org.apache.commons.jocl
Class JOCLContentHandler

java.lang.Object
  extended byorg.xml.sax.helpers.DefaultHandler
      extended byorg.apache.commons.jocl.JOCLContentHandler
All Implemented Interfaces:
ContentHandler, DTDHandler, EntityResolver, ErrorHandler

public class JOCLContentHandler
extends DefaultHandler

A ContentHandler for the Java Object Configuration Language.

JOCL provides an XML syntax for constructing arbitrary Java Object instances. It does not define a full XML document type (there's no root element), but rather an XML fragment describing the Objects to be constructed.

In a JOCL fragment, one may define a series of objects using the object element. A trivial example is:

 <object class="java.util.Date"/>
which constructs an instance of java.util.Date using the no-argument constructor.

After a "root-level" <object> element has been processed (that is, once endElement(java.lang.String,java.lang.String,java.lang.String) has been invoked by the XMLReader), it will be appended to a list of Objects maintained by the JOCLContentHandler.

(See size(), clear(), clear(int), getType(int), getValue(int), getTypeArray(), and getValueArray().)

You can list multiple object elements in a fragment. For example, after processing the JOCL fragment:

 <object class="java.util.Date"/>
 <object class="java.util.Date"/>
The getTypeArray() method will return an composed of two instances of java.util.Date. The sequence of Objects in the array will correspond to the sequence of <object> elements in the JOCL fragment.

As we've seen, when used with no child-elements, the <object> tag will cause the no-argument constructor of the specified class to be invoked. It is also possible to nest <object> tags to provide arguments for the constructor. For example, the fragment:

 <object class="mypackage.Foo">
   <object class="mypackage.Bar"/>
 </object>
will add an instance of mypackage.Foo to the object list, constructed via new mypackage.Foo(new mypackage.Bar()).

There is a special syntax available creating primative values and arguments, as well as for constructing Strings. Some examples:

 <byte value="3"/>
 <boolean value="false"/>
 <char value="c"/>
 <double value="3.14159"/>
 <float value="3.14"/>
 <int value="17"/>
 <long value="1700000"/>
 <short value="1"/>
 <string value="The quick brown fox..."/>

When invoked at the "root" level (that is, with no <object> parent), this will cause the corresponding "object wrapper" to be added to the list of Objects. The type for these objects will reflect the proper primative type, however. When invoked with an <object> parent, these will be treated as primitive arguments to the specified Object's constructor. For example, while:

 <int value="5"/>
 <int value="26"/>
 <int value="100"/>

results in three Integer instances being added to the list of values, with types corresponding to Integer, the fragment:

 <int value="5"/>
 <int value="26"/>
 <int value="100"/>

results in three Integer instances being added to the list of values, with types corresponding to Integer.TYPE.

Hence if you want to invoke the mypackage.Foo(java.lang.Integer,java.lang.Integer,java.lang.Integer) constructor, use:

 <object class="mypackage.Foo"/>
   <object class="java.lang.Integer"><int value="5"/></object>
   <object class="java.lang.Integer"><int value="26"/></object>
   <object class="java.lang.Integer"><int value="100"/></object>
 </object>

If you want to invoke the mypackage.Foo(int,int,int) constructor, use:

 <object class="mypackage.Foo"/>
   <int value="5"/>
   <int value="26"/>
   <int value="100"/>
 </object>

If you'd like to creat a null object, use:

 <object class="mypackage.Bar" null="true"/>

Here's a simple but complete example:

 <?xml version="1.0"?>
 <arbitrary-root xmlns="http://apache.org/xml/xmlns/jakarta/commons/jocl">
   <string value="Hello World!"/>
   <string/>
   <boolean/>
   <boolean value="true"/>
   <byte value="1"/>
   <short value="1"/>
   <int value="1"/>
   <long value="1"/>
   <float value="1.0"/>
   <double value="1.0"/>
   <object class="java.util.Date"/>
   <object class="java.util.Date">
    <int value="1"/>
    <int value="1"/>
    <int value="1"/>
   </object>
 </arbitrary-root>

