org.springframework.core

## Class MethodParameter

- java.lang.Object
- - org.springframework.core.MethodParameter

-     public class MethodParameter
      extends Object

  Helper class that encapsulates the specification of a method parameter, i.e. a Method or Constructor plus a parameter index and a nested type index for a declared generic type. Useful as a specification object to pass along.
  Since:
    2.0
  Author:
    Juergen Hoeller, Rob Harrop, Andy Clement
  See Also:
    `GenericCollectionTypeResolver`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `MethodParameter(Constructor constructor, int parameterIndex)` Create a new MethodParameter for the given constructor, with nesting level 1.
    `MethodParameter(Constructor constructor, int parameterIndex, int nestingLevel)` Create a new MethodParameter for the given constructor.
    `MethodParameter(Method method, int parameterIndex)` Create a new MethodParameter for the given method, with nesting level 1.
    `MethodParameter(Method method, int parameterIndex, int nestingLevel)` Create a new MethodParameter for the given method.
    `MethodParameter(MethodParameter original)` Copy constructor, resulting in an independent MethodParameter object based on the same metadata and cache state that the original object was in.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `decreaseNestingLevel()` Decrease this parameter's nesting level.
    `boolean` | `equals(Object obj)`
    `static MethodParameter` | `forMethodOrConstructor(Object methodOrConstructor, int parameterIndex)` Create a new MethodParameter for the given method or constructor.
    `Constructor` | `getConstructor()` Return the wrapped Constructor, if any.
    `Class<?>` | `getDeclaringClass()` Return the class that declares the underlying Method or Constructor.
    `Type` | `getGenericParameterType()` Return the generic type of the method/constructor parameter.
    `Method` | `getMethod()` Return the wrapped Method, if any.
    `<T extends Annotation> T` | `getMethodAnnotation(Class<T> annotationType)` Return the method/constructor annotation of the given type, if available.
    `Annotation[]` | `getMethodAnnotations()` Return the annotations associated with the target method/constructor itself.
    `Class<?>` | `getNestedParameterType()`
    `int` | `getNestingLevel()` Return the nesting level of the target type (typically 1; e.g.
    `<T extends Annotation> T` | `getParameterAnnotation(Class<T> annotationType)` Return the parameter annotation of the given type, if available.
    `Annotation[]` | `getParameterAnnotations()` Return the annotations associated with the specific method/constructor parameter.
    `int` | `getParameterIndex()` Return the index of the method/constructor parameter.
    `String` | `getParameterName()` Return the name of the method/constructor parameter.
    `Class<?>` | `getParameterType()` Return the type of the method/constructor parameter.
    `Integer` | `getTypeIndexForCurrentLevel()` Return the type index for the current nesting level.
    `Integer` | `getTypeIndexForLevel(int nestingLevel)` Return the type index for the specified nesting level.
    `int` | `hashCode()`
    `<T extends Annotation> boolean` | `hasParameterAnnotation(Class<T> annotationType)` Return true if the parameter has the given annotation type, and false if it doesn't.
    `boolean` | `hasParameterAnnotations()` Return true if the parameter has at least one annotation, false if it has none.
    `void` | `increaseNestingLevel()` Increase this parameter's nesting level.
    `void` | `initParameterNameDiscovery(ParameterNameDiscoverer parameterNameDiscoverer)` Initialize parameter name discovery for this method parameter.
    `void` | `setTypeIndexForCurrentLevel(int typeIndex)` Set the type index for the current nesting level.

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### MethodParameter

          public MethodParameter(Method method,
                         int parameterIndex)

      Create a new MethodParameter for the given method, with nesting level 1.
      Parameters:
        `method` - the Method to specify a parameter for
        `parameterIndex` - the index of the parameter

    - #### MethodParameter

          public MethodParameter(Method method,
                         int parameterIndex,
                         int nestingLevel)

      Create a new MethodParameter for the given method.
      Parameters:
        `method` - the Method to specify a parameter for
        `parameterIndex` - the index of the parameter (-1 for the method return type; 0 for the first method parameter, 1 for the second method parameter, etc)
        `nestingLevel` - the nesting level of the target type (typically 1; e.g. in case of a List of Lists, 1 would indicate the nested List, whereas 2 would indicate the element of the nested List)

    - #### MethodParameter

          public MethodParameter(Constructor constructor,
                         int parameterIndex)

      Create a new MethodParameter for the given constructor, with nesting level 1.
      Parameters:
        `constructor` - the Constructor to specify a parameter for
        `parameterIndex` - the index of the parameter

    - #### MethodParameter

          public MethodParameter(Constructor constructor,
                         int parameterIndex,
                         int nestingLevel)

      Create a new MethodParameter for the given constructor.
      Parameters:
        `constructor` - the Constructor to specify a parameter for
        `parameterIndex` - the index of the parameter
        `nestingLevel` - the nesting level of the target type (typically 1; e.g. in case of a List of Lists, 1 would indicate the nested List, whereas 2 would indicate the element of the nested List)

    - #### MethodParameter

          public MethodParameter(MethodParameter original)

      Copy constructor, resulting in an independent MethodParameter object based on the same metadata and cache state that the original object was in.
      Parameters:
        `original` - the original MethodParameter object to copy from

  - ### Method Detail

    - #### getMethod

          public Method getMethod()

      Return the wrapped Method, if any.

