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## org.apache.commons.configuration
Class XMLConfiguration

    java.lang.Object
      org.apache.commons.configuration.event.EventSource
          org.apache.commons.configuration.AbstractConfiguration
              org.apache.commons.configuration.HierarchicalConfiguration
                  org.apache.commons.configuration.AbstractHierarchicalFileConfiguration
                      org.apache.commons.configuration.XMLConfiguration

All Implemented Interfaces:
  Cloneable, Configuration, ConfigurationListener, EntityResolver, FileConfiguration, Serializable

Direct Known Subclasses:
  DefaultConfigurationBuilder, HierarchicalXMLConfiguration

public class XMLConfiguration
extends AbstractHierarchicalFileConfiguration
implements EntityResolver

A specialized hierarchical configuration class that is able to parse XML documents.

The parsed document will be stored keeping its structure. The class also tries to preserve as much information from the loaded XML document as possible, including comments and processing instructions. These will be contained in documents created by the `save()` methods, too.

Like other file based configuration classes this class maintains the name and path to the loaded configuration file. These properties can be altered using several setter methods, but they are not modified by `save()` and `load()` methods. If XML documents contain relative paths to other documents (e.g. to a DTD), these references are resolved based on the path set for this configuration.

By inheriting from ``AbstractConfiguration`` this class provides some extended functionality, e.g. interpolation of property values. Like in ``PropertiesConfiguration`` property values can contain delimiter characters (the comma ',' per default) and are then split into multiple values. This works for XML attributes and text content of elements as well. The delimiter can be escaped by a backslash. As an example consider the following XML fragment:

     <config>
       <array>10,20,30,40</array>
       <scalar>3\,1415</scalar>
       <cite text="To be or not to be\, this is the question!"/>
     </config>

Here the content of the `array` element will be split at the commas, so the `array` key will be assigned 4 values. In the `scalar` property and the `text` attribute of the `cite` element the comma is escaped, so that no splitting is performed.

The configuration API allows setting multiple values for a single attribute, e.g. something like the following is legal (assuming that the default expression engine is used):

     XMLConfiguration config = new XMLConfiguration();
     config.addProperty("test.dir[@name]", "C:\\Temp\\");
     config.addProperty("test.dir[@name]", "D:\\Data\\");

Because in XML such a constellation is not directly supported (an attribute can appear only once for a single element), the values are concatenated to a single value. If delimiter parsing is enabled (refer to the ``AbstractConfiguration.setDelimiterParsingDisabled(boolean)`` method), the current list delimiter character will be used as separator. Otherwise the pipe symbol ("|") will be used for this purpose. No matter which character is used as delimiter, it can always be escaped with a backslash. A backslash itself can also be escaped with another backslash. Consider the following example fragment from a configuration file:

     <directories names="C:\Temp\\|D:\Data\"/>

Here the backslash after Temp is escaped. This is necessary because it would escape the list delimiter (the pipe symbol assuming that list delimiter parsing is disabled) otherwise. So this attribute would have two values.

Note: You should ensure that the delimiter parsing disabled property is always consistent when you load and save a configuration file. Otherwise the values of properties can become corrupted.

Whitespace in the content of XML documents is trimmed per default. In most cases this is desired. However, sometimes whitespace is indeed important and should be treated as part of the value of a property as in the following example:

       <indent>    </indent>

Per default the spaces in the `indent` element will be trimmed resulting in an empty element. To tell `XMLConfiguration` that spaces are relevant the `xml:space` attribute can be used, which is defined in the XML specification. This will look as follows:

       <indent xml:space="preserve">    </indent>

The value of the `indent` property will now contain the spaces.

`XMLConfiguration` implements the ``FileConfiguration`` interface and thus provides full support for loading XML documents from different sources like files, URLs, or streams. A full description of these features can be found in the documentation of ``AbstractFileConfiguration``.

Note:Configuration objects of this type can be read concurrently by multiple threads. However if one of these threads modifies the object, synchronization has to be performed manually.

