PropertyHelper (Apache Ant API)
Description: declaration: package: org.apache.tools.ant, class: PropertyHelper

# Class PropertyHelper

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

All Implemented Interfaces:
  `GetProperty`

public class PropertyHelper extends Object implements GetProperty
Deals with properties - substitution, dynamic properties, etc.

This code has been heavily restructured for Ant 1.8.0. It is expected that custom PropertyHelper implementation that used the older chaining mechanism of Ant 1.6 won't work in all cases, and its usage is deprecated. The preferred way to customize Ant's property handling is by `adding` `delegates` of the appropriate subinterface and have this implementation use them.

When `expanding a string that may contain properties` this class will delegate the actual parsing to `parseProperties` inside the ParseProperties class which in turn uses the `PropertyExpander delegates` to find properties inside the string and this class to expand the property names found into the corresponding values.

When `looking up a property value` this class will first consult all `PropertyEvaluator` delegates and fall back to an internal map of "project properties" if no evaluator matched the property name.

When `setting a property value` this class will first consult all `PropertySetter` delegates and fall back to an internal map of "project properties" if no setter matched the property name.

Since:
  Ant 1.6

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static interface`
  `PropertyHelper.Delegate`
  Marker interface for a PropertyHelper delegate.
  `static interface`
  `PropertyHelper.PropertyEnumerator`
  Obtains the names of all known properties.
  `static interface`
  `PropertyHelper.PropertyEvaluator`
  Looks up a property's value based on its name.
  `static interface`
  `PropertyHelper.PropertySetter`
  Sets or overrides a property.

