com.sun.syndication.io.XmlReader Maven / Gradle / Ivy
/*
* Copyright 2004 Sun Microsystems, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package com.sun.syndication.io;
import java.io.*;
import java.net.URL;
import java.net.URLConnection;
import java.net.HttpURLConnection;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.text.MessageFormat;
/**
* Character stream that handles (or at least attemtps to) all the necessary Voodo 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.
*
* @author Alejandro Abdelnur
*
*/
public class XmlReader extends Reader {
private static final int BUFFER_SIZE = 4096;
private static final String UTF_8 = "UTF-8";
private static final String US_ASCII = "US-ASCII";
private static final String UTF_16BE = "UTF-16BE";
private static final String UTF_16LE = "UTF-16LE";
private static final String UTF_16 = "UTF-16";
private static String _staticDefaultEncoding = null;
private Reader _reader;
private String _encoding;
private String _defaultEncoding;
/**
* 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.
*
*
* @param encoding charset encoding to default to.
*/
public static void setDefaultEncoding(String encoding) {
_staticDefaultEncoding = encoding;
}
/**
* 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.
*
*
* @return the default encoding to use.
*/
public static String getDefaultEncoding() {
return _staticDefaultEncoding;
}
/**
* 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.
*
* @param file File to create a Reader from.
* @throws IOException thrown if there is a problem reading the file.
*
*/
public XmlReader(File file) throws IOException {
this(new FileInputStream(file));
}
/**
* 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.
*
* @param is InputStream to create a Reader from.
* @throws IOException thrown if there is a problem reading the stream.
*
*/
public XmlReader(InputStream is) throws IOException {
this(is,true);
}
/**
* 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 XmlReaderException is never thrown.
*
* @param is InputStream to create a Reader from.
* @param lenient indicates if the charset encoding detection should be relaxed.
* @param defaultEncoding default encoding to use if one cannot be detected.
* @throws IOException thrown if there is a problem reading the stream.
* @throws XmlReaderException thrown if the charset encoding could not be determined according to the specs.
*
*/
public XmlReader(InputStream is, boolean lenient, String defaultEncoding)
throws IOException, XmlReaderException {
_defaultEncoding = (defaultEncoding == null) ? _staticDefaultEncoding : defaultEncoding;
try {
doRawStream(is,lenient);
}
catch (XmlReaderException ex) {
if (!lenient) {
throw ex;
}
else {
doLenientDetection(null,ex);
}
}
}
/**
* 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 XmlReaderException is never thrown.
*
* @param is InputStream to create a Reader from.
* @param lenient indicates if the charset encoding detection should be relaxed.
* @throws IOException thrown if there is a problem reading the stream.
* @throws XmlReaderException thrown if the charset encoding could not be determined according to the specs.
*
*/
public XmlReader(InputStream is,boolean lenient) throws IOException, XmlReaderException {
this(is, lenient, null);
}
/**
* 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.
*
* @param url URL to create a Reader from.
* @throws IOException thrown if there is a problem reading the stream of the URL.
*
*/
public XmlReader(URL url) throws IOException {
this(url.openConnection());
}
/**
* 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.
*
* @param conn URLConnection to create a Reader from.
* @throws IOException thrown if there is a problem reading the stream of the URLConnection.
*
*/
public XmlReader(URLConnection conn) throws IOException {
_defaultEncoding = _staticDefaultEncoding;
boolean lenient = true;
if (conn instanceof HttpURLConnection) {
try {
doHttpStream(conn.getInputStream(),conn.getContentType(),lenient);
}
catch (XmlReaderException ex) {
doLenientDetection(conn.getContentType(),ex);
}
}
else
if (conn.getContentType()!=null) {
try {
doHttpStream(conn.getInputStream(),conn.getContentType(),lenient);
}
catch (XmlReaderException ex) {
doLenientDetection(conn.getContentType(),ex);
}
}
else {
try {
doRawStream(conn.getInputStream(),lenient);
}
catch (XmlReaderException ex) {
doLenientDetection(null,ex);
}
}
}
/**
* 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.
*
* @param is InputStream to create the reader from.
* @param httpContentType content-type header to use for the resolution of the charset encoding.
* @throws IOException thrown if there is a problem reading the file.
*
*/
public XmlReader(InputStream is,String httpContentType) throws IOException {
this(is,httpContentType,true);
}
/**
* 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 XmlReaderException is never thrown.
*
* @param is InputStream to create the reader from.
