UIComponentClassicTagBase (Java EE 5 SDK)

javax.faces.webapp Class UIComponentClassicTagBase

java.lang.Object
  javax.faces.webapp.UIComponentTagBase
      javax.faces.webapp.UIComponentClassicTagBase

所有已实现的接口:

BodyTag, IterationTag, JspIdConsumer, JspTag, Tag

直接已知子类:

UIComponentELTag, UIComponentTag

public abstract class UIComponentClassicTagBase

extends UIComponentTagBase

implements JspIdConsumer, BodyTag

UIComponentTagBase is the base class for all JSP tags that use the "classic" JSP tag interface that correspond to a UIComponent instance in the view. In Faces 1.2, all component tags are BodyTag instances to allow for the execution of the page to build the component tree, but not render it. Rendering happens only after the component tree is completely built.

UIComponentTag extends UIComponentClassicTagBase to add support for properties that conform to the Faces 1.1 EL.

UIComponentELTag extends UIComponentClassicTagBase class to add support for properties that conform to the EL API.

The default implementation allows the proper interweaving of template text, non-Faces JSP tag output, and Faces component tag output in the same page, as expected by the page author.

The CASE markers in the following example will be cited in the method descriptions of this class.

• CASE 1 describes template text and/or non-component custom tag output occurring as the child of a component tag, but before the first component tag child of that component tag.

• CASE 2 describes template text and/or non-component custom tag output occurring between two sibling component tags.

• CASE 3 describes template text and/or non-component custom tag output occurring as the child content of an <f:verbatim> tag at any point in the page.

• CASE 4 describes template text and/or non-component custom tag output occurring between the last child component tag and its enclosing parent component tag's end tag.

    <h:panelGrid style="color:red" border="4" columns="2">
      CASE 1
      <h:outputText value="component 1"/>
      CASE 2
      <h:outputText value="component 2"/>
      <f:verbatim>CASE 3</f:verbatim>
      <c:out value="${pageScope.CASE4}" />
    </h:panelGrid>

 

The preceding arrangement of faces component tags, must yield markup that will render identically to the following (assuming that ${pageScope.CASE4} evaluates to "CASE 4" without the quotes).

<table border="4" style="color:red">

  <tbody>

    <tr><td>CASE 1</td></tr> <tr><td>component 1</td></tr> 

    <tr><td>CASE 2</td> <tr><td>component 2</td></tr> 

    <tr><td>CASE 3</td> <td>CASE 4</td></tr>

  </tbody>

</table>

 

UNIQUE_ID_PREFIX

protected static final String UNIQUE_ID_PREFIX

Used as the prefix for ids. This is necessary to avoid uniqueness conflicts with the transient verbatim components.

另请参见:

常量字段

bodyContent

protected BodyContent bodyContent

The bodyContent for this tag handler.

pageContext

protected PageContext pageContext

The JSP PageContext for the page we are embedded in.

UIComponentClassicTagBase

public UIComponentClassicTagBase()

getDoStartValue

protected int getDoStartValue()
                       throws JspException

Return the flag value that should be returned from the doStart() method when it is called. Subclasses may override this method to return the appropriate value.

抛出异常:

JspException - to cause doStart() to throw an exception

getDoEndValue

protected int getDoEndValue()
                     throws JspException

Return the flag value that should be returned from the doEnd() method when it is called. Subclasses may override this method to return the appropriate value.

抛出异常:

JspException - to cause doEnd() to throw an exception

encodeBegin

protected void encodeBegin()
                    throws IOException

Deprecated. No encoding is done during JSP page execution. Encoding is deferred until the page has completed executing to allow the entire tree to be built before any encoding occurs.

Delegate to the encodeBegin() method of our corresponding UIComponent. This method is called from doStartTag(). Normally, delegation occurs unconditionally; however, this method is abstracted out so that advanced tags can conditionally perform this call.

抛出异常:

IOException - if an input/output error occurs

encodeChildren

protected void encodeChildren()
                       throws IOException

Deprecated. No encoding is done during JSP page execution. Encoding is deferred until the page has completed executing to allow the entire tree to be built before any encoding occurs.

Delegate to the encodeChildren() method of our corresponding UIComponent. This method is called from doStartTag(). Normally, delegation occurs unconditionally; however, this method is abstracted out so that advanced tags can conditionally perform this call.

抛出异常:

IOException - if an input/output error occurs

encodeEnd

protected void encodeEnd()
                  throws IOException

Deprecated. No encoding is done during JSP page execution. Encoding is deferred until the page has completed executing to allow the entire tree to be built before any encoding occurs.

