/*
* Copyright (c) 2002-2012 Alibaba Group Holding Limited.
* All rights reserved.
*
* 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.alibaba.citrus.expr.composite;
import static com.alibaba.citrus.util.CollectionUtil.*;
import java.util.List;
import com.alibaba.citrus.expr.Expression;
import com.alibaba.citrus.expr.ExpressionFactory;
import com.alibaba.citrus.expr.ExpressionParseException;
import com.alibaba.citrus.expr.jexl.JexlExpressionFactory;
/**
* 创建<code>CompositeExpression</code>的工厂。
*
* @author Michael Zhou
*/
public class CompositeExpressionFactory implements ExpressionFactory {
private ExpressionFactory factory;
/** 创建一个组合表达式的工厂，默认使用<code>JexlExpressionFactory</code>来解析子表达式。 */
public CompositeExpressionFactory() {
this.factory = new JexlExpressionFactory();
}
/**
* 创建一个组合表达式的工厂。
*
* @param factory 创建组合表达式中的子表达式的工厂
*/
public CompositeExpressionFactory(ExpressionFactory factory) {
this.factory = factory;
}
/**
* 创建表达式。
* <ul>
* <li>如果表达式中不包含“<code>${...}</code>”，则创建<code>ConstantExpression</code>。</li>
* <li>如果表达式以“<code>${</code>”开始，并以“<code>}</code>”结尾，则调用指定的
* <code>ExpressionFactory</code>来创建非组合表达式。</li>
* <li>如果表达式包含“<code>${...}</code>”，但在此之外还有别的字符，则创建
* <code>CompositeExpression</code>。</li>
* </ul>
*
* @param expr 表达式字符串
* @return 表达式
*/
public Expression createExpression(String expr) throws ExpressionParseException {
int length = expr.length();
int startIndex = expr.indexOf("${");
// 如果表达式不包含${}，则创建constant expression。
if (startIndex < 0) {
return new ConstantExpression(expr);
}
int endIndex = expr.indexOf("}", startIndex + 2);
if (endIndex < 0) {
throw new ExpressionParseException("Missing '}' character at the end of expression: " + expr);
}
// 如果表达式以${开头，以}结尾，则直接调用factory来创建表达式。
if (startIndex == 0 && endIndex == length - 1) {
return factory.createExpression(expr.substring(2, endIndex));
}
// 创建复合的表达式。
List<Expression> expressions = createLinkedList();
char ch = 0;
int i = 0;
StringBuffer chars = new StringBuffer();
StringBuffer exprBuff = new StringBuffer();
MAIN:
while (i < length) {
ch = expr.charAt(i);
switch (ch) {
case '$': {
if (i + 1 < length) {
++i;
ch = expr.charAt(i);
switch (ch) {
case '$': {
chars.append(ch);
break;
}
case '{': {
if (chars.length() > 0) {
expressions.add(new ConstantExpression(chars.toString()));
chars.delete(0, chars.length());
}
if (i + 1 < length) {
++i;
while (i < length) {
ch = expr.charAt(i);
{
switch (ch) {
case '"': {
exprBuff.append(ch);
++i;
DOUBLE_QUOTE:
while (i < length) {
ch = expr.charAt(i);
switch (ch) {
case '\\': {
++i;
exprBuff.append(ch);
break;
}
case '"': {
++i;
exprBuff.append(ch);
break DOUBLE_QUOTE;
}
default: {
++i;
exprBuff.append(ch);
}
}
}
break;
}
case '\'': {
exprBuff.append(ch);
++i;
SINGLE_QUOTE:
while (i < length) {
ch = expr.charAt(i);
switch (ch) {
case '\\': {
++i;
exprBuff.append(ch);
break;
}
case '\'': {
++i;
exprBuff.append(ch);
break SINGLE_QUOTE;
}
default: {
++i;
exprBuff.append(ch);
}
}
}
break;
}
case '}': {
expressions.add(factory.createExpression(exprBuff.toString()));
exprBuff.delete(0, exprBuff.length());
++i;
continue MAIN;
}
default: {
exprBuff.append(ch);
++i;
}
}
}
}
}
break;
}
default:
chars.append(ch);
}
} else {
chars.append(ch);
}
break;
}
default:
chars.append(ch);
}
++i;
}
if (chars.length() > 0) {
expressions.add(new ConstantExpression(chars.toString()));
}
return new CompositeExpression(expr, expressions);
}
}