Class TypeDescriptor
- All Implemented Interfaces:
Serializable
Capable of representing arrays and generic collection types.
- Since:
- 3.0
- Author:
- Keith Donald, Andy Clement, Juergen Hoeller, Phillip Webb, Sam Brannen, Stephane Nicoll
- See Also:
-
Constructor Summary
ConstructorDescriptionTypeDescriptor
(Field field) Create a new type descriptor from aField
.TypeDescriptor
(Property property) Create a new type descriptor from aProperty
.TypeDescriptor
(MethodParameter methodParameter) Create a new type descriptor from aMethodParameter
.TypeDescriptor
(ResolvableType resolvableType, Class<?> type, Annotation[] annotations) Create a new type descriptor from aResolvableType
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Method Summary
Modifier and TypeMethodDescriptionstatic TypeDescriptor
array
(TypeDescriptor elementTypeDescriptor) Create a new type descriptor as an array of the specified type.static TypeDescriptor
collection
(Class<?> collectionType, TypeDescriptor elementTypeDescriptor) Create a new type descriptor from aCollection
type.elementTypeDescriptor
(Object element) If this type is aCollection
or an array, creates an element TypeDescriptor from the provided collection or array element.boolean
static TypeDescriptor
Create a new type descriptor for an object.<T extends Annotation>
TgetAnnotation
(Class<T> annotationType) Obtain the annotation of the specifiedannotationType
that is on this type descriptor.Return the annotations associated with this type descriptor, if any.If this type is an array, returns the array's component type.If this type is aMap
and its key type is parameterized, returns the map's key type.getMapKeyTypeDescriptor
(Object mapKey) If this type is aMap
, creates a mapKeyTypeDescriptor
from the provided map key.If this type is aMap
and its value type is parameterized, returns the map's value type.getMapValueTypeDescriptor
(Object mapValue) If this type is aMap
, creates a mapValueTypeDescriptor
from the provided map value.getName()
Return the name of this type: the fully qualified class name.Class<?>
Variation ofgetType()
that accounts for a primitive type by returning its object wrapper type.Return the underlyingResolvableType
.Return the underlying source of the descriptor.Class<?>
getType()
The type of the backing class, method parameter, field, or property described by this TypeDescriptor.boolean
hasAnnotation
(Class<? extends Annotation> annotationType) Determine if this type descriptor has the specified annotation.int
hashCode()
boolean
isArray()
Is this type an array type?boolean
isAssignableTo
(TypeDescriptor typeDescriptor) Returns true if an object of this type descriptor can be assigned to the location described by the given type descriptor.boolean
Is this type aCollection
type?boolean
isMap()
Is this type aMap
type?boolean
Is this type a primitive type?static TypeDescriptor
map
(Class<?> mapType, TypeDescriptor keyTypeDescriptor, TypeDescriptor valueTypeDescriptor) Create a new type descriptor from aMap
type.Narrows thisTypeDescriptor
by setting its type to the class of the provided value.nested
(int nestingLevel) Create a type descriptor for a nested type declared within this descriptor.static TypeDescriptor
Create a type descriptor for a nested type declared within the field.static TypeDescriptor
Create a type descriptor for a nested type declared within the property.static TypeDescriptor
nested
(MethodParameter methodParameter, int nestingLevel) Create a type descriptor for a nested type declared within the method parameter.toString()
Cast thisTypeDescriptor
to a superclass or implemented interface preserving annotations and nested type context.static TypeDescriptor
Create a new type descriptor from the given type.
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Constructor Details
-
TypeDescriptor
Create a new type descriptor from aMethodParameter
.Use this constructor when a source or target conversion point is a constructor parameter, method parameter, or method return value.
- Parameters:
methodParameter
- the method parameter
-
TypeDescriptor
Create a new type descriptor from aField
.Use this constructor when a source or target conversion point is a field.
- Parameters:
field
- the field
-
TypeDescriptor
Create a new type descriptor from aProperty
.Use this constructor when a source or target conversion point is a property on a Java class.
- Parameters:
property
- the property
-
TypeDescriptor
public TypeDescriptor(ResolvableType resolvableType, @Nullable Class<?> type, @Nullable Annotation[] annotations) Create a new type descriptor from aResolvableType
.This constructor is used internally and may also be used by subclasses that support non-Java languages with extended type systems. It is public as of 5.1.4 whereas it was protected before.
