org.enhydra.xml.io
Class XmlReader

java.lang.Object
  |
  +--java.io.Reader
        |
        +--org.enhydra.xml.io.XmlReader

public class XmlReader
extends Reader

Character stream that handles (or at least attemtps to) all the necessary Voodo to figure out the charset encoding of the XML document within the stream.

IMPORTANT: This class is not related in any way to the org.xml.sax.XMLReader. This one IS a character stream.

All this has to be done without consuming characters from the stream, if not the XML parser will not recognized the document as a valid XML. This is not 100% true, but it's close enough (UTF-8 BOM is not handled by all parsers right now, XmlReader handles it and things work in all parsers).

The XmlReader class handles the charset encoding of XML documents in Files, raw streams and HTTP streams by offering a wide set of constructors.

By default the charset encoding detection is lenient, the constructor with the lenient flag can be used for an script (following HTTP MIME and XML specifications). All this is nicely explained by Mark Pilgrim in his blog, Determining the character encoding of a feed.

--- End Original Docs, Start XMLC modifications ---

NOTE: Modifications were made to support overriding the default fallback encoding as well as using GNU Regexp instead of JDK14 regular expressions. This makes XmlReader compatible with JDK1.3. The original source may be viewed at Rome Project XmlReader ViewCVS. The functionality provided by XmlReader is detailed in Rome's wiki. Effort should be made to keep this version of XmlReader, generally, in sync with Rome's official version, since they are, clearly, the experts in this area. The Rome version of XmlReader that this file is based on is CVS version 1.11.

Author:
Alejandro Abdelnur, Jacob Kjome

Fields inherited from class java.io.Reader
lock
 
Constructor Summary
XmlReader(File file)
          Creates a Reader for a File.
XmlReader(InputStream is)
          Creates a Reader for a raw InputStream.
XmlReader(InputStream is, String httpContentType)
          Creates a Reader using an InputStream an the associated content-type header.
XmlReader(InputStream is, String defaultEncoding, boolean lenient)
          Creates a Reader for a raw InputStream.
XmlReader(InputStream is, String httpContentType, String defaultEncoding, boolean lenient)
          Creates a Reader using an InputStream an the associated content-type header.
XmlReader(URL url)
          Creates a Reader using the InputStream of a URL.
XmlReader(URLConnection conn)
          Creates a Reader using the InputStream of a URLConnection.
 
Method Summary
 void close()
          Closes the XmlReader stream.
 String getEncoding()
          Returns the charset encoding of the XmlReader.
 int read(char[] buf, int offset, int len)
           
 
Methods inherited from class java.io.Reader
mark, markSupported, read, read, ready, reset, skip
 
Methods inherited from class java.lang.Object
, clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

XmlReader

public XmlReader(File file)
          throws IOException
Creates a Reader for a File.

It looks for the UTF-8 BOM first, if none sniffs the XML prolog charset, if this is also missing defaults to UTF-8.

It does a lenient charset encoding detection, check the constructor with the lenient parameter for details.

Parameters:
file - File to create a Reader from.
Throws:
IOException - thrown if there is a problem reading the file.

XmlReader

public XmlReader(InputStream is)
          throws IOException
Creates a Reader for a raw InputStream.

It follows the same logic used for files.

It does a lenient charset encoding detection, check the constructor with the lenient parameter for details.

Parameters:
is - InputStream to create a Reader from.
Throws:
IOException - thrown if there is a problem reading the stream.

XmlReader

public XmlReader(InputStream is,
                 String defaultEncoding,
                 boolean lenient)
          throws IOException,
                 XmlReaderException
Creates a Reader for a raw InputStream.

It follows the same logic used for files.

If lenient detection is indicated and the detection above fails as per specifications it then attempts the following:

If the content type was 'text/html' it replaces it with 'text/xml' and tries the detection again.

Else if the XML prolog had a charset encoding that encoding is used.

