org.apache.avalon.framework.configuration
Interface Configuration

All Known Subinterfaces:

MutableConfiguration

All Known Implementing Classes:

AbstractConfiguration, DefaultConfiguration

public interface Configuration

Configuration is a interface encapsulating a configuration node used to retrieve configuration values.

This is a "read only" interface preventing applications from modifying their own configurations. Once it is created, the information never changes.

Data Model

The data model is a subset of XML's; a single-rooted hierarchical tree where each node can contain multiple attributes, and leaf nodes can also contain a value. Reflecting this, Configurations are usually built from an XML file by the DefaultConfigurationBuilder class, or directly by a SAX parser using a SAXConfigurationHandler or NamespacedSAXConfigurationHandler event handler.

Namespace support

Since version 4.1, each Configuration node has a namespace associated with it, in the form of a string, accessible through getNamespace(). If no namespace is present, getNamespace will return blank (""). See DefaultConfigurationBuilder for details on how XML namespaces are mapped to Configuration namespaces.

Example

As an example, consider two Configurations (with and without namespaces) built from this XML:

 <my-system version="1.3" xmlns:doc="http://myco.com/documentation">
   <doc:desc>This is a highly fictitious config file</doc:desc>
   <widget name="fooWidget" initOrder="1" threadsafe="true"/>
 </my-system>
 

If namespace support is enabled (eg through DefaultConfigurationBuilder#DefaultConfigurationBuilder(boolean) new DefaultConfigurationBuilder(true)), then the xmlns:doc element will not translate into a Configuration attribute, and the doc:desc element will become a Configuration node with name "desc" and namespace "http://myco.com/documentation". The widget element will have namespace "".

If namespace support is disabled (the default for DefaultConfigurationBuilder), the above XML will translate directly to Configuration nodes. The my-system node will have an attribute named "xmlns:doc", and a child called "doc:desc".

Assuming the Configuration object is named conf, here is how the data could be retrieved:

Code	No namespaces	With namespaces
conf.getName()	my-system
conf.getAttributeNames().length	2	1
conf.getChildren().length	2
conf.getAttributeAsFloat("version")	1.3
conf.getChild("widget").getAttribute("name")	fooWidget
conf.getChild("widget") .getAttributeAsBoolean("threadsafe")	true
conf.getChild("widget").getLocation()	file:///home/jeff/tmp/java/avalon/src/java/new.xconf:4:60
conf.getChild("desc").getName()	desc (see getChild(String))	desc
conf.getChild("doc:desc").getName()	doc:desc	doc:desc (see getChild(String))
conf.getChild("desc").getValue()	ConfigurationException	This is a highly fictitious config file
conf.getChild("doc:desc").getValue()	This is a highly fictitious config file	ConfigurationException
conf.getChild("desc").getNamespace()		http://myco.com/documentation"

Type-safe utility methods are provided for retrieving attribute and element values as String, int, long, float and boolean.

Miscellanea

Currently, the configuration tree can only be traversed one node at a time, eg., through getChild("foo") or getChildren(). In a future release, it may be possible to access child nodes with an XPath-like syntax.

Checking for the existence of an attribute can be done as follows:

String value = conf.getAttribute( "myAttribute", null );
 if ( null == value )
 {
   // Do the processing applicable if the attribute isn't present.
 }
 

Version:

$Id: Configuration.java 156533 2005-03-08 14:51:40Z leif $

Author:

