Package org.apache.commons.io.input

Class XmlStreamReader

java.lang.Object

java.io.Reader

org.apache.commons.io.input.XmlStreamReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

public class XmlStreamReader
extends 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, use XmlStreamReader.Builder.

Originally developed for ROME under Apache License 2.0.

Since:

2.0

See Also:

• XmlStreamReader.Builder
• XmlStreamWriter

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	XmlStreamReader.Builder	Builds a new XmlStreamReader.

Field Summary

Fields

Modifier and Type	Field	Description
private static final ByteOrderMark[]	BOMS
private static final Pattern	CHARSET_PATTERN
private final String	defaultEncoding
private static final String	EBCDIC
private final String	encoding
static final Pattern	ENCODING_PATTERN	Pattern capturing the encoding of the 'xml' processing instruction.
private static final String	HTTP_EX_1
private static final String	HTTP_EX_2
private static final String	HTTP_EX_3
private static final String	RAW_EX_1
private static final String	RAW_EX_2
private final Reader	reader
private static final String	US_ASCII
private static final String	UTF_16
private static final String	UTF_16BE
private static final String	UTF_16LE
private static final String	UTF_32
private static final String	UTF_32BE
private static final String	UTF_32LE
private static final String	UTF_8
private static final ByteOrderMark[]	XML_GUESS_BYTES	UTF_16LE and UTF_32LE have the same two starting BOM bytes.

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Constructor	Description
XmlStreamReader(File file)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()
XmlStreamReader(InputStream inputStream)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()
XmlStreamReader(InputStream inputStream, boolean lenient)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()
XmlStreamReader(InputStream inputStream, boolean lenient, String defaultEncoding)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()
XmlStreamReader(InputStream inputStream, String httpContentType)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()
XmlStreamReader(InputStream inputStream, String httpContentType, boolean lenient)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()
XmlStreamReader(InputStream inputStream, String httpContentType, boolean lenient, String defaultEncoding)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()
XmlStreamReader(URL url)	Constructs a Reader using the InputStream of a URL.
XmlStreamReader(URLConnection urlConnection, String defaultEncoding)	Constructs a Reader using the InputStream of a URLConnection.
XmlStreamReader(Path file)	Deprecated. Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

Method Summary

Modifier and Type	Method	Description
static XmlStreamReader.Builder	builder()	Constructs a new XmlStreamReader.Builder.
void	close()	Closes the XmlStreamReader stream.
(package private) static String	getContentTypeEncoding(String httpContentType)	Gets the charset parameter value, null if not present, null if httpContentType is null.
(package private) static String	getContentTypeMime(String httpContentType)	Gets the MIME type or null if httpContentType is null.
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.
String	getEncoding()	Gets the charset encoding of the XmlStreamReader.
private static String	getXmlProlog(InputStream inputStream, String guessedEnc)	Gets the encoding declared in the <?xml encoding=...?>, null if none.
(package private) static boolean	isAppXml(String mime)	Tests if the MIME type belongs to the APPLICATION XML family.
(package private) static boolean	isTextXml(String mime)	Tests if the MIME type belongs to the TEXT XML family.
int	read(char[] buf, int offset, int len)	Reads the underlying reader's read(char[], int, int) method.
private String	toEncoding(BOMInputStream bomInput, BOMInputStream piInput, boolean lenient)	Process the raw stream.
private String	toEncoding(BOMInputStream bomInput, BOMInputStream piInput, boolean lenient, String httpContentType)	Processes an HTTP stream.
private String	toEncodingLenient(String httpContentType, XmlStreamReaderException ex)	Detects the encoding in lenient mode.
(package private) String	toHttpEncoding(String bomEnc, String xmlGuessEnc, String xmlEnc, boolean lenient, String httpContentType)	Calculates the HTTP encoding.
(package private) String	toRawEncoding(String bomEnc, String xmlGuessEnc, String xmlEnc)	Calculate the raw encoding.

Methods inherited from class java.io.Reader

mark, markSupported, read, read, read, ready, reset, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

UTF_8

private static final String UTF_8

US_ASCII

private static final String US_ASCII

UTF_16BE

private static final String UTF_16BE

UTF_16LE

private static final String UTF_16LE

UTF_32BE

private static final String UTF_32BE

See Also:

• Constant Field Values

UTF_32LE

private static final String UTF_32LE

See Also:

• Constant Field Values

UTF_16

private static final String UTF_16

UTF_32

private static final String UTF_32

See Also:

• Constant Field Values

EBCDIC

private static final String EBCDIC

See Also:

• Constant Field Values

BOMS

private static final ByteOrderMark[] BOMS

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 Pattern CHARSET_PATTERN

ENCODING_PATTERN

public static final Pattern ENCODING_PATTERN

Pattern capturing the encoding of the 'xml' processing instruction.

See also the NT-EncName XML specification.

Note the documented pattern is:

 EncName   ::=   [A-Za-z] ([A-Za-z0-9._] | '-')*
 

However this does not match all the aliases that are supported by Java. For example, '437', 'ISO_8859-1:1987' and 'ebcdic-de-273+euro'.