Else if the content type had a charset encoding that encoding is used.

Else 'UTF-8' is used.

If lenient detection is indicated an XmlReaderException is never thrown.

Parameters:
is - InputStream to create a Reader from.
defaultEncoding - if non-null, sets the default encoding from UTF-8 to the user specified default
lenient - indicates if the charset encoding detection should be relaxed.
Throws:
IOException - thrown if there is a problem reading the stream.
XmlReaderException - thrown if the charset encoding could not be determined according to the specs.

XmlReader

public XmlReader(URL url)
          throws IOException
Creates a Reader using the InputStream of a URL.

If the URL is not of type HTTP and there is not 'content-type' header in the fetched data it uses the same logic used for Files.

If the URL is a HTTP Url or there is a 'content-type' header in the fetched data it uses the same logic used for an InputStream with content-type.

It does a lenient charset encoding detection, check the constructor with the lenient parameter for details.

Parameters:
url - URL to create a Reader from.
Throws:
IOException - thrown if there is a problem reading the stream of the URL.

XmlReader

public XmlReader(URLConnection conn)
          throws IOException
Creates a Reader using the InputStream of a URLConnection.

If the URLConnection is not of type HttpURLConnection and there is not 'content-type' header in the fetched data it uses the same logic used for files.

If the URLConnection is a HTTP Url or there is a 'content-type' header in the fetched data it uses the same logic used for an InputStream with content-type.

It does a lenient charset encoding detection, check the constructor with the lenient parameter for details.

Parameters:
conn - URLConnection to create a Reader from.
Throws:
IOException - thrown if there is a problem reading the stream of the URLConnection.

XmlReader

public XmlReader(InputStream is,
                 String httpContentType)
          throws IOException
Creates a Reader using an InputStream an the associated content-type header.

First it checks if the stream has BOM. If there is not BOM checks the content-type encoding. If there is not content-type encoding checks the XML prolog encoding. If there is not XML prolog encoding uses the default encoding mandated by the content-type MIME type.

It does a lenient charset encoding detection, check the constructor with the lenient parameter for details.

Parameters:
is - InputStream to create the reader from.
httpContentType - content-type header to use for the resolution of the charset encoding.
Throws:
IOException - thrown if there is a problem reading the file.

XmlReader

public XmlReader(InputStream is,
                 String httpContentType,
                 String defaultEncoding,
                 boolean lenient)
          throws IOException,
                 XmlReaderException
Creates a Reader using an InputStream an the associated content-type header. This constructor is lenient regarding the encoding detection.

First it checks if the stream has BOM. If there is not BOM checks the content-type encoding. If there is not content-type encoding checks the XML prolog encoding. If there is not XML prolog encoding uses the default encoding mandated by the content-type MIME type.

If lenient detection is indicated and the detection above fails as per specifications it then attempts the following:

If the content type was 'text/html' it replaces it with 'text/xml' and tries the detection again.

Else if the XML prolog had a charset encoding that encoding is used.

Else if the content type had a charset encoding that encoding is used.

Else 'UTF-8' is used.

If lenient detection is indicated an XmlReaderException is never thrown.

Parameters:
is - InputStream to create the reader from.
httpContentType - content-type header to use for the resolution of the charset encoding.
defaultEncoding - if non-null, sets the default encoding from UTF-8 to the user specified default
lenient - indicates if the charset encoding detection should be relaxed.
Throws:
IOException - thrown if there is a problem reading the file.
XmlReaderException - thrown if the charset encoding could not be determined according to the specs.
Method Detail

getEncoding

public String getEncoding()
Returns the charset encoding of the XmlReader.

Returns:
charset encoding.

read

public int read(char[] buf,
                int offset,
                int len)
         throws IOException
Overrides:
read in class Reader

close

public void close()
           throws IOException
Closes the XmlReader stream.

Overrides:
close in class Reader
Throws:
IOException - thrown if there was a problem closing the stream.


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