org.apache.jasper.compiler.tagplugin

Interface TagPluginContext

public interface TagPluginContext

This interface allows the plugin author to make inqueries about the properties of the current tag, and to use Jasper resources to generate direct Java codes in place of tag handler invocations.

Method Summary

Methods

Modifier and Type	Method and Description
void	dontUseTagPlugin() Abandon optimization for this tag handler, and instruct Jasper to generate the tag handler calls, as usual.
void	generateAttribute(String attribute) Generate codesto evaluate value of a attribute in the custom tag The codes is a Java expression.
void	generateBody()
void	generateDeclaration(String id, String text) Generate a declaration in the of the generated class.
void	generateImport(String s) Generate an import statement
void	generateJavaSource(String s) Generate Java source codes
String	getConstantAttribute(String attribute)
TagPluginContext	getParentContext() Get the PluginContext for the parent of this custom tag.
Object	getPluginAttribute(String attr) Get the value of an attribute in the current tagplugin context.
String	getTemporaryVariableName()
boolean	isAttributeSpecified(String attribute)
boolean	isConstantAttribute(String attribute)
boolean	isScriptless()
void	setPluginAttribute(String attr, Object value) Associate the attribute with a value in the current tagplugin context.

Method Detail

isScriptless

boolean isScriptless()

Returns:

true if the body of the tag is scriptless.

isAttributeSpecified

boolean isAttributeSpecified(String attribute)

Parameters:

attribute - Name of the attribute

Returns:

true if the attribute is specified in the tag

getTemporaryVariableName

String getTemporaryVariableName()

Returns:

An unique temporary variable name that the plugin can use.

generateImport

void generateImport(String s)

Generate an import statement

Parameters:

s - Name of the import class, '*' allowed.

generateDeclaration

void generateDeclaration(String id,
                       String text)

Generate a declaration in the of the generated class. This can be used to declare an innter class, a method, or a class variable.

Parameters:

id - An unique ID identifying the declaration. It is not part of the declaration, and is used to ensure that the declaration will only appear once. If this method is invoked with the same id more than once in the translation unit, only the first declaration will be taken.

text - The text of the declaration.

generateJavaSource

void generateJavaSource(String s)

Generate Java source codes

isConstantAttribute

boolean isConstantAttribute(String attribute)

Returns:

true if the attribute is specified and its value is a translation-time constant.

getConstantAttribute

String getConstantAttribute(String attribute)

Returns:

A string that is the value of a constant attribute. Undefined if the attribute is not a (translation-time) constant. null if the attribute is not specified.

generateAttribute

void generateAttribute(String attribute)

Generate codesto evaluate value of a attribute in the custom tag The codes is a Java expression. NOTE: Currently cannot handle attributes that are fragments.

Parameters:

attribute - The specified attribute

generateBody

void generateBody()

dontUseTagPlugin

void dontUseTagPlugin()

Abandon optimization for this tag handler, and instruct Jasper to generate the tag handler calls, as usual. Should be invoked if errors are detected, or when the tag body is deemed too compilicated for optimization.

getParentContext

TagPluginContext getParentContext()

Get the PluginContext for the parent of this custom tag. NOTE: The operations available for PluginContext so obtained is limited to getPluginAttribute and setPluginAttribute, and queries (e.g. isScriptless(). There should be no calls to generate*().

Returns:

The pluginContext for the parent node. null if the parent is not a custom tag, or if the pluginConxt if not available (because useTagPlugin is false, e.g).

setPluginAttribute

void setPluginAttribute(String attr,
                      Object value)

Associate the attribute with a value in the current tagplugin context. The plugin attributes can be used for communication among tags that must work together as a group. See for an example.

getPluginAttribute

Object getPluginAttribute(String attr)

Get the value of an attribute in the current tagplugin context.