RAW_EX_1

private static final String RAW_EX_1

See Also:

• Constant Field Values

RAW_EX_2

private static final String RAW_EX_2

See Also:

• Constant Field Values

HTTP_EX_1

private static final String HTTP_EX_1

See Also:

• Constant Field Values

HTTP_EX_2

private static final String HTTP_EX_2

See Also:

• Constant Field Values

HTTP_EX_3

private static final String HTTP_EX_3

See Also:

• Constant Field Values

reader

private final Reader reader

encoding

private final String encoding

defaultEncoding

private final String defaultEncoding

Constructor Details

XmlStreamReader

@Deprecated
public XmlStreamReader(File file)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input is null.

IOException - thrown if there is a problem reading the file.

XmlStreamReader

@Deprecated
public XmlStreamReader(InputStream inputStream)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input stream is null.

IOException - thrown if there is a problem reading the stream.

XmlStreamReader

@Deprecated
public XmlStreamReader(InputStream inputStream,
 boolean lenient)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input stream is null.

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(InputStream inputStream,
 boolean lenient,
 String defaultEncoding)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input stream is null.

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(InputStream inputStream,
 String httpContentType)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input stream is null.

IOException - thrown if there is a problem reading the file.

XmlStreamReader

@Deprecated
public XmlStreamReader(InputStream inputStream,
 String httpContentType,
 boolean lenient)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input stream is null.

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(InputStream inputStream,
 String httpContentType,
 boolean lenient,
 String defaultEncoding)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input stream is null.

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(Path file)
                throws IOException

Deprecated.

Use builder(), XmlStreamReader.Builder, and XmlStreamReader.Builder.get()

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:

NullPointerException - if the input is null.

IOException - thrown if there is a problem reading the file.

Since:

2.11.0

XmlStreamReader

public XmlStreamReader(URL url)
                throws 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:

NullPointerException - if the input is null.

IOException - thrown if there is a problem reading the stream of the URL.

XmlStreamReader

public XmlStreamReader(URLConnection urlConnection,
 String defaultEncoding)
                throws 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:

NullPointerException - if the input is null.

IOException - thrown if there is a problem reading the stream of the URLConnection.

Method Details

builder

public static XmlStreamReader.Builder builder()

Constructs a new XmlStreamReader.Builder.

Returns:

a new XmlStreamReader.Builder.

Since:

2.12.0

getContentTypeEncoding

static String getContentTypeEncoding(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 String getContentTypeMime(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 String getXmlProlog(InputStream inputStream,
 String guessedEnc)
                            throws IOException

Gets 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.

isAppXml

static boolean isAppXml(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(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.

close

public void close()
           throws IOException

Closes the XmlStreamReader stream.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class Reader

Throws:

IOException - thrown if there was a problem closing the stream.

getDefaultEncoding

public 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 String getEncoding()

Gets the charset encoding of the XmlStreamReader.

Returns:

charset encoding.

read

public int read(char[] buf,
 int offset,
 int len)
         throws IOException

Reads the underlying reader's read(char[], int, int) method.

Specified by:

read in class 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:

IOException - if an I/O error occurs.

toEncoding

private String toEncoding(BOMInputStream bomInput,
 BOMInputStream piInput,
 boolean lenient)
                   throws IOException

Process the raw stream.

Parameters:

bomInput - BOMInputStream to detect byte order marks.

piInput - BOMInputStream to guess XML encoding.

lenient - 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.

toEncoding

private String toEncoding(BOMInputStream bomInput,
 BOMInputStream piInput,
 boolean lenient,
 String httpContentType)
                   throws IOException

Processes an HTTP stream.

Parameters:

bomInput - BOMInputStream to detect byte order marks.

piInput - BOMInputStream to guess XML encoding.

lenient - indicates if the charset encoding detection should be relaxed.

httpContentType - The HTTP content type.

Returns:

the encoding to be used.

Throws:

IOException - thrown if there is a problem reading the stream.

toEncodingLenient

private String toEncodingLenient(String httpContentType,
 XmlStreamReaderException ex)
                          throws IOException

Detects the encoding in lenient mode.

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.

toHttpEncoding

String toHttpEncoding(String bomEnc,
 String xmlGuessEnc,
 String xmlEnc,
 boolean lenient,
 String httpContentType)
               throws IOException

Calculates the HTTP encoding.

Parameters:

bomEnc - BOM encoding.

xmlGuessEnc - XML Guess encoding.

xmlEnc - XML encoding.

lenient - indicates if the charset encoding detection should be relaxed.

httpContentType - The HTTP content type.

Returns:

the HTTP encoding.

Throws:

IOException - thrown if there is a problem reading the stream.

toRawEncoding

String toRawEncoding(String bomEnc,
 String xmlGuessEnc,
 String xmlEnc)
              throws IOException

Calculate the raw encoding.

Parameters:

bomEnc - BOM encoding.

xmlGuessEnc - XML Guess encoding.

xmlEnc - XML encoding.

Returns:

the raw encoding.

Throws:

IOException - thrown if there is a problem reading the stream.