or.java

OpenJMS是一个开源的Java Message Service API 1.0.2 规范的实现,它包含有以下特性： *. 它既支持点到点（point-to-point）（PTP）模型和发布/订

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package org.exolab.jms.selector;

import javax.jms.Message;


/**
 * This class implements an 'and' expression.
 *
 * @version     $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
 * @author      <a href="mailto:[e-mail]">Tim Anderson</a>
 * @see         Expression
 * @see         LogicalOperator
 * @see         SBool
 */
class Or extends LogicalOperator {

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

    /**
     * Construct a new <code>And</code> operator
     *
     * @param lhs the left hand side of the expression
     * @param rhs the right hand side of the expression
     */
    public Or(final Expression lhs, final Expression rhs) {
        super("or", lhs, rhs);
    }

    /**
     * Evaluate the expression
     *
     * @param msg the message to use to obtain any header identifier and
     * property values
     * @return the evaluated result, or <code>null</code> if the value of the
     * expression is unknown
     * @throws TypeMismatchException if the expression tries to evaluate
     * mismatched types.
     */
    public SObject evaluate(final Message msg) throws TypeMismatchException {
        SBool result = null;
        SBool lhs = TypeCaster.castToBool(left().evaluate(msg), CONTEXT);
        if (lhs != null) {
            if (lhs.value()) {
                result = SBool.TRUE;
            } else {
                SBool rhs = TypeCaster.castToBool(right().evaluate(msg),
                    CONTEXT);
                result = lhs.or(rhs);
            }
        } else {
            SBool rhs = TypeCaster.castToBool(right().evaluate(msg), CONTEXT);
            if (rhs != null) {
                result = rhs.or(lhs);
            }
        }
        return result;
    }

} //-- Or