ConstantExpression.java

/**
 *   GRANITE DATA SERVICES
 *   Copyright (C) 2006-2015 GRANITE DATA SERVICES S.A.S.
 *
 *   This file is part of the Granite Data Services Platform.
 *
 *   Granite Data Services is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   Granite Data Services is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
 *   General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 *   USA, or see <http://www.gnu.org/licenses/>.
 */
package org.granite.gravity.selector;

import java.math.BigDecimal;

import javax.jms.JMSException;

/**
 * Represents a constant expression
 *
 * @version $Revision: 1.2 $
 */
public class ConstantExpression implements Expression {

    static class BooleanConstantExpression extends ConstantExpression implements BooleanExpression {
        public BooleanConstantExpression(Object value) {
            super(value);
        }
        public boolean matches(MessageEvaluationContext message) throws JMSException {
            Object object = evaluate(message);
            return object!=null && object==Boolean.TRUE;
        }
    }

    public static final BooleanConstantExpression NULL = new BooleanConstantExpression(null);
    public static final BooleanConstantExpression TRUE = new BooleanConstantExpression(Boolean.TRUE);
    public static final BooleanConstantExpression FALSE = new BooleanConstantExpression(Boolean.FALSE);

    private Object value;

    public static ConstantExpression createFromDecimal(String text) {

        // Strip off the 'l' or 'L' if needed.
        if( text.endsWith("l") || text.endsWith("L") )
            text = text.substring(0, text.length()-1);

        Number value;
        try {
            value = new Long(text);
        } catch ( NumberFormatException e) {
            // The number may be too big to fit in a long.
            value = new BigDecimal(text);
        }

        long l = value.longValue();
        if (Integer.MIN_VALUE <= l && l <= Integer.MAX_VALUE) {
            value = new Integer(value.intValue());
        }
        return new ConstantExpression(value);
    }

    public static ConstantExpression createFromHex(String text) {
        Number value = new Long(Long.parseLong(text.substring(2), 16));
        long l = value.longValue();
        if (Integer.MIN_VALUE <= l && l <= Integer.MAX_VALUE) {
            value = new Integer(value.intValue());
        }
        return new ConstantExpression(value);
    }

    public static ConstantExpression createFromOctal(String text) {
        Number value = new Long(Long.parseLong(text, 8));
        long l = value.longValue();
        if (Integer.MIN_VALUE <= l && l <= Integer.MAX_VALUE) {
            value = new Integer(value.intValue());
        }
        return new ConstantExpression(value);
    }

    public static ConstantExpression createFloat(String text) {
        Number value = new Double(text);
        return new ConstantExpression(value);
    }

    public ConstantExpression(Object value) {
        this.value = value;
    }

    public Object evaluate(MessageEvaluationContext message) throws JMSException {
        return value;
    }

    public Object getValue() {
        return value;
    }

    /**
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        if (value == null) {
            return "NULL";
        }
        if (value instanceof Boolean) {
            return ((Boolean) value).booleanValue() ? "TRUE" : "FALSE";
        }
        if (value instanceof String) {
            return encodeString((String) value);
        }
        return value.toString();
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {
        return toString().hashCode();
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object o) {

        if (o == null || !this.getClass().equals(o.getClass())) {
            return false;
        }
        return toString().equals(o.toString());

    }


    /**
     * Encodes the value of string so that it looks like it would look like
     * when it was provided in a selector.
     *
     * @param s the string to encode
     * @return the encoded string
     */
    public static String encodeString(String s) {
        StringBuffer b = new StringBuffer();
        b.append('\'');
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (c == '\'') {
                b.append(c);
            }
            b.append(c);
        }
        b.append('\'');
        return b.toString();
    }

}