typechecker.java

来自「OpenJMS是一个开源的Java Message Service API 1.」· Java 代码 · 共 199 行

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package org.exolab.jms.selector.parser;

import org.exolab.jms.selector.Identifiers;
import org.exolab.jms.selector.Type;
import org.exolab.jms.selector.TypeMismatchException;


/**
 * Utility class for performing type checking
 *
 * @version     $Revision: 1.1 $ $Date: 2004/11/26 01:50:45 $
 * @author      <a href="mailto:[e-mail]">Tim Anderson</a>
 * @see         SelectorAST
 * @see         SelectorTreeParser
 * @see         Type
 * @see         TypeMismatchException
 */
final class TypeChecker {

    /**
     * Private constructor
     */
    private TypeChecker() {
    }

    /**
     * Checks the return type of an expression against the expected type
     *
     * @param node the expression node
     * @param expected the expected type of the expression
     * @throws TypeMismatchException if the return type doesn't match that
     * expected
     */
    public static void check(final SelectorAST node, final Type expected)
        throws TypeMismatchException {

        Type type = node.getReturnType();
        if (type != expected && type != Type.UNDEFINED) {
            String msg = "expecting a " + expected + " expression, found a "
                + type;
            throw new TypeMismatchException(node.getContext(), msg);
        }
    }

    /**
     * Checks the return type of an expression against the expected type
     *
     * @param operator the expression operator
     * @param node the expression node
     * @param expected the expected type of the expression
     * @throws TypeMismatchException if the return type doesn't match that
     * expected
     */
    public static void check(final String operator, final SelectorAST node,
                             final Type expected)
        throws TypeMismatchException {

        Type type = node.getReturnType();
        if (type != expected && type != Type.UNDEFINED) {
            String msg = "expecting a " + expected
                + " expression for operator " + operator + ", found a " + type;
            throw new TypeMismatchException(node.getContext(), msg);
        }
    }

    /**
     * Checks the types of left and right hand sides of an expression against
     * the expected type
     *
     * @param operator the expression operator
     * @param left the left hand side of the expression
     * @param right the right hand side of the expression
     * @param expected the expected type of the expression
     * @throws TypeMismatchException if a type doesn't match that expected
     */
    public static void check(final String operator, final SelectorAST left,
                             final SelectorAST right, final Type expected)
        throws TypeMismatchException {

        check(operator, left, expected);
        check(operator, right, expected);
    }

    /**
     * Verifies if two expressions can be compared
     *
     * @param operator the comparison operator
     * @param left the left hand side of the expression
     * @param right the right hand side of the expression
     * @throws TypeMismatchException if the expressions can't be compared
     */
    public static void checkComparison(final String operator,
                                       final SelectorAST left,
                                       final SelectorAST right)
        throws TypeMismatchException {

        Type lhs = left.getReturnType();
        Type rhs = right.getReturnType();

        if (lhs == Type.UNDEFINED || rhs == Type.UNDEFINED) {
            // can't evaluate this at parse time.
        } else if (lhs == Type.STRING && rhs == Type.STRING) {
            checkStringComparison(operator, left, right);
        } else if ((lhs == Type.STRING && rhs != Type.STRING)
                   || (lhs == Type.BOOLEAN && rhs != Type.BOOLEAN)
                   || (lhs == Type.NUMERIC && rhs != Type.NUMERIC)) {
            String msg = "expecting a " + lhs + " expression for operator "
                + operator + ", found a " + rhs;
            throw new TypeMismatchException(right.getContext(), msg);
        }
    }

    /**
     * Verifies if two string expressions can be compared
     *
     * @param operator the comparison operator
     * @param left the left hand side of the expression
     * @param right the right hand side of the expression
     * @throws TypeMismatchException if the expressions can't be compared
     */
    public static void checkStringComparison(final String operator,
                                             final SelectorAST left,
                                             final SelectorAST right)
        throws TypeMismatchException {
        if (left.getType() == SelectorTokenTypes.IDENT
            && right.getType() == SelectorTokenTypes.STRING_LITERAL) {
            checkIdentifierComparison(left, right);
        } else if (left.getType() == SelectorTokenTypes.STRING_LITERAL
                   && right.getType() == SelectorTokenTypes.IDENT) {
            checkIdentifierComparison(right, left);
        }
    }

    /**
     * Verifies that an identifier may be compared to a string literal
     *
     * @param identifier the identifier
     * @param literal the string literal
     * @throws TypeMismatchException if the expressions can't be compared
     */
    public static void checkIdentifierComparison(final SelectorAST identifier,
                                                 final SelectorAST literal)
        throws TypeMismatchException {
        if (identifier.getText().equals(Identifiers.JMS_DELIVERY_MODE)) {
            String value = literal.getText();
            if (!value.equals(Identifiers.PERSISTENT)
                && !value.equals(Identifiers.NON_PERSISTENT)) {
                String msg = "Cannot compare JMSDeliveryMode with '"
                    + value + "'";
                throw new TypeMismatchException(identifier.getContext(), msg);
            }
        }
    }

} //-- TypeChecker