org.apache.commons.attributes
Class Attributes

java.lang.Object
  org.apache.commons.attributes.Attributes

public class Attributes

extends Object

API for accessing attributes.

General Notes on Errors

All Methods in this class may throw RepositoryError or subclasses thereof. This Error is thrown if an attribute repository can not be loaded for some Exceptional reason.

Rationale for Errors instead of Exceptions

The methods in this class throws Errors instead of Exceptions. This rationale behind this is that:

• The programmer should not have to wrap all accesses to the Attributes API in a try/catch clause.
• An Exception being thrown here is caused by missing classes or other "Error-like" conditions.

Null References

If a parameter to a method may not be null, and a null is passed to the method, a NullPointerException will be thrown, with the parameter name in the message.

Rationale for using this instead of IllegalArgumentException is that it is more precise - the reference was null.

Performance Notes

The process of loading attributes for a class is a (relatively) time-consuming process, as it involves some dynamic linking in the form of inheritable attributes, a lot of reflection and so on. However, once loaded the attributes are cached, so repeated access to them are fast. But despite this the process of finding one attribute of a given type or such operations does involve some iteration of HashSets that runs in linear time in the number of attributes associated with the program element, and you should avoid accessing attributes in your innermost loops if you can avoid it. For example, instead of:

 Class myClass = ...;
 for (int i = 0; i < 10000; i++) {
     if (Attributes.hasAttributeType (myClass, MyAttribute.class)) {
         doThis(myClass);
     } else {
         doThat(myClass);
     }
 }
 

do:

 Class myClass = ...;
 boolean shouldDoThis = Attributes.hasAttributeType (myClass, MyAttribute.class);
 for (int i = 0; i < 10000; i++) {
     if (shouldDoThis) {
         doThis(myClass);
     } else {
         doThat(myClass);
     }
 }
 

if the loop should run at maximum speed.

Since:

2.1

Constructor Summary

Attributes()

Method Summary

static Object	getAttribute(Class clazz, Class attributeClass) Get one attributes of a given type from a class.
static Object	getAttribute(Constructor constructor, Class attributeClass) Get one attributes of a given type from a constructor.
static Object	getAttribute(Field field, Class attributeClass) Get one attributes of a given type from a field.
static Object	getAttribute(Method method, Class attributeClass) Get one attributes of a given type from a method.
static Collection	getAttributes(Class clazz) Gets all attributes for a class.
static Collection	getAttributes(Class clazz, Class attributeClass) Get all attributes of a given type from a class.
static Collection	getAttributes(Constructor constructor) Gets all attributes for a constructor.
static Collection	getAttributes(Constructor constructor, Class attributeClass) Get all attributes of a given type from a constructor.
static Collection	getAttributes(Field field) Gets all attributes for a field.
static Collection	getAttributes(Field field, Class attributeClass) Get all attributes of a given type from a field.
static Collection	getAttributes(Method method) Gets all attributes for a method.
static Collection	getAttributes(Method method, Class attributeClass) Get all attributes of a given type from a method.
static Object	getParameterAttribute(Constructor constructor, int parameter, Class attributeClass) Get one attributes of a given type from a constructor's parameter.
static Object	getParameterAttribute(Method method, int parameter, Class attributeClass) Get one attributes of a given type from a parameter.
static Collection	getParameterAttributes(Constructor constructor, int parameter) Gets all attributes for a parameter of a constructor.
static Collection	getParameterAttributes(Constructor constructor, int parameter, Class attributeClass) Get all attributes of a given type from a method's parameter.
static Collection	getParameterAttributes(Method method, int parameter) Gets all attributes for a parameter of a method.
static Collection	getParameterAttributes(Method method, int parameter, Class attributeClass) Get all attributes of a given type from a method's parameter.
static Object	getReturnAttribute(Method method, Class attributeClass) Get one attributes of a given type from a method's return value.
static Collection	getReturnAttributes(Method method) Gets all attributes for the return value of a method.
static Collection	getReturnAttributes(Method method, Class attributeClass) Get all attributes of a given type from a method's return value.
static boolean	hasAttribute(Class clazz, Object attribute) Tests if a class has an attribute.
static boolean	hasAttribute(Constructor constructor, Object attribute) Tests if a constructor has an attribute.
static boolean	hasAttribute(Field field, Object attribute) Tests if a field has an attribute.
static boolean	hasAttribute(Method method, Object attribute) Tests if a method has an attribute.
static boolean	hasAttributeType(Class clazz, Class attributeClass) Tests if a class has an attribute of a given type.
static boolean	hasAttributeType(Constructor constructor, Class attributeClass) Tests if a constructor has an attribute of a given type.
static boolean	hasAttributeType(Field field, Class attributeClass) Tests if a field has an attribute of a given type.
static boolean	hasAttributeType(Method method, Class attributeClass) Tests if a method has an attribute of a given type.
static boolean	hasParameterAttribute(Constructor constructor, int parameter, Object attribute) Tests if a constructor's parameter has an attribute.
static boolean	hasParameterAttribute(Method method, int parameter, Object attribute) Tests if a method's parameter has an attribute.
static boolean	hasParameterAttributeType(Constructor constructor, int parameter, Class attributeClass) Tests if a constructor's parameter has an attribute of a given type.
static boolean	hasParameterAttributeType(Method method, int parameter, Class attributeClass) Tests if a method's parameter has an attribute of a given type.
static boolean	hasReturnAttribute(Method method, Object attribute) Tests if a method's return value has an attribute.
static boolean	hasReturnAttributeType(Method method, Class attributeClass) Tests if a method's return value has an attribute of a given type.
static void	setAttributes(RuntimeAttributeRepository repo) Set attributes for a given class.

