org.apache.tools.ant

Class IntrospectionHelper

java.lang.Object

org.apache.tools.ant.IntrospectionHelper

public final class IntrospectionHelper
extends Object

Helper class that collects the methods a task or nested element holds to set attributes, create nested elements or hold PCDATA elements. It contains hashtables containing classes that use introspection to handle all the invocation of the project-component specific methods. This class is somewhat complex, as it implements the O/X mapping between Ant XML and Java class instances. This is not the best place for someone new to Ant to start contributing to the codebase, as a change here can break the entire system in interesting ways. Always run a full test of Ant before checking in/submitting changes to this file. The class is final and has a private constructor. To get an instance for a specific (class,project) combination, use getHelper(Project,Class). This may return an existing version, or a new one ...do not make any assumptions about its uniqueness, or its validity after the Project instance has finished its build.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	IntrospectionHelper.Creator creator - allows use of create/store external to IntrospectionHelper.

Field Summary

Fields

Modifier and Type	Field and Description
protected static String	NOT_SUPPORTED_CHILD_POSTFIX part of the error message created by throwNotSupported.
protected static String	NOT_SUPPORTED_CHILD_PREFIX part of the error message created by throwNotSupported.

Method Summary

Modifier and Type	Method and Description
void	addText(Project project, Object element, String text) Adds PCDATA to an element, using the element's void addText(String) method, if it has one.
static void	clearCache() Clears the static cache of on build finished.
java.lang.reflect.Method	getAddTextMethod() Returns the addText method when the introspected class supports nested text.
Map<String,Class<?>>	getAttributeMap() Returns a read-only map of attributes supported by the introspected class.
java.lang.reflect.Method	getAttributeMethod(String attributeName) Returns the setter method of a named attribute.
Enumeration<String>	getAttributes() Returns an enumeration of the names of the attributes supported by the introspected class.
Class<?>	getAttributeType(String attributeName) Returns the type of a named attribute.
IntrospectionHelper.Creator	getElementCreator(Project project, String parentUri, Object parent, String elementName, UnknownElement ue) returns an object that creates and stores an object for an element of a parent.
java.lang.reflect.Method	getElementMethod(String elementName) Returns the adder or creator method of a named nested element.
Class<?>	getElementType(String elementName) Returns the type of a named nested element.
List<java.lang.reflect.Method>	getExtensionPoints() Returns a read-only list of extension points supported by the introspected class.
static IntrospectionHelper	getHelper(Class<?> c) Returns a helper for the given class, either from the cache or by creating a new instance.
static IntrospectionHelper	getHelper(Project p, Class<?> c) Returns a helper for the given class, either from the cache or by creating a new instance.
Map<String,Class<?>>	getNestedElementMap() Returns a read-only map of nested elements supported by the introspected class.
Enumeration<String>	getNestedElements() Returns an enumeration of the names of the nested elements supported by the introspected class.
boolean	isContainer() Indicates whether the introspected class is a task container, supporting arbitrary nested tasks/types.
boolean	isDynamic() Indicates whether the introspected class is a dynamic one, supporting arbitrary nested elements and/or attributes.
void	setAttribute(Project p, Object element, String attributeName, Object value) Sets the named attribute in the given element, which is part of the given project.
void	setAttribute(Project p, Object element, String attributeName, String value) Sets the named attribute in the given element, which is part of the given project.
void	storeElement(Project project, Object parent, Object child, String elementName) Stores a named nested element using a storage method determined by the initial introspection.
boolean	supportsCharacters() Returns whether or not the introspected class supports PCDATA.
boolean	supportsNestedElement(String elementName) Indicates if this element supports a nested element of the given name.
boolean	supportsNestedElement(String parentUri, String elementName) Indicate if this element supports a nested element of the given name.
boolean	supportsNestedElement(String parentUri, String elementName, Project project, Object parent) Indicate if this element supports a nested element of the given name.
boolean	supportsReflectElement(String parentUri, String elementName) Check if this element supports a nested element from reflection.
void	throwNotSupported(Project project, Object parent, String elementName) Utility method to throw a NotSupported exception

Methods inherited from class java.lang.Object

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

Field Detail

NOT_SUPPORTED_CHILD_POSTFIX

protected static final String NOT_SUPPORTED_CHILD_POSTFIX

part of the error message created by throwNotSupported.

Since:

Ant 1.8.0

See Also:

Constant Field Values

NOT_SUPPORTED_CHILD_PREFIX

protected static final String NOT_SUPPORTED_CHILD_PREFIX

part of the error message created by throwNotSupported.

