is updated before each call to child.processDecodes, so the child decode method can assume that the data model's rowData points to the model object associated with the row currently being decoded. Exactly the same process applies for the later validation and updateModel phases.

When the data model for the table is bound to a backing bean property, and no validation errors have occured during processing of a postback, the data model is refetched at the start of the rendering phase (ie after the update model phase) so that the contents of the data model can be changed as a result of the latest form submission. Because the saved row state must correspond to the elements within the data model, the row state must be discarded whenever a new data model is fetched; not doing this would cause all sorts of inconsistency issues. This does imply that changing the state of any of the members "submittedValue", "value" or "valid" of a component within the table during the invokeApplication phase has no effect on the rendering of the table. When a validation error has occurred, a new DataModel is not fetched, and the saved state of the child components is not discarded.

see Javadoc of the JSF Specification for more information.

Version:

$Revision: 1203044 $ $Date: 2011-11-16 23:22:07 -0500 (Wed, 16 Nov 2011) $

Author:

Manfred Geiler (latest modification by $Author: lu4242 $)

Field Summary

static String	COMPONENT_FAMILY
static String	COMPONENT_TYPE

Fields inherited from class javax.faces.component.UIComponent

bindings

Fields inherited from interface javax.faces.component.NamingContainer

SEPARATOR_CHAR

Constructor Summary

UIData()
Construct an instance of the UIData.

Method Summary

void	broadcast(FacesEvent event) Ensure that before the event's listeners are invoked this UIData component's "current row" is set to the row associated with the event.
void	encodeBegin(FacesContext context) Perform necessary actions when rendering of this component starts, before delegating to the inherited implementation which calls the associated renderer's encodeBegin method.
void	encodeEnd(FacesContext context)
String	getClientId(FacesContext context) Get a string which can be output to the response which uniquely identifies this UIComponent within the current view.
protected DataModel	getDataModel() Return the datamodel for this table, potentially fetching the data from a backing bean via a value-binding if this is the first time this method has been called.
String	getFamily()
int	getFirst() Defines the index of the first row to be displayed, starting from 0.
UIComponent	getFooter()
UIComponent	getHeader()
int	getRowCount()
Object	getRowData()
int	getRowIndex()
int	getRows() Defines the maximum number of rows of data to be displayed.
Object	getValue() An EL expression that specifies the data model that backs this table.
String	getVar() Defines the name of the request-scope variable that will hold the current row during iteration.
boolean	invokeOnComponent(FacesContext context, String clientId, ContextCallback callback) invokeOnComponent must be implemented in UIComponentBase too...
boolean	isRowAvailable()
void	processDecodes(FacesContext context)
void	processUpdates(FacesContext context) This isn't an input component, so just pass on the processUpdates call to child components and facets that might be input components.
void	processValidators(FacesContext context)
void	queueEvent(FacesEvent event) Modify events queued for any child components so that the UIData state will be correctly configured before the event's listeners are executed.
void	restoreState(FacesContext facesContext, Object state) Invoked in the "restore view" phase, this initialises this object's members from the values saved previously into the provided state object.
Object	saveState(FacesContext facesContext) Invoked after the render phase has completed, this method returns an object which can be passed to the restoreState of some other instance of UIComponentBase to reset that object's state to the same values as this object currently has.
protected void	setDataModel(DataModel dataModel)
void	setFirst(int first)
void	setFooter(UIComponent footer)
void	setHeader(UIComponent header)
void	setRowIndex(int rowIndex) Set the current row index that methods like getRowData use.
void	setRows(int rows) Set the maximum number of rows displayed in the table.
void	setValue(Object value)
void	setValueExpression(String name, javax.el.ValueExpression binding)
void	setVar(String var)

Methods inherited from class javax.faces.component.UIComponentBase

addFacesListener, decode, encodeChildren, findComponent, getAttributes, getChildCount, getChildren, getFacesContext, getFacesListeners, getFacet, getFacetCount, getFacets, getFacetsAndChildren, getId, getParent, getRenderer, getRendererType, getRendersChildren, getValueBinding, isRendered, isTransient, processRestoreState, processSaveState, removeFacesListener, restoreAttachedState, saveAttachedState, setId, setParent, setRendered, setRendererType, setTransient, setValueBinding

Methods inherited from class javax.faces.component.UIComponent

encodeAll, getContainerClientId, getValueExpression

Methods inherited from class java.lang.Object

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

Field Detail

COMPONENT_FAMILY

public static final String COMPONENT_FAMILY

See Also:

Constant Field Values

COMPONENT_TYPE

public static final String COMPONENT_TYPE

See Also:

Constant Field Values

Constructor Detail

UIData

public UIData()

Construct an instance of the UIData.

Method Detail

invokeOnComponent

public boolean invokeOnComponent(FacesContext context,
                                 String clientId,
                                 ContextCallback callback)
                          throws FacesException

Description copied from class: UIComponentBase

invokeOnComponent must be implemented in UIComponentBase too...

Overrides:

invokeOnComponent in class UIComponentBase

Parameters:

context - FacesContext for the current request

clientId - the id of the desired UIComponent clazz

callback - Implementation of the ContextCallback to be called

Returns:

has component been found ?

Throws:

FacesException

setFooter

public void setFooter(UIComponent footer)

getFooter

@JSFFacet
public UIComponent getFooter()

setHeader

public void setHeader(UIComponent header)

getHeader

@JSFFacet
public UIComponent getHeader()

isRowAvailable

public boolean isRowAvailable()

getRowCount

public int getRowCount()

getRowData

public Object getRowData()

getRowIndex

public int getRowIndex()

setRowIndex

public void setRowIndex(int rowIndex)

Set the current row index that methods like getRowData use.

Param rowIndex can be -1, meaning "no row".

