AttributeParser.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.jasper.compiler;
/**
* Converts a JSP attribute value into the unquoted equivalent. The attribute
* may contain EL expressions, in which case care needs to be taken to avoid any
* ambiguities. For example, consider the attribute values "${1+1}" and
* "\${1+1}". After unquoting, both appear as "${1+1}" but the first should
* evaluate to "2" and the second to "${1+1}". Literal \, $ and # need special
* treatment to ensure there is no ambiguity. The JSP attribute unquoting
* covers \\, \", \', \$, \#, %\>, <\%, &apos; and &quot;
*/
public class AttributeParser {
/**
* Parses the provided input String as a JSP attribute and returns an
* unquoted value.
*
* @param input The input.
* @param quote The quote character for the attribute or 0 for
* scripting expressions.
* @param isELIgnored Is expression language being ignored on the page
* where the JSP attribute is defined.
* @param isDeferredSyntaxAllowedAsLiteral
* Are deferred expressions treated as literals?
* @param strict Should the rules of JSP.1.6 for escaping of quotes
* be strictly applied?
* @param quoteAttributeEL Should the rules of JSP.1.6 for escaping in
* attributes be applied to EL in attribute values?
* @return An unquoted JSP attribute that, if it contains
* expression language can be safely passed to the EL
* processor without fear of ambiguity.
*/
public static String getUnquoted(String input, char quote,
boolean isELIgnored, boolean isDeferredSyntaxAllowedAsLiteral,
boolean strict, boolean quoteAttributeEL) {
return new AttributeParser(input, quote, isELIgnored,
isDeferredSyntaxAllowedAsLiteral, strict, quoteAttributeEL).getUnquoted();
}
/* The quoted input string. */
private final String input;
/* The quote used for the attribute - null for scripting expressions. */
private final char quote;
/* Is expression language being ignored - affects unquoting. \$ and \# are
* treated as literals rather than quoted values. */
private final boolean isELIgnored;
/* Are deferred expression treated as literals */
private final boolean isDeferredSyntaxAllowedAsLiteral;
/* If a quote appears that matches quote, must it always be escaped? See
* JSP.1.6.
*/
private final boolean strict;
private final boolean quoteAttributeEL;
/* The type ($ or #) of expression. Literals have a type of null. */
private final char type;
/* The length of the quoted input string. */
private final int size;
/* Tracks the current position of the parser in the input String. */
private int i = 0;
/* Indicates if the last character returned by nextChar() was escaped. */
private boolean lastChEscaped = false;
/* The unquoted result. */
private final StringBuilder result;
private AttributeParser(String input, char quote,
boolean isELIgnored, boolean isDeferredSyntaxAllowedAsLiteral,
boolean strict, boolean quoteAttributeEL) {
this.input = input;
this.quote = quote;
this.isELIgnored = isELIgnored;
this.isDeferredSyntaxAllowedAsLiteral =
isDeferredSyntaxAllowedAsLiteral;
this.strict = strict;
this.quoteAttributeEL = quoteAttributeEL;
this.type = getType(input);
this.size = input.length();
result = new StringBuilder(size);
}
/*
* Work through input looking for literals and expressions until the input
* has all been read.
*/
private String getUnquoted() {
while (i < size) {
parseLiteral();
parseEL();
}
return result.toString();
}
/*
* This method gets the next unquoted character and looks for
* - literals that need to be converted for EL processing
* \ -> type{'\\'}
* $ -> type{'$'}
* # -> type{'#'}
* - start of EL
* ${
* #{
* Note all the examples above *do not* include the escaping required to use
* the values in Java code.
*/
private void parseLiteral() {
boolean foundEL = false;
while (i < size && !foundEL) {
char ch = nextChar();
if (!isELIgnored && ch == '\\') {
if (type == 0) {
result.append("\\");
} else {
result.append(type);
result.append("{'\\\\'}");
}
} else if (!isELIgnored && ch == '$' && lastChEscaped){
if (type == 0) {
result.append("\\$");
} else {
result.append(type);
result.append("{'$'}");
}
} else if (!isELIgnored && ch == '#' && lastChEscaped){
// Note if isDeferredSyntaxAllowedAsLiteral==true, \# will
// not be treated as an escape
if (type == 0) {
result.append("\\#");
} else {
result.append(type);
result.append("{'#'}");
}
} else if (ch == type){
if (i < size) {
char next = input.charAt(i);
if (next == '{') {
foundEL = true;
// Move back to start of EL
i--;
} else {
result.append(ch);
}
} else {
result.append(ch);
}
} else {
result.append(ch);
}
}
}
/*
* Once inside EL, no need to unquote or convert anything. The EL is
* terminated by '}'. The only other valid location for '}' is inside a
* StringLiteral. The literals are delimited by '\'' or '\"'. The only other
* valid location for '\'' or '\"' is also inside a StringLiteral. A quote
* character inside a StringLiteral must be escaped if the same quote
* character is used to delimit the StringLiteral.