Since:
  commons-configuration 1.0
Version:
  $Revision: 721895 $, $Date: 2008-11-30 22:08:42 +0100 (So, 30 Nov 2008) $
Author:
  Jörg Schaible, Oliver Heger
See Also:
  Serialized Form

Nested Class Summary

Nested classes inherited from class org.apache.commons.configuration.AbstractHierarchicalFileConfiguration
`AbstractHierarchicalFileConfiguration.FileConfigurationDelegate`

Nested classes inherited from class org.apache.commons.configuration.HierarchicalConfiguration
`HierarchicalConfiguration.BuilderVisitor, HierarchicalConfiguration.Node, HierarchicalConfiguration.NodeVisitor`

Field Summary

Fields inherited from class org.apache.commons.configuration.HierarchicalConfiguration
`EVENT_ADD_NODES, EVENT_CLEAR_TREE, EVENT_SUBNODE_CHANGED`

Fields inherited from class org.apache.commons.configuration.AbstractConfiguration
`END_TOKEN, EVENT_ADD_PROPERTY, EVENT_CLEAR, EVENT_CLEAR_PROPERTY, EVENT_READ_PROPERTY, EVENT_SET_PROPERTY, START_TOKEN`

Constructor Summary
`XMLConfiguration()` Creates a new instance of `XMLConfiguration`.
`XMLConfiguration(File file)` Creates a new instance of `XMLConfiguration`.
`XMLConfiguration(HierarchicalConfiguration c)` Creates a new instance of `XMLConfiguration` and copies the content of the passed in configuration into this object.
`XMLConfiguration(String fileName)` Creates a new instance of `XMLConfiguration`.
`XMLConfiguration(URL url)` Creates a new instance of `XMLConfiguration`.

Method Summary
`void` | `addNodes(String key, Collection nodes)` Adds a collection of nodes directly to this configuration.
`void` | `clear()` Removes all properties from this configuration.
`Object` | `clone()` Creates a copy of this object.
`protected AbstractHierarchicalFileConfiguration.FileConfigurationDelegate` | `createDelegate()` Creates the file configuration delegate for this object.
`protected Document` | `createDocument()` Creates a DOM document from the internal tree of configuration nodes.
`protected DocumentBuilder` | `createDocumentBuilder()` Creates the `DocumentBuilder` to be used for loading files.
`protected HierarchicalConfiguration.Node` | `createNode(String name)` Creates a new node object.
`protected Transformer` | `createTransformer()` Creates and initializes the transformer used for save operations.
`Document` | `getDocument()` Returns the XML document this configuration was loaded from.
`DocumentBuilder` | `getDocumentBuilder()` Returns the `DocumentBuilder` object that is used for loading documents.
`String` | `getPublicID()` Returns the public ID of the DOCTYPE declaration from the loaded XML document.
`String` | `getRootElementName()` Returns the name of the root element.
`String` | `getSystemID()` Returns the system ID of the DOCTYPE declaration from the loaded XML document.
`void` | `initProperties(Document document, boolean elemRefs)` Initializes this configuration from an XML document.
`boolean` | `isAttributeSplittingDisabled()` Returns the flag whether attribute splitting is disabled.
`boolean` | `isValidating()` Returns the value of the validating flag.
`void` | `load(InputStream in)` Loads the configuration from the given input stream.
`void` | `load(Reader in)` Load the configuration from the given reader.
`void` | `registerEntityId(String publicId, URL entityURL)` Registers the specified DTD URL for the specified public identifier.
`InputSource` | `resolveEntity(String publicId, String systemId)` Resolves the requested external entity.
`void` | `save(Writer writer)` Saves the configuration to the specified writer.
`void` | `setAttributeSplittingDisabled(boolean attributeSplittingDisabled)` Sets a flag whether attribute splitting is disabled.
`void` | `setDocumentBuilder(DocumentBuilder documentBuilder)` Sets the `DocumentBuilder` object to be used for loading documents.
`void` | `setPublicID(String publicID)` Sets the public ID of the DOCTYPE declaration.
`void` | `setRootElementName(String name)` Sets the name of the root element.
`void` | `setSystemID(String systemID)` Sets the system ID of the DOCTYPE declaration.
`void` | `setValidating(boolean validating)` Sets the value of the validating flag.