Parameters:

rowIndex -

setValueExpression

public void setValueExpression(String name,
                               javax.el.ValueExpression binding)

Overrides:

setValueExpression in class UIComponent

getClientId

public String getClientId(FacesContext context)

Description copied from class: UIComponentBase

Get a string which can be output to the response which uniquely identifies this UIComponent within the current view.

The component should have an id attribute already assigned to it; however if the id property is currently null then a unique id is generated and set for this component. This only happens when components are programmatically created without ids, as components created by a ViewHandler should be assigned ids when they are created.

If this component is a descendant of a NamingContainer then the client id is of form "{namingContainerId}:{componentId}". Note that the naming container's id may itself be of compound form if it has an ancestor naming container. Note also that this only applies to naming containers; other UIComponent types in the component's ancestry do not affect the clientId.

Finally the renderer associated with this component is asked to convert the id into a suitable form. This allows escaping of any characters in the clientId which are significant for the markup language generated by that renderer.

Overrides:

getClientId in class UIComponentBase

queueEvent

public void queueEvent(FacesEvent event)

Modify events queued for any child components so that the UIData state will be correctly configured before the event's listeners are executed.

Child components or their renderers may register events against those child components. When the listener for that event is eventually invoked, it may expect the uidata's rowData and rowIndex to be referring to the same object that caused the event to fire.

The original queueEvent call against the child component has been forwarded up the chain of ancestors in the standard way, making it possible here to wrap the event in a new event whose source is this component, not the original one. When the event finally is executed, this component's broadcast method is invoked, which ensures that the UIData is set to be at the correct row before executing the original event.

Overrides:

queueEvent in class UIComponentBase

broadcast

public void broadcast(FacesEvent event)
               throws AbortProcessingException

Ensure that before the event's listeners are invoked this UIData component's "current row" is set to the row associated with the event.

See queueEvent for more details.

Overrides:

broadcast in class UIComponentBase

Parameters:

event - must not be null.

Throws:

AbortProcessingException

encodeBegin

public void encodeBegin(FacesContext context)
                 throws IOException

Perform necessary actions when rendering of this component starts, before delegating to the inherited implementation which calls the associated renderer's encodeBegin method.

Overrides:

encodeBegin in class UIComponentBase

Throws:

IOException

encodeEnd

public void encodeEnd(FacesContext context)
               throws IOException

Overrides:

encodeEnd in class UIComponentBase

Throws:

IOException

See Also:

UIComponentBase.encodeEnd(javax.faces.context.FacesContext)

processDecodes

public void processDecodes(FacesContext context)

Overrides:

processDecodes in class UIComponentBase

processValidators

public void processValidators(FacesContext context)

Overrides:

processValidators in class UIComponentBase

processUpdates

public void processUpdates(FacesContext context)

Description copied from class: UIComponentBase

This isn't an input component, so just pass on the processUpdates call to child components and facets that might be input components.

Components that were never rendered can't possibly be receiving update data (no corresponding fields were ever put into the response) so if this component is not rendered then this method does not invoke processUpdates on its children.

Overrides:

processUpdates in class UIComponentBase

getDataModel

protected DataModel getDataModel()

Return the datamodel for this table, potentially fetching the data from a backing bean via a value-binding if this is the first time this method has been called.

This is complicated by the fact that this table may be nested within another table. In this case a different datamodel should be fetched for each row. When nested within a parent table, the parent reference won't change but parent.getClientId() will, as the suffix changes depending upon the current row index. A map object on this component is therefore used to cache the datamodel for each row of the table. In the normal case where this table is not nested inside a component that changes its id (like a table does) then this map only ever has one entry.

setDataModel

protected void setDataModel(DataModel dataModel)

getValue

@JSFProperty
public Object getValue()

An EL expression that specifies the data model that backs this table.

The value referenced by the EL expression can be of any type.

• A value of type DataModel is used directly.
• Array-like parameters of type array-of-Object, java.util.List, java.sql.ResultSet or javax.servlet.jsp.jstl.sql.Result are wrapped in a corresponding DataModel that knows how to iterate over the elements.
• Other values are wrapped in a DataModel as a single row.

Note in particular that unordered collections, eg Set are not supported. Therefore if the value expression references such an object then the table will be considered to contain just one element - the collection itself.

setValue

public void setValue(Object value)

getFirst

@JSFProperty
public int getFirst()

Defines the index of the first row to be displayed, starting from 0.

setFirst

public void setFirst(int first)

getRows

@JSFProperty
public int getRows()

Defines the maximum number of rows of data to be displayed.

Specify zero to display all rows from the "first" row to the end of available data.

setRows

public void setRows(int rows)

Set the maximum number of rows displayed in the table.

getVar

@JSFProperty(literalOnly=true)
public String getVar()

Defines the name of the request-scope variable that will hold the current row during iteration.

During rendering of child components of this UIData, the variable with this name can be read to learn what the "rowData" object for the row currently being rendered is.

This value must be a static value, ie an EL expression is not permitted.

setVar

public void setVar(String var)

saveState

public Object saveState(FacesContext facesContext)

Description copied from class: UIComponentBase

Invoked after the render phase has completed, this method returns an object which can be passed to the restoreState of some other instance of UIComponentBase to reset that object's state to the same values as this object currently has.

Specified by:

saveState in interface StateHolder

Overrides:

saveState in class UIComponentBase

restoreState

public void restoreState(FacesContext facesContext,
                         Object state)

Description copied from class: UIComponentBase

Invoked in the "restore view" phase, this initialises this object's members from the values saved previously into the provided state object.

Specified by:

restoreState in interface StateHolder

Overrides:

restoreState in class UIComponentBase

state - is an object previously returned by the saveState method of this class.

getFamily

public String getFamily()

Specified by:

getFamily in class UIComponent