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 Voodoo 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 a 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.

    To build an instance, see XmlStreamReader.Builder.

    Originally developed for ROME under Apache License 2.0.

    Since:
    2.0
    See Also:
    XmlStreamWriter
    • Field Detail

      • UTF_8

        private static final java.lang.String UTF_8
      • US_ASCII

        private static final java.lang.String US_ASCII
      • UTF_16BE

        private static final java.lang.String UTF_16BE
      • UTF_16LE

        private static final java.lang.String UTF_16LE
      • UTF_16

        private static final java.lang.String UTF_16
      • XML_GUESS_BYTES

        private static final ByteOrderMark[] XML_GUESS_BYTES
        UTF_16LE and UTF_32LE have the same two starting BOM bytes.
      • CHARSET_PATTERN

        private static final java.util.regex.Pattern CHARSET_PATTERN
      • ENCODING_PATTERN

        public static final java.util.regex.Pattern ENCODING_PATTERN
        Pattern capturing the encoding of the "xml" processing instruction.
      • reader

        private final java.io.Reader reader
      • encoding

        private final java.lang.String encoding
      • defaultEncoding

        private final java.lang.String defaultEncoding
    • Constructor Detail

      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.io.File file)
                        throws java.io.IOException
        Constructs 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.lang.NullPointerException - if the input is null.
        java.io.IOException - thrown if there is a problem reading the file.
      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.io.InputStream inputStream)
                        throws java.io.IOException
        Constructs 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:
        inputStream - InputStream to create a Reader from.
        Throws:
        java.lang.NullPointerException - if the input stream is null.
        java.io.IOException - thrown if there is a problem reading the stream.
      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.io.InputStream inputStream,
                               boolean lenient)
                        throws java.io.IOException
        Constructs 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:
        inputStream - InputStream to create a Reader from.
        lenient - indicates if the charset encoding detection should be relaxed.
        Throws:
        java.lang.NullPointerException - if the input stream is null.
        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 specification.
      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.io.InputStream inputStream,
                               boolean lenient,
                               java.lang.String defaultEncoding)
                        throws java.io.IOException
        Constructs 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:
        inputStream - InputStream to create a Reader from.
        lenient - indicates if the charset encoding detection should be relaxed.
        defaultEncoding - The default encoding
        Throws:
        java.lang.NullPointerException - if the input stream is null.
        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 specification.
      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.io.InputStream inputStream,
                               java.lang.String httpContentType)
                        throws java.io.IOException
        Constructs a Reader using an InputStream and 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:
        inputStream - InputStream to create the reader from.
        httpContentType - content-type header to use for the resolution of the charset encoding.
        Throws:
        java.lang.NullPointerException - if the input stream is null.
        java.io.IOException - thrown if there is a problem reading the file.
      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.io.InputStream inputStream,
                               java.lang.String httpContentType,
                               boolean lenient)
                        throws java.io.IOException
        Constructs a Reader using an InputStream and 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:
        inputStream - 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.lang.NullPointerException - if the input stream is null.
        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 specification.
      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.io.InputStream inputStream,
                               java.lang.String httpContentType,
                               boolean lenient,
                               java.lang.String defaultEncoding)
                        throws java.io.IOException
        Constructs a Reader using an InputStream and 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:
        inputStream - 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.lang.NullPointerException - if the input stream is null.
        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 specification.
      • XmlStreamReader

        @Deprecated
        public XmlStreamReader​(java.nio.file.Path file)
                        throws java.io.IOException
        Constructs 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.lang.NullPointerException - if the input is null.
        java.io.IOException - thrown if there is a problem reading the file.
        Since:
        2.11.0
      • XmlStreamReader

        public XmlStreamReader​(java.net.URL url)
                        throws java.io.IOException
        Constructs 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.lang.NullPointerException - if the input is null.
        java.io.IOException - thrown if there is a problem reading the stream of the URL.
      • XmlStreamReader

        public XmlStreamReader​(java.net.URLConnection urlConnection,
                               java.lang.String defaultEncoding)
                        throws java.io.IOException
        Constructs 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:
        urlConnection - URLConnection to create a Reader from.
        defaultEncoding - The default encoding
        Throws:
        java.lang.NullPointerException - if the input is null.
        java.io.IOException - thrown if there is a problem reading the stream of the URLConnection.
    • Method Detail

      • getContentTypeEncoding

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

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

        private static java.lang.String getXmlProlog​(java.io.InputStream inputStream,
                                                     java.lang.String guessedEnc)
                                              throws java.io.IOException
        Gets the encoding declared in the , NULL if none.
        Parameters:
        inputStream - 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)
        Tests 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)
        Tests 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
      • 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
        Calculates 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.
      • 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.
      • 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.
      • doLenientDetection

        private java.lang.String doLenientDetection​(java.lang.String httpContentType,
                                                    XmlStreamReaderException ex)
                                             throws java.io.IOException
        Does 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.
      • 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.
      • getDefaultEncoding

        public java.lang.String getDefaultEncoding()
        Gets 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()
        Gets the charset encoding of the XmlStreamReader.
        Returns:
        charset encoding.
      • processHttpStream

        private java.lang.String processHttpStream​(BOMInputStream bomInput,
                                                   BOMInputStream piInput,
                                                   java.lang.String httpContentType,
                                                   boolean lenient)
                                            throws java.io.IOException
        Processes an HTTP stream.
        Parameters:
        bomInput - BOMInputStream to detect byte order marks
        piInput - 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.
      • read

        public int read​(char[] buf,
                        int offset,
                        int len)
                 throws java.io.IOException
        Reads 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.