Package org.apache.tools.ant

# Class ComponentHelper

java.lang.Object
org.apache.tools.ant.ComponentHelper

public class ComponentHelper extends Object
Component creation and configuration. The class is based around handing component definitions in an AntTypeTable. The old task/type methods have been kept for backward compatibly. Project will just delegate its calls to this class. A very simple hook mechanism is provided that allows users to plug in custom code. It is also possible to replace the default behavior (for example in an app embedding Ant)

Since:
  Ant1.6

## Field Summary

Fields
Modifier and Type
Field
Description
`static final String`
`COMPONENT_HELPER_REFERENCE`
reference under which we register ourselves with a project -"ant.ComponentHelper"

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`ComponentHelper()`
Creates a new ComponentHelper instance.

## Method Summary

Modifier and Type
Method
Description
`void`
`addDataTypeDefinition(String typeName, Class<?> typeClass)`
Adds a new datatype definition.
`void`
`addDataTypeDefinition(AntTypeDefinition def)`
Describe `addDataTypeDefinition` method here.
`void`
`addTaskDefinition(String taskName, Class<?> taskClass)`
Adds a new task definition to the project.
`void`
`checkTaskClass(Class<?> taskClass)`
Checks whether or not a class is suitable for serving as Ant task.
`Object`
`createComponent(String componentName)`
Create an object for a component.
`Object`
`createComponent(UnknownElement ue, String ns, String componentType)`
Factory method to create the components.
`Object`
`createDataType(String typeName)`
Creates a new instance of a data type.
`Task`
`createTask(String taskType)`
Creates a new instance of a task.
`String`
`diagnoseCreationFailure(String componentName, String type)`
Handler called to do decent diagnosis on instantiation failure.
`void`
`enterAntLib(String uri)`
Called at the start of processing an antlib.
`void`
`exitAntLib()`
Called at the end of processing an antlib.
`Hashtable<String,AntTypeDefinition>`
`getAntTypeTable()`
Returns the current datatype definition hashtable.
`Class<?>`
`getComponentClass(String componentName)`
Return the class of the component name.
`static ComponentHelper`
`getComponentHelper(Project project)`
Find a project component for a specific project, creating it if it does not exist.
`String`
`getCurrentAntlibUri()`
`Hashtable<String,Class<?>>`
`getDataTypeDefinitions()`
Returns the current type definition hashtable.
`AntTypeDefinition`
`getDefinition(String componentName)`
Return the antTypeDefinition for a componentName.
`String`
`getElementName(Object element)`
Returns a description of the type of the given element.
`String`
`getElementName(Object o, boolean brief)`
Returns a description of the type of the given element.
`static String`
`getElementName(Project p, Object o, boolean brief)`
Convenient way to get some element name even when you may not have a Project context.
`ComponentHelper`
`getNext()`
Get the next chained component helper.
`Project`
`getProject()`
Get the project.
`List<AntTypeDefinition>`
`getRestrictedDefinitions(String componentName)`
This returns a list of restricted definitions for a name.
`Hashtable<String,Class<?>>`
`getTaskDefinitions()`
Returns the current task definition hashtable.
`void`
`initDefaultDefinitions()`
This method is initialization code implementing the original ant component loading from /org/apache/tools/ant/taskdefs/default.properties and /org/apache/tools/ant/types/default.properties.
`void`
`initSubProject(ComponentHelper helper)`
Used with creating child projects.
`void`
`setNext(ComponentHelper next)`
Set the next chained component helper.
`void`
`setProject(Project project)`
Sets the project for this component helper.

### Methods inherited from class java.lang.Object

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

## Field Details

### COMPONENT_HELPER_REFERENCE

public static final String COMPONENT_HELPER_REFERENCE
reference under which we register ourselves with a project -"ant.ComponentHelper"

See Also:
  - Constant Field Values

## Constructor Details

### ComponentHelper

protected ComponentHelper()
Creates a new ComponentHelper instance.

## Method Details

### getProject

public Project getProject()
Get the project.

Returns:
  the project owner of this helper.

### getComponentHelper

public static ComponentHelper getComponentHelper(Project project)
Find a project component for a specific project, creating it if it does not exist.

Parameters:
  `project` - the project.
Returns:
  the project component for a specific project.

### setNext

public void setNext(ComponentHelper next)
Set the next chained component helper.

Parameters:
  `next` - the next chained component helper.

### getNext

public ComponentHelper getNext()
Get the next chained component helper.

Returns:
  the next chained component helper.

### setProject

public void setProject(Project project)
Sets the project for this component helper.

Parameters:
  `project` - the project for this helper.

### initSubProject

public void initSubProject(ComponentHelper helper)
Used with creating child projects. Each child project inherits the component definitions from its parent.

Parameters:
  `helper` - the component helper of the parent project.

### createComponent

public Object createComponent(UnknownElement ue, String ns, String componentType) throws BuildException
Factory method to create the components. This should be called by UnknownElement.

Parameters:
  `ue` - The Unknown Element creating this component.
  `ns` - Namespace URI. Also available as ue.getNamespace().
  `componentType` - The component type, Also available as ue.getComponentName().
Returns:
  the created component.
Throws:
  `BuildException` - if an error occurs.

### createComponent

public Object createComponent(String componentName)
Create an object for a component.

Parameters:
  `componentName` - the name of the component, if the component is in a namespace, the name is prefixed with the namespace uri and ":".
Returns:
  the class if found or null if not.

### getComponentClass

public Class<?> getComponentClass(String componentName)
Return the class of the component name.