Formally, a DTD for the JOCL grammar is as follows:

 <!ELEMENT object (object|byte|boolean|char|double|float|int|long|short|string)*>
 <!ATTLIST object
   class CDATA #REQUIRED
   null (true|false) "false">

 <!ELEMENT byte EMPTY>
 <!ATTLIST byte value CDATA #REQUIRED>

 <!ELEMENT boolean EMPTY>
 <!ATTLIST boolean value (true|false) #REQUIRED>

 <!ELEMENT char EMPTY>
 <!ATTLIST char value CDATA #REQUIRED>

 <!ELEMENT double EMPTY>
 <!ATTLIST double value CDATA #REQUIRED>

 <!ELEMENT float EMPTY>
 <!ATTLIST float value CDATA #REQUIRED>

 <!ELEMENT int EMPTY>
 <!ATTLIST int value CDATA #REQUIRED>

 <!ELEMENT long EMPTY>
 <!ATTLIST long value CDATA #REQUIRED>

 <!ELEMENT short EMPTY>
 <!ATTLIST short value CDATA #REQUIRED>

 <!ELEMENT string EMPTY>
 <!ATTLIST string value CDATA #REQUIRED>
 

This class can also be used as a base class for ContentHandlers that include JOCL as part of their grammar. Simply extend this class, and override the startElement(java.lang.String, java.lang.String, java.lang.String, org.xml.sax.Attributes), DefaultHandler.characters(char[], int, int), and endElement(java.lang.String, java.lang.String, java.lang.String) methods to handle your tags, and invoke the method of the parent class (i.e., super.XXX for elements and data that you don't handle.

A number of static methods are available for simply reading a list of objects from a InputStream, Reader or InputSource.

Note that this class is not synchronized.

Version:
$Revision: 892307 $ $Date: 2014-01-01 00:27:28 +0100 (Wed, 01 Jan 2014) $
Author:
Rodney Waldhoff

Field Summary
protected  boolean _acceptEmptyNamespaceForAttributes
          When true, I will treat attributes with an empty namespace URI as part of the JOCL namespace.
protected  boolean _acceptEmptyNamespaceForElements
          When true, I will treat elements with an empty namespace URI as part of the JOCL namespace.
protected  boolean _acceptJoclPrefixForAttributes
          When true, I will treat attributes with the JOCL_PREFIX but no namespace URI as being mapped to the jocl namespace.
protected  boolean _acceptJoclPrefixForElements
          When true, I will treat elements with the JOCL_PREFIX but no namespace URI as being mapped to the jocl namespace.
protected  org.apache.commons.jocl.JOCLContentHandler.ConstructorDetails _cur
          The object I'm currently working on.
protected  Locator _locator
          My Locator.
protected  ArrayList _typeList
          A list of the types (Classes) already created via the parse.
protected  ArrayList _valueList
          A list of the values (Objects) already created via the parse.
protected static String ATT_CLASS
          The name of the "object" element's "class" attribute.
protected static String ATT_ISNULL
          The name of the "object" element's "isnull" attribute.
protected static String ATT_VALUE
          The name of the "value" attribute.
protected static String ELT_BOOLEAN
          The name of the "boolean" element.
protected static String ELT_BYTE
          The name of the "byte" element.
protected static String ELT_CHAR
          The name of the "char" element.
protected static String ELT_DOUBLE
          The name of the "double" element.
protected static String ELT_FLOAT
          The name of the "float" element.
protected static String ELT_INT
          The name of the "int" element.
protected static String ELT_LONG
          The name of the "long" element.
protected static String ELT_OBJECT
          The name of the "object" element.
protected static String ELT_SHORT
          The name of the "short" element.
protected static String ELT_STRING
          The name of the "string" element.
static String JOCL_NAMESPACE_URI
          The JOCL namespace URI, http://apache.org/xml/xmlns/jakarta/commons/jocl.
static String JOCL_PREFIX
          The default JOCL prefix, jocl:.
 
