com.bstek.dorado.core.el.ExpressionCompiler.java Source code

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Here is the source code for com.bstek.dorado.core.el.ExpressionCompiler.java

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/*
 * This file is part of Dorado 7.x (http://dorado7.bsdn.org).
 * 
 * Copyright (c) 2002-2012 BSTEK Corp. All rights reserved.
 * 
 * This file is dual-licensed under the AGPLv3 (http://www.gnu.org/licenses/agpl-3.0.html) 
 * and BSDN commercial (http://www.bsdn.org/licenses) licenses.
 * 
 * If you are unsure which license is appropriate for your use, please contact the sales department
 * at http://www.bstek.com/contact.
 */

package com.bstek.dorado.core.el;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class ExpressionCompiler {
    private static final Log logger = LogFactory.getLog(ExpressionCompiler.class);

    private final static char ESCAPE_CHAR = '\\';
    private final static char SPECIAL_CHAR = '$';
    private final static char BRACKET_BEGIN = '{';
    private final static char BRACKET_END = '}';

    private ExpressionHandler handler;

    public ExpressionCompiler(ExpressionHandler handler) {
        super();
        this.handler = handler;
    }

    public List<Object> compileSections(String text) {
        if (StringUtils.isEmpty(text) || text.indexOf(SPECIAL_CHAR) < 0) {
            return null;
        }

        List<Object> sections = new ArrayList<Object>();
        String middleText = text;
        while (middleText != null) {
            MiddleExpression me = this.middleCompile(middleText);
            if (me == null) {
                sections.add(middleText);
                middleText = null;
            } else {
                sections.add(me.expression);
                middleText = me.nextText;
            }
        }

        return sections;
    }

    private MiddleExpression middleCompile(String text) {
        MiddleExpression me = null;
        if (text.startsWith("$${")) {
            me = nextMiddleExpression(text.substring(3));
        } else if (text.startsWith("${")) {
            me = nextMiddleExpression(text.substring(2));
        } else {
            me = nextString(text);
        }
        return me;
    }

    private MiddleExpression nextMiddleExpression(String text) {
        boolean stringed = false;
        boolean escaped = false;
        short bracketBeginCharFound = 0;//section{?

        try {
            StringBuffer section = new StringBuffer(text.length());
            char[] chars = text.toCharArray();
            for (int i = 0; i < chars.length; i++) {
                char c = chars[i];
                if (!escaped) {
                    if ('\'' == c || '\"' == c) {
                        stringed = !stringed;
                        section.append(c);
                        continue;
                    } else if (c == ESCAPE_CHAR) {
                        escaped = true;
                        continue;
                    }
                }

                if (stringed) {
                    section.append(c);
                    escaped = false;
                } else if (escaped) {
                    if (SPECIAL_CHAR == c || BRACKET_BEGIN == c || BRACKET_END == c) {
                        section.append(c);
                    } else {
                        section.append(ESCAPE_CHAR);
                        section.append(c);
                    }
                    escaped = false;
                } else if (BRACKET_BEGIN == c) {
                    bracketBeginCharFound++;
                    section.append(c);
                } else if (BRACKET_END == c) {
                    if (bracketBeginCharFound == 0) {
                        Object expression = this.handler.getJexlEngine().createExpression(section.toString());
                        MiddleExpression me = new MiddleExpression();
                        me.expression = expression;
                        if (i != chars.length - 1) {
                            me.nextText = text.substring(i + 1);
                        }
                        return me;
                    } else {
                        bracketBeginCharFound--;
                        section.append(c);
                    }
                } else {
                    section.append(c);
                }
            }
        } catch (Exception e) {
            logger.error(e, e);
        }

        return null;
    }

    private MiddleExpression nextString(String text) {
        boolean escaped = false;
        boolean specialCharFound = false;

        StringBuffer section = new StringBuffer(text.length());
        char[] chars = text.toCharArray();
        for (int i = 0; i < chars.length; i++) {
            char c = chars[i];
            if (!escaped) {
                if ('\'' == c || '\"' == c) {
                    section.append(c);
                    continue;
                } else if (c == ESCAPE_CHAR) {
                    escaped = true;
                    continue;
                }
            }

            if (escaped) {
                if (SPECIAL_CHAR == c || BRACKET_BEGIN == c || BRACKET_END == c) {
                    section.append(c);
                } else {
                    section.append(ESCAPE_CHAR);
                    section.append(c);
                }
                escaped = false;
            } else if (specialCharFound) {
                if (BRACKET_BEGIN == c) {
                    MiddleExpression me = new MiddleExpression();
                    me.expression = section.toString();
                    me.nextText = text.substring(i - 1);
                    return me;
                } else {
                    specialCharFound = false;
                    section.append(SPECIAL_CHAR);
                    section.append(c);
                }
            } else {
                if (SPECIAL_CHAR == c) {
                    specialCharFound = true;
                } else {
                    section.append(c);
                }
            }
        }

        MiddleExpression me = new MiddleExpression();
        me.expression = section.toString();
        return me;
    }

    private static class MiddleExpression {
        private Object expression;
        private String nextText;
    }
}