Package org.apache.commons.lang.reflect

## Class FieldUtils

- java.lang.Object
- - org.apache.commons.lang.reflect.FieldUtils

-     public class FieldUtils
      extends Object

  Utilities for working with fields by reflection. Adapted and refactored from the dormant [reflect] Commons sandbox component.

  The ability is provided to break the scoping restrictions coded by the programmer. This can allow fields to be changed that shouldn't be. This facility should be used with care.

  Since:
    2.5
  Version:
    $Id: FieldUtils.java 1057009 2011-01-09 19:48:06Z niallp $

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `FieldUtils()` | FieldUtils instances should NOT be constructed in standard programming.

  - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `static Field` | `getDeclaredField​(Class cls, String fieldName)` | Gets an accessible `Field` by name respecting scope.
    `static Field` | `getDeclaredField​(Class cls, String fieldName, boolean forceAccess)` | Gets an accessible `Field` by name breaking scope if requested.
    `static Field` | `getField​(Class cls, String fieldName)` | Gets an accessible `Field` by name respecting scope.
    `static Field` | `getField​(Class cls, String fieldName, boolean forceAccess)` | Gets an accessible `Field` by name breaking scope if requested.
    `static Object` | `readDeclaredField​(Object target, String fieldName)` | Read the named public field.
    `static Object` | `readDeclaredField​(Object target, String fieldName, boolean forceAccess)` | <p<>Gets a Field value by name.
    `static Object` | `readDeclaredStaticField​(Class cls, String fieldName)` | Gets a static Field value by name.
    `static Object` | `readDeclaredStaticField​(Class cls, String fieldName, boolean forceAccess)` | Gets a static Field value by name.
    `static Object` | `readField​(Object target, String fieldName)` | Read the named public field.
    `static Object` | `readField​(Object target, String fieldName, boolean forceAccess)` | Read the named field.
    `static Object` | `readField​(Field field, Object target)` | Read an accessible Field.
    `static Object` | `readField​(Field field, Object target, boolean forceAccess)` | Read a Field.
    `static Object` | `readStaticField​(Class cls, String fieldName)` | Read the named public static field.
    `static Object` | `readStaticField​(Class cls, String fieldName, boolean forceAccess)` | Read the named static field.
    `static Object` | `readStaticField​(Field field)` | Read an accessible static Field.
    `static Object` | `readStaticField​(Field field, boolean forceAccess)` | Read a static Field.
    `static void` | `writeDeclaredField​(Object target, String fieldName, Object value)` | Write a public field.
    `static void` | `writeDeclaredField​(Object target, String fieldName, Object value, boolean forceAccess)` | Write a public field.
    `static void` | `writeDeclaredStaticField​(Class cls, String fieldName, Object value)` | Write a named public static Field.
    `static void` | `writeDeclaredStaticField​(Class cls, String fieldName, Object value, boolean forceAccess)` | Write a named static Field.
    `static void` | `writeField​(Object target, String fieldName, Object value)` | Write a public field.
    `static void` | `writeField​(Object target, String fieldName, Object value, boolean forceAccess)` | Write a field.
    `static void` | `writeField​(Field field, Object target, Object value)` | Write an accessible field.
    `static void` | `writeField​(Field field, Object target, Object value, boolean forceAccess)` | Write a field.
    `static void` | `writeStaticField​(Class cls, String fieldName, Object value)` | Write a named public static Field.
    `static void` | `writeStaticField​(Class cls, String fieldName, Object value, boolean forceAccess)` | Write a named static Field.
    `static void` | `writeStaticField​(Field field, Object value)` | Write a public static Field.
    `static void` | `writeStaticField​(Field field, Object value, boolean forceAccess)` | Write a static Field.

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

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

- - ### Constructor Detail

    - #### FieldUtils

          public FieldUtils()

      FieldUtils instances should NOT be constructed in standard programming.

      This constructor is public to permit tools that require a JavaBean instance to operate.

  - ### Method Detail

    - #### getField

          public static Field getField​(Class cls,
                                       String fieldName)

      Gets an accessible `Field` by name respecting scope. Superclasses/interfaces will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
      Returns:
        the Field object
      Throws:
        `IllegalArgumentException` - if the class or field name is null

    - #### getField

          public static Field getField​(Class cls,
                                       String fieldName,
                                       boolean forceAccess)

      Gets an accessible `Field` by name breaking scope if requested. Superclasses/interfaces will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Returns:
        the Field object
      Throws:
        `IllegalArgumentException` - if the class or field name is null

    - #### getDeclaredField

          public static Field getDeclaredField​(Class cls,
                                               String fieldName)

      Gets an accessible `Field` by name respecting scope. Only the specified class will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
      Returns:
        the Field object
      Throws:
        `IllegalArgumentException` - if the class or field name is null

    - #### getDeclaredField

          public static Field getDeclaredField​(Class cls,
                                               String fieldName,
                                               boolean forceAccess)