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `PropertyHelper()`
  Default constructor.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `add(PropertyHelper.Delegate delegate)`
  Add the specified delegate object to this PropertyHelper.
  `boolean`
  `containsProperties(String value)`
  Learn whether a String contains replaceable properties.
  `void`
  `copyInheritedProperties(Project other)`
  Copies all user properties that have not been set on the command line or a GUI tool from this instance to the Project instance given as the argument.
  `void`
  `copyUserProperties(Project other)`
  Copies all user properties that have been set on the command line or a GUI tool from this instance to the Project instance given as the argument.
  `protected static Set<Class<? extends PropertyHelper.Delegate>>`
  `getDelegateInterfaces(PropertyHelper.Delegate d)`
  Get all Delegate interfaces (excluding Delegate itself) from the specified Delegate.
  `protected <D extends PropertyHelper.Delegate>
  List<D>`
  `getDelegates(Class<D> type)`
  Get the Collection of delegates of the specified type.
  `Collection<PropertyExpander>`
  `getExpanders()`
  Get the `expanders`.
  `Hashtable<String,Object>`
  `getInheritedProperties()`
  Returns a copy of the inherited property hashtable
  `protected Hashtable<String,Object>`
  `getInternalInheritedProperties()`
  special back door for subclasses, internal access to the hashtables
  `protected Hashtable<String,Object>`
  `getInternalProperties()`
  special back door for subclasses, internal access to the hashtables
  `protected Hashtable<String,Object>`
  `getInternalUserProperties()`
  special back door for subclasses, internal access to the hashtables
  `PropertyHelper`
  `getNext()`
  Deprecated.
  use the delegate mechanism instead
  `Project`
  `getProject()`
  Get this PropertyHelper's Project.
  `Hashtable<String,Object>`
  `getProperties()`
  Returns a copy of the properties table.
  `Object`
  `getProperty(String name)`
  Returns the value of a property, if it is set.
  `Object`
  `getProperty(String ns, String name)`
  Deprecated.
  namespaces are unnecessary.
  `static Object`
  `getProperty(Project project, String name)`
  A helper static method to get a property from a particular project.
  `static PropertyHelper`
  `getPropertyHelper(Project project)`
  Factory method to create a property processor.
  `Object`
  `getPropertyHook(String ns, String name, boolean user)`
  Deprecated.
  PropertyHelper chaining is deprecated.
  `Set<String>`
  `getPropertyNames()`
  Returns the names of all known properties.
  `Hashtable<String,Object>`
  `getUserProperties()`
  Returns a copy of the user property hashtable
  `Object`
  `getUserProperty(String name)`
  Returns the value of a user property, if it is set.
  `Object`
  `getUserProperty(String ns, String name)`
  Deprecated.
  namespaces are unnecessary.
  `Object`
  `parseProperties(String value)`
  Decode properties from a String representation.
  `void`
  `parsePropertyString(String value, Vector<String> fragments, Vector<String> propertyRefs)`
  Deprecated.
  use the other mechanisms of this class instead
  `String`
  `replaceProperties(String value)`
  Replaces `${xxx}` style constructions in the given value with the string value of the corresponding data types.
  `String`
  `replaceProperties(String ns, String value, Hashtable<String,Object> keys)`
  Replaces `${xxx}` style constructions in the given value with the string value of the corresponding data types.
  `void`
  `setInheritedProperty(String name, Object value)`
  Sets an inherited user property, which cannot be overwritten by set/unset property calls.
  `void`
  `setInheritedProperty(String ns, String name, Object value)`
  Deprecated.
  namespaces are unnecessary.
  `void`
  `setNewProperty(String name, Object value)`
  Sets a property if no value currently exists.
  `void`
  `setNewProperty(String ns, String name, Object value)`
  Deprecated.
  namespaces are unnecessary.
  `static void`
  `setNewProperty(Project project, String name, Object value)`
  A helper static method to set a new property from a particular project.
  `void`
  `setNext(PropertyHelper next)`
  Deprecated.
  use the delegate mechanism instead
  `void`
  `setProject(Project p)`
  Set the project for which this helper is performing property resolution.
  `boolean`
  `setProperty(String name, Object value, boolean verbose)`
  Default implementation of setProperty.
  `boolean`
  `setProperty(String ns, String name, Object value, boolean verbose)`
  Deprecated.
  namespaces are unnecessary.
  `static void`
  `setProperty(Project project, String name, Object value)`
  A helper static method to set a property from a particular project.
  `boolean`
  `setPropertyHook(String ns, String name, Object value, boolean inherited, boolean user, boolean isNew)`
  Deprecated.
  PropertyHelper chaining is deprecated.
  `void`
  `setUserProperty(String name, Object value)`
  Sets a user property, which cannot be overwritten by set/unset property calls.
  `void`
  `setUserProperty(String ns, String name, Object value)`
  Deprecated.
  namespaces are unnecessary.
  `boolean`
  `testIfCondition(Object value)`
  Returns true if the value is null or an empty string, can be interpreted as a true value or cannot be interpreted as a false value and a property of the value's name exists.
  `boolean`
  `testUnlessCondition(Object value)`
  Returns true if the value is null or an empty string, can be interpreted as a false value or cannot be interpreted as a true value and a property of the value's name doesn't exist.
  `static Boolean`
  `toBoolean(Object value)`
  If the given object can be interpreted as a true/false value, turn it into a matching Boolean - otherwise return null.

  ### Methods inherited from class Object

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

- ## Constructor Details

  - ### PropertyHelper

    protected PropertyHelper()
    Default constructor.

- ## Method Details

  - ### getProperty

    public static Object getProperty(Project project, String name)
    A helper static method to get a property from a particular project.
    Parameters:
      `project` - the project in question.
      `name` - the property name
    Returns:
      the value of the property if present, null otherwise.
    Since:
      Ant 1.8.0

  - ### setProperty

    public static void setProperty(Project project, String name, Object value)
    A helper static method to set a property from a particular project.
    Parameters:
      `project` - the project in question.
      `name` - the property name
      `value` - the value to use.
    Since:
      Ant 1.8.0

  - ### setNewProperty

    public static void setNewProperty(Project project, String name, Object value)
    A helper static method to set a new property from a particular project.
    Parameters:
      `project` - the project in question.
      `name` - the property name
      `value` - the value to use.
    Since:
      Ant 1.8.0

  - ### setProject

    public void setProject(Project p)
    Set the project for which this helper is performing property resolution.
    Parameters:
      `p` - the project instance.

