Package org.apache.camel.xml.io.util

Class XmlStreamReader

java.lang.Object

java.io.Reader

org.apache.camel.xml.io.util.XmlStreamReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

public class XmlStreamReader
extends Reader

Character stream that handles (or at least attempts to) 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, XmlReader handles it and things work in all parsers).

The XmlReader 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.

Field Summary

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Constructor	Description
XmlStreamReader(File file)	Creates a Reader for a File.
XmlStreamReader(InputStream is)	Creates a Reader for a raw InputStream.
XmlStreamReader(InputStream is, boolean lenient)	Creates a Reader for a raw InputStream.
XmlStreamReader(InputStream is, boolean lenient, String defaultEncoding)	Creates a Reader for a raw InputStream and uses the provided default encoding if none is determined.
XmlStreamReader(InputStream is, String httpContentType)	Creates a Reader using an InputStream and the associated content-type header.
XmlStreamReader(InputStream is, String httpContentType, boolean lenient)	Creates a Reader using an InputStream and the associated content-type header.
XmlStreamReader(InputStream is, 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)	Creates a Reader using the InputStream of a URLConnection.
XmlStreamReader(URLConnection conn, Map<String,String> requestHeaders)	Creates a Reader using the InputStream of a URLConnection.
XmlStreamReader(URL url, Map<String,String> requestHeaders)	Creates a Reader using the InputStream of a URL.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the XmlReader stream.
static 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.
String	getEncoding()	Returns the charset encoding of the XmlReader.
int	read(char[] buf, int offset, int len)
static void	setDefaultEncoding(String encoding)	Sets 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.

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(File file)
                throws 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:

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

XmlStreamReader

public XmlStreamReader(InputStream is)
                throws 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:

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

XmlStreamReader

public XmlStreamReader(InputStream is,
                       boolean lenient,
                       String defaultEncoding)
                throws IOException,
                       XmlStreamReaderException

Creates a Reader for a raw InputStream and uses the provided default encoding if none is determined.

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 - default encoding to use if one cannot be detected.

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.

XmlStreamReader

public XmlStreamReader(InputStream is,
                       boolean lenient)
                throws IOException,
                       XmlStreamReaderException

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:

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(URL url)
                throws 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:

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

XmlStreamReader

public XmlStreamReader(URL url,
                       Map<String,String> requestHeaders)
                throws 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.

requestHeaders - optional Map of headers to set on http request.

Throws:

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

XmlStreamReader

public XmlStreamReader(URLConnection conn)
                throws 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.

Throws:

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

XmlStreamReader

public XmlStreamReader(URLConnection conn,
                       Map<String,String> requestHeaders)
                throws 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.

requestHeaders - optional Map of headers to set on http request.

Throws:

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

XmlStreamReader

public XmlStreamReader(InputStream is,
                       String httpContentType)
                throws 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:

is - 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.

XmlStreamReader

public XmlStreamReader(InputStream is,
                       String httpContentType,
                       boolean lenient,
                       String defaultEncoding)
                throws IOException,
                       XmlStreamReaderException

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.

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 and 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 - default encoding to use if one cannot be detected.

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.

XmlStreamReader

public XmlStreamReader(InputStream is,
                       String httpContentType,
                       boolean lenient)
                throws IOException,
                       XmlStreamReaderException

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.

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 and 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:

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 static 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.

setDefaultEncoding

public static void setDefaultEncoding(String encoding)

Sets 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 set to NULL the content-type based rules are used.

By default it is NULL.

Parameters:

encoding - charset encoding to default to.

getEncoding

public String getEncoding()

Returns the charset encoding of the XmlReader.

Returns:

charset encoding.

read

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

Specified by:

read in class Reader

Throws:

IOException

close

public void close()
           throws IOException

Closes the XmlReader 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.