Since:

Ant 1.8.0

See Also:

Constant Field Values

Method Detail

addText

public void addText(Project project,
                    Object element,
                    String text)
             throws BuildException

Adds PCDATA to an element, using the element's void addText(String) method, if it has one. If no such method is present, a BuildException is thrown if the given text contains non-whitespace.

Parameters:

project - The project which the element is part of. Must not be null.

element - The element to add the text to. Must not be null.

text - The text to add. Must not be null.

Throws:

BuildException - if non-whitespace text is provided and no method is available to handle it, or if the handling method fails.

clearCache

public static void clearCache()

Clears the static cache of on build finished.

getAddTextMethod

public java.lang.reflect.Method getAddTextMethod()
                                          throws BuildException

Returns the addText method when the introspected class supports nested text.

Returns:

the method on this introspected class that adds nested text. Cannot be null.

Throws:

BuildException - if the introspected class does not support the nested text.

Since:

Ant 1.6.3

getAttributeMap

public Map<String,Class<?>> getAttributeMap()

Returns a read-only map of attributes supported by the introspected class.

Returns:

an attribute name to attribute Class unmodifiable map. Can be empty, but never null.

Since:

Ant 1.6.3

getAttributeMethod

public java.lang.reflect.Method getAttributeMethod(String attributeName)
                                            throws BuildException

Returns the setter method of a named attribute.

Parameters:

attributeName - The name of the attribute to find the setter method of. Must not be null.

Returns:

the method on this introspected class that sets this attribute. This will never be null.

Throws:

BuildException - if the introspected class does not support the named attribute.

Since:

Ant 1.6.3

getAttributes

public Enumeration<String> getAttributes()

Returns an enumeration of the names of the attributes supported by the introspected class.

Returns:

an enumeration of the names of the attributes supported by the introspected class.

See Also:

getAttributeMap()

getAttributeType

public Class<?> getAttributeType(String attributeName)
                          throws BuildException

Returns the type of a named attribute.

Parameters:

attributeName - The name of the attribute to find the type of. Must not be null.

Returns:

the type of the attribute with the specified name. This will never be null.

Throws:

BuildException - if the introspected class does not support the named attribute.

getElementCreator

public IntrospectionHelper.Creator getElementCreator(Project project,
                                                     String parentUri,
                                                     Object parent,
                                                     String elementName,
                                                     UnknownElement ue)

returns an object that creates and stores an object for an element of a parent.

Parameters:

project - Project to which the parent object belongs.

parentUri - The namespace uri of the parent object.

parent - Parent object used to create the creator object to create and store and instance of a subelement.

elementName - Name of the element to create an instance of.

ue - The unknown element associated with the element.

Returns:

a creator object to create and store the element instance.

getElementMethod

public java.lang.reflect.Method getElementMethod(String elementName)
                                          throws BuildException

Returns the adder or creator method of a named nested element.

Parameters:

elementName - The name of the attribute to find the setter method of. Must not be null.

Returns:

the method on this introspected class that adds or creates this nested element. Can be null when the introspected class is a dynamic configurator!

Throws:

BuildException - if the introspected class does not support the named nested element.

Since:

Ant 1.6.3

getElementType

public Class<?> getElementType(String elementName)
                        throws BuildException

Returns the type of a named nested element.

Parameters:

elementName - The name of the element to find the type of. Must not be null.

Returns:

the type of the nested element with the specified name. This will never be null.

Throws:

BuildException - if the introspected class does not support the named nested element.

getExtensionPoints

public List<java.lang.reflect.Method> getExtensionPoints()

Returns a read-only list of extension points supported by the introspected class.

A task/type or nested element with void methods named add() or addConfigured(), taking a single class or interface argument, supports extensions point. This method returns the list of all these void add[Configured](type) methods.

Returns:

a list of void, single argument add() or addConfigured() Methods of all supported extension points. These methods are sorted such that if the argument type of a method derives from another type also an argument of a method of this list, the method with the most derived argument will always appear first. Can be empty, but never null.

Since:

Ant 1.6.3

getHelper

public static IntrospectionHelper getHelper(Class<?> c)

Returns a helper for the given class, either from the cache or by creating a new instance.

Parameters:

c - The class for which a helper is required. Must not be null.

Returns:

a helper for the specified class

getHelper

public static IntrospectionHelper getHelper(Project p,
                                            Class<?> c)

Returns a helper for the given class, either from the cache or by creating a new instance. The method will make sure the helper will be cleaned up at the end of the project, and only one instance will be created for each class.

Parameters:

p - the project instance. Can be null, in which case the helper is not cached.

c - The class for which a helper is required. Must not be null.