Methods inherited from class java.lang.Object

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

Constructor Detail

Attributes

public Attributes()

Method Detail

getAttribute

public static Object getAttribute(Class clazz,
                                  Class attributeClass)
                           throws RepositoryError,
                                  MultipleAttributesError

Get one attributes of a given type from a class.

Parameters:

clazz - the class. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Returns:

the attribute instance, or null of none could be found.

Throws:

MultipleAttributesError - if the collection contains more than one instance of the specified class.

RepositoryError

Since:

2.1

getAttribute

public static Object getAttribute(Field field,
                                  Class attributeClass)
                           throws RepositoryError,
                                  MultipleAttributesError

Get one attributes of a given type from a field.

Parameters:

field - the field. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Returns:

the attribute instance, or null of none could be found.

Throws:

MultipleAttributesError - if the collection contains more than one instance of the specified class.

RepositoryError

Since:

2.1

getAttribute

public static Object getAttribute(Constructor constructor,
                                  Class attributeClass)
                           throws RepositoryError,
                                  MultipleAttributesError

Get one attributes of a given type from a constructor.

Parameters:

constructor - the constructor. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Returns:

the attribute instance, or null of none could be found.

Throws:

MultipleAttributesError - if the collection contains more than one instance of the specified class.

RepositoryError

Since:

2.1

getAttribute

public static Object getAttribute(Method method,
                                  Class attributeClass)
                           throws RepositoryError,
                                  MultipleAttributesError

Get one attributes of a given type from a method.

Parameters:

method - the method. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Returns:

the attribute instance, or null of none could be found.

Throws:

MultipleAttributesError - if the collection contains more than one instance of the specified class.

RepositoryError

Since:

2.1

getParameterAttribute

public static Object getParameterAttribute(Method method,
                                           int parameter,
                                           Class attributeClass)
                                    throws RepositoryError,
                                           MultipleAttributesError

Get one attributes of a given type from a parameter.

Parameters:

method - the method. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

parameter - index of the parameter in the method's parameter list.

Returns:

the attribute instance, or null of none could be found.

Throws:

MultipleAttributesError - if the collection contains more than one instance of the specified class.

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the method accepts.

RepositoryError

Since:

2.1

getParameterAttribute

public static Object getParameterAttribute(Constructor constructor,
                                           int parameter,
                                           Class attributeClass)
                                    throws RepositoryError,
                                           MultipleAttributesError

Get one attributes of a given type from a constructor's parameter.

Parameters:

constructor - the constructor. May not be null.

parameter - index of the parameter in the method's parameter list.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Returns:

the attribute instance, or null of none could be found.

Throws:

MultipleAttributesError - if the collection contains more than one instance of the specified class.

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the constructor accepts.

RepositoryError

Since:

2.1

getReturnAttribute

public static Object getReturnAttribute(Method method,
                                        Class attributeClass)
                                 throws RepositoryError,
                                        MultipleAttributesError

Get one attributes of a given type from a method's return value.

Parameters:

method - the method. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Returns:

the attribute instance, or null of none could be found.

Throws:

MultipleAttributesError - if the collection contains more than one instance of the specified class.

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Class clazz)
                                throws RepositoryError

Gets all attributes for a class.

Parameters:

clazz - the class. May not be null.

Throws:

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Method method)
                                throws RepositoryError

Gets all attributes for a method.

Parameters:

method - the method. May not be null.

