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org.bounce.com.sun.syndication.io
Class XmlReader

java.lang.Object
  extended by java.io.Reader
      extended by org.bounce.com.sun.syndication.io.XmlReader
All Implemented Interfaces:
java.io.Closeable, java.lang.Readable

public class XmlReader
extends java.io.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.

Author:
Alejandro Abdelnur

Field Summary
 
Fields inherited from class java.io.Reader
lock
 
Constructor Summary
XmlReader(java.io.File file)
          Creates a Reader for a File.
XmlReader(java.io.InputStream is)
          Creates a Reader for a raw InputStream.
XmlReader(java.io.InputStream is, boolean lenient)
          Creates a Reader for a raw InputStream.
XmlReader(java.io.InputStream is, java.lang.String httpContentType)
          Creates a Reader using an InputStream an the associated content-type header.
XmlReader(java.io.InputStream is, java.lang.String httpContentType, boolean lenient)
          Creates a Reader using an InputStream an the associated content-type header.
XmlReader(java.net.URL url)
          Creates a Reader using the InputStream of a URL.
XmlReader(java.net.URLConnection conn)
          Creates a Reader using the InputStream of a URLConnection.
 
Method Summary
 void close()
          Closes the XmlReader stream.
 java.lang.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, 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(java.io.File file)
          throws java.io.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:
java.io.IOException - thrown if there is a problem reading the file.

XmlReader

public XmlReader(java.io.InputStream is)
          throws java.io.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:
java.io.IOException - thrown if there is a problem reading the stream.

XmlReader

public XmlReader(java.io.InputStream is,
                 boolean lenient)
          throws java.io.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.
lenient - indicates if the charset encoding detection should be relaxed.
Throws:
java.io.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(java.net.URL url)
          throws java.io.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:
java.io.IOException - thrown if there is a problem reading the stream of the URL.

XmlReader

public XmlReader(java.net.URLConnection conn)
          throws java.io.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:
java.io.IOException - thrown if there is a problem reading the stream of the URLConnection.

XmlReader

public XmlReader(java.io.InputStream is,
                 java.lang.String httpContentType)
          throws java.io.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:
java.io.IOException - thrown if there is a problem reading the file.

XmlReader

public XmlReader(java.io.InputStream is,
                 java.lang.String httpContentType,
                 boolean lenient)
          throws java.io.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.
lenient - indicates if the charset encoding detection should be relaxed.
Throws:
java.io.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 java.lang.String getEncoding()
Returns the charset encoding of the XmlReader.

Returns:
charset encoding.

read

public int read(char[] buf,
                int offset,
                int len)
         throws java.io.IOException
Specified by:
read in class java.io.Reader
Throws:
java.io.IOException

close

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

Specified by:
close in interface java.io.Closeable
Specified by:
close in class java.io.Reader
Throws:
java.io.IOException - thrown if there was a problem closing the stream.

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