Class XmlStreamReader

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, java.lang.Readable

    public class XmlStreamReader
    extends java.io.Reader
    Character stream that handles 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, XmlStreamReader handles it and things work in all parsers).

    The XmlStreamReader 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.

    Originally developed for ROME under Apache License 2.0.

    Since:
    2.0
    Version:
    $Id: XmlStreamReader.java 1346400 2012-06-05 14:48:01Z ggregory $
    See Also:
    XmlStreamWriter
    • Constructor Summary

      Constructors 
      Constructor Description
      XmlStreamReader​(java.io.File file)
      Creates a Reader for a File.
      XmlStreamReader​(java.io.InputStream is)
      Creates a Reader for a raw InputStream.
      XmlStreamReader​(java.io.InputStream is, boolean lenient)
      Creates a Reader for a raw InputStream.
      XmlStreamReader​(java.io.InputStream is, boolean lenient, java.lang.String defaultEncoding)
      Creates a Reader for a raw InputStream.
      XmlStreamReader​(java.io.InputStream is, java.lang.String httpContentType)
      Creates a Reader using an InputStream an the associated content-type header.
      XmlStreamReader​(java.io.InputStream is, java.lang.String httpContentType, boolean lenient)
      Creates a Reader using an InputStream an the associated content-type header.
      XmlStreamReader​(java.io.InputStream is, java.lang.String httpContentType, boolean lenient, java.lang.String defaultEncoding)
      Creates a Reader using an InputStream an the associated content-type header.
      XmlStreamReader​(java.net.URL url)
      Creates a Reader using the InputStream of a URL.
      XmlStreamReader​(java.net.URLConnection conn, java.lang.String defaultEncoding)
      Creates a Reader using the InputStream of a URLConnection.
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      (package private) java.lang.String calculateHttpEncoding​(java.lang.String httpContentType, java.lang.String bomEnc, java.lang.String xmlGuessEnc, java.lang.String xmlEnc, boolean lenient)
      Calculate the HTTP encoding.
      (package private) java.lang.String calculateRawEncoding​(java.lang.String bomEnc, java.lang.String xmlGuessEnc, java.lang.String xmlEnc)
      Calculate the raw encoding.
      void close()
      Closes the XmlStreamReader stream.
      private java.lang.String doHttpStream​(BOMInputStream bom, BOMInputStream pis, java.lang.String httpContentType, boolean lenient)
      Process a HTTP stream.
      private java.lang.String doLenientDetection​(java.lang.String httpContentType, XmlStreamReaderException ex)
      Do lenient detection.
      private java.lang.String doRawStream​(BOMInputStream bom, BOMInputStream pis, boolean lenient)
      Process the raw stream.
      (package private) static java.lang.String getContentTypeEncoding​(java.lang.String httpContentType)
      Returns charset parameter value, NULL if not present, NULL if httpContentType is NULL.
      (package private) static java.lang.String getContentTypeMime​(java.lang.String httpContentType)
      Returns MIME type or NULL if httpContentType is NULL.
      java.lang.String getDefaultEncoding()
      Returns the default encoding to use if none is set in HTTP content-type, XML prolog and the rules based on content-type are not adequate.
      java.lang.String getEncoding()
      Returns the charset encoding of the XmlStreamReader.
      private static java.lang.String getXmlProlog​(java.io.InputStream is, java.lang.String guessedEnc)
      Returns the encoding declared in the , NULL if none.
      (package private) static boolean isAppXml​(java.lang.String mime)
      Indicates if the MIME type belongs to the APPLICATION XML family.
      (package private) static boolean isTextXml​(java.lang.String mime)
      Indicates if the MIME type belongs to the TEXT XML family.
      int read​(char[] buf, int offset, int len)
      Invokes the underlying reader's read(char[], int, int) method.
      • Methods inherited from class java.io.Reader

        mark, markSupported, nullReader, read, read, read, ready, reset, skip, transferTo
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • XmlStreamReader

        public XmlStreamReader​(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.
      • XmlStreamReader

        public XmlStreamReader​(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.
      • XmlStreamReader

        public XmlStreamReader​(java.io.InputStream is,
                               boolean lenient)
                        throws java.io.IOException
        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 XmlStreamReaderException 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.
        XmlStreamReaderException - thrown if the charset encoding could not be determined according to the specs.
      • XmlStreamReader

        public XmlStreamReader​(java.io.InputStream is,
                               boolean lenient,
                               java.lang.String defaultEncoding)
                        throws java.io.IOException
        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 XmlStreamReaderException is never thrown.

        Parameters:
        is - InputStream to create a Reader from.
        lenient - indicates if the charset encoding detection should be relaxed.
        defaultEncoding - The default encoding
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream.
        XmlStreamReaderException - thrown if the charset encoding could not be determined according to the specs.
      • XmlStreamReader

        public XmlStreamReader​(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.
      • XmlStreamReader

        public XmlStreamReader​(java.net.URLConnection conn,
                               java.lang.String defaultEncoding)
                        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.
        defaultEncoding - The default encoding
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream of the URLConnection.
      • XmlStreamReader

        public XmlStreamReader​(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.
      • XmlStreamReader

        public XmlStreamReader​(java.io.InputStream is,
                               java.lang.String httpContentType,
                               boolean lenient,
                               java.lang.String defaultEncoding)
                        throws java.io.IOException
        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 XmlStreamReaderException 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.
        defaultEncoding - The default encoding
        Throws:
        java.io.IOException - thrown if there is a problem reading the file.
        XmlStreamReaderException - thrown if the charset encoding could not be determined according to the specs.
      • XmlStreamReader

        public XmlStreamReader​(java.io.InputStream is,
                               java.lang.String httpContentType,
                               boolean lenient)
                        throws java.io.IOException
        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 XmlStreamReaderException 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.
        XmlStreamReaderException - thrown if the charset encoding could not be determined according to the specs.
    • Method Detail

      • getDefaultEncoding

        public java.lang.String getDefaultEncoding()
        Returns the default encoding to use if none is set in HTTP content-type, XML prolog and the rules based on content-type are not adequate.