Constructor Summary
JOCLContentHandler()
          Equivalent to JOCLContentHandler(true,true,true,true).
JOCLContentHandler(boolean emptyEltNS, boolean joclEltPrefix, boolean emptyAttrNS, boolean joclAttrPrefix)
          Construct a JOCLContentHandler.
 
Method Summary
protected  void addObject(Class type, Object val)
          Add the specified object either to my type/value list, or as an argument to the object I'm currently constructing.
 void clear()
          Clears all the values and types in my list.
 void clear(int i)
          Removes the value/type pair at the specified index.
 void endElement(String uri, String localName, String qname)
           
protected  String getAttributeValue(String localname, Attributes attr)
          Equivalent to getAttributeValue(localname,attr,null).
protected  String getAttributeValue(String localname, Attributes attr, String implied)
          Returns the value of attribute with the given localname within the JOCL namespace from the given set of Attributes.
 Class getType(int i)
          Returns the type of the object at the specified index.
 Object[] getTypeArray()
          Returns a shallow copy of my list of types.
 Object getValue(int i)
          Returns the value of the object at the specified index.
 Object[] getValueArray()
          Returns a shallow copy of my list of values.
protected  boolean isJoclNamespace(String uri, String localname, String qname)
          Returns true if the given attributes define an element within the JOCL namespace (according to my current configuration.)
static void main(String[] args)
          A simple tester method.
static JOCLContentHandler parse(File f)
          Parses a JOCL document from the specified file, using the XMLReader specified by the org.xml.sax.driver property.
static JOCLContentHandler parse(File f, XMLReader reader)
          Parses a JOCL document from the specified file, using the XMLReader specified by the org.xml.sax.driver property.
static JOCLContentHandler parse(InputSource in)
          Parses a JOCL document from the specified InputSource, using thethe XMLReader specified by the org.xml.sax.driver property.
static JOCLContentHandler parse(InputSource in, XMLReader reader)
          Parses a JOCL document from the specified InputSource, using the specified XMLReader.
static JOCLContentHandler parse(InputStream in)
          Parses a JOCL document from the specified InputStream, using the XMLReader specified by the org.xml.sax.driver property.
static JOCLContentHandler parse(InputStream in, XMLReader reader)
          Parses a JOCL document from the specified InputStream, using the specified XMLReader.
static JOCLContentHandler parse(Reader in)
          Parses a JOCL document from the specified Reader, using the XMLReader specified by the org.xml.sax.driver property.
static JOCLContentHandler parse(Reader in, XMLReader reader)
          Parses a JOCL document from the specified Reader, using the specified XMLReader.
 void setDocumentLocator(Locator locator)
           
 int size()
          Returns the number of values and types in my list.
 void startElement(String uri, String localName, String qname, Attributes attr)
           
 
Methods inherited from class org.xml.sax.helpers.DefaultHandler
characters, endDocument, endPrefixMapping, error, fatalError, ignorableWhitespace, notationDecl, processingInstruction, resolveEntity, skippedEntity, startDocument, startPrefixMapping, unparsedEntityDecl, warning
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

JOCL_NAMESPACE_URI

public static final String JOCL_NAMESPACE_URI
The JOCL namespace URI, http://apache.org/xml/xmlns/jakarta/commons/jocl.

See Also:
Constant Field Values

JOCL_PREFIX

public static final String JOCL_PREFIX
The default JOCL prefix, jocl:.

See Also:
Constant Field Values

_typeList

protected ArrayList _typeList
A list of the types (Classes) already created via the parse.


_valueList

protected ArrayList _valueList
A list of the values (Objects) already created via the parse.


_cur

protected org.apache.commons.jocl.JOCLContentHandler.ConstructorDetails _cur
The object I'm currently working on.


_acceptEmptyNamespaceForElements

protected boolean _acceptEmptyNamespaceForElements
When true, I will treat elements with an empty namespace URI as part of the JOCL namespace.

