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/*--
Copyright (C) 2011-2012 Jason Hunter & Brett McLaughlin.
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"This product includes software developed by the
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This software consists of voluntary contributions made by many
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created by Jason Hunter and
Brett McLaughlin . For more information
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* The assumption is that the DTD is valid.
*
* We need to pull out 4 elements of data:
*
* - The root element name
*
- The SystemID (if available)
*
- The PublicID (if available)
*
- The internal subset (if available)
*
*
* The internal-subset should be re-formatted to conform to the JDOM 'standard'
* where each declaration starts on a new line indented with 2 spaces. This
* 'standard' is defined by the way that JDOM formats the DTD declarations in the
* SAX parse process, which fires individual events for the content in the DTD.
*
* We can do this all with a well-structured regular expression, which is
* actually simpler than trying to fish out all the components ourselves....
*
*
* @author Rolf Lear
*
*/
public class DTDParser {
/*
* =======================================================================
*
* READ THIS...
*
*
* This code works by using a reg-ex to parse a valid DTD document.
* The pattern is complicated (not as complicated as an actual parser).
*
* Because the pattern is complicated, this code creates a pattern 'database'
* and then 'pulls' patterns from the database to create the final regex.
* The database patterns are pulled to transform a pattern template into a
* final regular expression. This template is called the 'meta-pattern'.
*
* So, the pattern is not kept in its final form, but rather it is built
* up at class initialization time based on the meta-pattern, and the
* pattern database in the map.
*
* This is the final pattern: (broken over a few lines)
*
* [\s\r\n\t]*]+)([\s\r\n\t]+
* ((SYSTEM[\s\r\n\t]+(('([^']*)')|("([^"]*)")))|
* (PUBLIC[\s\r\n\t]+(('([^']*)')|("([^"]*)"))([\s\r\n\t]+
* (('([^']*)')|("([^"]*)")))?)))?([\s\r\n\t]*\[(.*)\])?
* [\s\r\n\t]*>[\s\r\n\t]*
*
* You will agree that it's simpler to build the pattern than to read it....
*
* With the above in mind, you can easily follow the way the pattern is
* built as it is simply a repeating use of some of the base constructs.
* =======================================================================
*/
/**
* This is the meta-pattern.
*
*
* - Where you see ' os ' there is optional space.
*
- Where you see ' name ' there is the element name.
*
- Where you see ' ms ' there is mandatory space.
*
- Where you see ' id ' there is some quoted identifier.
*
- Where you see ' internal ' there is the internal subset.
*
* Anything else will become part of the final regex.
*
* Space (' ') was chosen for the token delimiter because it
* makes the meta-pattern easy to read. There are a couple of places in
* this expression where there are two ' ' together, and it is critical
* that it does not change because there will be missed token matches then.
*/
private static final String metapattern =
// The lead-in and the Element name
" os os ";
/**
* This builds a substitution map containing the raw patterns for
* certain types of content we expect.
* @return The populated map.
*/
private static final HashMap populatePatterns() {
HashMap p = new HashMap();
// The name is important to understand. The assumption is that the
// doctype is valid, hence it is easier to search for what the name is
// not, and not what it is. The name will be terminated with either
// white-space, [ or >
p.put("name", "[^ \\n\\r\\t\\[>]+"); // element name.
// whitespace: S ::= (#x20 | #x9 | #xD | #xA)+
p.put("ms", "[ \\n\\r\\t]+"); // mandatory whitespace.
p.put("os", "[ \\n\\r\\t]*"); // optional whitespace.
// A quoted 'id'/"id" is anything except the quote
// we need to do parenthesis in this to get grouping to work.
// also need parenthesis to make the | or condition work
p.put("id", "(('([^']*)')|(\"([^\"]*)\"))"); // quoted id.
// The internal subset is treated differently by the code, and the
// [ ] bracing around the internal subset is specified in the main regex
p.put("internal", ".*"); // internal subset.
return p;
}
/**
* This method substitutes the simple tokens in the meta-pattern with
* the declared values in the map.
* @param map The map containing substitution tokens/patterns
* @param input The meta-pattern to do the substitutions on.
* @return The substituted pattern
*/
private static final Pattern buildPattern(
HashMap map, String input) {
// we are going to search for tokens. Each token is marked by a space.
// space was chosen because it makes the meta-pattern easy to read.
final Pattern search = Pattern.compile(" (\\w+) ");
final Matcher mat = search.matcher(input);
StringBuilder sb = new StringBuilder();
int pos = 0;
while (mat.find()) {
String rep = map.get(mat.group(1));
// we wrote this, it can't happen ;-). Live with a 'null' append.
// if (rep == null) {
// throw new IllegalArgumentException(
// "No definition of token '" + mat.group() + "'.");
// }
// can't use appendReplacement as we have to escape '\' chars.
// and Pattern.quote() does not help
// mat.appendReplacement(sb, rep);
sb.append(input.substring(pos, mat.start()));
sb.append(rep);
pos = mat.end();
}
sb.append(input.substring(pos));
return Pattern.compile(sb.toString(), Pattern.DOTALL);
}
/**
* The following Pattern is the final result after
* parsing/tokenizing/substituting the meta-pattern.