  - ### getProject

    public Project getProject()
    Get this PropertyHelper's Project.
    Returns:
      Project

  - ### setNext

    @Deprecated public void setNext(PropertyHelper next)
    Deprecated.
    use the delegate mechanism instead
    Prior to Ant 1.8.0 there have been 2 ways to hook into property handling: - you can replace the main PropertyHelper. The replacement is required to support the same semantics (of course :-) - you can chain a property helper capable of storing some properties. Again, you are required to respect the immutability semantics (at least for non-dynamic properties)

    As of Ant 1.8.0 this method is never invoked by any code inside of Ant itself.

    Parameters:
      `next` - the next property helper in the chain.

  - ### getNext

    @Deprecated public PropertyHelper getNext()
    Deprecated.
    use the delegate mechanism instead
    Get the next property helper in the chain.

    As of Ant 1.8.0 this method is never invoked by any code inside of Ant itself except the `setPropertyHook` and `getPropertyHook` methods in this class.

    Returns:
      the next property helper.

  - ### getPropertyHelper

    public static PropertyHelper getPropertyHelper(Project project)
    Factory method to create a property processor. Users can provide their own or replace it using "ant.PropertyHelper" reference. User tasks can also add themselves to the chain, and provide dynamic properties.
    Parameters:
      `project` - the project for which the property helper is required.
    Returns:
      the project's property helper.

  - ### getExpanders

    public Collection<PropertyExpander> getExpanders()
    Get the `expanders`.
    Returns:
      the expanders.
    Since:
      Ant 1.8.0

  - ### setPropertyHook

    @Deprecated public boolean setPropertyHook(String ns, String name, Object value, boolean inherited, boolean user, boolean isNew)
    Deprecated.
    PropertyHelper chaining is deprecated.
    Sets a property. Any existing property of the same name is overwritten, unless it is a user property. If all helpers return false, the property will be saved in the default properties table by setProperty.

    As of Ant 1.8.0 this method is never invoked by any code inside of Ant itself.

    Parameters:
      `ns` - The namespace that the property is in (currently not used.
      `name` - The name of property to set. Must not be `null`.
      `value` - The new value of the property. Must not be `null`.
      `inherited` - True if this property is inherited (an [sub]ant[call] property).
      `user` - True if this property is a user property.
      `isNew` - True is this is a new property.
    Returns:
      true if this helper has stored the property, false if it couldn't. Each helper should delegate to the next one (unless it has a good reason not to).

  - ### getPropertyHook

    @Deprecated public Object getPropertyHook(String ns, String name, boolean user)
    Deprecated.
    PropertyHelper chaining is deprecated.
    Get a property. If all hooks return null, the default tables will be used.

    As of Ant 1.8.0 this method is never invoked by any code inside of Ant itself.

    Parameters:
      `ns` - namespace of the sought property.
      `name` - name of the sought property.
      `user` - True if this is a user property.
    Returns:
      The property, if returned by a hook, or null if none.

  - ### parsePropertyString

    @Deprecated public void parsePropertyString(String value, Vector<String> fragments, Vector<String> propertyRefs) throws BuildException
    Deprecated.
    use the other mechanisms of this class instead
    Parses a string containing `${xxx}` style property references into two lists. The first list is a collection of text fragments, while the other is a set of string property names. `null` entries in the first list indicate a property reference from the second list.

    Delegates to `parsePropertyStringDefault`.

    As of Ant 1.8.0 this method is never invoked by any code inside of Ant itself except {ProjectHelper#parsePropertyString ProjectHelper.parsePropertyString}.