See Also:
JOCL_NAMESPACE_URI

_acceptJoclPrefixForElements

protected boolean _acceptJoclPrefixForElements
When true, I will treat elements with the JOCL_PREFIX but no namespace URI as being mapped to the jocl namespace.

See Also:
JOCL_PREFIX, JOCL_NAMESPACE_URI

_acceptEmptyNamespaceForAttributes

protected boolean _acceptEmptyNamespaceForAttributes
When true, I will treat attributes with an empty namespace URI as part of the JOCL namespace.

See Also:
JOCL_NAMESPACE_URI

_acceptJoclPrefixForAttributes

protected boolean _acceptJoclPrefixForAttributes
When true, I will treat attributes with the JOCL_PREFIX but no namespace URI as being mapped to the jocl namespace.

See Also:
JOCL_PREFIX, JOCL_NAMESPACE_URI

_locator

protected Locator _locator
My Locator.


ELT_OBJECT

protected static final String ELT_OBJECT
The name of the "object" element.

See Also:
Constant Field Values

ATT_CLASS

protected static final String ATT_CLASS
The name of the "object" element's "class" attribute.

See Also:
Constant Field Values

ATT_ISNULL

protected static final String ATT_ISNULL
The name of the "object" element's "isnull" attribute.

See Also:
Constant Field Values

ELT_BOOLEAN

protected static final String ELT_BOOLEAN
The name of the "boolean" element.

See Also:
Constant Field Values

ELT_BYTE

protected static final String ELT_BYTE
The name of the "byte" element.

See Also:
Constant Field Values

ELT_CHAR

protected static final String ELT_CHAR
The name of the "char" element.

See Also:
Constant Field Values

ELT_DOUBLE

protected static final String ELT_DOUBLE
The name of the "double" element.

See Also:
Constant Field Values

ELT_FLOAT

protected static final String ELT_FLOAT
The name of the "float" element.

See Also:
Constant Field Values

ELT_INT

protected static final String ELT_INT
The name of the "int" element.

See Also:
Constant Field Values

ELT_LONG

protected static final String ELT_LONG
The name of the "long" element.

See Also:
Constant Field Values

ELT_SHORT

protected static final String ELT_SHORT
The name of the "short" element.

See Also:
Constant Field Values

ELT_STRING

protected static final String ELT_STRING
The name of the "string" element.

See Also:
Constant Field Values

ATT_VALUE

protected static final String ATT_VALUE
The name of the "value" attribute.

See Also:
Constant Field Values
Constructor Detail

JOCLContentHandler

public JOCLContentHandler()
Equivalent to JOCLContentHandler(true,true,true,true).


JOCLContentHandler

public JOCLContentHandler(boolean emptyEltNS,
                          boolean joclEltPrefix,
                          boolean emptyAttrNS,
                          boolean joclAttrPrefix)
Construct a JOCLContentHandler.

Parameters:
emptyEltNS - when true I should assume any element with an empty namespace is within the JOCL namespace
joclEltPrefix - when true I should assume any element who's prefix is jocl: and who's namespace is empty is within the JOCL namespace
emptyAttrNS - when true I should assume any attribute with an empty namespace is within the JOCL namespace
joclAttrPrefix - when true I should assume any attribute who's prefix is jocl: and who's namespace is empty is within the JOCL namespace
Method Detail

main

public static void main(String[] args)
                 throws Exception
A simple tester method. Reads a JOCL document from standard in and prints a list of the objects created to standard out. (Use the org.xml.sax.driver system property to specify an XMLReader.