*/
private static final Pattern pattern =
buildPattern(populatePatterns(), metapattern);
/*
* This pattern relies on pattern grouping to easily pull the values from
* the Matcher. Look at the following to get an idea of the groups that
* come from the reg-ex
*
* 0 ->
* 1 -> root
* 2 -> SYSTEM "system"
* 3 -> SYSTEM "system"
* 4 -> SYSTEM "system"
* 5 -> "system"
* 6 -> null
* 7 -> null
* 8 -> "system"
* 9 -> system
* 10 -> null
* 11 -> null
* 12 -> null
* 13 -> null
* 14 -> null
* 15 -> null
* 16 -> null
* 17 -> null
* 18 -> null
* 19 -> null
* 20 -> null
* 21 -> null
* 22 -> [internal]
* 23 -> internal
*
*
* 0 ->
* 1 -> root
* 2 -> PUBLIC 'public' 'system'
* 3 -> PUBLIC 'public' 'system'
* 4 -> null
* 5 -> null
* 6 -> null
* 7 -> null
* 8 -> null
* 9 -> null
* 10 -> PUBLIC 'public' 'system'
* 11 -> 'public'
* 12 -> 'public'
* 13 -> public
* 14 -> null
* 15 -> null
* 16 -> 'system'
* 17 -> 'system'
* 18 -> 'system'
* 19 -> system
* 20 -> null
* 21 -> null
* 22 -> [internal]
* 23 -> internal
*
*
*/
/**
* Looks in any number of matched groups for a value. Returns the first set
* value. The assumption is that, depending on the pattern matches, the
* value could be in a few different locations.
* @param mat The match that has succeeded
* @param groups The groups to check for a value.
* @return The first found value.
*/
private static final String getGroup(final Matcher mat, final int...groups) {
for (final int g : groups) {
final String s = mat.group(g);
if (s != null) {
return s;
}
}
return null;
}
/**
* return true if the input character is one of the types recognized in the
* DTD spec.
* @param ch The char to check
* @return true if it is a space, tab, newline, or carriage-return.
*/
private static final boolean isWhite(char ch) {
return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r';
}
/**
* Reformat an internal subset.... Each declaration starts on an indented
* newline.
* @param internal the input DocType declaration as found in a StAX Reader.
* @return the formatted input.
*/
private static String formatInternal(String internal) {
StringBuilder sb = new StringBuilder(internal.length());
char quote = ' ';
boolean white = true;
for (char ch : internal.toCharArray()) {
if (quote == ' ') {
// we are not in a quoted value...
if (isWhite(ch)) {
if (!white) {
// this will be the first whitespace.
// replace it with a single ' '
sb.append(' ');
white = true;
}
// subsequent (unquoted) whitespace is ignored
} else {
if (ch == '\'' || ch == '"') {
// we are entering a quoted value.
quote = ch;
} else if (ch == '<') {
// we are starting some form of declaration.
sb.append(" ");
}
if (ch == '>') {
// we are ending a declaration.
if (white) {
// the declaration ended with whitespace, which we
// remove.
sb.setCharAt(sb.length() - 1, ch);
} else {
// the declaration had no whitespace at the end. OK
sb.append(ch);
}
// all declarations end with a new-line.
sb.append('\n');
// and subsequent lines start as trimmed whitespace.
white = true;
} else {
sb.append(ch);
white = false;
}
}
} else {
// we are in a quoted value...
if (ch == quote) {
//we are leaving the quoted value.
quote = ' ';
}
sb.append(ch);
}
}
return sb.toString();
}
/**
* Parse out a DOCTYPE declaration as supplied by the standard StAX
* readers.
*
* Using 'XML' terminology, this method assumes that the input is
* both 'well-formed' and 'valid'. The assumptions that this class makes
* ensure that the 'right thing' is done for valid content, but invalid
* content may or may not fail with a JDOMException. The behaviour of this
* method with invalid input is 'undefined'.
*
* @param input the input DOCTYPE string to parse. Must be valid.
* @param factory The JDOM factory to use to build the JDOM DocType.
* @return The input string as a DocType.
* @throws JDOMException if the DocType is not generated.
*/
public static DocType parse(final String input, final JDOMFactory factory)
throws JDOMException {
// Match the input to the DOCTYPE pattern matcher.
final Matcher mat = pattern.matcher(input);
if (!mat.matches()) {
throw new JDOMException("Doctype input does not appear to be valid: " + input);
}
// Get the four data components.
final String docemt = mat.group(1);
final String sysid = getGroup(mat, 7, 9, 19, 21);
final String pubid = getGroup(mat, 13, 15);
final String internal = getGroup(mat, 23);
// Use the appropriate constructor for the DocType.
DocType dt = null;
if (pubid != null) {
dt = factory.docType(docemt, pubid, sysid);
} else if (sysid != null) {
dt = factory.docType(docemt, sysid);
} else {
dt = factory.docType(docemt);
}
// Set the internal subset, if any.
if (internal != null) {
dt.setInternalSubset(formatInternal(internal));
}
return dt;
}
/**
* Make instances 'impossible'. Everything is static.
*/
private DTDParser() {
// nothing, you are not allowed instances of this class.
}
}