*/
private void parseEL() {
boolean endEL = false;
boolean insideLiteral = false;
char literalQuote = 0;
while (i < size && !endEL) {
char ch;
if (quoteAttributeEL) {
ch = nextChar();
} else {
ch = input.charAt(i++);
}
if (ch == '\'' || ch == '\"') {
if (insideLiteral) {
if (literalQuote == ch) {
insideLiteral = false;
}
} else {
insideLiteral = true;
literalQuote = ch;
}
result.append(ch);
} else if (ch == '\\') {
result.append(ch);
if (insideLiteral && size < i) {
if (quoteAttributeEL) {
ch = nextChar();
} else {
ch = input.charAt(i++);
}
result.append(ch);
}
} else if (ch == '}') {
if (!insideLiteral) {
endEL = true;
}
result.append(ch);
} else {
result.append(ch);
}
}
}
/*
* Returns the next unquoted character and sets the lastChEscaped flag to
* indicate if it was quoted/escaped or not.
* ' is always unquoted to '
* " is always unquoted to "
* \" is always unquoted to "
* \' is always unquoted to '
* \\ is always unquoted to \
* \$ is unquoted to $ if EL is not being ignored
* \# is unquoted to # if EL is not being ignored
* <\% is always unquoted to <%
* %\> is always unquoted to %>
*/
private char nextChar() {
lastChEscaped = false;
char ch = input.charAt(i);
if (ch == '&') {
if (i + 5 < size && input.charAt(i + 1) == 'a' &&
input.charAt(i + 2) == 'p' && input.charAt(i + 3) == 'o' &&
input.charAt(i + 4) == 's' && input.charAt(i + 5) == ';') {
ch = '\'';
i += 6;
} else if (i + 5 < size && input.charAt(i + 1) == 'q' &&
input.charAt(i + 2) == 'u' && input.charAt(i + 3) == 'o' &&
input.charAt(i + 4) == 't' && input.charAt(i + 5) == ';') {
ch = '\"';
i += 6;
} else {
++i;
}
} else if (ch == '\\' && i + 1 < size) {
ch = input.charAt(i + 1);
if (ch == '\\' || ch == '\"' || ch == '\'' ||
(!isELIgnored &&
(ch == '$' ||
(!isDeferredSyntaxAllowedAsLiteral &&
ch == '#')))) {
i += 2;
lastChEscaped = true;
} else {
ch = '\\';
++i;
}
} else if (ch == '<' && (i + 2 < size) && input.charAt(i + 1) == '\\' &&
input.charAt(i + 2) == '%') {
// Note this is a hack since nextChar only returns a single char
// It is safe since <% does not require special treatment for EL
// or for literals
result.append('<');
i+=3;
return '%';
} else if (ch == '%' && i + 2 < size && input.charAt(i + 1) == '\\' &&
input.charAt(i + 2) == '>') {
// Note this is a hack since nextChar only returns a single char
// It is safe since %> does not require special treatment for EL
// or for literals
result.append('%');
i+=3;
return '>';
} else if (ch == quote && strict) {
String msg = Localizer.getMessage("jsp.error.attribute.noescape",
input, ""+ quote);
throw new IllegalArgumentException(msg);
} else {
++i;
}
return ch;
}
/*
* Determines the type of expression by looking for the first unquoted ${
* or #{.
*/
private char getType(String value) {
if (value == null) {
return 0;
}
if (isELIgnored) {
return 0;
}
int j = 0;
int len = value.length();
char current;
while (j < len) {
current = value.charAt(j);
if (current == '\\') {
// Escape character - skip a character
j++;
} else if (current == '#' && !isDeferredSyntaxAllowedAsLiteral) {
if (j < (len -1) && value.charAt(j + 1) == '{') {
return '#';
}
} else if (current == '$') {
if (j < (len - 1) && value.charAt(j + 1) == '{') {
return '$';
}
}
j++;
}
return 0;
}
}