Avalon Development Team

Method Summary

java.lang.String	getAttribute(java.lang.String paramName) Return the value of specified attribute.
java.lang.String	getAttribute(java.lang.String name, java.lang.String defaultValue) Returns the value of the attribute specified by its name as a String, or the default value if no attribute by that name exists or is empty.
boolean	getAttributeAsBoolean(java.lang.String paramName) Return the boolean value of the specified parameter contained in this node.
boolean	getAttributeAsBoolean(java.lang.String name, boolean defaultValue) Returns the value of the attribute specified by its name as a boolean, or the default value if no attribute by that name exists or is empty.
double	getAttributeAsDouble(java.lang.String paramName) Return the double value of the specified parameter contained in this node.
double	getAttributeAsDouble(java.lang.String name, double defaultValue) Returns the value of the attribute specified by its name as a double, or the default value if no attribute by that name exists or is empty.
float	getAttributeAsFloat(java.lang.String paramName) Return the float value of the specified parameter contained in this node.
float	getAttributeAsFloat(java.lang.String name, float defaultValue) Returns the value of the attribute specified by its name as a float, or the default value if no attribute by that name exists or is empty.
int	getAttributeAsInteger(java.lang.String paramName) Return the int value of the specified attribute contained in this node.
int	getAttributeAsInteger(java.lang.String name, int defaultValue) Returns the value of the attribute specified by its name as a int, or the default value if no attribute by that name exists or is empty.
long	getAttributeAsLong(java.lang.String name) Returns the value of the attribute specified by its name as a long.
long	getAttributeAsLong(java.lang.String name, long defaultValue) Returns the value of the attribute specified by its name as a long, or the default value if no attribute by that name exists or is empty.
java.lang.String[]	getAttributeNames() Return an array of all attribute names.
Configuration	getChild(java.lang.String child) Return a new Configuration instance encapsulating the specified child node.
Configuration	getChild(java.lang.String child, boolean createNew) Return a Configuration instance encapsulating the specified child node.
Configuration[]	getChildren() Return an Array of Configuration elements containing all node children.
Configuration[]	getChildren(java.lang.String name) Return an Array of Configuration elements containing all node children with the specified name.
java.lang.String	getLocation() Return a string describing location of Configuration.
java.lang.String	getName() Return the name of the node.
java.lang.String	getNamespace() Returns a string indicating which namespace this Configuration node belongs to.
java.lang.String	getValue() Return the String value of the node.
java.lang.String	getValue(java.lang.String defaultValue) Returns the value of the configuration element as a String.
boolean	getValueAsBoolean() Return the boolean value of the node.
boolean	getValueAsBoolean(boolean defaultValue) Returns the value of the configuration element as a boolean.
double	getValueAsDouble() Return the double value of the node.
double	getValueAsDouble(double defaultValue) Returns the value of the configuration element as a double.
float	getValueAsFloat() Return the float value of the node.
float	getValueAsFloat(float defaultValue) Returns the value of the configuration element as a float.
int	getValueAsInteger() Return the int value of the node.
int	getValueAsInteger(int defaultValue) Returns the value of the configuration element as an int.
long	getValueAsLong() Return the long value of the node.
long	getValueAsLong(long defaultValue) Returns the value of the configuration element as a long.

Method Detail

getName

public java.lang.String getName()

Return the name of the node.

Returns:

name of the Configuration node.

getLocation

public java.lang.String getLocation()

Return a string describing location of Configuration. Location can be different for different mediums (ie "file:line" for normal XML files or "table:primary-key" for DB based configurations);

Returns:

a string describing location of Configuration

getNamespace

public java.lang.String getNamespace()
                              throws ConfigurationException

Returns a string indicating which namespace this Configuration node belongs to.

What this returns is dependent on the configuration file and the Configuration builder. If the Configuration builder does not support namespaces, this method will return a blank string.

In the case of DefaultConfigurationBuilder, the namespace will be the URI associated with the XML element. Eg.,:

 <foo xmlns:x="http://blah.com">
   <x:bar/>
 </foo>
 

The namespace of foo will be "", and the namespace of bar will be "http://blah.com".

Returns:

a String identifying the namespace of this Configuration.

Throws:

ConfigurationException - if an error occurs

Since:

4.1

getChild

public Configuration getChild(java.lang.String child)

Return a new Configuration instance encapsulating the specified child node.

If no such child node exists, an empty Configuration will be returned, allowing constructs such as conf.getChild("foo").getChild("bar").getChild("baz").getValue("default");

If you wish to get a null return when no element is present, use getChild("foo", false).

Parameters:

child - The name of the child node.

Returns:

Configuration

getChild

public Configuration getChild(java.lang.String child,
                              boolean createNew)

Return a Configuration instance encapsulating the specified child node.

