- java.lang.Object
-
- jdk.dynalink.NamespaceOperation
-
- All Implemented Interfaces:
Operation
public final class NamespaceOperation extends Object implements Operation
Describes an operation that operates on at least oneNamespaceof an object. E.g. a property getter would be described asOperation propertyGetter = new NamespaceOperation( StandardOperation.GET, StandardNamespace.PROPERTY);They are often combined withNamedOperation, e.g. to express a property getter for a property named "color", you would construct:Operation colorPropertyGetter = new NamedOperation( new NamespaceOperation( StandardOperation.GET, StandardNamespace.PROPERTY), "color");While
NamespaceOperationcan be constructed directly, it is often convenient to use theOperation.withNamespace(Namespace)andOperation.withNamespaces(Namespace...)factory methods instead, e.g.:Operation getElementOrPropertyEmpty = StandardOperation.GET .withNamespace(StandardNamespace.PROPERTY) .named("color");Operations on multiple namespaces
If multiple namespaces are specified, the namespaces are treated as alternatives to each other in order of preference. The semantics of such operation is "first applicable". That is, a composite ofGET:PROPERTY|ELEMENT:colorshould be interpreted as get the property named "color" on the object, but if the property does not exist, then get the collection element named "color" instead.Operations with multiple namespaces are helpful in implementation of languages that don't distinguish between one or more of the namespaces, or when expressing operations against objects that can be considered both ordinary objects and collections, e.g. Java
Mapobjects. AGET:PROPERTY|ELEMENT:emptyoperation against a Java map will always match theMap.isEmpty()property, butGET:ELEMENT|PROPERTY:emptywill actually match a map element with key"empty"if the map contains that key, and only fall back to theisEmpty()property getter if the map does not contain the key. If the source language mandates this semantics, it can be easily achieved using operations on multiple namespaces.Even if the language itself doesn't distinguish between some of the namespaces, it can be helpful to map different syntaxes to different namespace orderings. E.g. the source expression
obj.colorcould map toGET:PROPERTY|ELEMENT|METHOD:color, but a different source expression that looks like collection element accessobj[key]could be expressed instead asGET:ELEMENT|PROPERTY|METHODin order to favor the element semantics. Finally, if the retrieved value is subsequently called, then it makes sense to bringMETHODto the front of the namespace list: the getter part of the source expressionobj.color()could beGET:METHOD|PROPERTY|ELEMENT:colorand the one forobj[key]()could beGET:METHOD|ELEMENT|PROPERTY.The base operation of a namespace operation can not itself be a namespace or named operation, but rather one of simple operations such are elements of
StandardOperation. A namespace operation itself can serve as the base operation of a named operation, though; a typical way to construct e.g. theGET:ELEMENT|PROPERTY:emptyfrom above would be:Operation getElementOrPropertyEmpty = StandardOperation.GET .withNamespaces( StandardNamespace.ELEMENT, StandardNamespace.PROPERTY) .named("empty");
-
-
Constructor Summary
Constructors Constructor Description NamespaceOperation(Operation baseOperation, Namespace... namespaces)Constructs a new namespace operation.