- Parameters:
resolvableType
- the resolvable typetype
- the backing type (ornull
if it should get resolved)annotations
- the type annotations- Since:
- 4.0
-
-
Method Details
-
getObjectType
Variation ofgetType()
that accounts for a primitive type by returning its object wrapper type.This is useful for conversion service implementations that wish to normalize to object-based types and not work with primitive types directly.
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getType
The type of the backing class, method parameter, field, or property described by this TypeDescriptor.Returns primitive types as-is. See
getObjectType()
for a variation of this operation that resolves primitive types to their corresponding Object types if necessary.- See Also:
-
getResolvableType
Return the underlyingResolvableType
.- Since:
- 4.0
-
getSource
Return the underlying source of the descriptor. Will return aField
,MethodParameter
orType
depending on how theTypeDescriptor
was constructed. This method is primarily to provide access to additional type information or meta-data that alternative JVM languages may provide.- Since:
- 4.0
-
nested
Create a type descriptor for a nested type declared within this descriptor.- Parameters:
nestingLevel
- the nesting level of the collection/array element or map key/value declaration within the property- Returns:
- the nested type descriptor at the specified nesting level, or
null
if it could not be obtained - Since:
- 6.1
-
narrow
Narrows thisTypeDescriptor
by setting its type to the class of the provided value.If the value is
null
, no narrowing is performed and this TypeDescriptor is returned unchanged.Designed to be called by binding frameworks when they read property, field, or method return values. Allows such frameworks to narrow a TypeDescriptor built from a declared property, field, or method return value type. For example, a field declared as
java.lang.Object
would be narrowed tojava.util.HashMap
if it was set to ajava.util.HashMap
value. The narrowed TypeDescriptor can then be used to convert the HashMap to some other type. Annotation and nested type context is preserved by the narrowed copy.- Parameters:
value
- the value to use for narrowing this type descriptor- Returns:
- this TypeDescriptor narrowed (returns a copy with its type updated to the class of the provided value)
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upcast
Cast thisTypeDescriptor
to a superclass or implemented interface preserving annotations and nested type context.- Parameters:
superType
- the supertype to cast to (can benull
)- Returns:
- a new TypeDescriptor for the up-cast type
- Throws:
IllegalArgumentException
- if this type is not assignable to the super-type- Since:
- 3.2
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getName
Return the name of this type: the fully qualified class name. -
isPrimitive
public boolean isPrimitive()Is this type a primitive type? -
getAnnotations
Return the annotations associated with this type descriptor, if any.- Returns:
- the annotations, or an empty array if none
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hasAnnotation
Determine if this type descriptor has the specified annotation.As of Spring Framework 4.2, this method supports arbitrary levels of meta-annotations.
- Parameters:
annotationType
- the annotation type- Returns:
true
if the annotation is present
-
getAnnotation
Obtain the annotation of the specifiedannotationType
that is on this type descriptor.As of Spring Framework 4.2, this method supports arbitrary levels of meta-annotations.
- Parameters:
annotationType
- the annotation type- Returns:
- the annotation, or
null
if no such annotation exists on this type descriptor
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isAssignableTo
Returns true if an object of this type descriptor can be assigned to the location described by the given type descriptor.For example,
valueOf(String.class).isAssignableTo(valueOf(CharSequence.class))
returnstrue
because a String value can be assigned to a CharSequence variable. On the other hand,valueOf(Number.class).isAssignableTo(valueOf(Integer.class))
returnsfalse
because, while all Integers are Numbers, not all Numbers are Integers.For arrays, collections, and maps, element and key/value types are checked if declared. For example, a
List<String>
field value is assignable to aCollection<CharSequence>
field, butList<Number>
is not assignable toList<Integer>
.- Returns:
true
if this type is assignable to the type represented by the provided type descriptor- See Also:
-
isCollection
public boolean isCollection()Is this type aCollection
type? -
isArray
public boolean isArray()Is this type an array type? -
getElementTypeDescriptor
If this type is an array, returns the array's component type. If this type is aStream
, returns the stream's component type. If this type is aCollection
and it is parameterized, returns the Collection's element type. If the Collection is not parameterized, returnsnull
indicating the element type is not declared.- Returns:
- the array component type or Collection element type, or
null
if this type is not an array type or ajava.util.Collection
or if its element type is not parameterized - See Also:
-
elementTypeDescriptor
If this type is aCollection
or an array, creates an element TypeDescriptor from the provided collection or array element.Narrows the
elementType
property to the class of the provided collection or array element. For example, if this describes ajava.util.List<java.lang.Number>
and the element argument is ajava.lang.Integer
, the returned TypeDescriptor will bejava.lang.Integer
. If this describes ajava.util.List<?>
and the element argument is ajava.lang.Integer
, the returned TypeDescriptor will bejava.lang.Integer
as well.Annotation and nested type context will be preserved in the narrowed TypeDescriptor that is returned.