Parameters:

child - The name of the child node.

createNew - If true, a new Configuration will be created and returned if the specified child does not exist. If false, null will be returned when the specified child doesn't exist.

Returns:

Configuration

getChildren

public Configuration[] getChildren()

Return an Array of Configuration elements containing all node children. The array order will reflect the order in the source config file.

Returns:

All child nodes

getChildren

public Configuration[] getChildren(java.lang.String name)

Return an Array of Configuration elements containing all node children with the specified name. The array order will reflect the order in the source config file.

Parameters:

name - The name of the children to get.

Returns:

The child nodes with name name

getAttributeNames

public java.lang.String[] getAttributeNames()

Return an array of all attribute names.

The order of attributes in this array can not be relied on. As with XML, a Configuration's attributes are an unordered set. If your code relies on order, eg conf.getAttributeNames()[0], then it is liable to break if a different XML parser is used.

Returns:

a String[] value

getAttribute

public java.lang.String getAttribute(java.lang.String paramName)
                              throws ConfigurationException

Return the value of specified attribute.

Parameters:

paramName - The name of the parameter you ask the value of.

Returns:

String value of attribute.

Throws:

ConfigurationException - If no attribute with that name exists.

getAttributeAsInteger

public int getAttributeAsInteger(java.lang.String paramName)
                          throws ConfigurationException

Return the int value of the specified attribute contained in this node.

Parameters:

paramName - The name of the parameter you ask the value of.

Returns:

int value of attribute

Throws:

ConfigurationException - If no parameter with that name exists. or if conversion to int fails.

getAttributeAsLong

public long getAttributeAsLong(java.lang.String name)
                        throws ConfigurationException

Returns the value of the attribute specified by its name as a long.

Parameters:

name - The name of the parameter you ask the value of.

Returns:

long value of attribute

Throws:

ConfigurationException - If no parameter with that name exists. or if conversion to long fails.

getAttributeAsFloat

public float getAttributeAsFloat(java.lang.String paramName)
                          throws ConfigurationException

Return the float value of the specified parameter contained in this node.

Parameters:

paramName - The name of the parameter you ask the value of.

Returns:

float value of attribute

Throws:

ConfigurationException - If no parameter with that name exists. or if conversion to float fails.

getAttributeAsDouble

public double getAttributeAsDouble(java.lang.String paramName)
                            throws ConfigurationException

Return the double value of the specified parameter contained in this node.

Parameters:

paramName - The name of the parameter you ask the value of.

Returns:

double value of attribute

Throws:

ConfigurationException - If no parameter with that name exists. or if conversion to double fails.

getAttributeAsBoolean

public boolean getAttributeAsBoolean(java.lang.String paramName)
                              throws ConfigurationException

Return the boolean value of the specified parameter contained in this node.

Parameters:

paramName - The name of the parameter you ask the value of.

Returns:

boolean value of attribute

Throws:

ConfigurationException - If no parameter with that name exists. or if conversion to boolean fails.

getValue

public java.lang.String getValue()
                          throws ConfigurationException

Return the String value of the node.

Returns:

the value of the node.

Throws:

ConfigurationException - if an error occurs

getValueAsInteger

public int getValueAsInteger()
                      throws ConfigurationException

Return the int value of the node.

Returns:

the value of the node.

Throws:

ConfigurationException - If conversion to int fails.

getValueAsFloat

public float getValueAsFloat()
                      throws ConfigurationException

Return the float value of the node.

Returns:

the value of the node.

Throws:

ConfigurationException - If conversion to float fails.

getValueAsDouble

public double getValueAsDouble()
                        throws ConfigurationException

Return the double value of the node.

Returns:

the value of the node.

Throws:

ConfigurationException - If conversion to double fails.

getValueAsBoolean

public boolean getValueAsBoolean()
                          throws ConfigurationException

Return the boolean value of the node.

Returns:

the value of the node.

Throws:

ConfigurationException - If conversion to boolean fails.

getValueAsLong

public long getValueAsLong()
                    throws ConfigurationException

Return the long value of the node.