    Parameters:
      `value` - Text to parse. Must not be `null`.
      `fragments` - List to add text fragments to. Must not be `null`.
      `propertyRefs` - List to add property names to. Must not be `null`.
    Throws:
      `BuildException` - if the string contains an opening `${` without a closing `}`

  - ### replaceProperties

    public String replaceProperties(String ns, String value, Hashtable<String,Object> keys) throws BuildException
    Replaces `${xxx}` style constructions in the given value with the string value of the corresponding data types.

    Delegates to the one-arg version, completely ignoring the ns and keys parameters.

    Parameters:
      `ns` - The namespace for the property.
      `value` - The string to be scanned for property references. May be `null`, in which case this method returns immediately with no effect.
      `keys` - Mapping (String to Object) of property names to their values. If `null`, only project properties will be used.
    Returns:
      the original string with the properties replaced, or `null` if the original string is `null`.
    Throws:
      `BuildException` - if the string contains an opening `${` without a closing `}`

  - ### replaceProperties

    public String replaceProperties(String value) throws BuildException
    Replaces `${xxx}` style constructions in the given value with the string value of the corresponding data types.
    Parameters:
      `value` - The string to be scanned for property references. May be `null`, in which case this method returns immediately with no effect.
    Returns:
      the original string with the properties replaced, or `null` if the original string is `null`.
    Throws:
      `BuildException` - if the string contains an opening `${` without a closing `}`

  - ### parseProperties

    public Object parseProperties(String value) throws BuildException
    Decode properties from a String representation. If the entire contents of the String resolve to a single property, that value is returned. Otherwise a String is returned.
    Parameters:
      `value` - The string to be scanned for property references. May be `null`, in which case this method returns immediately with no effect.
    Returns:
      the original string with the properties replaced, or `null` if the original string is `null`.
    Throws:
      `BuildException` - if the string contains an opening `${` without a closing `}`

  - ### containsProperties

    public boolean containsProperties(String value)
    Learn whether a String contains replaceable properties.
    Parameters:
      `value` - the String to check.
    Returns:
      `true` if `value` contains property notation.

  - ### setProperty

    @Deprecated public boolean setProperty(String ns, String name, Object value, boolean verbose)
    Deprecated.
    namespaces are unnecessary.
    Default implementation of setProperty. Will be called from Project. This is the original 1.5 implementation, with calls to the hook added.

    Delegates to the three-arg version, completely ignoring the ns parameter.

    Parameters:
      `ns` - The namespace for the property (currently not used).
      `name` - The name of the property.
      `value` - The value to set the property to.
      `verbose` - If this is true output extra log messages.
    Returns:
      true if the property is set.

  - ### setProperty

    public boolean setProperty(String name, Object value, boolean verbose)
    Default implementation of setProperty. Will be called from Project.
    Parameters:
      `name` - The name of the property.
      `value` - The value to set the property to.
      `verbose` - If this is true output extra log messages.
    Returns:
      true if the property is set.

  - ### setNewProperty

    @Deprecated public void setNewProperty(String ns, String name, Object value)
    Deprecated.
    namespaces are unnecessary.
    Sets a property if no value currently exists. If the property exists already, a message is logged and the method returns with no other effect.

    Delegates to the two-arg version, completely ignoring the ns parameter.

    Parameters:
      `ns` - The namespace for the property (currently not used).
      `name` - The name of property to set. Must not be `null`.
      `value` - The new value of the property. Must not be `null`.
    Since:
      Ant 1.6

  - ### setNewProperty

    public void setNewProperty(String name, Object value)
    Sets a property if no value currently exists. If the property exists already, a message is logged and the method returns with no other effect.
    Parameters:
      `name` - The name of property to set. Must not be `null`.
      `value` - The new value of the property. Must not be `null`.
    Since:
      Ant 1.8.0

  - ### setUserProperty

    @Deprecated public void setUserProperty(String ns, String name, Object value)
    Deprecated.
    namespaces are unnecessary.
    Sets a user property, which cannot be overwritten by set/unset property calls. Any previous value is overwritten.