- Parameters:
element
- the collection or array element- Returns:
- an element type descriptor, narrowed to the type of the provided element
- See Also:
-
isMap
public boolean isMap()Is this type aMap
type? -
getMapKeyTypeDescriptor
If this type is aMap
and its key type is parameterized, returns the map's key type. If the Map's key type is not parameterized, returnsnull
indicating the key type is not declared.- Returns:
- the Map key type, or
null
if this type is a Map but its key type is not parameterized - Throws:
IllegalStateException
- if this type is not ajava.util.Map
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getMapKeyTypeDescriptor
If this type is aMap
, creates a mapKeyTypeDescriptor
from the provided map key.Narrows the
mapKeyType
property to the class of the provided map key. For example, if this describes ajava.util.Map<java.lang.Number, java.lang.String>
and the key argument is ajava.lang.Integer
, the returned TypeDescriptor will bejava.lang.Integer
. If this describes ajava.util.Map<?, ?>
and the key argument is ajava.lang.Integer
, the returned TypeDescriptor will bejava.lang.Integer
as well.Annotation and nested type context will be preserved in the narrowed TypeDescriptor that is returned.
- Parameters:
mapKey
- the map key- Returns:
- the map key type descriptor
- Throws:
IllegalStateException
- if this type is not ajava.util.Map
- See Also:
-
getMapValueTypeDescriptor
If this type is aMap
and its value type is parameterized, returns the map's value type.If the Map's value type is not parameterized, returns
null
indicating the value type is not declared.- Returns:
- the Map value type, or
null
if this type is a Map but its value type is not parameterized - Throws:
IllegalStateException
- if this type is not ajava.util.Map
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getMapValueTypeDescriptor
If this type is aMap
, creates a mapValueTypeDescriptor
from the provided map value.Narrows the
mapValueType
property to the class of the provided map value. For example, if this describes ajava.util.Map<java.lang.String, java.lang.Number>
and the value argument is ajava.lang.Integer
, the returned TypeDescriptor will bejava.lang.Integer
. If this describes ajava.util.Map<?, ?>
and the value argument is ajava.lang.Integer
, the returned TypeDescriptor will bejava.lang.Integer
as well.Annotation and nested type context will be preserved in the narrowed TypeDescriptor that is returned.
- Parameters:
mapValue
- the map value- Returns:
- the map value type descriptor
- Throws:
IllegalStateException
- if this type is not ajava.util.Map
- See Also:
-
equals
-
hashCode
public int hashCode() -
toString
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forObject
Create a new type descriptor for an object.Use this factory method to introspect a source object before asking the conversion system to convert it to some other type.
If the provided object is
null
, returnsnull
, else callsvalueOf(Class)
to build a TypeDescriptor from the object's class.- Parameters:
source
- the source object- Returns:
- the type descriptor
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valueOf
Create a new type descriptor from the given type.Use this to instruct the conversion system to convert an object to a specific target type, when no type location such as a method parameter or field is available to provide additional conversion context.
Generally prefer use of
forObject(Object)
for constructing type descriptors from source objects, as it handles thenull
object case.- Parameters:
type
- the class (may benull
to indicateObject.class
)- Returns:
- the corresponding type descriptor
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collection
public static TypeDescriptor collection(Class<?> collectionType, @Nullable TypeDescriptor elementTypeDescriptor) Create a new type descriptor from aCollection
type.Useful for converting to typed Collections.