Returns:

the value of the node.

Throws:

ConfigurationException - If conversion to long fails.

getValue

public java.lang.String getValue(java.lang.String defaultValue)

Returns the value of the configuration element as a String. If the configuration value is not set, the default value will be used.

Parameters:

defaultValue - The default value desired.

Returns:

String value of the Configuration, or default if none specified.

getValueAsInteger

public int getValueAsInteger(int defaultValue)

Returns the value of the configuration element as an int. If the configuration value is not set, the default value will be used.

Parameters:

defaultValue - The default value desired.

Returns:

int value of the Configuration, or default if none specified.

getValueAsLong

public long getValueAsLong(long defaultValue)

Returns the value of the configuration element as a long. If the configuration value is not set, the default value will be used.

Parameters:

defaultValue - The default value desired.

Returns:

long value of the Configuration, or default if none specified.

getValueAsFloat

public float getValueAsFloat(float defaultValue)

Returns the value of the configuration element as a float. If the configuration value is not set, the default value will be used.

Parameters:

defaultValue - The default value desired.

Returns:

float value of the Configuration, or default if none specified.

getValueAsDouble

public double getValueAsDouble(double defaultValue)

Returns the value of the configuration element as a double. If the configuration value is not set, the default value will be used.

Parameters:

defaultValue - The default value desired.

Returns:

float value of the Configuration, or default if none specified.

getValueAsBoolean

public boolean getValueAsBoolean(boolean defaultValue)

Returns the value of the configuration element as a boolean. If the configuration value is not set, the default value will be used.

Parameters:

defaultValue - The default value desired.

Returns:

boolean value of the Configuration, or default if none specified.

getAttribute

public java.lang.String getAttribute(java.lang.String name,
                                     java.lang.String defaultValue)

Returns the value of the attribute specified by its name as a String, or the default value if no attribute by that name exists or is empty.

Parameters:

name - The name of the attribute you ask the value of.

defaultValue - The default value desired.

Returns:

String value of attribute. It will return the default value if the named attribute does not exist, or if the value is not set.

getAttributeAsInteger

public int getAttributeAsInteger(java.lang.String name,
                                 int defaultValue)

Returns the value of the attribute specified by its name as a int, or the default value if no attribute by that name exists or is empty.

Parameters:

name - The name of the attribute you ask the value of.

defaultValue - The default value desired.

Returns:

int value of attribute. It will return the default value if the named attribute does not exist, or if the value is not set.

getAttributeAsLong

public long getAttributeAsLong(java.lang.String name,
                               long defaultValue)

Returns the value of the attribute specified by its name as a long, or the default value if no attribute by that name exists or is empty.

Parameters:

name - The name of the attribute you ask the value of.

defaultValue - The default value desired.

Returns:

long value of attribute. It will return the default value if the named attribute does not exist, or if the value is not set.

getAttributeAsFloat

public float getAttributeAsFloat(java.lang.String name,
                                 float defaultValue)

Returns the value of the attribute specified by its name as a float, or the default value if no attribute by that name exists or is empty.

Parameters:

name - The name of the attribute you ask the value of.

defaultValue - The default value desired.

Returns:

float value of attribute. It will return the default value if the named attribute does not exist, or if the value is not set.

getAttributeAsDouble

public double getAttributeAsDouble(java.lang.String name,
                                   double defaultValue)

Returns the value of the attribute specified by its name as a double, or the default value if no attribute by that name exists or is empty.

Parameters:

name - The name of the attribute you ask the value of.

defaultValue - The default value desired.

Returns:

float value of attribute. It will return the default value if the named attribute does not exist, or if the value is not set.

getAttributeAsBoolean

public boolean getAttributeAsBoolean(java.lang.String name,
                                     boolean defaultValue)

Returns the value of the attribute specified by its name as a boolean, or the default value if no attribute by that name exists or is empty.

Parameters:

name - The name of the attribute you ask the value of.

defaultValue - The default value desired.

Returns:

boolean value of attribute. It will return the default value if the named attribute does not exist, or if the value is not set.