## org.springframework.core
Class Constants

    java.lang.Object
      org.springframework.core.Constants

    public class Constants

extends Object

This class can be used to parse other classes containing constant definitions in public static final members. The `asXXXX` methods of this class allow these constant values to be accessed via their string names.

Consider class Foo containing `public final static int CONSTANT1 = 66;` An instance of this class wrapping `Foo.class` will return the constant value of 66 from its `asNumber` method given the argument `"CONSTANT1"`.

This class is ideal for use in PropertyEditors, enabling them to recognize the same names as the constants themselves, and freeing them from maintaining their own mapping.

Since:
  16.03.2003
Author:
  Rod Johnson, Juergen Hoeller

Constructor Summary
`Constants(Class<?> clazz)` Create a new Constants converter class wrapping the given class.

Method Summary
`Number` `asNumber(String code)` Return a constant value cast to a Number.
`Object` `asObject(String code)` Parse the given String (upper or lower case accepted) and return the appropriate value if it's the name of a constant field in the class that we're analysing.
`String` `asString(String code)` Return a constant value as a String.
`String` `getClassName()` Return the name of the analyzed class.
`protected Map<String,Object>` `getFieldCache()` Exposes the field cache to subclasses: a Map from String field name to object value.
`Set<String>` `getNames(String namePrefix)` Return all names of the given group of constants.
`Set<String>` `getNamesForProperty(String propertyName)` Return all names of the group of constants for the given bean property name.
`Set<String>` `getNamesForSuffix(String nameSuffix)` Return all names of the given group of constants.
`int` `getSize()` Return the number of constants exposed.
`Set<Object>` `getValues(String namePrefix)` Return all values of the given group of constants.
`Set<Object>` `getValuesForProperty(String propertyName)` Return all values of the group of constants for the given bean property name.
`Set<Object>` `getValuesForSuffix(String nameSuffix)` Return all values of the given group of constants.
`String` `propertyToConstantNamePrefix(String propertyName)` Convert the given bean property name to a constant name prefix.
`String` `toCode(Object value, String namePrefix)` Look up the given value within the given group of constants.
`String` `toCodeForProperty(Object value, String propertyName)` Look up the given value within the group of constants for the given bean property name.
`String` `toCodeForSuffix(Object value, String nameSuffix)` Look up the given value within the given group of constants.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### Constants

    public Constants(Class<?> clazz)

  Create a new Constants converter class wrapping the given class.

  All public static final variables will be exposed, whatever their type.

  Parameters:
    `clazz` - the class to analyze
  Throws:
    `IllegalArgumentException` - if the supplied `clazz` is `null`

Method Detail

### getClassName

    public final String getClassName()

  Return the name of the analyzed class.

### getSize

    public final int getSize()

  Return the number of constants exposed.

### getFieldCache

    protected final Map<String,Object> getFieldCache()

  Exposes the field cache to subclasses: a Map from String field name to object value.

### asNumber

    public Number asNumber(String code)
                    throws ConstantException

  Return a constant value cast to a Number.

  Parameters:
    `code` - the name of the field (never `null`)
  Returns:
    the Number value
  Throws:
    `ConstantException` - if the field name wasn't found or if the type wasn't compatible with Number
  See Also:
    `asObject(java.lang.String)`

### asString

    public String asString(String code)
                    throws ConstantException

  Return a constant value as a String.

  Parameters:
    `code` - the name of the field (never `null`)
  Returns:
    the String value Works even if it's not a string (invokes `toString()`).
  Throws:
    `ConstantException` - if the field name wasn't found
  See Also:
    `asObject(java.lang.String)`

### asObject

    public Object asObject(String code)
                    throws ConstantException

  Parse the given String (upper or lower case accepted) and return the appropriate value if it's the name of a constant field in the class that we're analysing.

  Parameters:
    `code` - the name of the field (never `null`)
  Returns:
    the Object value
  Throws:
    `ConstantException` - if there's no such field

### getNames

    public Set<String> getNames(String namePrefix)

  Return all names of the given group of constants.

  Note that this method assumes that constants are named in accordance with the standard Java convention for constant values (i.e. all uppercase). The supplied `namePrefix` will be uppercased (in a locale-insensitive fashion) prior to the main logic of this method kicking in.