For example, a
List<String>
could be converted to aList<EmailAddress>
by converting to a targetType built with this method. The method call to construct such aTypeDescriptor
would look something like:collection(List.class, TypeDescriptor.valueOf(EmailAddress.class));
- Parameters:
collectionType
- the collection type, which must implementCollection
.elementTypeDescriptor
- a descriptor for the collection's element type, used to convert collection elements- Returns:
- the collection type descriptor
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map
public static TypeDescriptor map(Class<?> mapType, @Nullable TypeDescriptor keyTypeDescriptor, @Nullable TypeDescriptor valueTypeDescriptor) Create a new type descriptor from aMap
type.Useful for converting to typed Maps.
For example, a
Map<String, String>
could be converted to aMap<Id, EmailAddress>
by converting to a targetType built with this method: The method call to construct such a TypeDescriptor would look something like:map(Map.class, TypeDescriptor.valueOf(Id.class), TypeDescriptor.valueOf(EmailAddress.class));
- Parameters:
mapType
- the map type, which must implementMap
keyTypeDescriptor
- a descriptor for the map's key type, used to convert map keysvalueTypeDescriptor
- the map's value type, used to convert map values- Returns:
- the map type descriptor
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array
Create a new type descriptor as an array of the specified type.For example to create a
Map<String,String>[]
use:TypeDescriptor.array(TypeDescriptor.map(Map.class, TypeDescriptor.value(String.class), TypeDescriptor.value(String.class)));
- Parameters:
elementTypeDescriptor
- theTypeDescriptor
of the array element ornull
- Returns:
- an array
TypeDescriptor
ornull
ifelementTypeDescriptor
isnull
- Since:
- 3.2.1
-
nested
Create a type descriptor for a nested type declared within the method parameter.For example, if the methodParameter is a
List<String>
and the nesting level is 1, the nested type descriptor will be String.class.If the methodParameter is a
List<List<String>>
and the nesting level is 2, the nested type descriptor will also be a String.class.If the methodParameter is a
Map<Integer, String>
and the nesting level is 1, the nested type descriptor will be String, derived from the map value.If the methodParameter is a
List<Map<Integer, String>>
and the nesting level is 2, the nested type descriptor will be String, derived from the map value.Returns
null
if a nested type cannot be obtained because it was not declared. For example, if the method parameter is aList<?>
, the nested type descriptor returned will benull
.- Parameters:
methodParameter
- the method parameter with a nestingLevel of 1nestingLevel
- the nesting level of the collection/array element or map key/value declaration within the method parameter- Returns:
- the nested type descriptor at the specified nesting level,
or
null
if it could not be obtained - Throws:
IllegalArgumentException
- if the nesting level of the inputMethodParameter
argument is not 1, or if the types up to the specified nesting level are not of collection, array, or map types
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nested
Create a type descriptor for a nested type declared within the field.For example, if the field is a
List<String>
and the nesting level is 1, the nested type descriptor will beString.class
.If the field is a
List<List<String>>
and the nesting level is 2, the nested type descriptor will also be aString.class
.If the field is a
Map<Integer, String>
and the nesting level is 1, the nested type descriptor will be String, derived from the map value.If the field is a
List<Map<Integer, String>>
and the nesting level is 2, the nested type descriptor will be String, derived from the map value.Returns
null
if a nested type cannot be obtained because it was not declared. For example, if the field is aList<?>
, the nested type descriptor returned will benull
.- Parameters:
field
- the fieldnestingLevel
- the nesting level of the collection/array element or map key/value declaration within the field- Returns:
- the nested type descriptor at the specified nesting level,
or
null
if it could not be obtained - Throws:
IllegalArgumentException
- if the types up to the specified nesting level are not of collection, array, or map types
-
nested
Create a type descriptor for a nested type declared within the property.For example, if the property is a
List<String>
and the nesting level is 1, the nested type descriptor will beString.class
.If the property is a
List<List<String>>
and the nesting level is 2, the nested type descriptor will also be aString.class
.If the property is a
Map<Integer, String>
and the nesting level is 1, the nested type descriptor will be String, derived from the map value.If the property is a
List<Map<Integer, String>>
and the nesting level is 2, the nested type descriptor will be String, derived from the map value.Returns
null
if a nested type cannot be obtained because it was not declared. For example, if the property is aList<?>
, the nested type descriptor returned will benull
.- Parameters:
property
- the propertynestingLevel
- the nesting level of the collection/array element or map key/value declaration within the property- Returns:
- the nested type descriptor at the specified nesting level, or
null
if it could not be obtained - Throws:
IllegalArgumentException
- if the types up to the specified nesting level are not of collection, array, or map types
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