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/*
* 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;
import org.apache.jasper.JasperException;
import org.apache.jasper.JasperMessages;
import org.apache.jasper.compiler.ELNode.ELText;
import org.apache.jasper.compiler.ELNode.Function;
import org.apache.jasper.compiler.ELNode.Root;
import org.apache.jasper.compiler.ELNode.Text;
/**
* This class implements a parser for EL expressions.
*
* It takes strings of the form xxx${..}yyy${..}zzz etc, and turn it into a
* ELNode.Nodes.
*
* Currently, it only handles text outside ${..} and functions in ${ ..}.
*
* @author Kin-man Chung
*/
public class ELParser {
private Token curToken; // current token
private Token prevToken; // previous token
private String whiteSpace = "";
private final ELNode.Nodes expr;
private ELNode.Nodes ELexpr;
private int index; // Current index of the expression
private final String expression; // The EL expression
private char type;
private final boolean isDeferredSyntaxAllowedAsLiteral;
private static final String reservedWords[] = { "and", "div", "empty",
"eq", "false", "ge", "gt", "instanceof", "le", "lt", "mod", "ne",
"not", "null", "or", "true" };
public ELParser(String expression, boolean isDeferredSyntaxAllowedAsLiteral) {
index = 0;
this.expression = expression;
this.isDeferredSyntaxAllowedAsLiteral = isDeferredSyntaxAllowedAsLiteral;
expr = new ELNode.Nodes();
}
/**
* Parse an EL expression
*
* @param expression
* The input expression string of the form Char* ('${' Char*
* '}')* Char*
* @param isDeferredSyntaxAllowedAsLiteral
* Are deferred expressions treated as literals?
* @return Parsed EL expression in ELNode.Nodes
*/
public static ELNode.Nodes parse(String expression,
boolean isDeferredSyntaxAllowedAsLiteral) {
ELParser parser = new ELParser(expression,
isDeferredSyntaxAllowedAsLiteral);
while (parser.hasNextChar()) {
String text = parser.skipUntilEL();
if (text.length() > 0) {
parser.expr.add(new ELNode.Text(text));
}
ELNode.Nodes elexpr = parser.parseEL();
if (!elexpr.isEmpty()) {
parser.expr.add(new ELNode.Root(elexpr, parser.type));
}
}
return parser.expr;
}
/**
* Parse an EL expression string '${...}'. Currently only separates the EL
* into functions and everything else.
*
* @return An ELNode.Nodes representing the EL expression
*
* Note: This cannot be refactored to use the standard EL implementation as
* the EL API does not provide the level of access required to the
* parsed expression.
*/
private ELNode.Nodes parseEL() {
StringBuilder buf = new StringBuilder();
ELexpr = new ELNode.Nodes();
curToken = null;
prevToken = null;
int openBraces = 0;
while (hasNext()) {
curToken = nextToken();
if (curToken instanceof Char) {
if (curToken.toChar() == '}') {
openBraces--;
if (openBraces < 0) {
break;
}
} else if (curToken.toChar() == '{') {
openBraces++;
}
buf.append(curToken.toString());
} else {
// Output whatever is in buffer
if (buf.length() > 0) {
ELexpr.add(new ELNode.ELText(buf.toString()));
buf.setLength(0);
}
if (!parseFunction()) {
ELexpr.add(new ELNode.ELText(curToken.toString()));
}
}
}
if (curToken != null) {
buf.append(curToken.getWhiteSpace());
}
if (buf.length() > 0) {
ELexpr.add(new ELNode.ELText(buf.toString()));
}
return ELexpr;
}
/**
* Parse for a function FunctionInvokation ::= (identifier ':')? identifier
* '(' (Expression (,Expression)*)? ')' Note: currently we don't parse
* arguments
*/
private boolean parseFunction() {
if (!(curToken instanceof Id) || isELReserved(curToken.toTrimmedString()) ||
prevToken instanceof Char && prevToken.toChar() == '.') {
return false;
}
String s1 = null; // Function prefix
String s2 = curToken.toTrimmedString(); // Function name
int start = index - curToken.toString().length();
Token original = curToken;
if (hasNext()) {
int mark = getIndex() - whiteSpace.length();
curToken = nextToken();
if (curToken.toChar() == ':') {
if (hasNext()) {
Token t2 = nextToken();
if (t2 instanceof Id) {
s1 = s2;
s2 = t2.toTrimmedString();
if (hasNext()) {
curToken = nextToken();
}
}
}
}
if (curToken.toChar() == '(') {
ELexpr.add(new ELNode.Function(s1, s2, expression.substring(start, index - 1)));
return true;
}
curToken = original;
setIndex(mark);
}
return false;
}
/**
* Test if an id is a reserved word in EL
*/
private boolean isELReserved(String id) {
int i = 0;
int j = reservedWords.length;
while (i < j) {
int k = (i + j) / 2;
int result = reservedWords[k].compareTo(id);
if (result == 0) {
return true;
}
if (result < 0) {
i = k + 1;
} else {
j = k;
}
}
return false;
}
/**
* Skip until an EL expression ('${' || '#{') is reached, allowing escape
* sequences '\$' and '\#'.
