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com.sun.syndication.io
Class XmlReader  view XmlReader download XmlReader.java

java.lang.Object
  extended byjava.io.Reader
      extended bycom.sun.syndication.io.XmlReader

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.


Field Summary
private  java.lang.String _encoding
           
private  java.io.Reader _reader
           
private static java.util.regex.Pattern CHARSET_PATTERN
           
private static java.util.regex.Pattern ENCODING_PATTERN
           
private static java.text.MessageFormat HTTP_EX_1
           
private static java.text.MessageFormat HTTP_EX_2
           
private static java.text.MessageFormat HTTP_EX_3
           
private static int PUSHBACK_MAX_SIZE
           
private static java.text.MessageFormat RAW_EX_1
           
private static java.text.MessageFormat RAW_EX_2
           
private static java.lang.String US_ASCII
           
private static java.lang.String UTF_16
           
private static java.lang.String UTF_16BE
           
private static java.lang.String UTF_16LE
           
private static java.lang.String UTF_8
           
 
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
private static java.lang.String calculateHttpEncoding(java.lang.String cTMime, java.lang.String cTEnc, java.lang.String bomEnc, java.lang.String xmlGuessEnc, java.lang.String xmlEnc, java.io.InputStream is, boolean lenient)
           
private static java.lang.String calculateRawEncoding(java.lang.String bomEnc, java.lang.String xmlGuessEnc, java.lang.String xmlEnc, java.io.InputStream is)
           
 void close()
          Closes the XmlReader stream.
private  void doHttpStream(java.io.InputStream is, java.lang.String httpContentType, boolean lenient)
           
private  void doLenientDetection(java.lang.String httpContentType, XmlReaderException ex)
           
private  void doRawStream(java.io.InputStream is, boolean lenient)
           
private static java.lang.String getBOMEncoding(java.io.PushbackInputStream is)
           
private static java.lang.String getContentTypeEncoding(java.lang.String httpContentType)
           
private static java.lang.String getContentTypeMime(java.lang.String httpContentType)
           
 java.lang.String getEncoding()
          Returns the charset encoding of the XmlReader.
private static java.lang.String getXMLGuessEncoding(java.io.PushbackInputStream is)
           
private static java.lang.String getXmlProlog(java.io.PushbackInputStream is, java.lang.String guessedEnc)
           
private static boolean isAppXml(java.lang.String mime)
           
private static boolean isTextXml(java.lang.String mime)
           
private  void prepareReader(java.io.InputStream is, java.lang.String encoding)
           
 int read(char[] buf, int offset, int len)
          Read chars from a stream and stores them into a caller supplied buffer.
 
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
 

Field Detail

PUSHBACK_MAX_SIZE

private static final int PUSHBACK_MAX_SIZE
See Also:
Constant Field Values

UTF_8

private static final java.lang.String UTF_8
See Also:
Constant Field Values

US_ASCII

private static final java.lang.String US_ASCII
See Also:
Constant Field Values

UTF_16BE

private static final java.lang.String UTF_16BE
See Also:
Constant Field Values

UTF_16LE

private static final java.lang.String UTF_16LE
See Also:
Constant Field Values

UTF_16

private static final java.lang.String UTF_16
See Also:
Constant Field Values

_reader

private java.io.Reader _reader

_encoding

private java.lang.String _encoding

CHARSET_PATTERN

private static final java.util.regex.Pattern CHARSET_PATTERN

ENCODING_PATTERN

private static final java.util.regex.Pattern ENCODING_PATTERN

RAW_EX_1

private static final java.text.MessageFormat RAW_EX_1

RAW_EX_2

private static final java.text.MessageFormat RAW_EX_2

HTTP_EX_1

private static final java.text.MessageFormat HTTP_EX_1

HTTP_EX_2

private static final java.text.MessageFormat HTTP_EX_2

HTTP_EX_3

private static final java.text.MessageFormat HTTP_EX_3
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.


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.


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.


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.


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.


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.


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.

Method Detail

doLenientDetection

private void doLenientDetection(java.lang.String httpContentType,
                                XmlReaderException ex)
                         throws java.io.IOException

getEncoding

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


read

public int read(char[] buf,
                int offset,
                int len)
         throws java.io.IOException
Description copied from class: java.io.Reader
Read chars from a stream and stores them into a caller supplied buffer. It starts storing the data at index offset into the buffer and attempts to read len chars. This method can return before reading the number of chars requested. The actual number of chars read is returned as an int. A -1 is returned to indicate the end of the stream.

This method will block until some data can be read.

This method operates by calling the single char read() method in a loop until the desired number of chars are read. The read loop stops short if the end of the stream is encountered or if an IOException is encountered on any read operation except the first. If the first attempt to read a chars fails, the IOException is allowed to propagate upward. And subsequent IOException is caught and treated identically to an end of stream condition. Subclasses can (and should if possible) override this method to provide a more efficient implementation.


close

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


doRawStream

private void doRawStream(java.io.InputStream is,
                         boolean lenient)
                  throws java.io.IOException

doHttpStream

private void doHttpStream(java.io.InputStream is,
                          java.lang.String httpContentType,
                          boolean lenient)
                   throws java.io.IOException

prepareReader

private void prepareReader(java.io.InputStream is,
                           java.lang.String encoding)
                    throws java.io.IOException

calculateRawEncoding

private static java.lang.String calculateRawEncoding(java.lang.String bomEnc,
                                                     java.lang.String xmlGuessEnc,
                                                     java.lang.String xmlEnc,
                                                     java.io.InputStream is)
                                              throws java.io.IOException

calculateHttpEncoding

private static java.lang.String calculateHttpEncoding(java.lang.String cTMime,
                                                      java.lang.String cTEnc,
                                                      java.lang.String bomEnc,
                                                      java.lang.String xmlGuessEnc,
                                                      java.lang.String xmlEnc,
                                                      java.io.InputStream is,
                                                      boolean lenient)
                                               throws java.io.IOException

getContentTypeMime

private static java.lang.String getContentTypeMime(java.lang.String httpContentType)

getContentTypeEncoding

private static java.lang.String getContentTypeEncoding(java.lang.String httpContentType)

getBOMEncoding

private static java.lang.String getBOMEncoding(java.io.PushbackInputStream is)
                                        throws java.io.IOException

getXMLGuessEncoding

private static java.lang.String getXMLGuessEncoding(java.io.PushbackInputStream is)
                                             throws java.io.IOException

getXmlProlog

private static java.lang.String getXmlProlog(java.io.PushbackInputStream is,
                                             java.lang.String guessedEnc)
                                      throws java.io.IOException

isAppXml

private static boolean isAppXml(java.lang.String mime)

isTextXml

private static boolean isTextXml(java.lang.String mime)