      Gets an accessible `Field` by name breaking scope if requested. Only the specified class will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. False will only match public fields.
      Returns:
        the Field object
      Throws:
        `IllegalArgumentException` - if the class or field name is null

    - #### readStaticField

          public static Object readStaticField​(Field field)
                                        throws IllegalAccessException

      Read an accessible static Field.
      Parameters:
        `field` - to read
      Returns:
        the field value
      Throws:
        `IllegalArgumentException` - if the field is null or not static
        `IllegalAccessException` - if the field is not accessible

    - #### readStaticField

          public static Object readStaticField​(Field field,
                                               boolean forceAccess)
                                        throws IllegalAccessException

      Read a static Field.
      Parameters:
        `field` - to read
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method.
      Returns:
        the field value
      Throws:
        `IllegalArgumentException` - if the field is null or not static
        `IllegalAccessException` - if the field is not made accessible

    - #### readStaticField

          public static Object readStaticField​(Class cls,
                                               String fieldName)
                                        throws IllegalAccessException

      Read the named public static field. Superclasses will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
      Returns:
        the value of the field
      Throws:
        `IllegalArgumentException` - if the class or field name is null
        `IllegalAccessException` - if the field is not accessible

    - #### readStaticField

          public static Object readStaticField​(Class cls,
                                               String fieldName,
                                               boolean forceAccess)
                                        throws IllegalAccessException

      Read the named static field. Superclasses will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Returns:
        the Field object
      Throws:
        `IllegalArgumentException` - if the class or field name is null
        `IllegalAccessException` - if the field is not made accessible

    - #### readDeclaredStaticField

          public static Object readDeclaredStaticField​(Class cls,
                                                       String fieldName)
                                                throws IllegalAccessException

      Gets a static Field value by name. The field must be public. Only the specified class will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
      Returns:
        the value of the field
      Throws:
        `IllegalArgumentException` - if the class or field name is null
        `IllegalAccessException` - if the field is not accessible

    - #### readDeclaredStaticField

          public static Object readDeclaredStaticField​(Class cls,
                                                       String fieldName,
                                                       boolean forceAccess)
                                                throws IllegalAccessException

      Gets a static Field value by name. Only the specified class will be considered.
      Parameters:
        `cls` - the class to reflect, must not be null
        `fieldName` - the field name to obtain
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Returns:
        the Field object
      Throws:
        `IllegalArgumentException` - if the class or field name is null
        `IllegalAccessException` - if the field is not made accessible

    - #### readField

          public static Object readField​(Field field,
                                         Object target)
                                  throws IllegalAccessException

      Read an accessible Field.
      Parameters:
        `field` - the field to use
        `target` - the object to call on, may be null for static fields
      Returns:
        the field value
      Throws:
        `IllegalArgumentException` - if the field is null
        `IllegalAccessException` - if the field is not accessible

    - #### readField

          public static Object readField​(Field field,
                                         Object target,
                                         boolean forceAccess)
                                  throws IllegalAccessException

      Read a Field.
      Parameters:
        `field` - the field to use
        `target` - the object to call on, may be null for static fields
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method.
      Returns:
        the field value
      Throws:
        `IllegalArgumentException` - if the field is null
        `IllegalAccessException` - if the field is not made accessible

    - #### readField

          public static Object readField​(Object target,
                                         String fieldName)
                                  throws IllegalAccessException

      Read the named public field. Superclasses will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
      Returns:
        the value of the field
      Throws:
        `IllegalArgumentException` - if the class or field name is null
        `IllegalAccessException` - if the named field is not public

    - #### readField

          public static Object readField​(Object target,
                                         String fieldName,
                                         boolean forceAccess)
                                  throws IllegalAccessException

      Read the named field. Superclasses will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Returns:
        the field value
      Throws:
        `IllegalArgumentException` - if the class or field name is null
        `IllegalAccessException` - if the named field is not made accessible

    - #### readDeclaredField

          public static Object readDeclaredField​(Object target,
                                                 String fieldName)
                                          throws IllegalAccessException

      Read the named public field. Only the class of the specified object will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
      Returns:
        the value of the field
      Throws:
        `IllegalArgumentException` - if the class or field name is null
        `IllegalAccessException` - if the named field is not public

    - #### readDeclaredField

          public static Object readDeclaredField​(Object target,
                                                 String fieldName,
                                                 boolean forceAccess)
                                          throws IllegalAccessException

      <p<>Gets a Field value by name. Only the class of the specified object will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Returns:
        the Field object
      Throws:
        `IllegalArgumentException` - if `target` or `fieldName` is null
        `IllegalAccessException` - if the field is not made accessible

    - #### writeStaticField

          public static void writeStaticField​(Field field,
                                              Object value)
                                       throws IllegalAccessException