Returns:

a helper for the specified class

getNestedElementMap

public Map<String,Class<?>> getNestedElementMap()

Returns a read-only map of nested elements supported by the introspected class.

Returns:

a nested-element name to nested-element Class unmodifiable map. Can be empty, but never null.

Since:

Ant 1.6.3

getNestedElements

public Enumeration<String> getNestedElements()

Returns an enumeration of the names of the nested elements supported by the introspected class.

Returns:

an enumeration of the names of the nested elements supported by the introspected class.

See Also:

getNestedElementMap()

isContainer

public boolean isContainer()

Indicates whether the introspected class is a task container, supporting arbitrary nested tasks/types.

Returns:

true if the introspected class is a container; false otherwise.

Since:

Ant 1.6.3

See Also:

TaskContainer

isDynamic

public boolean isDynamic()

Indicates whether the introspected class is a dynamic one, supporting arbitrary nested elements and/or attributes.

Returns:

true if the introspected class is dynamic; false otherwise.

Since:

Ant 1.6.3

See Also:

DynamicElement, DynamicElementNS

setAttribute

public void setAttribute(Project p,
                         Object element,
                         String attributeName,
                         Object value)
                  throws BuildException

Sets the named attribute in the given element, which is part of the given project.

Parameters:

p - The project containing the element. This is used when files need to be resolved. Must not be null.

element - The element to set the attribute in. Must not be null.

attributeName - The name of the attribute to set. Must not be null.

value - The value to set the attribute to. This may be interpreted or converted to the necessary type if the setter method doesn't accept an object of the supplied type.

Throws:

BuildException - if the introspected class doesn't support the given attribute, or if the setting method fails.

setAttribute

public void setAttribute(Project p,
                         Object element,
                         String attributeName,
                         String value)
                  throws BuildException

Sets the named attribute in the given element, which is part of the given project.

Parameters:

p - The project containing the element. This is used when files need to be resolved. Must not be null.

element - The element to set the attribute in. Must not be null.

attributeName - The name of the attribute to set. Must not be null.

value - The value to set the attribute to. This may be interpreted or converted to the necessary type if the setter method doesn't just take a string. Must not be null.

Throws:

BuildException - if the introspected class doesn't support the given attribute, or if the setting method fails.

storeElement

public void storeElement(Project project,
                         Object parent,
                         Object child,
                         String elementName)
                  throws BuildException

Stores a named nested element using a storage method determined by the initial introspection. If no appropriate storage method is available, this method returns immediately.

Parameters:

project - Ignored in this implementation. May be null.

parent - Parent instance to store the child in. Must not be null.

child - Child instance to store in the parent. Should not be null.

elementName - Name of the child element to store. May be null, in which case this method returns immediately.

Throws:

BuildException - if the storage method fails.

supportsCharacters

public boolean supportsCharacters()

Returns whether or not the introspected class supports PCDATA.

Returns:

whether or not the introspected class supports PCDATA.

supportsNestedElement

public boolean supportsNestedElement(String elementName)

Indicates if this element supports a nested element of the given name.

Parameters:

elementName - the name of the nested element being checked

Returns:

true if the given nested element is supported

supportsNestedElement

public boolean supportsNestedElement(String parentUri,
                                     String elementName)

Indicate if this element supports a nested element of the given name.

Note that this method will always return true if the introspected class is dynamic or contains a method named "add" with void return type and a single argument. To ge a more thorough answer, use the four-arg version of this method instead.

Parameters:

parentUri - the uri of the parent

elementName - the name of the nested element being checked

Returns:

true if the given nested element is supported

supportsNestedElement

public boolean supportsNestedElement(String parentUri,
                                     String elementName,
                                     Project project,
                                     Object parent)

Indicate if this element supports a nested element of the given name.

Note that this method will always return true if the introspected class is dynamic, so be prepared to catch an exception about unsupported children when calling getElementCreator.

Parameters:

parentUri - the uri of the parent

elementName - the name of the nested element being checked

project - currently executing project instance

parent - the parent element

Returns:

true if the given nested element is supported

Since:

Ant 1.8.0.

supportsReflectElement

public boolean supportsReflectElement(String parentUri,
                                      String elementName)

Check if this element supports a nested element from reflection.

Parameters:

parentUri - the uri of the parent

elementName - the name of the nested element being checked

Returns:

true if the given nested element is supported

Since:

Ant 1.8.0

throwNotSupported

public void throwNotSupported(Project project,
                              Object parent,
                              String elementName)

Utility method to throw a NotSupported exception

Parameters:

project - the Project instance.

parent - the object which doesn't support a requested element

elementName - the name of the Element which is trying to be created.