        If it is NULL the content-type based rules are used.

        Returns:
        the default encoding to use.
      • getEncoding

        public java.lang.String getEncoding()
        Returns the charset encoding of the XmlStreamReader.
        Returns:
        charset encoding.
      • read

        public int read​(char[] buf,
                        int offset,
                        int len)
                 throws java.io.IOException
        Invokes the underlying reader's read(char[], int, int) method.
        Specified by:
        read in class java.io.Reader
        Parameters:
        buf - the buffer to read the characters into
        offset - The start offset
        len - The number of bytes to read
        Returns:
        the number of characters read or -1 if the end of stream
        Throws:
        java.io.IOException - if an I/O error occurs
      • close

        public void close()
                   throws java.io.IOException
        Closes the XmlStreamReader stream.
        Specified by:
        close in interface java.lang.AutoCloseable
        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.
      • doRawStream

        private java.lang.String doRawStream​(BOMInputStream bom,
                                             BOMInputStream pis,
                                             boolean lenient)
                                      throws java.io.IOException
        Process the raw stream.
        Parameters:
        bom - BOMInputStream to detect byte order marks
        pis - BOMInputStream to guess XML encoding
        lenient - indicates if the charset encoding detection should be relaxed.
        Returns:
        the encoding to be used
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream.
      • doHttpStream

        private java.lang.String doHttpStream​(BOMInputStream bom,
                                              BOMInputStream pis,
                                              java.lang.String httpContentType,
                                              boolean lenient)
                                       throws java.io.IOException
        Process a HTTP stream.
        Parameters:
        bom - BOMInputStream to detect byte order marks
        pis - BOMInputStream to guess XML encoding
        httpContentType - The HTTP content type
        lenient - indicates if the charset encoding detection should be relaxed.
        Returns:
        the encoding to be used
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream.
      • doLenientDetection

        private java.lang.String doLenientDetection​(java.lang.String httpContentType,
                                                    XmlStreamReaderException ex)
                                             throws java.io.IOException
        Do lenient detection.
        Parameters:
        httpContentType - content-type header to use for the resolution of the charset encoding.
        ex - The thrown exception
        Returns:
        the encoding
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream.
      • calculateRawEncoding

        java.lang.String calculateRawEncoding​(java.lang.String bomEnc,
                                              java.lang.String xmlGuessEnc,
                                              java.lang.String xmlEnc)
                                       throws java.io.IOException
        Calculate the raw encoding.
        Parameters:
        bomEnc - BOM encoding
        xmlGuessEnc - XML Guess encoding
        xmlEnc - XML encoding
        Returns:
        the raw encoding
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream.
      • calculateHttpEncoding

        java.lang.String calculateHttpEncoding​(java.lang.String httpContentType,
                                               java.lang.String bomEnc,
                                               java.lang.String xmlGuessEnc,
                                               java.lang.String xmlEnc,
                                               boolean lenient)
                                        throws java.io.IOException
        Calculate the HTTP encoding.
        Parameters:
        httpContentType - The HTTP content type
        bomEnc - BOM encoding
        xmlGuessEnc - XML Guess encoding
        xmlEnc - XML encoding
        lenient - indicates if the charset encoding detection should be relaxed.
        Returns:
        the HTTP encoding
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream.
      • getContentTypeMime

        static java.lang.String getContentTypeMime​(java.lang.String httpContentType)
        Returns MIME type or NULL if httpContentType is NULL.
        Parameters:
        httpContentType - the HTTP content type
        Returns:
        The mime content type
      • getContentTypeEncoding

        static java.lang.String getContentTypeEncoding​(java.lang.String httpContentType)
        Returns charset parameter value, NULL if not present, NULL if httpContentType is NULL.
        Parameters:
        httpContentType - the HTTP content type
        Returns:
        The content type encoding (upcased)
      • getXmlProlog

        private static java.lang.String getXmlProlog​(java.io.InputStream is,
                                                     java.lang.String guessedEnc)
                                              throws java.io.IOException
        Returns the encoding declared in the , NULL if none.
        Parameters:
        is - InputStream to create the reader from.
        guessedEnc - guessed encoding
        Returns:
        the encoding declared in the
        Throws:
        java.io.IOException - thrown if there is a problem reading the stream.
      • isAppXml

        static boolean isAppXml​(java.lang.String mime)
        Indicates if the MIME type belongs to the APPLICATION XML family.
        Parameters:
        mime - The mime type
        Returns:
        true if the mime type belongs to the APPLICATION XML family, otherwise false
      • isTextXml

        static boolean isTextXml​(java.lang.String mime)
        Indicates if the MIME type belongs to the TEXT XML family.
        Parameters:
        mime - The mime type
        Returns:
        true if the mime type belongs to the TEXT XML family, otherwise false