* @param httpContentType content-type header to use for the resolution of the charset encoding.
* @param lenient indicates if the charset encoding detection should be relaxed.
* @param defaultEncoding default encoding to use if one cannot be detected.
* @throws IOException thrown if there is a problem reading the file.
* @throws XmlReaderException thrown if the charset encoding could not be determined according to the specs.
*
*/
public XmlReader(InputStream is,String httpContentType,boolean lenient, String defaultEncoding)
throws IOException, XmlReaderException {
_defaultEncoding = (defaultEncoding == null) ? _staticDefaultEncoding : defaultEncoding;
try {
doHttpStream(is,httpContentType,lenient);
}
catch (XmlReaderException ex) {
if (!lenient) {
throw ex;
}
else {
doLenientDetection(httpContentType,ex);
}
}
}
/**
* 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 XmlReaderException is never thrown.
*
* @param is InputStream to create the reader from.
* @param httpContentType content-type header to use for the resolution of the charset encoding.
* @param lenient indicates if the charset encoding detection should be relaxed.
* @throws IOException thrown if there is a problem reading the file.
* @throws XmlReaderException thrown if the charset encoding could not be determined according to the specs.
*
*/
public XmlReader(InputStream is, String httpContentType, boolean lenient)
throws IOException, XmlReaderException {
this(is, httpContentType, lenient, null);
}
private void doLenientDetection(String httpContentType,XmlReaderException ex) throws IOException {
if (httpContentType!=null) {
if (httpContentType.startsWith("text/html")) {
httpContentType = httpContentType.substring("text/html".length());
httpContentType = "text/xml" + httpContentType;
try {
doHttpStream(ex.getInputStream(),httpContentType,true);
ex = null;
}
catch (XmlReaderException ex2) {
ex = ex2;
}
}
}
if (ex!=null) {
String encoding = ex.getXmlEncoding();
if (encoding==null) {
encoding = ex.getContentTypeEncoding();
}
if (encoding==null) {
encoding = (_defaultEncoding == null) ? UTF_8 : _defaultEncoding;
}
prepareReader(ex.getInputStream(),encoding);
}
}
/**
* Returns the charset encoding of the XmlReader.
*
* @return charset encoding.
*
*/
public String getEncoding() {
return _encoding;
}
public int read(char[] buf,int offset,int len) throws IOException {
return _reader.read(buf,offset,len);
}
/**
* Closes the XmlReader stream.
*
* @throws IOException thrown if there was a problem closing the stream.
*
*/
public void close() throws IOException {
_reader.close();
}
private void doRawStream(InputStream is,boolean lenient) throws IOException {
BufferedInputStream pis = new BufferedInputStream(is, BUFFER_SIZE);
String bomEnc = getBOMEncoding(pis);
String xmlGuessEnc = getXMLGuessEncoding(pis);
String xmlEnc = getXmlProlog(pis,xmlGuessEnc);
String encoding = calculateRawEncoding(bomEnc, xmlGuessEnc, xmlEnc, pis);
prepareReader(pis,encoding);
}
private void doHttpStream(InputStream is,String httpContentType,boolean lenient) throws IOException {
BufferedInputStream pis = new BufferedInputStream(is, BUFFER_SIZE);
String cTMime = getContentTypeMime(httpContentType);
String cTEnc = getContentTypeEncoding(httpContentType);
String bomEnc = getBOMEncoding(pis);
String xmlGuessEnc = getXMLGuessEncoding(pis);
String xmlEnc = getXmlProlog(pis,xmlGuessEnc);
String encoding = calculateHttpEncoding(cTMime, cTEnc, bomEnc, xmlGuessEnc, xmlEnc, pis,lenient);
prepareReader(pis,encoding);
}
private void prepareReader(InputStream is,String encoding) throws IOException {