Parameters:
  `componentName` - the name of the component, if the component is in a namespace, the name is prefixed with the namespace uri and ":".
Returns:
  the class if found or null if not.

### getDefinition

public AntTypeDefinition getDefinition(String componentName)
Return the antTypeDefinition for a componentName.

Parameters:
  `componentName` - the name of the component.
Returns:
  the ant definition or null if not present.

### initDefaultDefinitions

public void initDefaultDefinitions()
This method is initialization code implementing the original ant component loading from /org/apache/tools/ant/taskdefs/default.properties and /org/apache/tools/ant/types/default.properties.

### addTaskDefinition

public void addTaskDefinition(String taskName, Class<?> taskClass)
Adds a new task definition to the project. Attempting to override an existing definition with an equivalent one (i.e. with the same classname) results in a verbose log message. Attempting to override an existing definition with a different one results in a warning log message.

Parameters:
  `taskName` - The name of the task to add. Must not be `null`.
  `taskClass` - The full name of the class implementing the task. Must not be `null`.
Throws:
  `BuildException` - if the class is unsuitable for being an Ant task. An error level message is logged before this exception is thrown.
See Also:
  - `checkTaskClass(Class)`

### checkTaskClass

public void checkTaskClass(Class<?> taskClass) throws BuildException
Checks whether or not a class is suitable for serving as Ant task. Ant task implementation classes must be public, concrete, and have a no-arg constructor.

Parameters:
  `taskClass` - The class to be checked. Must not be `null`.
Throws:
  `BuildException` - if the class is unsuitable for being an Ant task. An error level message is logged before this exception is thrown.

### getTaskDefinitions

public Hashtable<String,Class<?>> getTaskDefinitions()
Returns the current task definition hashtable. The returned hashtable is "live" and so should not be modified. Also, the returned table may be modified asynchronously.

Returns:
  a map of from task name to implementing class (String to Class).

### getDataTypeDefinitions

public Hashtable<String,Class<?>> getDataTypeDefinitions()
Returns the current type definition hashtable. The returned hashtable is "live" and so should not be modified.

Returns:
  a map of from type name to implementing class (String to Class).

### getRestrictedDefinitions

public List<AntTypeDefinition> getRestrictedDefinitions(String componentName)
This returns a list of restricted definitions for a name. The returned List is "live" and so should not be modified. Also, the returned list may be modified asynchronously. Any access must be guarded with a lock on the list itself.

Parameters:
  `componentName` - the name to use.
Returns:
  the list of restricted definitions for a particular name.

### addDataTypeDefinition

public void addDataTypeDefinition(String typeName, Class<?> typeClass)
Adds a new datatype definition. Attempting to override an existing definition with an equivalent one (i.e. with the same classname) results in a verbose log message. Attempting to override an existing definition with a different one results in a warning log message, but the definition is changed.

Parameters:
  `typeName` - The name of the datatype. Must not be `null`.
  `typeClass` - The full name of the class implementing the datatype. Must not be `null`.

### addDataTypeDefinition

public void addDataTypeDefinition(AntTypeDefinition def)
Describe `addDataTypeDefinition` method here.

Parameters:
  `def` - an `AntTypeDefinition` value.

### getAntTypeTable

public Hashtable<String,AntTypeDefinition> getAntTypeTable()
Returns the current datatype definition hashtable. The returned hashtable is "live" and so should not be modified.

Returns:
  a map of from datatype name to datatype definition (String to `AntTypeDefinition`).

### createTask

public Task createTask(String taskType) throws BuildException
Creates a new instance of a task. Called from Project.createTask(), which can be called by tasks.

Parameters:
  `taskType` - The name of the task to create an instance of. Must not be `null`.
Returns:
  an instance of the specified task, or `null` if the task name is not recognised.
Throws:
  `BuildException` - if the task name is recognised but task creation fails.

### createDataType

public Object createDataType(String typeName) throws BuildException
Creates a new instance of a data type.

Parameters:
  `typeName` - The name of the data type to create an instance of. Must not be `null`.
Returns:
  an instance of the specified data type, or `null` if the data type name is not recognised.
Throws:
  `BuildException` - if the data type name is recognised but instance creation fails.

### getElementName

public String getElementName(Object element)
Returns a description of the type of the given element.

This is useful for logging purposes.

Parameters:
  `element` - The element to describe. Must not be `null`.
Returns:
  a description of the element type.
Since:
  Ant 1.6

### getElementName

public String getElementName(Object o, boolean brief)
Returns a description of the type of the given element.

This is useful for logging purposes.

Parameters:
  `o` - The element to describe. Must not be `null`.
  `brief` - whether to use a brief description.
Returns:
  a description of the element type.
Since:
  Ant 1.7

### getElementName

public static String getElementName(Project p, Object o, boolean brief)
Convenient way to get some element name even when you may not have a Project context.

Parameters:
  `p` - The optional Project instance.
  `o` - The element to describe. Must not be `null`.
  `brief` - whether to use a brief description.
Returns:
  a description of the element type.
Since:
  Ant 1.7

### enterAntLib

public void enterAntLib(String uri)
Called at the start of processing an antlib.

Parameters:
  `uri` - the uri that is associated with this antlib.

### getCurrentAntlibUri

public String getCurrentAntlibUri()

Returns:
  the current antlib uri.

### exitAntLib

public void exitAntLib()
Called at the end of processing an antlib.

### diagnoseCreationFailure

public String diagnoseCreationFailure(String componentName, String type)
Handler called to do decent diagnosis on instantiation failure.

Parameters:
  `componentName` - component name.
  `type` - component type, used in error messages
Returns:
  a string containing as much diagnostics info as possible.