Throws:

RepositoryError

Since:

2.1

getParameterAttributes

public static Collection getParameterAttributes(Method method,
                                                int parameter)
                                         throws RepositoryError

Gets all attributes for a parameter of a method.

Parameters:

method - the method. May not be null.

parameter - the index of the parameter in the method's parameter list.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the method accepts.

RepositoryError

Since:

2.1

getParameterAttributes

public static Collection getParameterAttributes(Constructor constructor,
                                                int parameter)
                                         throws RepositoryError

Gets all attributes for a parameter of a constructor.

Parameters:

constructor - the constructor. May not be null.

parameter - the index of the parameter in the constructor's parameter list.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the constructor accepts.

RepositoryError

Since:

2.1

getReturnAttributes

public static Collection getReturnAttributes(Method method)
                                      throws RepositoryError

Gets all attributes for the return value of a method.

Parameters:

method - the method. May not be null.

Throws:

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Field field)
                                throws RepositoryError

Gets all attributes for a field.

Parameters:

field - the field. May not be null.

Throws:

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Constructor constructor)
                                throws RepositoryError

Gets all attributes for a constructor.

Parameters:

constructor - the constructor. May not be null.

Throws:

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Class clazz,
                                       Class attributeClass)
                                throws RepositoryError

Get all attributes of a given type from a class. For all objects o in the returned collection, o.getClass() == attributeClass.

Parameters:

clazz - the class. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Field field,
                                       Class attributeClass)
                                throws RepositoryError

Get all attributes of a given type from a field. For all objects o in the returned collection, o.getClass() == attributeClass.

Parameters:

field - the field. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Constructor constructor,
                                       Class attributeClass)
                                throws RepositoryError

Get all attributes of a given type from a constructor. For all objects o in the returned collection, o.getClass() == attributeClass.

Parameters:

constructor - the constructor. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

getAttributes

public static Collection getAttributes(Method method,
                                       Class attributeClass)
                                throws RepositoryError

Get all attributes of a given type from a method. For all objects o in the returned collection, o.getClass() == attributeClass.

Parameters:

method - the method. May not be null.

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

getParameterAttributes

public static Collection getParameterAttributes(Method method,
                                                int parameter,
                                                Class attributeClass)
                                         throws RepositoryError

Get all attributes of a given type from a method's parameter. For all objects o in the returned collection, o.getClass() == attributeClass.

Parameters:

method - the method. May not be null.

parameter - index of the parameter in the method's parameter list

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the method accepts.

RepositoryError

Since:

2.1

getParameterAttributes

public static Collection getParameterAttributes(Constructor constructor,
                                                int parameter,
                                                Class attributeClass)
                                         throws RepositoryError

Get all attributes of a given type from a method's parameter. For all objects o in the returned collection, o.getClass() == attributeClass.

Parameters:

constructor - the constructor. May not be null.

parameter - index of the parameter in the constructor's parameter list

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the constructor accepts.

RepositoryError

Since:

2.1

getReturnAttributes

public static Collection getReturnAttributes(Method method,
                                             Class attributeClass)
                                      throws RepositoryError

Get all attributes of a given type from a method's return value. For all objects o in the returned collection, o.getClass() == attributeClass.

Parameters:

method - the method

attributeClass - the type of attribute wanted. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

hasAttributeType

public static boolean hasAttributeType(Class clazz,
                                       Class attributeClass)
                                throws RepositoryError

Tests if a class has an attribute of a given type. That is, is there any attribute attr such that attr.getClass() == attributeClass?

Parameters:

clazz - the class. May not be null.

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

hasAttributeType

public static boolean hasAttributeType(Field field,
                                       Class attributeClass)
                                throws RepositoryError

Tests if a field has an attribute of a given type. That is, is there any attribute attr such that attr.getClass() == attributeClass?

Parameters:

field - the field. May not be null.

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

hasAttributeType

public static boolean hasAttributeType(Constructor constructor,
                                       Class attributeClass)
                                throws RepositoryError

Tests if a constructor has an attribute of a given type. That is, is there any attribute attr such that attr.getClass() == attributeClass?

Parameters:

constructor - the constructor. May not be null.

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

hasAttributeType

public static boolean hasAttributeType(Method method,
                                       Class attributeClass)
                                throws RepositoryError

Tests if a method has an attribute of a given type. That is, is there any attribute attr such that attr.getClass() == attributeClass?

Parameters:

method - the method. May not be null.