_reader = new InputStreamReader(is,encoding);
_encoding = encoding;
}
// InputStream is passed for XmlReaderException creation only
private String calculateRawEncoding(String bomEnc, String xmlGuessEnc, String xmlEnc, InputStream is) throws IOException {
String encoding;
if (bomEnc==null) {
if (xmlGuessEnc==null || xmlEnc==null) {
encoding = (_defaultEncoding == null) ? UTF_8 : _defaultEncoding;
}
else
if (xmlEnc.equals(UTF_16) && (xmlGuessEnc.equals(UTF_16BE) || xmlGuessEnc.equals(UTF_16LE))) {
encoding = xmlGuessEnc;
}
else {
encoding = xmlEnc;
}
}
else
if (bomEnc.equals(UTF_8)) {
if (xmlGuessEnc!=null && !xmlGuessEnc.equals(UTF_8)) {
throw new XmlReaderException(RAW_EX_1.format(new Object[]{bomEnc,xmlGuessEnc,xmlEnc}),
bomEnc,xmlGuessEnc,xmlEnc,is);
}
if (xmlEnc!=null && !xmlEnc.equals(UTF_8)) {
throw new XmlReaderException(RAW_EX_1.format(new Object[]{bomEnc,xmlGuessEnc,xmlEnc}),
bomEnc,xmlGuessEnc,xmlEnc,is);
}
encoding = UTF_8;
}
else
if (bomEnc.equals(UTF_16BE) || bomEnc.equals(UTF_16LE)) {
if (xmlGuessEnc!=null && !xmlGuessEnc.equals(bomEnc)) {
throw new IOException(RAW_EX_1.format(new Object[]{bomEnc,xmlGuessEnc,xmlEnc}));
}
if (xmlEnc!=null && !xmlEnc.equals(UTF_16) && !xmlEnc.equals(bomEnc)) {
throw new XmlReaderException(RAW_EX_1.format(new Object[]{bomEnc,xmlGuessEnc,xmlEnc}),
bomEnc,xmlGuessEnc,xmlEnc,is);
}
encoding =bomEnc;
}
else {
throw new XmlReaderException(RAW_EX_2.format(new Object[]{bomEnc,xmlGuessEnc,xmlEnc}),
bomEnc,xmlGuessEnc,xmlEnc,is);
}
return encoding;
}
// InputStream is passed for XmlReaderException creation only
private String calculateHttpEncoding(String cTMime, String cTEnc, String bomEnc, String xmlGuessEnc, String xmlEnc, InputStream is,boolean lenient) throws IOException {
String encoding;
if (lenient & xmlEnc!=null) {
encoding = xmlEnc;
}
else {
boolean appXml = isAppXml(cTMime);
boolean textXml = isTextXml(cTMime);
if (appXml || textXml) {
if (cTEnc==null) {
if (appXml) {
encoding = calculateRawEncoding(bomEnc, xmlGuessEnc, xmlEnc, is);
}
else {
encoding = (_defaultEncoding == null) ? US_ASCII : _defaultEncoding;
}
}
else
if (bomEnc!=null && (cTEnc.equals(UTF_16BE) || cTEnc.equals(UTF_16LE))) {
throw new XmlReaderException(HTTP_EX_1.format(new Object[]{cTMime,cTEnc,bomEnc,xmlGuessEnc,xmlEnc}),
cTMime,cTEnc,bomEnc,xmlGuessEnc,xmlEnc,is);
}
else
if (cTEnc.equals(UTF_16)) {
if (bomEnc!=null && bomEnc.startsWith(UTF_16)) {
encoding = bomEnc;
}
else {
throw new XmlReaderException(HTTP_EX_2.format(new Object[]{cTMime,cTEnc,bomEnc,xmlGuessEnc,xmlEnc}),
cTMime,cTEnc,bomEnc,xmlGuessEnc,xmlEnc,is);
}
}
else {
encoding = cTEnc;
}
}
else {
throw new XmlReaderException(HTTP_EX_3.format(new Object[]{cTMime,cTEnc,bomEnc,xmlGuessEnc,xmlEnc}),
cTMime,cTEnc,bomEnc,xmlGuessEnc,xmlEnc,is);
}
}
return encoding;
}
// returns MIME type or NULL if httpContentType is NULL
private static String getContentTypeMime(String httpContentType) {
String mime = null;
if (httpContentType!=null) {
int i = httpContentType.indexOf(";");
mime = ((i==-1) ? httpContentType : httpContentType.substring(0,i)).trim();
}
return mime;
}
private static final Pattern CHARSET_PATTERN = Pattern.compile("charset=([.[^; ]]*)");
// returns charset parameter value, NULL if not present, NULL if httpContentType is NULL
private static String getContentTypeEncoding(String httpContentType) {
String encoding = null;
if (httpContentType!=null) {
int i = httpContentType.indexOf(";");
if (i>-1) {
String postMime = httpContentType.substring(i+1);
Matcher m = CHARSET_PATTERN.matcher(postMime);
encoding = (m.find()) ? m.group(1) : null;
encoding = (encoding!=null) ? encoding.toUpperCase() : null;