Throws:
Exception

parse

public static JOCLContentHandler parse(File f)
                                throws SAXException,
                                       FileNotFoundException,
                                       IOException
Parses a JOCL document from the specified file, using the XMLReader specified by the org.xml.sax.driver property. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
f - a File containing the JOCL document
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
FileNotFoundException
IOException

parse

public static JOCLContentHandler parse(Reader in)
                                throws SAXException,
                                       IOException
Parses a JOCL document from the specified Reader, using the XMLReader specified by the org.xml.sax.driver property. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
in - a Reader containing the JOCL document
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
IOException

parse

public static JOCLContentHandler parse(InputStream in)
                                throws SAXException,
                                       IOException
Parses a JOCL document from the specified InputStream, using the XMLReader specified by the org.xml.sax.driver property. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
in - a InputStream containing the JOCL document
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
IOException

parse

public static JOCLContentHandler parse(InputSource in)
                                throws SAXException,
                                       IOException
Parses a JOCL document from the specified InputSource, using thethe XMLReader specified by the org.xml.sax.driver property. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
in - a InputSource containing the JOCL document
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
IOException

parse

public static JOCLContentHandler parse(File f,
                                       XMLReader reader)
                                throws SAXException,
                                       FileNotFoundException,
                                       IOException
Parses a JOCL document from the specified file, using the XMLReader specified by the org.xml.sax.driver property. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
f - a File containing the JOCL document
reader - the XMLReader to use to parse the file
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
FileNotFoundException
IOException

parse

public static JOCLContentHandler parse(Reader in,
                                       XMLReader reader)
                                throws SAXException,
                                       IOException
Parses a JOCL document from the specified Reader, using the specified XMLReader. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
in - a Reader containing the JOCL document
reader - the XMLReader to use to parse the document
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
IOException

parse

public static JOCLContentHandler parse(InputStream in,
                                       XMLReader reader)
                                throws SAXException,
                                       IOException
Parses a JOCL document from the specified InputStream, using the specified XMLReader. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
in - a InputStream containing the JOCL document
reader - the XMLReader to use to parse the document
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
IOException

parse

public static JOCLContentHandler parse(InputSource in,
                                       XMLReader reader)
                                throws SAXException,
                                       IOException
Parses a JOCL document from the specified InputSource, using the specified XMLReader. The returned JOCLContentHandler will contain the list of objects described by the file.

Parameters:
in - a InputSource containing the JOCL document
reader - the XMLReader to use to parse the document
Returns:
a JOCLContentHandler containing the list of objects described by the JOCL document
Throws:
SAXException
IOException

size

public int size()
Returns the number of values and types in my list.

Returns:
the number of values and types in my list.

clear

public void clear()
Clears all the values and types in my list.


clear

public void clear(int i)
Removes the value/type pair at the specified index.


getType

public Class getType(int i)
Returns the type of the object at the specified index.


getValue

public Object getValue(int i)
Returns the value of the object at the specified index.


getValueArray

public Object[] getValueArray()
Returns a shallow copy of my list of values.


getTypeArray

public Object[] getTypeArray()
Returns a shallow copy of my list of types.


startElement

public void startElement(String uri,
                         String localName,
                         String qname,
                         Attributes attr)
                  throws SAXException
Throws:
SAXException

endElement

public void endElement(String uri,
                       String localName,
                       String qname)
                throws SAXException
Throws:
SAXException

setDocumentLocator

public void setDocumentLocator(Locator locator)

isJoclNamespace

protected boolean isJoclNamespace(String uri,
                                  String localname,
                                  String qname)
Returns true if the given attributes define an element within the JOCL namespace (according to my current configuration.)

See Also:
_acceptEmptyNamespaceForElements, _acceptJoclPrefixForElements

getAttributeValue

protected String getAttributeValue(String localname,
                                   Attributes attr)
Equivalent to getAttributeValue(localname,attr,null).


getAttributeValue

protected String getAttributeValue(String localname,
                                   Attributes attr,
                                   String implied)
Returns the value of attribute with the given localname within the JOCL namespace from the given set of Attributes. If no such attribute can be found, returns implied.

Parameters:
localname - the unqualified name of the attribute to look for
attr - the Attributes in which to find the value
implied - the default value for the attribute
Returns:
the value of attribute with the given localname within the JOCL namespace from the given set of Attributes. If no such attribute can be found, returns implied.

addObject

protected void addObject(Class type,
                         Object val)
Add the specified object either to my type/value list, or as an argument to the object I'm currently constructing.



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