Delegate to the encodeEnd() method of our corresponding UIComponent. This method is called from doStartTag(). Normally, delegation occurs unconditionally; however, this method is abstracted out so that advanced tags can conditionally perform this call.

抛出异常:

IOException - if an input/output error occurs

setPageContext

public void setPageContext(PageContext pageContext)

Set the PageContext of the page containing this tag instance.

规范说明:

setPageContext in interface Tag

参数:

pageContext - The enclosing PageContext

getParent

public Tag getParent()

Return the Tag that is the parent of this instance.

规范说明:

getParent in interface Tag

返回:

the current parent, or null if none.

另请参见:

TagSupport.findAncestorWithClass(javax.servlet.jsp.tagext.Tag, java.lang.Class)

setParent

public void setParent(Tag parent)

Set the Tag that is the parent of this instance.

规范说明:

setParent in interface Tag

参数:

parent - The new parent Tag

setupResponseWriter

protected void setupResponseWriter()

Set up the ResponseWriter for the current response, if this has not been done already.

@deprecated. ViewHandler.renderView(javax.faces.context.FacesContext, javax.faces.component.UIViewRoot) is now responsible for setting up the response writer. This method is now a no-op.

findComponent

protected UIComponent findComponent(FacesContext context)
                             throws JspException

Find and return the UIComponent, from the component tree, that corresponds to this tag handler instance. If there is no such UIComponent, create one and add it as a child or facet of the UIComponent associated with our nearest enclosing UIComponentTag. The process for locating or creating the component is:

1. If we have previously located this component, return it.
2. Locate the parent component by looking for a parent UIComponentTag instance, and ask it for its component. If there is no parent UIComponentTag instance, this tag represents the root component, so get it from the current Tree and return it.
3. If this UIComponentTag instance has the facetName attribute set, ask the parent UIComponent for a facet with this name. If not found, create one, call setProperties() with the new component as a parameter, and register it under this name. Return the found or created facet UIComponent.
4. Determine the component id to be assigned to the new component, as follows: if this UIComponentTag has an id attribute set, use that value; otherwise, generate an identifier that is guaranteed to be the same for this UIComponent every time this page is processed (i.e. one based on the location of all UIComponentTag instances without an id attribute set).
5. Ask the parent UIComponent for a child with this identifier. If not found, create one, call setProperties() with the new component as a parameter, and register it as a child with this identifier. Return the found or created child UIComponent.

When creating a component, the process is:

1. Retrieve the component type by calling UIComponentTagBase.getComponentType()
2. If the component has a binding attribute, create an expression from it, and call Application.createComponent(java.lang.String) with that expression, the FacesContext, and the component type. Store the expression using the key "binding".
3. Otherwise, call Application.createComponent(java.lang.String) with only the component type.
4. Call setProperties().
5. Add the new component as a child or facet of its parent

抛出异常:

JspException

getParentUIComponentClassicTagBase

public static UIComponentClassicTagBase getParentUIComponentClassicTagBase(PageContext context)

Locate and return the nearest enclosing UIComponentClassicTagBase if any; otherwise, return null.

参数:

context - PageContext for the current page

getIndexOfNextChildTag

protected int getIndexOfNextChildTag()

Description copied from class: UIComponentTagBase

Return the index of the next child to be added as a child of this tag. The default implementation maintains a list of created components and returns the size of the list.

规范说明:

getIndexOfNextChildTag in class UIComponentTagBase

addChild

protected void addChild(UIComponent child)

Description copied from class: UIComponentTagBase

Add the component identifier of the specified UIComponent to the list of component identifiers created or located by nested UIComponentTags processing this request.

规范说明:

addChild in class UIComponentTagBase

参数:

child - New child whose identifier should be added

addFacet

protected void addFacet(String name)

Description copied from class: UIComponentTagBase

Add the facet name of the specified facet to the list of facet names created or located by nested UIComponentTags processing this request.

