Class Rule

java.lang.Object
org.apache.commons.digester3.Rule
Direct Known Subclasses:
AbstractMethodRule, BeanPropertySetterRule, CallMethodRule, CallParamRule, FactoryCreateRule, IncludeRule, NodeCreateRule, ObjectCreateRule, ObjectParamRule, PathCallParamRule, PatternRule, PluginCreateRule, PluginDeclarationRule, SetNamespaceURIRule, SetNestedPropertiesAliasRule, SetNestedPropertiesIgnoreRule, SetNestedPropertiesRule, SetNestedPropertiesRule.AnyChildRule, SetPropertiesAliasRule, SetPropertiesIgnoreRule, SetPropertiesRule, SetPropertyRule

public abstract class Rule extends Object
Concrete implementations of this class implement actions to be taken when a corresponding nested pattern of XML elements has been matched.

Writing a custom Rule is considered perfectly normal when using Digester, and is encouraged whenever the default set of Rule classes don't meet your requirements; the digester framework can help process xml even when the built-in rules aren't quite what is needed. Creating a custom Rule is just as easy as subclassing javax.servlet.http.HttpServlet for webapps, or javax.swing.Action for GUI applications.

If a rule wishes to manipulate a digester stack (the default object stack, a named stack, or the parameter stack) then it should only ever push objects in the rule's begin method and always pop exactly the same number of objects off the stack during the rule's end method. Of course peeking at the objects on the stacks can be done from anywhere.

Rule objects should be stateless, ie they should not update any instance member during the parsing process. A rule instance that changes state will encounter problems if invoked in a "nested" manner; this can happen if the same instance is added to digester multiple times or if a wildcard pattern is used which can match both an element and a child of the same element. The digester object stack and named stacks should be used to store any state that a rule requires, making the rule class safe under all possible uses.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private Digester
    The Digester with which this Rule is associated.
    private String
    The namespace URI for which this Rule is relevant, if any.
  • Constructor Summary

    Constructors
    Constructor
    Description
     
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    begin(String namespace, String name, Attributes attributes)
    This method is called when the beginning of a matching XML element is encountered.
    void
    body(String namespace, String name, String text)
    This method is called when the body of a matching XML element is encountered.
    void
    end(String namespace, String name)
    This method is called when the end of a matching XML element is encountered.
    void
    This method is called after all parsing methods have been called, to allow Rules to remove temporary data.
    Return the Digester with which this Rule is associated.
    Return the namespace URI for which this Rule is relevant, if any.
    void
    Set the Digester with which this Rule is associated.
    void
    setNamespaceURI(String namespaceURI)
    Set the namespace URI for which this Rule is relevant, if any.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • digester

      private Digester digester
      The Digester with which this Rule is associated.
    • namespaceURI

      private String namespaceURI
      The namespace URI for which this Rule is relevant, if any.
  • Constructor Details

    • Rule

      public Rule()
  • Method Details

    • getDigester

      public Digester getDigester()
      Return the Digester with which this Rule is associated.
      Returns:
      the Digester with which this Rule is associated
    • setDigester

      public void setDigester(Digester digester)
      Set the Digester with which this Rule is associated.
      Parameters:
      digester - the Digester with which this Rule is associated
    • getNamespaceURI

      public String getNamespaceURI()
      Return the namespace URI for which this Rule is relevant, if any.
      Returns:
      the namespace URI for which this Rule is relevant, if any
    • setNamespaceURI

      public void setNamespaceURI(String namespaceURI)
      Set the namespace URI for which this Rule is relevant, if any.
      Parameters:
      namespaceURI - Namespace URI for which this Rule is relevant, or null to match independent of namespace.
    • begin

      public void begin(String namespace, String name, Attributes attributes) throws Exception
      This method is called when the beginning of a matching XML element is encountered.
      Parameters:
      namespace - the namespace URI of the matching element, or an empty string if the parser is not namespace aware or the element has no namespace
      name - the local name if the parser is namespace aware, or just the element name otherwise
      attributes - The attribute list of this element
      Throws:
      Exception - if any error occurs
      Since:
      Digester 1.4
    • body

      public void body(String namespace, String name, String text) throws Exception
      This method is called when the body of a matching XML element is encountered. If the element has no body, this method is called with an empty string as the body text.
      Parameters:
      namespace - the namespace URI of the matching element, or an empty string if the parser is not namespace aware or the element has no namespace
      name - the local name if the parser is namespace aware, or just the element name otherwise
      text - The text of the body of this element
      Throws:
      Exception - if any error occurs
      Since:
      Digester 1.4
    • end

      public void end(String namespace, String name) throws Exception
      This method is called when the end of a matching XML element is encountered.
      Parameters:
      namespace - the namespace URI of the matching element, or an empty string if the parser is not namespace aware or the element has no namespace
      name - the local name if the parser is namespace aware, or just the element name otherwise
      Throws:
      Exception - if any error occurs
      Since:
      Digester 1.4
    • finish

      public void finish() throws Exception
      This method is called after all parsing methods have been called, to allow Rules to remove temporary data.
      Throws:
      Exception - if any error occurs