*
* @return The text string up to the EL expression
*/
private String skipUntilEL() {
StringBuilder buf = new StringBuilder();
while (hasNextChar()) {
char ch = nextChar();
if (ch == '\\') {
// Is this the start of a "\${" or "\#{" escape sequence?
char p0 = peek(0);
char p1 = peek(1);
if ((p0 == '$' || (p0 == '#' && !isDeferredSyntaxAllowedAsLiteral)) && p1 == '{') {
buf.append(nextChar());
buf.append(nextChar());
} else {
buf.append(ch);
}
} else if ((ch == '$' || (ch == '#' && !isDeferredSyntaxAllowedAsLiteral)) &&
peek(0) == '{') {
this.type = ch;
nextChar();
break;
} else {
buf.append(ch);
}
}
return buf.toString();
}
/**
* Escape '$' and '#', inverting the unescaping performed in
* {@link #skipUntilEL()}.
*
* @param input Non-EL input to be escaped
* @param isDeferredSyntaxAllowedAsLiteral
*
* @return The escaped version of the input
*/
static String escapeLiteralExpression(String input,
boolean isDeferredSyntaxAllowedAsLiteral) {
int len = input.length();
int lastAppend = 0;
StringBuilder output = null;
for (int i = 0; i < len; i++) {
char ch = input.charAt(i);
if (ch =='$' || (!isDeferredSyntaxAllowedAsLiteral && ch == '#')) {
if (i + 1 < len && input.charAt(i + 1) == '{') {
if (output == null) {
output = new StringBuilder(len + 20);
}
output.append(input.substring(lastAppend, i));
lastAppend = i + 1;
output.append('\\');
output.append(ch);
}
}
}
if (output == null) {
return input;
} else {
output.append(input.substring(lastAppend, len));
return output.toString();
}
}
/**
* Escape '\\', '\'' and '\"', inverting the unescaping performed in
* {@link #skipUntilEL()}.
*
* @param input Non-EL input to be escaped
* @param isDeferredSyntaxAllowedAsLiteral
*
* @return The escaped version of the input
*/
private static String escapeELText(String input) {
int len = input.length();
char quote = 0;
int lastAppend = 0;
int start = 0;
int end = len;
// Look to see if the value is quoted
String trimmed = input.trim();
int trimmedLen = trimmed.length();
if (trimmedLen > 1) {
// Might be quoted
quote = trimmed.charAt(0);
if (quote == '\'' || quote == '\"') {
if (trimmed.charAt(trimmedLen - 1) != quote) {
throw JasperMessages.MESSAGES.invalidStringLiteral(input);
}
start = input.indexOf(quote) + 1;
end = start + trimmedLen - 2;
} else {
quote = 0;
}
}
StringBuilder output = null;
for (int i = start; i < end; i++) {
char ch = input.charAt(i);
if (ch == '\\' || ch == quote) {
if (output == null) {
output = new StringBuilder(len + 20);
}
output.append(input.substring(lastAppend, i));
lastAppend = i + 1;
output.append('\\');
output.append(ch);
}
}
if (output == null) {
return input;
} else {
output.append(input.substring(lastAppend, len));
return output.toString();
}
}
/*
* @return true if there is something left in EL expression buffer other
* than white spaces.
*/
private boolean hasNext() {
skipSpaces();
return hasNextChar();
}
private String getAndResetWhiteSpace() {
String result = whiteSpace;
whiteSpace = "";
return result;
}
/*
* Implementation note: This method assumes that it is always preceded by a
* call to hasNext() in order for whitespace handling to be correct.
*
* @return The next token in the EL expression buffer.
