org.apache.avalon.framework.configuration

Interface Configuration

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 Configuration. 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:

CodeNo namespacesWith namespaces
conf.getName()my-system
conf.getAttributeNames().length 21
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)desc
conf.getChild("doc:desc").getName() doc:descdoc:desc (see getChild)
conf.getChild("desc").getValue() ConfigurationExceptionThis is a highly fictitious config file
conf.getChild("doc:desc").getValue() This is a highly fictitious config fileConfigurationException
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 Configuration. 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 08:51:40 -0600 (Tue, 08 Mar 2005) leif $

Author: Avalon Development Team

Method Summary
StringgetAttribute(String paramName)
Return the value of specified attribute.
StringgetAttribute(String name, 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.
booleangetAttributeAsBoolean(String paramName)
Return the boolean value of the specified parameter contained in this node.
booleangetAttributeAsBoolean(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.
doublegetAttributeAsDouble(String paramName)
Return the double value of the specified parameter contained in this node.
doublegetAttributeAsDouble(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.
floatgetAttributeAsFloat(String paramName)
Return the float value of the specified parameter contained in this node.
floatgetAttributeAsFloat(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.
intgetAttributeAsInteger(String paramName)
Return the int value of the specified attribute contained in this node.
intgetAttributeAsInteger(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.
longgetAttributeAsLong(String name)
Returns the value of the attribute specified by its name as a long.
longgetAttributeAsLong(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.
String[]getAttributeNames()
Return an array of all attribute names.
ConfigurationgetChild(String child)
Return a new Configuration instance encapsulating the specified child node.
ConfigurationgetChild(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(String name)
Return an Array of Configuration elements containing all node children with the specified name.
StringgetLocation()
Return a string describing location of Configuration.
StringgetName()
Return the name of the node.
StringgetNamespace()
Returns a string indicating which namespace this Configuration node belongs to.
StringgetValue()
Return the String value of the node.
StringgetValue(String defaultValue)
Returns the value of the configuration element as a String.
booleangetValueAsBoolean()
Return the boolean value of the node.
booleangetValueAsBoolean(boolean defaultValue)
Returns the value of the configuration element as a boolean.
doublegetValueAsDouble()
Return the double value of the node.
doublegetValueAsDouble(double defaultValue)
Returns the value of the configuration element as a double.
floatgetValueAsFloat()
Return the float value of the node.
floatgetValueAsFloat(float defaultValue)
Returns the value of the configuration element as a float.
intgetValueAsInteger()
Return the int value of the node.
intgetValueAsInteger(int defaultValue)
Returns the value of the configuration element as an int.
longgetValueAsLong()
Return the long value of the node.
longgetValueAsLong(long defaultValue)
Returns the value of the configuration element as a long.

Method Detail

getAttribute

public String getAttribute(String paramName)
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.

getAttribute

public String getAttribute(String name, 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.

getAttributeAsBoolean

public boolean getAttributeAsBoolean(String paramName)
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.

getAttributeAsBoolean

public boolean getAttributeAsBoolean(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.

getAttributeAsDouble

public double getAttributeAsDouble(String paramName)
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.

getAttributeAsDouble

public double getAttributeAsDouble(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.

getAttributeAsFloat

public float getAttributeAsFloat(String paramName)
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.

getAttributeAsFloat

public float getAttributeAsFloat(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.

getAttributeAsInteger

public int getAttributeAsInteger(String paramName)
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.

getAttributeAsInteger

public int getAttributeAsInteger(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(String name)
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.

getAttributeAsLong

public long getAttributeAsLong(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.

getAttributeNames

public 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

getChild

public Configuration getChild(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(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(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

getLocation

public 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

getName

public String getName()
Return the name of the node.

Returns: name of the Configuration node.

getNamespace

public String getNamespace()
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

getValue

public String getValue()
Return the String value of the node.

Returns: the value of the node.

Throws: ConfigurationException if an error occurs

getValue

public String getValue(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.

getValueAsBoolean

public boolean getValueAsBoolean()
Return the boolean value of the node.

Returns: the value of the node.

Throws: ConfigurationException If conversion to boolean fails.

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.

getValueAsDouble

public double getValueAsDouble()
Return the double value of the node.

Returns: the value of the node.

Throws: ConfigurationException If conversion to double fails.

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.

getValueAsFloat

public float getValueAsFloat()
Return the float value of the node.

Returns: the value of the node.

Throws: ConfigurationException If conversion to float fails.

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.

getValueAsInteger

public int getValueAsInteger()
Return the int value of the node.

Returns: the value of the node.

Throws: ConfigurationException If conversion to int fails.

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()
Return the long value of the node.

Returns: the value of the node.

Throws: ConfigurationException If conversion to long fails.

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.