    Delegates to the two-arg version, completely ignoring the ns parameter.

    Parameters:
      `ns` - The namespace for the property (currently not used).
      `name` - The name of property to set. Must not be `null`.
      `value` - The new value of the property. Must not be `null`.

  - ### setUserProperty

    public void setUserProperty(String name, Object value)
    Sets a user property, which cannot be overwritten by set/unset property calls. Any previous value is overwritten.

    Does `not` consult any delegates.

    Parameters:
      `name` - The name of property to set. Must not be `null`.
      `value` - The new value of the property. Must not be `null`.

  - ### setInheritedProperty

    @Deprecated public void setInheritedProperty(String ns, String name, Object value)
    Deprecated.
    namespaces are unnecessary.
    Sets an inherited user property, which cannot be overwritten by set/unset property calls. Any previous value is overwritten. Also marks these properties as properties that have not come from the command line.

    Delegates to the two-arg version, completely ignoring the ns parameter.

    Parameters:
      `ns` - The namespace for the property (currently not used).
      `name` - The name of property to set. Must not be `null`.
      `value` - The new value of the property. Must not be `null`.

  - ### setInheritedProperty

    public void setInheritedProperty(String name, Object value)
    Sets an inherited user property, which cannot be overwritten by set/unset property calls. Any previous value is overwritten. Also marks these properties as properties that have not come from the command line.

    Does `not` consult any delegates.

    Parameters:
      `name` - The name of property to set. Must not be `null`.
      `value` - The new value of the property. Must not be `null`.

  - ### getProperty

    @Deprecated public Object getProperty(String ns, String name)
    Deprecated.
    namespaces are unnecessary.
    Returns the value of a property, if it is set. You can override this method in order to plug your own storage.

    Delegates to the one-arg version ignoring the ns parameter.

    Parameters:
      `ns` - The namespace for the property (currently not used).
      `name` - The name of the property. May be `null`, in which case the return value is also `null`.
    Returns:
      the property value, or `null` for no match or if a `null` name is provided.

  - ### getProperty

    public Object getProperty(String name)
    Returns the value of a property, if it is set.

    This is the method that is invoked by {Project#getProperty Project.getProperty}.

    You can override this method in order to plug your own storage but the recommended approach is to add your own implementation of `PropertyEvaluator` instead.

    Specified by:
      `getProperty` in interface `GetProperty`
    Parameters:
      `name` - The name of the property. May be `null`, in which case the return value is also `null`.
    Returns:
      the property value, or `null` for no match or if a `null` name is provided.

  - ### getPropertyNames

    public Set<String> getPropertyNames()
    Returns the names of all known properties.
    Returns:
      the names of all known properties.
    Since:
      1.10.9

  - ### getUserProperty

    @Deprecated public Object getUserProperty(String ns, String name)
    Deprecated.
    namespaces are unnecessary.
    Returns the value of a user property, if it is set.

    Delegates to the one-arg version ignoring the ns parameter.

    Parameters:
      `ns` - The namespace for the property (currently not used).
      `name` - The name of the property. May be `null`, in which case the return value is also `null`.
    Returns:
      the property value, or `null` for no match or if a `null` name is provided.

  - ### getUserProperty

    public Object getUserProperty(String name)
    Returns the value of a user property, if it is set.

    Does `not` consult any delegates.

    Parameters:
      `name` - The name of the property. May be `null`, in which case the return value is also `null`.
    Returns:
      the property value, or `null` for no match or if a `null` name is provided.

  - ### getProperties

    public Hashtable<String,Object> getProperties()
    Returns a copy of the properties table.

    Does not contain properties held by implementations of delegates (like local properties).

