javax.servlet.jsp.tagext.TagLibraryValidator Maven / Gradle / Ivy
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package javax.servlet.jsp.tagext;
import java.util.Map;
/**
* Translation-time validator class for a JSP page.
* A validator operates on the XML view associated with the JSP page.
*
*
* The TLD file associates a TagLibraryValidator class and some init
* arguments with a tag library.
*
*
* The JSP container is reponsible for locating an appropriate
* instance of the appropriate subclass by
*
*
* - new a fresh instance, or reuse an available one
*
- invoke the setInitParams(Map) method on the instance
*
*
* once initialized, the validate(String, String, PageData) method will
* be invoked, where the first two arguments are the prefix
* and uri for this tag library in the XML View. The prefix is intended
* to make it easier to produce an error message. However, it is not
* always accurate. In the case where a single URI is mapped to more
* than one prefix in the XML view, the prefix of the first URI is provided.
* Therefore, to provide high quality error messages in cases where the
* tag elements themselves are checked, the prefix parameter should be
* ignored and the actual prefix of the element should be used instead.
* TagLibraryValidators should always use the uri to identify elements
* as beloning to the tag library, not the prefix.
*
*
* A TagLibraryValidator instance
* may create auxiliary objects internally to perform
* the validation (e.g. an XSchema validator) and may reuse it for all
* the pages in a given translation run.
*
*
* The JSP container is not guaranteed to serialize invocations of
* validate() method, and TagLibraryValidators should perform any
* synchronization they may require.
*
*
* As of JSP 2.0, a JSP container must provide a jsp:id attribute to
* provide higher quality validation errors.
* The container will track the JSP pages
* as passed to the container, and will assign to each element
* a unique "id", which is passed as the value of the jsp:id
* attribute. Each XML element in the XML view available will
* be extended with this attribute. The TagLibraryValidator
* can then use the attribute in one or more ValidationMessage
* objects. The container then, in turn, can use these
* values to provide more precise information on the location
* of an error.
*
*
* The actual prefix of the id attribute may or may not be
* jsp but it will always map to the namespace
* http://java.sun.com/JSP/Page. A TagLibraryValidator
* implementation must rely on the uri, not the prefix, of the id
* attribute.
*/
abstract public class TagLibraryValidator {
/**
* Sole constructor. (For invocation by subclass constructors,
* typically implicit.)
*/
public TagLibraryValidator() {
}
/**
* Set the init data in the TLD for this validator.
* Parameter names are keys, and parameter values are the values.
*
* @param map A Map describing the init parameters
*/
public void setInitParameters(Map map) {
initParameters = map;
}
/**
* Get the init parameters data as an immutable Map.
* Parameter names are keys, and parameter values are the values.
*
* @return The init parameters as an immutable map.
*/
public Map getInitParameters() {
return initParameters;
}
/**
* Validate a JSP page.
* This will get invoked once per unique tag library URI in the
* XML view. This method will return null if the page is valid; otherwise
* the method should return an array of ValidationMessage objects.
* An array of length zero is also interpreted as no errors.
*
* @param prefix the first prefix with which the tag library is
* associated, in the XML view. Note that some tags may use
* a different prefix if the namespace is redefined.
* @param uri the tag library's unique identifier
* @param page the JspData page object
* @return A null object, or zero length array if no errors, an array
* of ValidationMessages otherwise.
*/
public ValidationMessage[] validate(String prefix, String uri,
PageData page)
{
return null;
}
/**
* Release any data kept by this instance for validation purposes.
*/
public void release() {
}
// Private data
private Map initParameters;
}