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
voiddontUseTagPlugin()
Abandon optimization for this tag handler, and instruct Jasper to generate the tag handler calls, as usual.
voidgenerateAttribute(String attribute)
Generate codesto evaluate value of a attribute in the custom tag The codes is a Java expression.
voidgenerateBody()
Generate codes for the body of the custom tag
voidgenerateDeclaration(String id, String text)
Generate a declaration in the of the generated class.
voidgenerateImport(String s)
Generate an import statement
voidgenerateJavaSource(String s)
Generate Java source codes
StringgetConstantAttribute(String attribute)
TagPluginContextgetParentContext()
Get the PluginContext for the parent of this custom tag.
ObjectgetPluginAttribute(String attr)
Get the value of an attribute in the current tagplugin context.
StringgetTemporaryVariableName()
booleanisAttributeSpecified(String attribute)
booleanisConstantAttribute(String attribute)
booleanisScriptless()
voidsetPluginAttribute(String attr, Object value)
Associate the attribute with a value in the current tagplugin context.

Method Detail

dontUseTagPlugin

public 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.

generateAttribute

public 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

public void generateBody()
Generate codes for the body of the custom tag

generateDeclaration

public 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.

generateImport

public void generateImport(String s)
Generate an import statement

Parameters: s Name of the import class, '*' allowed.

generateJavaSource

public void generateJavaSource(String s)
Generate Java source codes

getConstantAttribute

public 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.

getParentContext

public 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).

getPluginAttribute

public Object getPluginAttribute(String attr)
Get the value of an attribute in the current tagplugin context.

getTemporaryVariableName

public String getTemporaryVariableName()

Returns: An unique temporary variable name that the plugin can use.

isAttributeSpecified

public boolean isAttributeSpecified(String attribute)

Parameters: attribute Name of the attribute

Returns: true if the attribute is specified in the tag

isConstantAttribute

public boolean isConstantAttribute(String attribute)

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

isScriptless

public boolean isScriptless()

Returns: true if the body of the tag is scriptless.

setPluginAttribute

public 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.
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