*/
private Token nextToken() {
prevToken = curToken;
if (hasNextChar()) {
char ch = nextChar();
if (Character.isJavaIdentifierStart(ch)) {
int start = index - 1;
while (index < expression.length() &&
Character.isJavaIdentifierPart(
ch = expression.charAt(index))) {
nextChar();
}
return new Id(getAndResetWhiteSpace(), expression.substring(start, index));
}
if (ch == '\'' || ch == '"') {
return parseQuotedChars(ch);
} else {
// For now...
return new Char(getAndResetWhiteSpace(), ch);
}
}
return null;
}
/*
* Parse a string in single or double quotes, allowing for escape sequences
* '\\', '\"' and "\'"
*/
private Token parseQuotedChars(char quote) {
StringBuilder buf = new StringBuilder();
buf.append(quote);
while (hasNextChar()) {
char ch = nextChar();
if (ch == '\\') {
ch = nextChar();
if (ch == '\\' || ch == '\'' || ch == '\"') {
buf.append(ch);
} else {
throw JasperMessages.MESSAGES.invalidQuoting(expression);
}
} else if (ch == quote) {
buf.append(ch);
break;
} else {
buf.append(ch);
}
}
return new QuotedString(getAndResetWhiteSpace(), buf.toString());
}
/*
* A collection of low level parse methods dealing with character in the EL
* expression buffer.
*/
private void skipSpaces() {
int start = index;
while (hasNextChar()) {
char c = expression.charAt(index);
if (c > ' ')
break;
index++;
}
whiteSpace = expression.substring(start, index);
}
private boolean hasNextChar() {
return index < expression.length();
}
private char nextChar() {
if (index >= expression.length()) {
return (char) -1;
}
return expression.charAt(index++);
}
private char peek(int advance) {
int target = index + advance;
if (target >= expression.length()) {
return (char) -1;
}
return expression.charAt(target);
}
private int getIndex() {
return index;
}
private void setIndex(int i) {
index = i;
}
/*
* Represents a token in EL expression string
*/
private static class Token {
protected final String whiteSpace;
Token(String whiteSpace) {
this.whiteSpace = whiteSpace;
}
char toChar() {
return 0;
}
@Override
public String toString() {
return whiteSpace;
}
String toTrimmedString() {
return "";
}
String getWhiteSpace() {
return whiteSpace;
}
}
/*
* Represents an ID token in EL
*/
private static class Id extends Token {
String id;
Id(String whiteSpace, String id) {
super(whiteSpace);
this.id = id;
}
@Override
public String toString() {
return whiteSpace + id;
}
@Override
String toTrimmedString() {
return id;
}
}
/*
* Represents a character token in EL
*/
private static class Char extends Token {
private char ch;
Char(String whiteSpace, char ch) {
super(whiteSpace);
this.ch = ch;
}
@Override
char toChar() {
return ch;
}
@Override
public String toString() {
return whiteSpace + ch;
}
@Override
String toTrimmedString() {
return "" + ch;
}
}
/*
* Represents a quoted (single or double) string token in EL
*/
private static class QuotedString extends Token {
private String value;
QuotedString(String whiteSpace, String v) {
super(whiteSpace);
this.value = v;
}
@Override
public String toString() {
return whiteSpace + value;
}
@Override
String toTrimmedString() {
return value;
}
}
public char getType() {
return type;
}
static class TextBuilder extends ELNode.Visitor {
protected final boolean isDeferredSyntaxAllowedAsLiteral;
protected final StringBuilder output = new StringBuilder();
protected TextBuilder(boolean isDeferredSyntaxAllowedAsLiteral) {
this.isDeferredSyntaxAllowedAsLiteral = isDeferredSyntaxAllowedAsLiteral;
}
public String getText() {
return output.toString();
}
@Override
public void visit(Root n) throws JasperException {
output.append(n.getType());
output.append('{');
n.getExpression().visit(this);
output.append('}');
}
@Override
public void visit(Function n) throws JasperException {
output.append(escapeLiteralExpression(n.getOriginalText(), isDeferredSyntaxAllowedAsLiteral));
output.append('(');
}
@Override
public void visit(Text n) throws JasperException {
output.append(escapeLiteralExpression(n.getText(),isDeferredSyntaxAllowedAsLiteral));
}
@Override
public void visit(ELText n) throws JasperException {
output.append(escapeELText(n.getText()));
}
}
}