}
if (encoding != null &&
((encoding.startsWith("\"") && encoding.endsWith("\"")) ||
(encoding.startsWith("'") && encoding.endsWith("'"))
)) {
encoding = encoding.substring(1, encoding.length() - 1);
}
}
return encoding;
}
// returns the BOM in the stream, NULL if not present,
// if there was BOM the in the stream it is consumed
private static String getBOMEncoding(BufferedInputStream is) throws IOException {
String encoding = null;
int[] bytes = new int[3];
is.mark(3);
bytes[0] = is.read();
bytes[1] = is.read();
bytes[2] = is.read();
if (bytes[0] == 0xFE && bytes[1] == 0xFF) {
encoding = UTF_16BE;
is.reset();
is.read();
is.read();
}
else
if (bytes[0] == 0xFF && bytes[1] == 0xFE) {
encoding = UTF_16LE;
is.reset();
is.read();
is.read();
}
else
if (bytes[0] == 0xEF && bytes[1] == 0xBB && bytes[2] == 0xBF) {
encoding = UTF_8;
}
else {
is.reset();
}
return encoding;
}
// returns the best guess for the encoding by looking the first bytes of the stream, ', NULL if none
private static String getXmlProlog(BufferedInputStream is,String guessedEnc) throws IOException {
String encoding = null;
if (guessedEnc!=null) {
byte[] bytes = new byte[BUFFER_SIZE];
is.mark(BUFFER_SIZE);
int offset = 0;
int max = BUFFER_SIZE;
int c = is.read(bytes,offset,max);
int firstGT = -1;
while (c!=-1 && firstGT==-1 && offset< BUFFER_SIZE) {
offset += c;
max -= c;
c = is.read(bytes,offset,max);
firstGT = new String(bytes, 0, offset).indexOf(">");
}
if (firstGT == -1) {
if (c == -1) {
throw new IOException("Unexpected end of XML stream");
}
else {
throw new IOException("XML prolog or ROOT element not found on first " + offset + " bytes");
}
}
int bytesRead = offset;
if (bytesRead>0) {
is.reset();
Reader reader = new InputStreamReader(new ByteArrayInputStream(bytes,0,firstGT + 1), guessedEnc);
BufferedReader bReader = new BufferedReader(reader);
StringBuffer prolog = new StringBuffer();
String line = bReader.readLine();
while (line != null) {
prolog.append(line);
line = bReader.readLine();
}
Matcher m = ENCODING_PATTERN.matcher(prolog);
if (m.find()) {
encoding = m.group(1).toUpperCase();
encoding = encoding.substring(1,encoding.length()-1);
}
}
}
return encoding;
}
// indicates if the MIME type belongs to the APPLICATION XML family
private static boolean isAppXml(String mime) {
return mime!=null &&
(mime.equals("application/xml") ||
mime.equals("application/xml-dtd") ||
mime.equals("application/xml-external-parsed-entity") ||
(mime.startsWith("application/") && mime.endsWith("+xml")));
}
// indicates if the MIME type belongs to the TEXT XML family
private static boolean isTextXml(String mime) {
return mime!=null &&
(mime.equals("text/xml") ||
mime.equals("text/xml-external-parsed-entity") ||
(mime.startsWith("text/") && mime.endsWith("+xml")));
}
private static final MessageFormat RAW_EX_1 = new MessageFormat(
"Invalid encoding, BOM [{0}] XML guess [{1}] XML prolog [{2}] encoding mismatch");
private static final MessageFormat RAW_EX_2 = new MessageFormat(
"Invalid encoding, BOM [{0}] XML guess [{1}] XML prolog [{2}] unknown BOM");
private static final MessageFormat HTTP_EX_1 = new MessageFormat(
"Invalid encoding, CT-MIME [{0}] CT-Enc [{1}] BOM [{2}] XML guess [{3}] XML prolog [{4}], BOM must be NULL");
private static final MessageFormat HTTP_EX_2 = new MessageFormat(
"Invalid encoding, CT-MIME [{0}] CT-Enc [{1}] BOM [{2}] XML guess [{3}] XML prolog [{4}], encoding mismatch");
private static final MessageFormat HTTP_EX_3 = new MessageFormat(
"Invalid encoding, CT-MIME [{0}] CT-Enc [{1}] BOM [{2}] XML guess [{3}] XML prolog [{4}], Invalid MIME");
}