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ActiveMQ example source code file (ConstantExpression.java)

This example ActiveMQ source code file (ConstantExpression.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - ActiveMQ tags/keywords

booleanconstantexpression, booleanconstantexpression, constantexpression, constantexpression, false, jmsexception, math, null, number, number, object, object, string, stringbuffer, true

The ActiveMQ ConstantExpression.java source code

/**
 * 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.activemq.filter;

import java.math.BigDecimal;

import javax.jms.JMSException;

/**
 * Represents a constant expression
 * 
 * 
 */
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 ConstantExpression(Object value) {
        this.value = 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 = Integer.valueOf(value.intValue());
        }
        return new ConstantExpression(value);
    }

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

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

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

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

    public Object getValue() {
        return value;
    }

    /**
     * @see java.lang.Object#toString()
     */
    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()
     */
    public int hashCode() {
        return toString().hashCode();
    }

    /**
     * TODO: more efficient hashCode()
     * 
     * @see java.lang.Object#equals(java.lang.Object)
     */
    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 string
     * @return
     */
    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();
    }

}

Other ActiveMQ examples (source code examples)

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