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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Constants.ConstantException Exception thrown when the Constants class is asked for an invalid constant name.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
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 Constants.ConstantException

Return a constant value cast to a Number.

Parameters:

code - the name of the field (never null)

Returns:

the Number value

Throws:

Constants.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 Constants.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:

Constants.ConstantException - if the field name wasn't found

See Also:

asObject(java.lang.String)

asObject

public Object asObject(String code)
                throws Constants.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:

Constants.ConstantException - if there's no such field

getNames

public Set<String> getNames(@Nullable
                            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(@Nullable
                                     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(@Nullable
                             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(@Nullable
                                      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,
                     @Nullable
                     String namePrefix)
              throws Constants.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:

Constants.ConstantException - if the value wasn't found

toCodeForProperty

public String toCodeForProperty(Object value,
                                String propertyName)
                         throws Constants.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:

Constants.ConstantException - if the value wasn't found

See Also:

propertyToConstantNamePrefix(java.lang.String)

toCodeForSuffix

public String toCodeForSuffix(Object value,
                              @Nullable
                              String nameSuffix)
                       throws Constants.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:

Constants.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)