Package org.apache.commons.configuration

Class XMLConfiguration

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable, Configuration, ConfigurationErrorListener, ConfigurationListener, FileConfiguration, FileSystemBased, Reloadable, EntityRegistry, org.xml.sax.EntityResolver
    Direct Known Subclasses:
    DefaultConfigurationBuilder, HierarchicalXMLConfiguration
    public class XMLConfiguration
extends AbstractHierarchicalFileConfiguration
implements org.xml.sax.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:
    Serialized Form

    • 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​(java.lang.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

    • Method Detail

      • getRootElementName

        public java.lang.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​(java.lang.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 javax.xml.parsers.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​(javax.xml.parsers.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 java.lang.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​(java.lang.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 java.lang.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​(java.lang.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​(org.xml.sax.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 org.xml.sax.EntityResolver getEntityResolver()
        Returns the EntityResolver.
        Returns:
        The EntityResolver.
        Since:
        1.7

      • 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 org.w3c.dom.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​(org.w3c.dom.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 javax.xml.parsers.DocumentBuilder createDocumentBuilder()
                                                           throws javax.xml.parsers.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:
        javax.xml.parsers.ParserConfigurationException - if an error occurs
        Since:
        1.2

      • load

        public void load​(java.io.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

      • createTransformer

        protected javax.xml.transform.Transformer createTransformer()
                                                     throws javax.xml.transform.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:
        javax.xml.transform.TransformerException - if an error occurs
        Since:
        1.3

      • clone

        public java.lang.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

      • addNodes

        public void addNodes​(java.lang.String key,
                     java.util.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​(java.lang.String publicId,
                             java.net.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:
        java.lang.IllegalArgumentException - if the public ID is undefined
        Since:
        1.5

      • resolveEntity

        @Deprecated
public org.xml.sax.InputSource resolveEntity​(java.lang.String publicId,
                                             java.lang.String systemId)
                                      throws org.xml.sax.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 org.xml.sax.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:
        org.xml.sax.SAXException - if a parsing exception occurs
        Since:
        1.5

      • getRegisteredEntities

        public java.util.Map<java.lang.String,​java.net.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