Methods inherited from class org.apache.commons.configuration.AbstractHierarchicalFileConfiguration
`addPropertyDirect, clearProperty, clearTree, configurationChanged, containsKey, fetchNodeList, getBasePath, getDelegate, getEncoding, getFile, getFileName, getKeys, getKeys, getProperty, getReloadingStrategy, getURL, isAutoSave, isEmpty, load, load, load, load, load, reload, save, save, save, save, save, save, setAutoSave, setBasePath, setDelegate, setEncoding, setFile, setFileName, setProperty, setReloadingStrategy, setURL, subnodeConfigurationChanged`

Methods inherited from class org.apache.commons.configuration.HierarchicalConfiguration
`clearNode, clearNode, clearReferences, configurationAt, configurationAt, configurationsAt, createAddPath, createSubnodeConfiguration, createSubnodeConfiguration, fetchAddNode, findLastPathNode, findPropertyNodes, getDefaultExpressionEngine, getExpressionEngine, getMaxIndex, getRoot, getRootNode, interpolatedConfiguration, nodeDefined, nodeDefined, removeNode, removeNode, setDefaultExpressionEngine, setExpressionEngine, setRoot, setRootNode, subset`

Methods inherited from class org.apache.commons.configuration.AbstractConfiguration
`addErrorLogListener, addProperty, append, clearPropertyDirect, copy, createInterpolator, getBigDecimal, getBigDecimal, getBigInteger, getBigInteger, getBoolean, getBoolean, getBoolean, getByte, getByte, getByte, getDefaultListDelimiter, getDelimiter, getDouble, getDouble, getDouble, getFloat, getFloat, getFloat, getInt, getInt, getInteger, getInterpolator, getList, getList, getListDelimiter, getLogger, getLong, getLong, getLong, getProperties, getProperties, getShort, getShort, getShort, getString, getString, getStringArray, getSubstitutor, interpolate, interpolate, interpolateHelper, isDelimiterParsingDisabled, isThrowExceptionOnMissing, resolveContainerStore, setDefaultListDelimiter, setDelimiter, setDelimiterParsingDisabled, setListDelimiter, setLogger, setThrowExceptionOnMissing`

Methods inherited from class org.apache.commons.configuration.event.EventSource
`addConfigurationListener, addErrorListener, clearConfigurationListeners, clearErrorListeners, createErrorEvent, createEvent, fireError, fireEvent, getConfigurationListeners, getErrorListeners, isDetailEvents, removeConfigurationListener, removeErrorListener, setDetailEvents`

Methods inherited from class java.lang.Object
`equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Methods inherited from interface org.apache.commons.configuration.Configuration
`addProperty, getBigDecimal, getBigDecimal, getBigInteger, getBigInteger, getBoolean, getBoolean, getBoolean, getByte, getByte, getByte, getDouble, getDouble, getDouble, getFloat, getFloat, getFloat, getInt, getInt, getInteger, getList, getList, getLong, getLong, getLong, getProperties, getShort, getShort, getShort, getString, getString, getStringArray, subset`

Constructor Detail

### XMLConfiguration

    public XMLConfiguration()

  Creates a new instance of `XMLConfiguration`.

### XMLConfiguration

    public XMLConfiguration(HierarchicalConfiguration c)

  Creates a new instance of `XMLConfiguration` and copies the content of the passed in configuration into this object. Note that only the data of the passed in configuration will be copied. If, for instance, the other configuration is a `XMLConfiguration`, too, things like comments or processing instructions will be lost.

Parameters:
  `c` - the configuration to copy
Since:
  1.4

### XMLConfiguration

    public XMLConfiguration(String fileName)
                     throws ConfigurationException

  Creates a new instance of `XMLConfiguration`. The configuration is loaded from the specified file

Parameters:
  `fileName` - the name of the file to load
Throws:
  `ConfigurationException` - if the file cannot be loaded

### XMLConfiguration

    public XMLConfiguration(File file)
                     throws ConfigurationException

  Creates a new instance of `XMLConfiguration`. The configuration is loaded from the specified file.

Parameters:
  `file` - the file
Throws:
  `ConfigurationException` - if an error occurs while loading the file

### XMLConfiguration

    public XMLConfiguration(URL url)
                     throws ConfigurationException

  Creates a new instance of `XMLConfiguration`. The configuration is loaded from the specified URL.

Parameters:
  `url` - the URL
Throws:
  `ConfigurationException` - if loading causes an error

Method Detail

### getRootElementName

    public String getRootElementName()

  Returns the name of the root element. If this configuration was loaded from a XML document, the name of this document's root element is returned. Otherwise it is possible to set a name for the root element that will be used when this configuration is stored.

  Returns:
    the name of the root element

### setRootElementName

    public void setRootElementName(String name)

  Sets the name of the root element. This name is used when this configuration object is stored in an XML file. Note that setting the name of the root element works only if this configuration has been newly created. If the configuration was loaded from an XML file, the name cannot be changed and an `UnsupportedOperationException` exception is thrown. Whether this configuration has been loaded from an XML document or not can be found out using the `getDocument()` method.

  Parameters:
    `name` - the name of the root element

### getDocumentBuilder

    public DocumentBuilder getDocumentBuilder()

  Returns the `DocumentBuilder` object that is used for loading documents. If no specific builder has been set, this method returns null.

  Returns:
    the `DocumentBuilder` for loading new documents
  Since:
    1.2

### setDocumentBuilder

    public void setDocumentBuilder(DocumentBuilder documentBuilder)

  Sets the `DocumentBuilder` object to be used for loading documents. This method makes it possible to specify the exact document builder. So an application can create a builder, configure it for its special needs, and then pass it to this method.

  Parameters:
    `documentBuilder` - the document builder to be used; if undefined, a default builder will be used
  Since:
    1.2

### getPublicID

    public String getPublicID()

  Returns the public ID of the DOCTYPE declaration from the loaded XML document. This is null if no document has been loaded yet or if the document does not contain a DOCTYPE declaration with a public ID.

  Returns:
    the public ID
  Since:
    1.3

### setPublicID

    public void setPublicID(String publicID)

  Sets the public ID of the DOCTYPE declaration. When this configuration is saved, a DOCTYPE declaration will be constructed that contains this public ID.

  Parameters:
    `publicID` - the public ID
  Since:
    1.3

### getSystemID

    public String getSystemID()

  Returns the system ID of the DOCTYPE declaration from the loaded XML document. This is null if no document has been loaded yet or if the document does not contain a DOCTYPE declaration with a system ID.

  Returns:
    the system ID
  Since:
    1.3

### setSystemID

    public void setSystemID(String systemID)

  Sets the system ID of the DOCTYPE declaration. When this configuration is saved, a DOCTYPE declaration will be constructed that contains this system ID.

  Parameters:
    `systemID` - the system ID
  Since:
    1.3

### isValidating

    public boolean isValidating()

  Returns the value of the validating flag.

  Returns:
    the validating flag
  Since:
    1.2

### setValidating

    public void setValidating(boolean validating)

  Sets the value of the validating flag. This flag determines whether DTD validation should be performed when loading XML documents. This flag is evaluated only if no custom `DocumentBuilder` was set.

  Parameters:
    `validating` - the validating flag
  Since:
    1.2

### isAttributeSplittingDisabled

    public boolean isAttributeSplittingDisabled()

  Returns the flag whether attribute splitting is disabled.

  Returns:
    the flag whether attribute splitting is disabled
  Since:
    1.6
  See Also:
    `setAttributeSplittingDisabled(boolean)`

### setAttributeSplittingDisabled

    public void setAttributeSplittingDisabled(boolean attributeSplittingDisabled)

  Sets a flag whether attribute splitting is disabled.

  The Configuration API allows adding multiple values to an attribute. This is problematic when storing the configuration because in XML an attribute can appear only once with a single value. To solve this problem, per default multiple attribute values are concatenated using a special separator character and split again when the configuration is loaded. The separator character is either the list delimiter character (see `AbstractConfiguration.setListDelimiter(char)`) or the pipe symbol ("|") if list delimiter parsing is disabled.

  In some constellations the splitting of attribute values can have undesired effects, especially if list delimiter parsing is disabled and attributes may contain the "|" character. In these cases it is possible to disable the attribute splitting mechanism by calling this method with a boolean value set to false. If attribute splitting is disabled, the values of attributes will not be processed, but stored as configuration properties exactly as they are returned by the XML parser.

  Note that in this mode multiple attribute values cannot be handled correctly. It is possible to create a `XMLConfiguration` object, add multiple values to an attribute and save it. When the configuration is loaded again and attribute splitting is disabled, the attribute will only have a single value, which is the concatenation of all values set before. So it lies in the responsibility of the application to carefully set the values of attributes.

  As is true for the `AbstractConfiguration.setDelimiterParsingDisabled(boolean)` method, this method must be called before the configuration is loaded. So it can't be used together with one of the constructors expecting the specification of the file to load. Instead the default constructor has to be used, then `setAttributeSplittingDisabled(false)` has to be called, and finally the configuration can be loaded using one of its `load()` methods.

  Parameters:
    `attributeSplittingDisabled` - true for disabling attribute splitting, false for enabling it
  Since:
    1.6
  See Also:
    `AbstractConfiguration.setDelimiterParsingDisabled(boolean)`

### getDocument

    public Document getDocument()

  Returns the XML document this configuration was loaded from. The return value is null if this configuration was not loaded from a XML document.

  Returns:
    the XML document this configuration was loaded from

### clear

    public void clear()

  Removes all properties from this configuration. If this configuration was loaded from a file, the associated DOM document is also cleared.

  Specified by:
    `clear` in interface `Configuration`
  Overrides:
    `clear` in class `AbstractConfiguration`

### initProperties

    public void initProperties(Document document,
                               boolean elemRefs)

  Initializes this configuration from an XML document.

  Parameters:
    `document` - the document to be parsed
    `elemRefs` - a flag whether references to the XML elements should be set

### createDocumentBuilder

    protected DocumentBuilder createDocumentBuilder()
                                             throws ParserConfigurationException

  Creates the `DocumentBuilder` to be used for loading files. This implementation checks whether a specific `DocumentBuilder` has been set. If this is the case, this one is used. Otherwise a default builder is created. Depending on the value of the validating flag this builder will be a validating or a non validating `DocumentBuilder`.

  Returns:
    the `DocumentBuilder` for loading configuration files
  Throws:
    `ParserConfigurationException` - if an error occurs
  Since:
    1.2

### createDocument

    protected Document createDocument()
                               throws ConfigurationException

  Creates a DOM document from the internal tree of configuration nodes.

  Returns:
    the new document
  Throws:
    `ConfigurationException` - if an error occurs

### createNode

    protected HierarchicalConfiguration.Node createNode(String name)

  Creates a new node object. This implementation returns an instance of the `XMLNode` class.

  Overrides:
    `createNode` in class `HierarchicalConfiguration`
  Parameters:
    `name` - the node's name
  Returns:
    the new node

### load

    public void load(InputStream in)
              throws ConfigurationException

  Loads the configuration from the given input stream.

  Specified by:
    `load` in interface `FileConfiguration`
  Overrides:
    `load` in class `AbstractHierarchicalFileConfiguration`
  Parameters:
    `in` - the input stream
  Throws:
    `ConfigurationException` - if an error occurs

### load

    public void load(Reader in)
              throws ConfigurationException

  Load the configuration from the given reader. Note that the `clear()` method is not called, so the properties contained in the loaded file will be added to the actual set of properties.

  Specified by:
    `load` in interface `FileConfiguration`
  Parameters:
    `in` - An InputStream.
  Throws:
    `ConfigurationException` - if an error occurs

### save

    public void save(Writer writer)
              throws ConfigurationException

  Saves the configuration to the specified writer.

  Specified by:
    `save` in interface `FileConfiguration`
  Parameters:
    `writer` - the writer used to save the configuration
  Throws:
    `ConfigurationException` - if an error occurs

### createTransformer

    protected Transformer createTransformer()
                                     throws TransformerException

  Creates and initializes the transformer used for save operations. This base implementation initializes all of the default settings like indention mode and the DOCTYPE. Derived classes may overload this method if they have specific needs.

  Returns:
    the transformer to use for a save operation
  Throws:
    `TransformerException` - if an error occurs
  Since:
    1.3

### clone

    public Object clone()

  Creates a copy of this object. The new configuration object will contain the same properties as the original, but it will lose any connection to a source document (if one exists). This is to avoid race conditions if both the original and the copy are modified and then saved.

  Overrides:
    `clone` in class `HierarchicalConfiguration`
  Returns:
    the copy

### createDelegate

    protected AbstractHierarchicalFileConfiguration.FileConfigurationDelegate createDelegate()

  Creates the file configuration delegate for this object. This implementation will return an instance of a class derived from `FileConfigurationDelegate` that deals with some specialities of `XMLConfiguration`.

  Overrides:
    `createDelegate` in class `AbstractHierarchicalFileConfiguration`
  Returns:
    the delegate for this object

### addNodes

    public void addNodes(String key,
                         Collection nodes)

  Adds a collection of nodes directly to this configuration. This implementation ensures that the nodes to be added are of the correct node type (they have to be converted to `XMLNode` if necessary).

  Overrides:
    `addNodes` in class `AbstractHierarchicalFileConfiguration`
  Parameters:
    `key` - the key where the nodes are to be added
    `nodes` - the collection with the new nodes
  Since:
    1.5

### registerEntityId

    public void registerEntityId(String publicId,
                                 URL entityURL)

  Registers the specified DTD URL for the specified public identifier.

  `XMLConfiguration` contains an internal `EntityResolver` implementation. This maps `PUBLICID`'s to URLs (from which the resource will be loaded). A common use case for this method is to register local URLs (possibly computed at runtime by a class loader) for DTDs. This allows the performance advantage of using a local version without having to ensure every `SYSTEM` URI on every processed XML document is local. This implementation provides only basic functionality. If more sophisticated features are required, using `setDocumentBuilder(DocumentBuilder)` to set a custom `DocumentBuilder` (which also can be initialized with a custom `EntityResolver`) is recommended.

  Note: This method will have no effect when a custom `DocumentBuilder` has been set. (Setting a custom `DocumentBuilder` overrides the internal implementation.)

  Note: This method must be called before the configuration is loaded. So the default constructor of `XMLConfiguration` should be used, the location of the configuration file set, `registerEntityId()` called, and finally the `load()` method can be invoked.

  Parameters:
    `publicId` - Public identifier of the DTD to be resolved
    `entityURL` - The URL to use for reading this DTD
  Throws:
    `IllegalArgumentException` - if the public ID is undefined
  Since:
    1.5

### resolveEntity

    public InputSource resolveEntity(String publicId,
                                     String systemId)
                              throws SAXException

  Resolves the requested external entity. This is the default implementation of the `EntityResolver` interface. It checks the passed in public ID against the registered entity IDs and uses a local URL if possible.

  Specified by:
    `resolveEntity` in interface `EntityResolver`
  Parameters:
    `publicId` - the public identifier of the entity being referenced
    `systemId` - the system identifier of the entity being referenced
  Returns:
    an input source for the specified entity
  Throws:
    `SAXException` - if a parsing exception occurs
  Since:
    1.5

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