Package org.hortonmachine.gears.utils.style.sld

Class XmlCharsetDetector

java.lang.Object

org.hortonmachine.gears.utils.style.sld.XmlCharsetDetector

public class XmlCharsetDetector
extends Object

Provides a methods that can be used to detect charset of some XML document and (optionally) return a reader that is aware of this charset and can correctly decode document's data.

Field Summary

Fields

Modifier and Type	Field	Description
protected static Logger	LOGGER

Constructor Summary

Constructors

Constructor	Description
XmlCharsetDetector()

Method Summary

Modifier and Type	Method	Description
static Reader	createReader(InputStream istream, EncodingInfo encInfo)	Creates a new reader on top of the given InputStream using existing (external) encoding information.
static Reader	getCharsetAwareReader(InputStream istream)	Use this variant when you aren't interested in encoding data, and just want to get a suitable reader for incoming request.
static Reader	getCharsetAwareReader(InputStream istream, EncodingInfo encInfo)	Based on Xerces-J code, this method will try its best to return a reader which is able to decode content of incoming XML document properly.
static EncodingInfo	getEncodingName(byte[] b4, int count)	Returns the IANA encoding name that is auto-detected from the bytes specified, with the endian-ness of that encoding where appropriate.
protected static String	getXmlEncoding(Reader reader)	Gets the encoding of the xml request made to the dispatcher.

Methods inherited from class java.lang.Object

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

Field Detail

LOGGER

protected static Logger LOGGER

Constructor Detail

XmlCharsetDetector

public XmlCharsetDetector()

Method Detail

getCharsetAwareReader

public static Reader getCharsetAwareReader(InputStream istream,
                                           EncodingInfo encInfo)
                                    throws IOException,
                                           UnsupportedCharsetException

Based on Xerces-J code, this method will try its best to return a reader which is able to decode content of incoming XML document properly. To achieve this goal, it first infers general encoding scheme of the above document and then uses this information to extract actual charset from XML declaration. In any recoverable error situation default UTF-8 reader will be created.

Parameters:

istream - Byte stream (most probably obtained with HttpServletRequest.getInputStream that gives access to XML document in question).

encInfo - Instance of EncodingInfo where information about detected charset will be stored. You can then use it, for example, to form a response encoded with this charset.

Throws:

IOException - in case of any unrecoverable I/O errors.

UnsupportedCharsetException - InputStreamReader's constructor will probably throw this exception if inferred charset of XML document is not supported by current JVM.

getCharsetAwareReader

public static Reader getCharsetAwareReader(InputStream istream)
                                    throws IOException,
                                           UnsupportedCharsetException

Use this variant when you aren't interested in encoding data, and just want to get a suitable reader for incoming request.

Parameters:

istream - See getCharsetAwareReader(InputStream, EncodingInfo).

Throws:

IOException

UnsupportedCharsetException

createReader

public static Reader createReader(InputStream istream,
                                  EncodingInfo encInfo)
                           throws IllegalArgumentException,
                                  UnsupportedEncodingException

Creates a new reader on top of the given InputStream using existing (external) encoding information. Unlike getCharsetAwareReader, this method never tries to detect charset or encoding scheme of InputStream's data. This also means that it must be provided with valid EncodingInfo instance, which may be obtained, for example, from previous getCharsetAwareReader(InputStream, EncodingInfo) call.

Parameters:

istream - byte-stream containing textual (presumably XML) data

encInfo - correctly initialized object which holds information of the above byte-stream's contents charset.

Throws:

IllegalArgumentException - if charset name is not specified

UnsupportedEncodingException - in cases when specified charset is not supported by platform or due to invalid byte order for ISO-10646-UCS-2|4 charsets.

getEncodingName

public static EncodingInfo getEncodingName(byte[] b4,
                                           int count)

Returns the IANA encoding name that is auto-detected from the bytes specified, with the endian-ness of that encoding where appropriate. Note, that encoding obtained this way is only an encoding scheme of the request, i.e. step 1 of detection process. To learn the exact charset of the request data, you should also perform step 2 - read XML declaration and get the value of its encoding pseudoattribute.

Parameters:

b4 - The first four bytes of the input.

count - The number of bytes actually read.

Returns:

Instance of EncodingInfo incapsulating all encoding-related data.

getXmlEncoding

protected static String getXmlEncoding(Reader reader)

Gets the encoding of the xml request made to the dispatcher. This works by reading the temp file where we are storing the request, looking to match the header specified encoding that should be present on all xml files. This call should only be made after the temp file has been set. If no encoding is found, or if an IOError is encountered then null shall be returned.

Parameters:

reader - This character stream is supposed to contain XML data (i.e. it should start with valid XML declaration).

Returns:

The encoding specified in the xml header read from the supplied character stream.