defaultexpressionfactory.java

实现了Jms的服务器源码,支持多种适配器,DB,FTP,支持多种数据库

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package org.exolab.jms.selector;

import java.util.HashSet;

import org.exolab.jms.selector.parser.SelectorTokenTypes;


/**
 * Default implementation of {@link ExpressionFactory}
 *
 * @version     $Revision: 1.4 $ $Date: 2003/08/09 15:49:50 $
 * @author      <a href="mailto:[e-mail]">Tim Anderson</a>
 * @see         ExpressionFactory
 * @see         SelectorTokenTypes
 */
public final class DefaultExpressionFactory implements ExpressionFactory {

    /**
     * Create a binary operator expression
     *
     * @param operator the operator token type from SelectorTokenTypes
     * @param left the left-hand side of the binary expression
     * @param right the right-hand side of the binary expression
     * @return a new binary expression
     * @throws SelectorException if the operator is not a valid binary operator
     */
    public Expression binaryOperator(final int operator, final Expression left,
                                     final Expression right)
        throws SelectorException {

        Expression result = null;
        switch (operator) {
            case SelectorTokenTypes.LITERAL_and:
                result = new And(left, right);
                break;
            case SelectorTokenTypes.LITERAL_or:
                result = new Or(left, right);
                break;
            case SelectorTokenTypes.EQUAL:
                result = new Equal(left, right);
                break;
            case SelectorTokenTypes.NOT_EQUAL:
                result = new NotEqual(left, right);
                break;
            case SelectorTokenTypes.LT:
                result = new Less(left, right);
                break;
            case SelectorTokenTypes.GT:
                result = new Greater(left, right);
                break;
            case SelectorTokenTypes.LE:
                result = new LessEqual(left, right);
                break;
            case SelectorTokenTypes.GE:
                result = new GreaterEqual(left, right);
                break;
            case SelectorTokenTypes.PLUS:
                result = new Add(left, right);
                break;
            case SelectorTokenTypes.MINUS:
                result = new Subtract(left, right);
                break;
            case SelectorTokenTypes.MULTIPLY:
                result = new Multiply(left, right);
                break;
            case SelectorTokenTypes.DIVIDE:
                result = new Divide(left, right);
                break;
            default:
                throw new SelectorException("Unknown binary operator type: "
                                            + operator);
        }
        return result;
    }

    /**
     * Create an unary operator expression
     *
     * @param operator the operator token type from SelectorTokenTypes
     * @param operand the expression to apply the operator to
     * @return a new unary expression
     * @throws SelectorException if the operator is not a valid unary operator
     */
    public Expression unaryOperator(final int operator,
                                    final Expression operand)
        throws SelectorException {
        Expression result = null;
        switch (operator) {
            case SelectorTokenTypes.LITERAL_not:
                result = new Not(operand);
                break;
            case SelectorTokenTypes.UNARY_MINUS:
                result = new UnaryMinus(operand);
                break;
            default:
                throw new SelectorException("Unknown unary operator type: "
                                            + operator);
        }
        return result;
    }

    /**
     * Create an identifier expression
     *
     * @param name the name of the identifier
     * @return a new identifier expression
     * @throws SelectorException is name is not a valid identifier
     */
    public Expression identifier(final String name) throws SelectorException {
        return new Identifier(name);
    }

    /**
     * Create an 'is null' expression
     *
     * @param identifier the identifer expression to apply the 'is null' test
     * @return an 'is null' expression
     * @throws SelectorException for any error
     */
    public Expression isNull(final Expression identifier)
        throws SelectorException {
        return new IsExpression((Identifier) identifier);
    }

    /**
     * Create a 'like' expression
     *
     * @param identifier the identifer to apply the 'like' test to
     * @param pattern the search pattern
     * @param escape the escape character. This may be null
     * @return a new 'like' expression
     * @throws SelectorException if the pattern or escape is invalid
     */
    public Expression like(final Expression identifier, final String pattern,
                           final String escape) throws SelectorException {
        return new LikeExpression((Identifier) identifier, pattern, escape);
    }

    /**
     * Create a 'between' expression that returns the result of:<br/>
     * <code>num1 >= num2 and num1 <= num3</code>
     * when evaluated
     *
     * @param num1 an arithmethic expression
     * @param num2 an arithmethic expression
     * @param num3 an arithmethic expression
     * @return a new 'between' expression
     * @throws SelectorException for any error
     */
    public Expression between(final Expression num1, final Expression num2,
                              final Expression num3) throws SelectorException {
        return new BetweenExpression(num1, num2, num3);
    }

    /**
     * Create an 'in' expression
     *
     * @param identifier string identifer to apply the 'in' test to
     * @param set the set of string values to compare against
     * @return a new 'in' expression
     * @throws SelectorException for any error
     */
    public Expression in(final Expression identifier, final HashSet set)
        throws SelectorException {
        return new InExpression((Identifier) identifier, set);
    }

    /**
     * Create a literal expression
     *
     * @param type the operator token type from SelectorTokenTypes
     * @param text the literal text
     * @return a new literal expression
     * @throws SelectorException if type is not a valid literal type
     */
    public Expression literal(final int type, final String text)
        throws SelectorException {
        Expression result = null;
        switch (type) {
            case SelectorTokenTypes.NUM_FLOAT:
                result = Literal.approxNumericLiteral(text);
                break;
            case SelectorTokenTypes.NUM_INT:
                result = Literal.exactNumericLiteral(text);
                break;
            case SelectorTokenTypes.STRING_LITERAL:
                result = Literal.stringLiteral(text);
                break;
            case SelectorTokenTypes.LITERAL_true:
                result = Literal.booleanLiteral(true);
                break;
            case SelectorTokenTypes.LITERAL_false:
                result = Literal.booleanLiteral(false);
                break;
            default:
                throw new SelectorException("Unknown literal type: " + type);
        }

        return result;
    }

} //-- DefaultExpressionFactory