      Write a public static Field.
      Parameters:
        `field` - to write
        `value` - to set
      Throws:
        `IllegalArgumentException` - if the field is null or not static
        `IllegalAccessException` - if the field is not public or is final

    - #### writeStaticField

          public static void writeStaticField​(Field field,
                                              Object value,
                                              boolean forceAccess)
                                       throws IllegalAccessException

      Write a static Field.
      Parameters:
        `field` - to write
        `value` - to set
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Throws:
        `IllegalArgumentException` - if the field is null or not static
        `IllegalAccessException` - if the field is not made accessible or is final

    - #### writeStaticField

          public static void writeStaticField​(Class cls,
                                              String fieldName,
                                              Object value)
                                       throws IllegalAccessException

      Write a named public static Field. Superclasses will be considered.
      Parameters:
        `cls` - Class on which the Field is to be found
        `fieldName` - to write
        `value` - to set
      Throws:
        `IllegalArgumentException` - if the field cannot be located or is not static
        `IllegalAccessException` - if the field is not public or is final

    - #### writeStaticField

          public static void writeStaticField​(Class cls,
                                              String fieldName,
                                              Object value,
                                              boolean forceAccess)
                                       throws IllegalAccessException

      Write a named static Field. Superclasses will be considered.
      Parameters:
        `cls` - Class on which the Field is to be found
        `fieldName` - to write
        `value` - to set
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Throws:
        `IllegalArgumentException` - if the field cannot be located or is not static
        `IllegalAccessException` - if the field is not made accessible or is final

    - #### writeDeclaredStaticField

          public static void writeDeclaredStaticField​(Class cls,
                                                      String fieldName,
                                                      Object value)
                                               throws IllegalAccessException

      Write a named public static Field. Only the specified class will be considered.
      Parameters:
        `cls` - Class on which the Field is to be found
        `fieldName` - to write
        `value` - to set
      Throws:
        `IllegalArgumentException` - if the field cannot be located or is not static
        `IllegalAccessException` - if the field is not public or is final

    - #### writeDeclaredStaticField

          public static void writeDeclaredStaticField​(Class cls,
                                                      String fieldName,
                                                      Object value,
                                                      boolean forceAccess)
                                               throws IllegalAccessException

      Write a named static Field. Only the specified class will be considered.
      Parameters:
        `cls` - Class on which the Field is to be found
        `fieldName` - to write
        `value` - to set
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Throws:
        `IllegalArgumentException` - if the field cannot be located or is not static
        `IllegalAccessException` - if the field is not made accessible or is final

    - #### writeField

          public static void writeField​(Field field,
                                        Object target,
                                        Object value)
                                 throws IllegalAccessException

      Write an accessible field.
      Parameters:
        `field` - to write
        `target` - the object to call on, may be null for static fields
        `value` - to set
      Throws:
        `IllegalArgumentException` - if the field is null
        `IllegalAccessException` - if the field is not accessible or is final

    - #### writeField

          public static void writeField​(Field field,
                                        Object target,
                                        Object value,
                                        boolean forceAccess)
                                 throws IllegalAccessException

      Write a field.
      Parameters:
        `field` - to write
        `target` - the object to call on, may be null for static fields
        `value` - to set
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Throws:
        `IllegalArgumentException` - if the field is null
        `IllegalAccessException` - if the field is not made accessible or is final

    - #### writeField

          public static void writeField​(Object target,
                                        String fieldName,
                                        Object value)
                                 throws IllegalAccessException

      Write a public field. Superclasses will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
        `value` - to set
      Throws:
        `IllegalArgumentException` - if `target` or `fieldName` is null
        `IllegalAccessException` - if the field is not accessible

    - #### writeField

          public static void writeField​(Object target,
                                        String fieldName,
                                        Object value,
                                        boolean forceAccess)
                                 throws IllegalAccessException

      Write a field. Superclasses will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
        `value` - to set
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Throws:
        `IllegalArgumentException` - if `target` or `fieldName` is null
        `IllegalAccessException` - if the field is not made accessible

    - #### writeDeclaredField

          public static void writeDeclaredField​(Object target,
                                                String fieldName,
                                                Object value)
                                         throws IllegalAccessException

      Write a public field. Only the specified class will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
        `value` - to set
      Throws:
        `IllegalArgumentException` - if `target` or `fieldName` is null
        `IllegalAccessException` - if the field is not made accessible

    - #### writeDeclaredField

          public static void writeDeclaredField​(Object target,
                                                String fieldName,
                                                Object value,
                                                boolean forceAccess)
                                         throws IllegalAccessException

      Write a public field. Only the specified class will be considered.
      Parameters:
        `target` - the object to reflect, must not be null
        `fieldName` - the field name to obtain
        `value` - to set
        `forceAccess` - whether to break scope restrictions using the `setAccessible` method. `False` will only match public fields.
      Throws:
        `IllegalArgumentException` - if `target` or `fieldName` is null
        `IllegalAccessException` - if the field is not made accessible