org.olat.core.configuration
Class PersistedProperties

java.lang.Object
  org.olat.core.logging.LogDelegator
      org.olat.core.configuration.PersistedProperties

public class PersistedProperties
extends LogDelegator

Description:
The PersistedProperties features reading and writing of configuration properties from and to properties files for module and application configuration.

The idea is that the system can be configured with default values within the module code either by a spring configuration or by using hardcoded default values. Those default values are overridden by the values stored in the properties files found in the user space of the system ( olatdata/system/configuration/fully.qualified.ClassName.properties ). Installing updates will not overwrite those properties files, the 'old' configuration is available immediately to the sytem without reconfiguration.

The developer should provide a GUI for each of those values that can be configured at runtime. It is up to the programmer if the system needs a reboot or not.

After constructing an instance of this class the setXXXPropertyDefault() methods must be called to set the default values in case no user configuration is found. This is where you can set the values you get from the spring or the old olat_config.xml module configuration.

After the default values have been set, using the getXXXPropertyValue() you will get the current configuration value. The PersistedProperties class will first look in properties from the filesystem and if nothing found, use the setted default values.

The class does also provide setXXXProperty() methods. Setting a property will store it always in the user space properties file olatdata/system/configuration/fully.qualified.ClassName.properties . It will not modify any spring or olat_config.xml file. The setter methods can be stored immediately after each set or remain transient until the explicit savePropertiesAndFireChangedEvent() method is called.

To work properly in a cluster environment, the class will fire a PersitedPropertiesChangedEvent at the end of each save cycle. This event must be catched by the class that is using this PersistingProperties. When constructing the PersistingProperties, a reference to the using class must be provided. The PersistingProperties deals with registering and unregistering of the event listeners for the multi-node events, this is hidden to the using class.

When finished, the destroy() method must be called. In most cases this will be at system shutdown time.

NOTE 1: By replacing the OLAT code with a new version all configurations made will remain since the configuration is stored in the user space and not in the OLAT web application directory. This greatly simplifies upgrading without reconfiguring everything.

NOTE 2: When you saved a configuration using the set and save methods in this class, the default configuration in your olat_config.xml or spring configuration becomes irrelevant. Changing the values in olat_config.xml or your spring file will have no effect whatsoever.

NOTE 3: At any time, the configuration properties files at olatdata/system/configuration/ can be deleted. The system then uses the default values provided in your olat_confix.xml, your spring configuration or your hardcoded default values provided at init time.

NOTE 4: As a developer you must decide if a configuration can be reflected in realtime or if you must reboot the system. In the first case you can savely use the getter methods to read the configuration every time you need the value, in the second case you should make a copy of the configuration value at init time and operate only with the copy.

NOTE 5: In extreme conditions the get/set methods might not be cluster save. Make sure you use a cluster wide GUI lock in the admin interfaces that makes use of the setter methods and you are on the save side. On the other hand it is very unlikely that something really bad happens, the properties files are just overwritten by the next save.

Events thrown by this class:

• PersistedPropertiesChangedEvent in case the configuration got changed

Initial Date: 01.10.2007

Author:

Florian Gnägi, http://www.frentix.com

Constructor Summary

PersistedProperties(GenericEventListener propertiesChangedEventListener)
Constructor for a PersistedProperties object.

Method Summary

void	clearAndSaveProperties() Clear the properties and save the empty properties to the file system.
java.util.Properties	createPropertiesFromPersistedProperties() Clone the persisted properties to a standard properties object.
void	destroy() Call this method when the PersitedProperties is not used anymore.
boolean	getBooleanPropertyValue(java.lang.String propertyName) Return a boolean value for certain propertyName
int	getIntPropertyValue(java.lang.String propertyName) Retrun an int value for a certain propertyName
java.lang.String	getStringPropertyValue(java.lang.String propertyName, boolean allowEmptyString) Return a string value for certain propertyName-parameter.
void	savePropertiesAndFireChangedEvent() Save the properties configuration to disk and notify other nodes about change.
void	setBooleanProperty(java.lang.String propertyName, boolean value, boolean saveConfiguration) Set a boolean property
void	setBooleanPropertyDefault(java.lang.String propertyName, boolean value) Set a default value for a boolean property
void	setIntProperty(java.lang.String propertyName, int value, boolean saveConfiguration) Set an int property
void	setIntPropertyDefault(java.lang.String propertyName, int value) Set a default value for an integer property
void	setStringProperty(java.lang.String propertyName, java.lang.String value, boolean saveConfiguration) Set a string property
void	setStringPropertyDefault(java.lang.String propertyName, java.lang.String value) Set a default value for a string property

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PersistedProperties

public PersistedProperties(GenericEventListener propertiesChangedEventListener)

Constructor for a PersistedProperties object. The calling class must implement the GenericEventListener and provide a reference to itself.

Parameters:

propertiesChangedEventListener -

Method Detail

destroy

public final void destroy()

Call this method when the PersitedProperties is not used anymore. Will remove the event listener for change events on this class

getIntPropertyValue

public int getIntPropertyValue(java.lang.String propertyName)

Retrun an int value for a certain propertyName

Parameters:

propertyName -

Returns:

the value from the configuration or the default value or 0

getStringPropertyValue

public java.lang.String getStringPropertyValue(java.lang.String propertyName,
                                               boolean allowEmptyString)

Return a string value for certain propertyName-parameter.

Parameters:

propertyName -

allowEmptyString - true: empty strings are valid values; false: emtpy strings are discarded

Returns:

the value from the configuration or the default value or ""/NULL (depending on allowEmptyString flag)

getBooleanPropertyValue

public boolean getBooleanPropertyValue(java.lang.String propertyName)

Return a boolean value for certain propertyName

Parameters:

propertyName -

Returns:

the value from the configuration or the default value or false

setStringProperty

public void setStringProperty(java.lang.String propertyName,
                              java.lang.String value,
                              boolean saveConfiguration)

Set a string property

Parameters:

propertyName - The key

value - The Value

saveConfiguration - true: will save property and fire event; false: will not save, but set a dirty flag

setIntProperty

public void setIntProperty(java.lang.String propertyName,
                           int value,
                           boolean saveConfiguration)

Set an int property

Parameters:

propertyName - The key

value - The Value

saveConfiguration - true: will save property and fire event; false: will not save, but set a dirty flag

setBooleanProperty

public void setBooleanProperty(java.lang.String propertyName,
                               boolean value,
                               boolean saveConfiguration)

Set a boolean property

Parameters:

propertyName - The key

value - The Value

saveConfiguration - true: will save property and fire event; false: will not save, but set a dirty flag

setStringPropertyDefault

public void setStringPropertyDefault(java.lang.String propertyName,
                                     java.lang.String value)

Set a default value for a string property

Parameters:

propertyName -

value -

setIntPropertyDefault

public void setIntPropertyDefault(java.lang.String propertyName,
                                  int value)

Set a default value for an integer property

Parameters:

propertyName -

value -

setBooleanPropertyDefault

public void setBooleanPropertyDefault(java.lang.String propertyName,
                                      boolean value)

Set a default value for a boolean property

Parameters:

propertyName -

value -

savePropertiesAndFireChangedEvent

public void savePropertiesAndFireChangedEvent()

Save the properties configuration to disk and notify other nodes about change. This is only done when there are dirty changes, otherwhile the method call does nothing.

clearAndSaveProperties

public void clearAndSaveProperties()

Clear the properties and save the empty properties to the file system.

createPropertiesFromPersistedProperties

public java.util.Properties createPropertiesFromPersistedProperties()

Clone the persisted properties to a standard properties object.

Returns: