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:
Serializable, Cloneable, Configuration, ConfigurationErrorListener, ConfigurationListener, FileConfiguration, FileSystemBased, Reloadable, EntityRegistry, EntityResolver
Direct Known Subclasses:
DefaultConfigurationBuilder, HierarchicalXMLConfiguration
public class XMLConfiguration extends AbstractHierarchicalFileConfiguration implements EntityResolver, EntityRegistry

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:
$Id: XMLConfiguration.java 1534429 2013-10-22 00:45:36Z henning $
Author:
Jörg Schaible
See Also:

  • Constructor Details

    • 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 ofXMLConfiguration. 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 Details

    • 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/Schema 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

    • isSchemaValidation

      public boolean isSchemaValidation()
      Returns the value of the schemaValidation flag.
      Returns:
      the schemaValidation flag
      Since:
      1.7

    • setSchemaValidation

      public void setSchemaValidation(boolean schemaValidation)
      Sets the value of the schemaValidation flag. This flag determines whether DTD or Schema validation should be used. This flag is evaluated only if no custom DocumentBuilder was set. If set to true the XML document must contain a schemaLocation definition that provides resolvable hints to the required schemas.
      Parameters:
      schemaValidation - the validating flag
      Since:
      1.7

    • setEntityResolver

      public void setEntityResolver(EntityResolver resolver)
      Sets a new EntityResolver. Setting this will cause RegisterEntityId to have no effect.
      Parameters:
      resolver - The EntityResolver to use.
      Since:
      1.7

    • getEntityResolver

      public EntityResolver getEntityResolver()
      Returns the EntityResolver.
      Returns:
      The EntityResolver.
      Since:
      1.7

    • 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

      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:

    • 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 HierarchicalConfiguration

    • 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

    • validate

      public void validate() throws ConfigurationException
      Validate the document against the Schema.
      Throws:
      ConfigurationException - if the validation fails.

    • 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 specialties of XMLConfiguration.
      Overrides:
      createDelegate in class AbstractHierarchicalFileConfiguration
      Returns:
      the delegate for this object

    • addNodes

      public void addNodes(String key, Collection<? extends ConfigurationNode> 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.

      Specified by:
      registerEntityId in interface EntityRegistry
      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

      @Deprecated public InputSource resolveEntity(String publicId, String systemId) throws SAXException
      Deprecated.
      Use getEntityResolver().resolveEntity()
      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

    • getRegisteredEntities

      public Map<String,URL> getRegisteredEntities()
      Returns a map with the entity IDs that have been registered using the registerEntityId() method.
      Specified by:
      getRegisteredEntities in interface EntityRegistry
      Returns:
      a map with the registered entity IDs