Class XmlStreamReader
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Readable
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:
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final ByteOrderMark[]
private static final Pattern
private final String
private static final String
private final String
static final Pattern
Pattern capturing the encoding of the "xml" processing instruction.private static final String
private static final String
private static final String
private static final String
private static final String
private final Reader
private static final String
private static final String
private static final String
private static final String
private static final String
private static final String
private static final String
private static final String
private static final ByteOrderMark[]
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Constructor Summary
ConstructorsConstructorDescriptionXmlStreamReader
(File file) Creates a Reader for a File.XmlStreamReader
(InputStream inputStream) Creates a Reader for a raw InputStream.XmlStreamReader
(InputStream inputStream, boolean lenient) Creates a Reader for a raw InputStream.XmlStreamReader
(InputStream inputStream, boolean lenient, String defaultEncoding) Creates a Reader for a raw InputStream.XmlStreamReader
(InputStream inputStream, String httpContentType) Creates a Reader using an InputStream and the associated content-type header.XmlStreamReader
(InputStream inputStream, String httpContentType, boolean lenient) Creates a Reader using an InputStream and the associated content-type header.XmlStreamReader
(InputStream inputStream, String httpContentType, boolean lenient, String defaultEncoding) Creates a Reader using an InputStream and the associated content-type header.XmlStreamReader
(URL url) Creates a Reader using the InputStream of a URL.XmlStreamReader
(URLConnection conn, String defaultEncoding) Creates a Reader using the InputStream of a URLConnection.XmlStreamReader
(Path file) Creates a Reader for a File. -
Method Summary
Modifier and TypeMethodDescription(package private) String
calculateHttpEncoding
(String httpContentType, String bomEnc, String xmlGuessEnc, String xmlEnc, boolean lenient) Calculate the HTTP encoding.(package private) String
calculateRawEncoding
(String bomEnc, String xmlGuessEnc, String xmlEnc) Calculate the raw encoding.void
close()
Closes the XmlStreamReader stream.private String
doLenientDetection
(String httpContentType, XmlStreamReaderException ex) Do lenient detection.private String
doRawStream
(BOMInputStream bom, BOMInputStream pis, boolean lenient) Process the raw stream.(package private) static String
getContentTypeEncoding
(String httpContentType) Returns charset parameter value, NULL if not present, NULL if httpContentType is NULL.(package private) static String
getContentTypeMime
(String httpContentType) Returns MIME type or NULL if httpContentType is NULL.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.Returns the charset encoding of the XmlStreamReader.private static String
getXmlProlog
(InputStream inputStream, String guessedEnc) Returns the encoding declared in the <?xml encoding=...?>, NULL if none.(package private) static boolean
Indicates if the MIME type belongs to the APPLICATION XML family.(package private) static boolean
Indicates if the MIME type belongs to the TEXT XML family.private String
processHttpStream
(BOMInputStream bom, BOMInputStream pis, String httpContentType, boolean lenient) Process a HTTP stream.int
read
(char[] buf, int offset, int len) Invokes the underlying reader'sread(char[], int, int)
method.
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Field Details
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UTF_8
- See Also:
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US_ASCII
- See Also:
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UTF_16BE
- See Also:
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UTF_16LE
- See Also:
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UTF_32BE
- See Also:
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UTF_32LE
- See Also:
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UTF_16
- See Also:
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UTF_32
- See Also:
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EBCDIC
- See Also:
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BOMS
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XML_GUESS_BYTES
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CHARSET_PATTERN
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ENCODING_PATTERN
Pattern capturing the encoding of the "xml" processing instruction. -
RAW_EX_1
- See Also:
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RAW_EX_2
- See Also:
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HTTP_EX_1
- See Also:
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HTTP_EX_2
- See Also:
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HTTP_EX_3
- See Also:
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reader
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encoding
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defaultEncoding
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Constructor Details
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XmlStreamReader
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:
IOException
- thrown if there is a problem reading the file.
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XmlStreamReader
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:
IOException
- thrown if there is a problem reading the stream.
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XmlStreamReader
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:
IOException
- thrown if there is a problem reading the stream.XmlStreamReaderException
- thrown if the charset encoding could not be determined according to the specs.