    Returns:
      a hashtable containing all properties (including user properties).

  - ### getUserProperties

    public Hashtable<String,Object> getUserProperties()
    Returns a copy of the user property hashtable

    Does not contain properties held by implementations of delegates (like local properties).

    Returns:
      a hashtable containing just the user properties

  - ### getInheritedProperties

    public Hashtable<String,Object> getInheritedProperties()
    Returns a copy of the inherited property hashtable

    Does not contain properties held by implementations of delegates (like local properties).

    Returns:
      a hashtable containing just the inherited properties

  - ### getInternalProperties

    protected Hashtable<String,Object> getInternalProperties()
    special back door for subclasses, internal access to the hashtables
    Returns:
      the live hashtable of all properties

  - ### getInternalUserProperties

    protected Hashtable<String,Object> getInternalUserProperties()
    special back door for subclasses, internal access to the hashtables
    Returns:
      the live hashtable of user properties

  - ### getInternalInheritedProperties

    protected Hashtable<String,Object> getInternalInheritedProperties()
    special back door for subclasses, internal access to the hashtables
    Returns:
      the live hashtable inherited properties

  - ### copyInheritedProperties

    public void copyInheritedProperties(Project other)
    Copies all user properties that have not been set on the command line or a GUI tool from this instance to the Project instance given as the argument.

    To copy all "user" properties, you will also have to call `copyUserProperties`.

    Does not copy properties held by implementations of delegates (like local properties).

    Parameters:
      `other` - the project to copy the properties to. Must not be null.
    Since:
      Ant 1.6

  - ### copyUserProperties

    public void copyUserProperties(Project other)
    Copies all user properties that have been set on the command line or a GUI tool from this instance to the Project instance given as the argument.

    To copy all "user" properties, you will also have to call `copyInheritedProperties`.

    Does not copy properties held by implementations of delegates (like local properties).

    Parameters:
      `other` - the project to copy the properties to. Must not be null.
    Since:
      Ant 1.6

  - ### add

    public void add(PropertyHelper.Delegate delegate)
    Add the specified delegate object to this PropertyHelper. Delegates are processed in LIFO order.
    Parameters:
      `delegate` - the delegate to add.
    Since:
      Ant 1.8.0

  - ### getDelegates

    protected <D extends PropertyHelper.Delegate> List<D> getDelegates(Class<D> type)
    Get the Collection of delegates of the specified type.
    Type Parameters:
      `D` - desired type.
    Parameters:
      `type` - delegate type.
    Returns:
      Collection.
    Since:
      Ant 1.8.0

  - ### getDelegateInterfaces

    protected static Set<Class<? extends PropertyHelper.Delegate>> getDelegateInterfaces(PropertyHelper.Delegate d)
    Get all Delegate interfaces (excluding Delegate itself) from the specified Delegate.
    Parameters:
      `d` - the Delegate to inspect.
    Returns:
      Set<Class>
    Since:
      Ant 1.8.0

  - ### toBoolean

    public static Boolean toBoolean(Object value)
    If the given object can be interpreted as a true/false value, turn it into a matching Boolean - otherwise return null.
    Parameters:
      `value` - Object
    Returns:
      Boolean
    Since:
      Ant 1.8.0

  - ### testIfCondition

    public boolean testIfCondition(Object value)
    Returns true if the value is null or an empty string, can be interpreted as a true value or cannot be interpreted as a false value and a property of the value's name exists.
    Parameters:
      `value` - Object
    Returns:
      boolean
    Since:
      Ant 1.8.0

  - ### testUnlessCondition

    public boolean testUnlessCondition(Object value)
    Returns true if the value is null or an empty string, can be interpreted as a false value or cannot be interpreted as a true value and a property of the value's name doesn't exist.
    Parameters:
      `value` - Object
    Returns:
      boolean
    Since:
      Ant 1.8.0