Package org.apache.commons.io.input

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.

    Originally developed for ROME under Apache License 2.0.

    Since:
    2.0
    See Also:
    XmlStreamWriter

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.util.regex.Pattern ENCODING_PATTERN
      Pattern capturing the encoding of the "xml" processing instruction.

      • Fields inherited from class java.io.Reader

        lock

    • Constructor Summary

      Constructors 
      Constructor Description
      XmlStreamReader​(java.io.File file)
      Creates a Reader for a File.
      XmlStreamReader​(java.io.InputStream inputStream)
      Creates a Reader for a raw InputStream.
      XmlStreamReader​(java.io.InputStream inputStream, boolean lenient)
      Creates a Reader for a raw InputStream.
      XmlStreamReader​(java.io.InputStream inputStream, boolean lenient, java.lang.String defaultEncoding)
      Creates a Reader for a raw InputStream.
      XmlStreamReader​(java.io.InputStream inputStream, java.lang.String httpContentType)
      Creates a Reader using an InputStream and the associated content-type header.
      XmlStreamReader​(java.io.InputStream inputStream, java.lang.String httpContentType, boolean lenient)
      Creates a Reader using an InputStream and the associated content-type header.
      XmlStreamReader​(java.io.InputStream inputStream, java.lang.String httpContentType, boolean lenient, java.lang.String defaultEncoding)
      Creates a Reader using an InputStream and 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.
      XmlStreamReader​(java.nio.file.Path file)
      Creates a Reader for a File.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void close()
      Closes the XmlStreamReader stream.
      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.
      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

    • Field Detail

      • ENCODING_PATTERN

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

    • 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 inputStream)
                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:
        inputStream - 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 inputStream,
                       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:
        inputStream - 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 inputStream,
                       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:
        inputStream - 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.io.InputStream inputStream,
                       java.lang.String httpContentType)
                throws java.io.IOException
        Creates 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.io.IOException - thrown if there is a problem reading the file.

      • XmlStreamReader

        public XmlStreamReader​(java.io.InputStream inputStream,
                       java.lang.String httpContentType,
                       boolean lenient)
                throws java.io.IOException
        Creates 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.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 inputStream,
                       java.lang.String httpContentType,
                       boolean lenient,
                       java.lang.String defaultEncoding)
                throws java.io.IOException
        Creates 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.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.nio.file.Path 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.
        Since:
        2.11.0

      • 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.

    • Method Detail

      • 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.

      • 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.