规范说明:

addFacet in class UIComponentTagBase

参数:

name - Facet name to be added

createVerbatimComponentFromBodyContent

protected UIComponent createVerbatimComponentFromBodyContent()

Create a transient UIOutput component from the body content, of this tag instance or return null if there is no body content, the body content is whitespace, or the body content is a comment.

createVerbatimComponent

protected UIOutput createVerbatimComponent()

Use the Application instance to create a new component with the following characteristics.

componentType is javax.faces.HtmlOutputText.

transient is true.

escape is false.

id is FacesContext.getViewRoot().createUniqueId()

addVerbatimBeforeComponent

protected void addVerbatimBeforeComponent(UIComponentClassicTagBase parentTag,
                                          UIComponent verbatim,
                                          UIComponent component)

Add verbatim as a sibling of component in component in the parent's child list. verbatim is added to the list at the position immediatly preceding component.

addVerbatimAfterComponent

protected void addVerbatimAfterComponent(UIComponentClassicTagBase parentTag,
                                         UIComponent verbatim,
                                         UIComponent component)

Add verbatim as a sibling of component in component in the parent's child list. verbatim is added to the list at the position immediatly following component.

doStartTag

public int doStartTag()
               throws JspException

Perform any processing necessary to find (or create) the UIComponent instance in the view corresponding to this tag instance in the page and, if and only if a component was created, insert it into the tree at the proper location as expected by the page author. Secondarily, cause a transient UIOutput component to be created and placed in the tree before the UIComponent instance for this tag. The value of this UIOutput component must include anything covered by CASE 1 or CASE 2 in the class description.

The default implementation, which is intended to be sufficient for most components, implements this secondary requirement by calling getParentUIComponentClassicTagBase(javax.servlet.jsp.PageContext), and calling createVerbatimComponentFromBodyContent() on the result. It then adds the returned component to the tree before the actual component for this tag instance instance by calling addVerbatimBeforeComponent(javax.faces.webapp.UIComponentClassicTagBase, javax.faces.component.UIComponent, javax.faces.component.UIComponent).

Before returning, the component is pushed onto the component stack for this response to enable the getParentUIComponentClassicTagBase(javax.servlet.jsp.PageContext) method to work properly.

The flag value to be returned is acquired by calling the getDoStartValue() method, which tag subclasses may override if they do not want the default value.

规范说明:

doStartTag in interface Tag

返回:

EVAL_BODY_INCLUDE if the tag wants to process body, SKIP_BODY if it does not want to process it.

抛出异常:

JspException - if an error occurs

另请参见:

BodyTag

doEndTag

public int doEndTag()
             throws JspException

Perform any processing necessary to handle the content implications of CASE 3 in the class description.

The default implementation, which is intended to be sufficient for most components, calls createVerbatimComponentFromBodyContent() on this instance and adds it as a child of the component for this tag's component at the end of the child list. In addition, the following housekeeping steps are taken.

• Retrieve from the UIComponent the set of component ids of child components created by UIComponentTag instances the last time this page was processed (if any). Compare it to the list of children created during this page processing pass, and remove all children present in the old list but not the new. Save the new list as a component attribute so that it gets saved as part of the component's state.
• Retrieve from the UIComponent the set of facet names of facets created by UIComponentTag instances the last time this page was processed (if any). Compare it to the list of facets created during this page processing pass, and remove all facets present in the old list but not the new. Save the new list as a component attribute so that it gets saved as part of the component's state.
• Release all references to the component, and pop it from the component stack for this response, removing the stack if this was the outermost component.

The flag value to be returned is acquired by calling the getDoEndValue() method, which tag subclasses may override if they do not want the default value.

规范说明:

doEndTag in interface Tag

返回:

indication of whether to continue evaluating the JSP page.

抛出异常:

JspException - if an error occurs

release

public void release()

Release any resources allocated during the execution of this tag handler.

规范说明:

release in interface Tag

getDoAfterBodyValue

protected int getDoAfterBodyValue()
                           throws JspException

Return the flag value that should be returned from the doAfterBody() method when it is called. Subclasses may override this method to return the appropriate value.

抛出异常:

JspException

setBodyContent

public void setBodyContent(BodyContent bodyContent)

Set the bodyContent for this tag handler. This method is invoked by the JSP page implementation object at most once per action invocation, before doInitiBody(). This method will not be invoked for empty tags or for non-empty tags whose doStartTag() method returns SKIP_BODY or EVAL_BODY_INCLUDE.

规范说明:

setBodyContent in interface BodyTag

参数:

bodyContent - The new BodyContent for this tag

另请参见:

BodyTag.doInitBody(), IterationTag.doAfterBody()

getPreviousOut

public JspWriter getPreviousOut()

Get the JspWriter from our BodyContent.

getBodyContent

public BodyContent getBodyContent()

doInitBody

public void doInitBody()
                throws JspException

Prepare for evaluation of the body. This method is invoked by the JSP page implementation object after setBodyContent() and before the first time the body is to be evaluated. This method will not be invoked for empty tags or for non-empty tags whose doStartTag() method returns SKIP_BODY or EVAL_BODY_INCLUDE.