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

hasParameterAttributeType

public static boolean hasParameterAttributeType(Method method,
                                                int parameter,
                                                Class attributeClass)
                                         throws RepositoryError

Tests if a method's parameter has an attribute of a given type. That is, is there any attribute attr such that attr.getClass() == attributeClass?

Parameters:

method - the method. May not be null.

parameter - the index of the parameter in the method's parameter list.

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the method accepts.

RepositoryError

Since:

2.1

hasParameterAttributeType

public static boolean hasParameterAttributeType(Constructor constructor,
                                                int parameter,
                                                Class attributeClass)
                                         throws RepositoryError

Tests if a constructor's parameter has an attribute of a given type. That is, is there any attribute attr such that attr.getClass() == attributeClass?

Parameters:

constructor - the constructor. May not be null.

parameter - the index of the parameter in the constructor's parameter list.

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the constructor accepts.

RepositoryError

Since:

2.1

hasReturnAttributeType

public static boolean hasReturnAttributeType(Method method,
                                             Class attributeClass)
                                      throws RepositoryError

Tests if a method's return value has an attribute of a given type. That is, is there any attribute attr such that attr.getClass() == attributeClass?

Parameters:

method - the method. May not be null.

attributeClass - the type of attribute. May be null, but this will not match anything.

Throws:

RepositoryError

Since:

2.1

hasAttribute

public static boolean hasAttribute(Class clazz,
                                   Object attribute)
                            throws RepositoryError

Tests if a class has an attribute. That is, is there any attribute attr such that attr.equals(attribute)?

Parameters:

clazz - the class. May not be null.

attribute - the attribute to compare to.

Throws:

RepositoryError

Since:

2.1

hasAttribute

public static boolean hasAttribute(Field field,
                                   Object attribute)
                            throws RepositoryError

Tests if a field has an attribute. That is, is there any attribute attr such that attr.equals(attribute)?

Parameters:

field - the field. May not be null.

attribute - the attribute to compare to.

Throws:

RepositoryError

Since:

2.1

hasAttribute

public static boolean hasAttribute(Constructor constructor,
                                   Object attribute)
                            throws RepositoryError

Tests if a constructor has an attribute. That is, is there any attribute attr such that attr.equals(attribute)?

Parameters:

constructor - the constructor. May not be null.

attribute - the attribute to compare to.

Throws:

RepositoryError

Since:

2.1

hasAttribute

public static boolean hasAttribute(Method method,
                                   Object attribute)
                            throws RepositoryError

Tests if a method has an attribute. That is, is there any attribute attr such that attr.equals(attribute)?

Parameters:

method - the method. May not be null.

attribute - the attribute to compare to.

Throws:

RepositoryError

Since:

2.1

hasParameterAttribute

public static boolean hasParameterAttribute(Method method,
                                            int parameter,
                                            Object attribute)
                                     throws RepositoryError

Tests if a method's parameter has an attribute. That is, is there any attribute attr such that attr.equals(attribute)?

Parameters:

method - the method. May not be null.

parameter - the index of the parameter in the method's parameter list.

attribute - the attribute to compare to.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the method accepts.

RepositoryError

Since:

2.1

hasParameterAttribute

public static boolean hasParameterAttribute(Constructor constructor,
                                            int parameter,
                                            Object attribute)
                                     throws RepositoryError

Tests if a constructor's parameter has an attribute. That is, is there any attribute attr such that attr.equals(attribute)?

Parameters:

constructor - the constructor. May not be null.

parameter - the index of the parameter in the constructor's parameter list.

attribute - the attribute to compare to.

Throws:

ParameterIndexOutOfBoundsException - if the parameter index is < 0 or greater than the number of parameters the constructor accepts.

RepositoryError

Since:

2.1

hasReturnAttribute

public static boolean hasReturnAttribute(Method method,
                                         Object attribute)
                                  throws RepositoryError

Tests if a method's return value has an attribute. That is, is there any attribute attr such that attr.equals(attribute)?

Parameters:

method - the method. May not be null.

attribute - the attribute to compare to.

Throws:

RepositoryError

Since:

2.1

setAttributes

public static void setAttributes(RuntimeAttributeRepository repo)
                          throws IllegalStateException

Set attributes for a given class. The class must not have attributes set for it already (i.e. you can't redefine the attributes of a class at runtime). This because it really messes up the concept of inheritable attributes, and because the attribute set associated with a class is immutable, like the set of methods and fields.

Parameters:

repo - The repository. The repository will be sealed before any attributes are set. This to guarantee that the repository remains constant during setting.

Throws:

IllegalStateException - if the class whose attributes are defined already have attributes defined for it (even if it has no attributes).

Since:

2.1