betweenexpression.java

来自「OpenJMS是一个开源的Java Message Service API 1.」· Java 代码 · 共 149 行

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package org.exolab.jms.selector;

import javax.jms.Message;


/**
 * This class implements a 'between' expression.
 * This is a boolean expression of the form:
 *    numeric-expr1 between numeric-expr2 and numeric-expr3
 * This is equivalent to:
 *    numeric-expr1 >= numeric-expr2 and numeric-expr1 <= numeric-expr3
 *
 * @version     $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
 * @author      <a href="mailto:[e-mail]">Tim Anderson</a>
 * @see         Expression
 * @see         SBool
 */
class BetweenExpression implements Expression {

    /**
     *  Corresponds to numeric-expr1
     */
    private final Expression _num1;

    /**
     *  Corresponds to numeric-expr2
     */
    private final Expression _num2;

    /**
     *  Corresponds to numeric-expr3
     */
    private final Expression _num3;

    /**
     * The expression context, for error reporting purposes
     */
    private static final String CONTEXT = "between expression";


    /**
     * Construct an expression that returns num1 >= num2 and num1 <= num3
     * when evaluated
     *
     * @param       num1            arithmetic expression
     * @param       num2            arithmetic expression representing the
     *                              lower bound
     * @param       num3            arithmetic expression representing the
     *                              upper bound
     */
    public BetweenExpression(final Expression num1, final Expression num2,
                             final Expression num3) {
        _num1 = num1;
        _num2 = num2;
        _num3 = num3;
    }

    /**
     * Evaluate the 'between' expression
     *
     * @param msg the message to evalulate the expression against
     * @return an SBool instance
     * @throws TypeMismatchException if any of the expressions are not numeric
     */
    public final SObject evaluate(final Message msg)
        throws TypeMismatchException {
        SBool result = null;
        SNumber val1 = TypeCaster.castToNumber(_num1.evaluate(msg), CONTEXT);
        if (val1 != null) {
            SNumber val2 = TypeCaster.castToNumber(_num2.evaluate(msg),
                CONTEXT);
            if (val2 != null) {
                SNumber val3 = TypeCaster.castToNumber(_num3.evaluate(msg),
                    CONTEXT);
                if (val3 != null) {
                    if (val1.greaterEqual(val2).value()
                        && val1.lessEqual(val3).value()) {
                        result = SBool.TRUE;
                    } else {
                        result = SBool.FALSE;
                    }
                }
            }
        }
        return result;
    }

    /**
     * Return a string representation of this expression
     *
     * @return a string representation of this expression
     */
    public final String toString() {
        StringBuffer result = new StringBuffer();
        result.append('(');
        result.append(_num1.toString());
        result.append(" between ");
        result.append(_num2.toString());
        result.append(" and ");
        result.append(_num3.toString());
        result.append(')');
        return result.toString();
    }

} //-- BetweenExpression