-
Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description booleancontains(Namespace namespace)Returns true if this namespace operation contains a namespace equal to the specified namespace.static booleancontains(Operation op, Operation baseOperation, Namespace namespace)Returns true if the specified operation is aNamespaceOperationand its base operation is equal to the specified operation, and it contains the specified namespace.booleanequals(Object obj)Returns true if the other object is also a namespace operation and their base operation and namespaces are equal.OperationgetBaseOperation()Returns the base operation of this named operation.static OperationgetBaseOperation(Operation op)If the passed operation is a namespace operation, returns itsgetBaseOperation(), otherwise returns the operation as is.NamespacegetNamespace(int i)Returns the i-th namespace in this namespace operation.intgetNamespaceCount()Returns the number of namespaces in this namespace operation.Namespace[]getNamespaces()Returns the namespaces in this namespace operation.static Namespace[]getNamespaces(Operation op)If the passed operation is a namespace operation, returns itsgetNamespaces(), otherwise returns an empty array.inthashCode()Returns the hash code of this namespace operation.StringtoString()Returns the string representation of this namespace operation.-
Methods declared in class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
-
Methods declared in interface jdk.dynalink.Operation
named, withNamespace, withNamespaces
-
-
-
-
Constructor Detail
-
NamespaceOperation
public NamespaceOperation(Operation baseOperation, Namespace... namespaces)
Constructs a new namespace operation.- Parameters:
baseOperation- the base operation that operates on one or more namespaces.namespaces- one or more namespaces this operation operates on.- Throws:
IllegalArgumentException- if less than one namespace is specified, or the base operation is itself aNamespaceOperationor aNamedOperation.NullPointerException- if either thenamespacesarray or any of its elements arenull, or ifbaseOperationisnull.
-
-
Method Detail
-
getBaseOperation
public Operation getBaseOperation()
Returns the base operation of this named operation.- Returns:
- the base operation of this named operation.
-
getNamespaces
public Namespace[] getNamespaces()
Returns the namespaces in this namespace operation. The returned array is a copy and changes to it don't have effect on this object.- Returns:
- the namespaces in this namespace operation.
-
getNamespaceCount
public int getNamespaceCount()
Returns the number of namespaces in this namespace operation.- Returns:
- the number of namespaces in this namespace operation.
-
getNamespace
public Namespace getNamespace(int i)
Returns the i-th namespace in this namespace operation.- Parameters:
i- the namespace index- Returns:
- the i-th namespace in this namespace operation.
- Throws:
IndexOutOfBoundsException- if the index is out of range.
-
contains
public boolean contains(Namespace namespace)
Returns true if this namespace operation contains a namespace equal to the specified namespace.- Parameters:
namespace- the namespace being searched for. Must not be null.- Returns:
- true if the if this namespace operation contains a namespace equal to the specified namespace.
-
equals
public boolean equals(Object obj)
Returns true if the other object is also a namespace operation and their base operation and namespaces are equal.- Overrides:
equalsin classObject- Parameters:
obj- the object to compare to- Returns:
- true if this object is equal to the other one, false otherwise.
- See Also:
Object.hashCode()
-
hashCode
public int hashCode()
Returns the hash code of this namespace operation. Defined to be equal tobaseOperation.hashCode() + 31 * Arrays.hashCode(namespaces).- Overrides:
hashCodein classObject- Returns:
- the receiver's hash.
- See Also:
Object.equals(java.lang.Object)
-
toString
public String toString()
Returns the string representation of this namespace operation. Defined to be thetoStringof its base operation, followed by a colon character, followed with the list of its namespaces separated with the vertical line character (e.g."GET:PROPERTY|ELEMENT").
-
getBaseOperation
public static Operation getBaseOperation(Operation op)
If the passed operation is a namespace operation, returns itsgetBaseOperation(), otherwise returns the operation as is.- Parameters:
op- the operation- Returns:
- the base operation of the passed operation.
-
getNamespaces
public static Namespace[] getNamespaces(Operation op)
If the passed operation is a namespace operation, returns itsgetNamespaces(), otherwise returns an empty array.- Parameters:
op- the operation- Returns:
- the namespaces of the passed operation.
-
contains
public static boolean contains(Operation op, Operation baseOperation, Namespace namespace)
Returns true if the specified operation is aNamespaceOperationand its base operation is equal to the specified operation, and it contains the specified namespace. If it is not aNamespaceOperation, then it returns false.- Parameters:
op- the operation. Must not be null.baseOperation- the base operation being searched for. Must not be null.namespace- the namespace being searched for. Must not be null.- Returns:
- true if the if the passed operation is a
NamespaceOperation, its base operation equals the searched base operation, and contains a namespace equal to the searched namespace.
-
-