  Parameters:
    `namePrefix` - prefix of the constant names to search (may be `null`)
  Returns:
    the set of constant names

### getNamesForProperty

    public Set<String> getNamesForProperty(String propertyName)

  Return all names of the group of constants for the given bean property name.

  Parameters:
    `propertyName` - the name of the bean property
  Returns:
    the set of values
  See Also:
    `propertyToConstantNamePrefix(java.lang.String)`

### getNamesForSuffix

    public Set<String> getNamesForSuffix(String nameSuffix)

  Return all names of the given group of constants.

  Note that this method assumes that constants are named in accordance with the standard Java convention for constant values (i.e. all uppercase). The supplied `nameSuffix` will be uppercased (in a locale-insensitive fashion) prior to the main logic of this method kicking in.

  Parameters:
    `nameSuffix` - suffix of the constant names to search (may be `null`)
  Returns:
    the set of constant names

### getValues

    public Set<Object> getValues(String namePrefix)

  Return all values of the given group of constants.

  Note that this method assumes that constants are named in accordance with the standard Java convention for constant values (i.e. all uppercase). The supplied `namePrefix` will be uppercased (in a locale-insensitive fashion) prior to the main logic of this method kicking in.

  Parameters:
    `namePrefix` - prefix of the constant names to search (may be `null`)
  Returns:
    the set of values

### getValuesForProperty

    public Set<Object> getValuesForProperty(String propertyName)

  Return all values of the group of constants for the given bean property name.

  Parameters:
    `propertyName` - the name of the bean property
  Returns:
    the set of values
  See Also:
    `propertyToConstantNamePrefix(java.lang.String)`

### getValuesForSuffix

    public Set<Object> getValuesForSuffix(String nameSuffix)

  Return all values of the given group of constants.

  Note that this method assumes that constants are named in accordance with the standard Java convention for constant values (i.e. all uppercase). The supplied `nameSuffix` will be uppercased (in a locale-insensitive fashion) prior to the main logic of this method kicking in.

  Parameters:
    `nameSuffix` - suffix of the constant names to search (may be `null`)
  Returns:
    the set of values

### toCode

    public String toCode(Object value,
                         String namePrefix)
                  throws ConstantException

  Look up the given value within the given group of constants.

  Will return the first match.

  Parameters:
    `value` - constant value to look up
    `namePrefix` - prefix of the constant names to search (may be `null`)
  Returns:
    the name of the constant field
  Throws:
    `ConstantException` - if the value wasn't found

### toCodeForProperty

    public String toCodeForProperty(Object value,
                                    String propertyName)
                             throws ConstantException

  Look up the given value within the group of constants for the given bean property name. Will return the first match.

  Parameters:
    `value` - constant value to look up
    `propertyName` - the name of the bean property
  Returns:
    the name of the constant field
  Throws:
    `ConstantException` - if the value wasn't found
  See Also:
    `propertyToConstantNamePrefix(java.lang.String)`

### toCodeForSuffix

    public String toCodeForSuffix(Object value,
                                  String nameSuffix)
                           throws ConstantException

  Look up the given value within the given group of constants.

  Will return the first match.

  Parameters:
    `value` - constant value to look up
    `nameSuffix` - suffix of the constant names to search (may be `null`)
  Returns:
    the name of the constant field
  Throws:
    `ConstantException` - if the value wasn't found

### propertyToConstantNamePrefix

    public String propertyToConstantNamePrefix(String propertyName)

  Convert the given bean property name to a constant name prefix.

  Uses a common naming idiom: turning all lower case characters to upper case, and prepending upper case characters with an underscore.

  Example: "imageSize" -> "IMAGE_SIZE"
  Example: "imagesize" -> "IMAGESIZE".
  Example: "ImageSize" -> "_IMAGE_SIZE".
  Example: "IMAGESIZE" -> "_I_M_A_G_E_S_I_Z_E"

  Parameters:
    `propertyName` - the name of the bean property
  Returns:
    the corresponding constant name prefix
  See Also:
    `getValuesForProperty(java.lang.String)`, `toCodeForProperty(java.lang.Object, java.lang.String)`