PortletPreferences (Java Portlet Specification V2.0 1.0 API)

```
public interface PortletPreferences
```
The PortletPreferences interface allows the portlet to store configuration data. It is not the purpose of this interface to replace general purpose databases.
There are two different types of preferences:
- modifiable preferences - these preferences can be changed by the portlet in any standard portlet mode (EDIT, HELP, VIEW). Per default every preference is modifiable.
- read-only preferences - these preferences cannot be changed by the portlet in any standard portlet mode, but may be changed by administrative modes. Preferences are read-only, if the are defined in the deployment descriptor with read-only set to true, or if the portlet container restricts write access.
Changes are persisted when the store method is called. The store method can only be invoked within the scope of a processAction call. Changes that are not persisted are discarded when the processAction or render method ends.

Method Summary

Methods
Modifier and Type	Method and Description
`Map<String,String[]>`	`getMap()` Returns a `Map` of the preferences.
`Enumeration<String>`	`getNames()` Returns all of the keys that have an associated value, or an empty `Enumeration` if no keys are available.
`String`	`getValue(String key, String def)` Returns the first String value associated with the specified key of this preference.
`String[]`	`getValues(String key, String[] def)` Returns the String array value associated with the specified key in this preference.
`boolean`	`isReadOnly(String key)` Returns true, if the value of this key is defined as read-only and thus cannot be modified by the user.
`void`	`reset(String key)` Resets or removes the value associated with the specified key.
`void`	`setValue(String key, String value)` Associates the specified String value with the specified key in this preference.
`void`	`setValues(String key, String[] values)` Associates the specified String array value with the specified key in this preference.
`void`	`store()` Commits all changes made to the preferences via the `set` methods in the persistent store.

- Method Detail
  - isReadOnly
```
boolean isReadOnly(String key)
```
    Returns true, if the value of this key is defined as read-only and thus cannot be modified by the user.
    Modifiable preferences can be changed by the portlet in any standard portlet mode (EDIT, HELP, VIEW). Per default every preference is modifiable.
    Read-only preferences cannot be changed by the portlet in any standard portlet mode, but inside of custom modes, like the CONFIG mode, it may be allowed changing them.
    Preferences are read-only, if they are defined in the deployment descriptor with read-only set to true, or if the portlet container restricts write access.
    Note that even if this call returns false and the preference key is modifiable in general it does not mean that it is modifiable in the scope of the current request, e.g. if this request is a render request.
    
    Returns:
    false, if the value of this key can be changed, or if the key is not known
    
    Throws:
    
    IllegalArgumentException - if key is null.
  - getValue
```
String getValue(String key,
              String def)
```
    Returns the first String value associated with the specified key of this preference. If there is one or more preference values associated with the given key it returns the first associated value. If there are no preference values associated with the given key, or the backing preference database is unavailable, it returns the given default value. A null value is treated as a non-existent value.
    
    Parameters:
    key - key for which the associated value is to be returned
    def - the value to be returned in the event that there is no value available associated with this key.
    
    Returns:
    the value associated with key, or def if no value is associated with key, or the backing store is inaccessible.
    
    Throws:
    
    IllegalArgumentException - if key is null. (A null value for def is permitted.)
    See Also:
    getValues(String, String[])
  - getValues
```
String[] getValues(String key,
                 String[] def)
```
    Returns the String array value associated with the specified key in this preference.
    Returns the specified default if there is no value associated with the key, or if the backing store is inaccessible. A null value is treated as a non-existent value.
    If the implementation supports stored defaults and such a default exists and is accessible, it is used in favor of the specified default.
    
    Parameters:
    key - key for which associated value is to be returned.
    def - the value to be returned in the event that this preference node has no value associated with key or the associated value cannot be interpreted as a String array, or the backing store is inaccessible.
    
    Returns:
    the String array value associated with key, or def if the associated value does not exist.
    
    Throws:
    
    IllegalArgumentException - if key is null. (A null value for def is permitted.)
    See Also:
    getValue(String,String)
  - setValue
```
void setValue(String key,
            String value)
              throws ReadOnlyException
```
    Associates the specified String value with the specified key in this preference.
    The key cannot be null, but null values for the value parameter are allowed.
    If the same key contained already a String or String[] value it must be replaced by the new value.
    
    Parameters:
    key - key with which the specified value is to be associated.
    value - value to be associated with the specified key.
    
    Throws:
    
    ReadOnlyException - if this preference cannot be modified for this request
    
    IllegalArgumentException - if key is null, or key.length() or value.length are to long. The maximum length for key and value are implementation specific.
    See Also:
    setValues(String, String[])
  - setValues
```
void setValues(String key,
             String[] values)
               throws ReadOnlyException
```
    Associates the specified String array value with the specified key in this preference.
    The key cannot be null, but null values in the values parameter are allowed.
    If the same key contained already a String or String[] value it must be replaced by the new value.
    
    Parameters:
    key - key with which the value is to be associated
    values - values to be associated with key
    
    Throws:
    
    IllegalArgumentException - if key is null, or key.length() is to long or value.size is to large. The maximum length for key and maximum size for value are implementation specific.
    
    ReadOnlyException - if this preference cannot be modified for this request
    See Also:
    setValue(String,String)
  - getNames
```
Enumeration<String> getNames()
```
    Returns all of the keys that have an associated value, or an empty Enumeration if no keys are available.
    
    Returns:
    an Enumeration of the keys that have an associated value, or an empty Enumeration if no keys are available.
  - getMap
```
Map<String,String[]> getMap()
```
    Returns a Map of the preferences.
    The values in the returned Map are from type String array (String[]).
    If no preferences exist this method returns an empty Map.
    
    Returns:
    an immutable Map containing preference names as keys and preference values as map values, or an empty Map if no preference exist. The keys in the preference map are of type String. The values in the preference map are of type String array (String[]).
  - reset
```
void reset(String key)
           throws ReadOnlyException
```
    Resets or removes the value associated with the specified key.
    If this implementation supports stored defaults, and there is such a default for the specified preference, the given key will be reset to the stored default.
    If there is no default available the key will be removed.
    
    Parameters:
    key - to reset
    
    Throws:
    
    IllegalArgumentException - if key is null.
    
    ReadOnlyException - if this preference cannot be modified for this request
  - store
```
void store()
           throws IOException,
                  ValidatorException
```
    Commits all changes made to the preferences via the set methods in the persistent store.
    If this call returns successful, all changes are made persistent. If this call fails, no changes are made in the persistent store. This call is an atomic operation regardless of how many preference attributes have been modified.
    All changes made to preferences not followed by a call to the store method are discarded when the portlet finishes the processAction method.
    If a validator is defined for this preferences in the deployment descriptor, this validator is called before the actual store is performed to check whether the given preferences are valid. If this check fails a ValidatorException is thrown.
    
    Throws:
    
    IOException - if changes cannot be written into the backend store
    
    ValidatorException - if the validation performed by the associated validator fails
    
    IllegalStateException - if this method is called inside a render call
    See Also:
    PreferencesValidator

Interface PortletPreferences

Method Summary

Method Detail

isReadOnly

getValue

getValues

setValue

setValues

getNames

getMap

reset

store