      Note: Either Method or Constructor is available.

      Returns:
        the Method, or `null` if none

    - #### getConstructor

          public Constructor getConstructor()

      Return the wrapped Constructor, if any.

      Note: Either Method or Constructor is available.

      Returns:
        the Constructor, or `null` if none

    - #### getDeclaringClass

          public Class<?> getDeclaringClass()

      Return the class that declares the underlying Method or Constructor.

    - #### getParameterIndex

          public int getParameterIndex()

      Return the index of the method/constructor parameter.
      Returns:
        the parameter index (never negative)

    - #### getParameterType

          public Class<?> getParameterType()

      Return the type of the method/constructor parameter.
      Returns:
        the parameter type (never `null`)

    - #### getGenericParameterType

          public Type getGenericParameterType()

      Return the generic type of the method/constructor parameter.
      Returns:
        the parameter type (never `null`)

    - #### getNestedParameterType

          public Class<?> getNestedParameterType()

    - #### getMethodAnnotations

          public Annotation[] getMethodAnnotations()

      Return the annotations associated with the target method/constructor itself.

    - #### getMethodAnnotation

          public <T extends Annotation> T getMethodAnnotation(Class<T> annotationType)

      Return the method/constructor annotation of the given type, if available.
      Parameters:
        `annotationType` - the annotation type to look for
      Returns:
        the annotation object, or `null` if not found

    - #### getParameterAnnotations

          public Annotation[] getParameterAnnotations()

      Return the annotations associated with the specific method/constructor parameter.

    - #### getParameterAnnotation

          public <T extends Annotation> T getParameterAnnotation(Class<T> annotationType)

      Return the parameter annotation of the given type, if available.
      Parameters:
        `annotationType` - the annotation type to look for
      Returns:
        the annotation object, or `null` if not found

    - #### hasParameterAnnotations

          public boolean hasParameterAnnotations()

      Return true if the parameter has at least one annotation, false if it has none.

    - #### hasParameterAnnotation

          public <T extends Annotation> boolean hasParameterAnnotation(Class<T> annotationType)

      Return true if the parameter has the given annotation type, and false if it doesn't.

    - #### initParameterNameDiscovery

          public void initParameterNameDiscovery(ParameterNameDiscoverer parameterNameDiscoverer)

      Initialize parameter name discovery for this method parameter.

      This method does not actually try to retrieve the parameter name at this point; it just allows discovery to happen when the application calls `getParameterName()` (if ever).

    - #### getParameterName

          public String getParameterName()

      Return the name of the method/constructor parameter.
      Returns:
        the parameter name (may be `null` if no parameter name metadata is contained in the class file or no `ParameterNameDiscoverer` has been set to begin with)

    - #### increaseNestingLevel

          public void increaseNestingLevel()

      Increase this parameter's nesting level.
      See Also:
        `getNestingLevel()`

    - #### decreaseNestingLevel

          public void decreaseNestingLevel()

      Decrease this parameter's nesting level.
      See Also:
        `getNestingLevel()`

    - #### getNestingLevel

          public int getNestingLevel()

      Return the nesting level of the target type (typically 1; e.g. in case of a List of Lists, 1 would indicate the nested List, whereas 2 would indicate the element of the nested List).

    - #### setTypeIndexForCurrentLevel

          public void setTypeIndexForCurrentLevel(int typeIndex)

      Set the type index for the current nesting level.
      Parameters:
        `typeIndex` - the corresponding type index (or `null` for the default type index)
      See Also:
        `getNestingLevel()`

    - #### getTypeIndexForCurrentLevel

          public Integer getTypeIndexForCurrentLevel()

      Return the type index for the current nesting level.
      Returns:
        the corresponding type index, or `null` if none specified (indicating the default type index)
      See Also:
        `getNestingLevel()`

    - #### getTypeIndexForLevel

          public Integer getTypeIndexForLevel(int nestingLevel)

      Return the type index for the specified nesting level.
      Parameters:
        `nestingLevel` - the nesting level to check
      Returns:
        the corresponding type index, or `null` if none specified (indicating the default type index)

    - #### equals

          public boolean equals(Object obj)

      Overrides:
        `equals` in class `Object`

    - #### hashCode

          public int hashCode()

      Overrides:
        `hashCode` in class `Object`

    - #### forMethodOrConstructor

          public static MethodParameter forMethodOrConstructor(Object methodOrConstructor,
                                               int parameterIndex)

      Create a new MethodParameter for the given method or constructor.

      This is a convenience constructor for scenarios where a Method or Constructor reference is treated in a generic fashion.

      Parameters:
        `methodOrConstructor` - the Method or Constructor to specify a parameter for
        `parameterIndex` - the index of the parameter
      Returns:
        the corresponding MethodParameter instance