规范说明:

doInitBody in interface BodyTag

抛出异常:

JspException - if an error is encountered

另请参见:

IterationTag.doAfterBody()

doAfterBody

public int doAfterBody()
                throws JspException

Perform any processing necessary to handle the content implications of CASE 4 in the class description.

Return result from getDoAfterBodyValue()

规范说明:

doAfterBody in interface IterationTag

返回:

whether additional evaluations of the body are desired

抛出异常:

JspException - if an error is encountered

setId

public void setId(String id)

Set the component identifier for our component. If the argument begins with UIViewRoot.UNIQUE_ID_PREFIX throw an IllegalArgumentException

规范说明:

setId in class UIComponentTagBase

参数:

id - The new component identifier. This may not start with UIViewRoot.UNIQUE_ID_PREFIX.

抛出异常:

IllegalArgumentException - if the argument is non-null and starts with UIViewRoot.UNIQUE_ID_PREFIX.

getId

protected String getId()

Return the id value assigned by the page author.

getFacesJspId

protected String getFacesJspId()

If this method has been called before on this tag's useful lifetime (before release() was called), return the previously returned value. Otherwise, if getJspId() returns non-null, prepend UNIQUE_ID_PREFIX to the jspId and return the result.

getCreatedComponents

protected List<String> getCreatedComponents()

Returns the List of UIComponent ids created or located by nested UIComponentTags while processing the current request.

setJspId

public void setJspId(String id)

Defined on JspIdConsumer. This method is called by the container before doStartTag(). The argument is guaranteed to be unique within the page.

IMPLEMENTATION NOTE: This method will detect where we are in an include and assign a unique ID for each include in a particular 'logical page'. This allows us to avoid possible duplicate ID situations for included pages that have components without explicit IDs.

规范说明:

setJspId in interface JspIdConsumer

参数:

id - the container generated id for this tag, guaranteed to be unique within the page.

getJspId

public String getJspId()

setProperties

protected abstract void setProperties(UIComponent component)

Override properties and attributes of the specified component, if the corresponding properties of this tag handler instance were explicitly set. This method must be called ONLY if the specified UIComponent was in fact created during the execution of this tag handler instance, and this call will occur BEFORE the UIComponent is added to the view.

Tag subclasses that want to support additional set properties must ensure that the base class setProperties() method is still called. A typical implementation that supports extra properties foo and bar would look something like this:

 protected void setProperties(UIComponent component) {
   super.setProperties(component);
   if (foo != null) {
     component.setAttribute("foo", foo);
   }
   if (bar != null) {
     component.setAttribute("bar", bar);
   }
 }
 

The default implementation overrides the following properties:

• rendered - Set if a value for the rendered property is specified for this tag handler instance.
• rendererType - Set if the getRendererType() method returns a non-null value.

参数:

component - UIComponent whose properties are to be overridden

createComponent

protected abstract UIComponent createComponent(FacesContext context,
                                               String newId)
                                        throws JspException

Create and return a new child component of the type returned by calling getComponentType(). If this UIComponentTag has a non-null binding attribute, this is done by call Application.createComponent(java.lang.String) with the expression created for the binding attribute, and the expression will be stored on the component. Otherwise, Application.createComponent(java.lang.String) is called with only the component type. Finally, initialize the components id and other properties.

参数:

context - FacesContext for the current request

newId - id of the component

抛出异常:

JspException

hasBinding

protected abstract boolean hasBinding()

Return true if this component has a non-null binding attribute. This method is necessary to allow subclasses that expose the binding property as an Faces 1.1 style EL property as well as subclasses that expose it as an EL API property.

getComponentInstance

public UIComponent getComponentInstance()

Return the UIComponent instance that is associated with this tag instance. This method is designed to be used by tags nested within this tag, and only returns useful results between the execution of doStartTag() and doEndTag() on this tag instance.

规范说明:

getComponentInstance in class UIComponentTagBase

getCreated

public boolean getCreated()

Return true if we dynamically created a new component instance during execution of this tag. This method is designed to be used by tags nested within this tag, and only returns useful results between the execution of doStartTag() and doEndTag() on this tag instance.

规范说明:

getCreated in class UIComponentTagBase

getFacesContext

protected FacesContext getFacesContext()

Description copied from class: UIComponentTagBase

Return the FacesContext instance for the current request. This value will be non-null only from the beginning of doStartTag() through the end of doEndTag() for each tag instance.

规范说明:

getFacesContext in class UIComponentTagBase

getFacetName

protected String getFacetName()

Return the facet name that we should be stored under, if any; otherwise, return null (indicating that we will be a child component).

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