org.springframework.core

Class GenericTypeResolver

java.lang.Object

org.springframework.core.GenericTypeResolver

public abstract class GenericTypeResolver
extends Object

Helper class for resolving generic types against type variables.

Mainly intended for usage within the framework, resolving method parameter types even when they are declared generically.

Since:

2.5.2

Author:

Juergen Hoeller, Rob Harrop, Sam Brannen

See Also:

GenericCollectionTypeResolver

Constructor Summary

Constructors

Constructor and Description
GenericTypeResolver()

Method Summary

Methods

Modifier and Type	Method and Description
static Type	getTargetType(MethodParameter methodParam) Determine the target type for the given parameter specification.
static Map<TypeVariable,Type>	getTypeVariableMap(Class<?> clazz) Build a mapping of TypeVariable names to concrete classes for the specified Class.
static Class<?>	resolveParameterType(MethodParameter methodParam, Class<?> clazz) Determine the target type for the given generic parameter type.
static Class<?>	resolveReturnType(Method method, Class<?> clazz) Determine the target type for the generic return type of the given method, where formal type variables are declared on the given class.
static Class<?>	resolveReturnTypeArgument(Method method, Class<?> genericIfc) Resolve the single type argument of the given generic interface against the given target method which is assumed to return the given interface or an implementation of it.
static Class<?>	resolveReturnTypeForGenericMethod(Method method, Object[] args) Deprecated. in favor of resolveReturnTypeForFactoryMethod in the internal AutowireUtils class in the beans module; we do not expect other use of it!
static Class<?>	resolveType(Type genericType, Map<TypeVariable,Type> typeVariableMap) Resolve the specified generic type against the given TypeVariable map.
static Class<?>	resolveTypeArgument(Class<?> clazz, Class<?> genericIfc) Resolve the single type argument of the given generic interface against the given target class which is assumed to implement the generic interface and possibly declare a concrete type for its type variable.
static Class<?>[]	resolveTypeArguments(Class<?> clazz, Class<?> genericIfc) Resolve the type arguments of the given generic interface against the given target class which is assumed to implement the generic interface and possibly declare concrete types for its type variables.

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericTypeResolver

public GenericTypeResolver()

Method Detail

getTargetType

public static Type getTargetType(MethodParameter methodParam)

Determine the target type for the given parameter specification.

Parameters:

methodParam - the method parameter specification

Returns:

the corresponding generic parameter type

resolveParameterType

public static Class<?> resolveParameterType(MethodParameter methodParam,
                            Class<?> clazz)

Determine the target type for the given generic parameter type.

Parameters:

methodParam - the method parameter specification

clazz - the class to resolve type variables against

Returns:

the corresponding generic parameter or return type

resolveReturnType

public static Class<?> resolveReturnType(Method method,
                         Class<?> clazz)

Determine the target type for the generic return type of the given method, where formal type variables are declared on the given class.

Parameters:

method - the method to introspect

clazz - the class to resolve type variables against

Returns:

the corresponding generic parameter or return type

See Also:

resolveReturnTypeForGenericMethod(java.lang.reflect.Method, java.lang.Object[])

resolveReturnTypeForGenericMethod

@Deprecated
public static Class<?> resolveReturnTypeForGenericMethod(Method method,
                                                    Object[] args)

Deprecated. in favor of resolveReturnTypeForFactoryMethod in the internal AutowireUtils class in the beans module; we do not expect other use of it!

Determine the target type for the generic return type of the given generic method, where formal type variables are declared on the given method itself.

For example, given a factory method with the following signature, if resolveReturnTypeForGenericMethod() is invoked with the reflected method for creatProxy() and an Object[] array containing MyService.class, resolveReturnTypeForGenericMethod() will infer that the target return type is MyService.

public static <T> T createProxy(Class<T> clazz)

Possible Return Values

• the target return type, if it can be inferred
• the standard return type, if the given method does not declare any formal type variables
• the standard return type, if the target return type cannot be inferred (e.g., due to type erasure)
• null, if the length of the given arguments array is shorter than the length of the formal argument list for the given method

Parameters:

method - the method to introspect, never null

args - the arguments that will be supplied to the method when it is invoked, never null

Returns:

the resolved target return type, the standard return type, or null

Since:

3.2

resolveReturnTypeArgument

public static Class<?> resolveReturnTypeArgument(Method method,
                                 Class<?> genericIfc)

Resolve the single type argument of the given generic interface against the given target method which is assumed to return the given interface or an implementation of it.

Parameters:

method - the target method to check the return type of

genericIfc - the generic interface or superclass to resolve the type argument from

Returns:

the resolved parameter type of the method return type, or null if not resolvable or if the single argument is of type WildcardType.

resolveTypeArgument

public static Class<?> resolveTypeArgument(Class<?> clazz,
                           Class<?> genericIfc)

Resolve the single type argument of the given generic interface against the given target class which is assumed to implement the generic interface and possibly declare a concrete type for its type variable.

Parameters:

clazz - the target class to check against

genericIfc - the generic interface or superclass to resolve the type argument from

Returns:

the resolved type of the argument, or null if not resolvable

resolveTypeArguments

public static Class<?>[] resolveTypeArguments(Class<?> clazz,
                              Class<?> genericIfc)

Resolve the type arguments of the given generic interface against the given target class which is assumed to implement the generic interface and possibly declare concrete types for its type variables.

Note: In Spring 3.2, this method doesn't return null in all scenarios where it should. To be fixed in Spring 4.0; for client code, this just means it might see null in a few more cases then where it now sees an array with a single Object type.

Parameters:

clazz - the target class to check against

genericIfc - the generic interface or superclass to resolve the type argument from

Returns:

the resolved type of each argument, with the array size matching the number of actual type arguments, or null if not resolvable

resolveType

public static Class<?> resolveType(Type genericType,
                   Map<TypeVariable,Type> typeVariableMap)

Resolve the specified generic type against the given TypeVariable map.

Parameters:

genericType - the generic type to resolve

typeVariableMap - the TypeVariable Map to resolved against

Returns:

the type if it resolves to a Class, or Object.class otherwise

getTypeVariableMap

public static Map<TypeVariable,Type> getTypeVariableMap(Class<?> clazz)

Build a mapping of TypeVariable names to concrete classes for the specified Class. Searches all super types, enclosing types and interfaces.