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XmlStreamReader
public XmlStreamReader(InputStream inputStream, boolean lenient, String defaultEncoding) throws 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:
IOException
- thrown if there is a problem reading the stream.XmlStreamReaderException
- thrown if the charset encoding could not be determined according to the specs.
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XmlStreamReader
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:
IOException
- thrown if there is a problem reading the file.
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XmlStreamReader
public XmlStreamReader(InputStream inputStream, String httpContentType, boolean lenient) throws 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:
IOException
- thrown if there is a problem reading the file.XmlStreamReaderException
- thrown if the charset encoding could not be determined according to the specs.
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XmlStreamReader
public XmlStreamReader(InputStream inputStream, String httpContentType, boolean lenient, String defaultEncoding) throws 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:
IOException
- thrown if there is a problem reading the file.XmlStreamReaderException
- thrown if the charset encoding could not be determined according to the specs.
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XmlStreamReader
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:
IOException
- thrown if there is a problem reading the file.- Since:
- 2.11.0
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XmlStreamReader
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:
IOException
- thrown if there is a problem reading the stream of the URL.
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XmlStreamReader
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:
IOException
- thrown if there is a problem reading the stream of the URLConnection.
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Method Details
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getContentTypeEncoding
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)
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getContentTypeMime
Returns MIME type or NULL if httpContentType is NULL.- Parameters:
httpContentType
- the HTTP content type- Returns:
- The mime content type
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getXmlProlog
Returns the encoding declared in the <?xml encoding=...?>, NULL if none.- Parameters:
inputStream
- InputStream to create the reader from.guessedEnc
- guessed encoding- Returns:
- the encoding declared in the <?xml encoding=...?>
- Throws:
IOException
- thrown if there is a problem reading the stream.
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isAppXml
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
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isTextXml
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
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calculateHttpEncoding
String calculateHttpEncoding(String httpContentType, String bomEnc, String xmlGuessEnc, String xmlEnc, boolean lenient) throws IOException Calculate the HTTP encoding.- Parameters:
httpContentType
- The HTTP content typebomEnc
- BOM encodingxmlGuessEnc
- XML Guess encodingxmlEnc
- XML encodinglenient
- indicates if the charset encoding detection should be relaxed.- Returns:
- the HTTP encoding
- Throws:
IOException
- thrown if there is a problem reading the stream.
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calculateRawEncoding
Calculate the raw encoding.- Parameters:
bomEnc
- BOM encodingxmlGuessEnc
- XML Guess encodingxmlEnc
- XML encoding- Returns:
- the raw encoding
- Throws:
IOException
- thrown if there is a problem reading the stream.
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close
Closes the XmlStreamReader stream.- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in classReader
- Throws:
IOException
- thrown if there was a problem closing the stream.
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doLenientDetection
private String doLenientDetection(String httpContentType, XmlStreamReaderException ex) throws 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:
IOException
- thrown if there is a problem reading the stream.
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doRawStream
private String doRawStream(BOMInputStream bom, BOMInputStream pis, boolean lenient) throws IOException Process the raw stream.- Parameters:
bom
- BOMInputStream to detect byte order markspis
- BOMInputStream to guess XML encodinglenient
- indicates if the charset encoding detection should be relaxed.- Returns:
- the encoding to be used
- Throws:
IOException
- thrown if there is a problem reading the stream.
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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.
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getEncoding
Returns the charset encoding of the XmlStreamReader.- Returns:
- charset encoding.
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processHttpStream
private String processHttpStream(BOMInputStream bom, BOMInputStream pis, String httpContentType, boolean lenient) throws IOException Process a HTTP stream.- Parameters:
bom
- BOMInputStream to detect byte order markspis
- BOMInputStream to guess XML encodinghttpContentType
- The HTTP content typelenient
- indicates if the charset encoding detection should be relaxed.- Returns:
- the encoding to be used
- Throws:
IOException
- thrown if there is a problem reading the stream.
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read
Invokes the underlying reader'sread(char[], int, int)
method.- Specified by:
read
in classReader
- Parameters:
buf
- the buffer to read the characters intooffset
- The start offsetlen
- The number of bytes to read- Returns:
- the number of characters read or -1 if the end of stream
- Throws:
IOException
- if an I/O error occurs.
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