taglibs-rdc/src/main/java/org/apache/taglibs/rdc/ISBN.java

/*
 * 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.taglibs.rdc;

import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import org.apache.taglibs.rdc.core.BaseModel;

/**
 * Datamodel for the isbn (International Standards Book number) RDC. 
 * The isbn RDC is associated with the International Standards Book 
 * Number input and a pattern to which the input must confirm. The 
 * ISBN is a 10 digit number and should conform to this length.
 *
 * @author Tanveer Faruquie
 * @author Rahul Akolkar
 */

public class ISBN extends BaseModel {
    // The isbn RDC is associated with the International Standards Book Number
    // input and a pattern to which the input must confirm. The 
    // ISBN is a 10 digit
    // number and should conform to this length.

    // Serial Version UID
    private static final long serialVersionUID = 1L;
    // The ISBN input must conform to this pattern
    private String pattern;

    // Error codes, defined in configuration file
    /**A constant for Error Code stating Invalid ISBN Code */
    public static final int ERR_INVALID_ISBN_CODE = 1;

    /**A constant for Error Code stating the incorrect length of ISBN Code */
    public static final int ERR_NEED_CORRECT_LENGTH_ISBN_CODE = 2;

    // the length of ISBN is 10
    public static final int ISBN_LENGTH = 10;

    /**
      * Sets default values for all data members
      */
    public ISBN() {
        super();
        // Default pattern allows any combination of digits or X
        this.pattern = "[0-9X]+";
    }


    /**
     * Sets the pattern string to which the ISBN must conform
     * 
     * @param pattern the pattern string to which the ISBN must conform
     */
    public void setPattern(String pattern) {
        if (pattern != null) {
            try {
                Pattern.compile(pattern);
                this.pattern = pattern;
            } catch (PatternSyntaxException e) {
                throw new IllegalArgumentException("pattern attribute of \"" +
                    getId()    + "\" ssn tag not in proper format.");
            }
        }
    }

    /**
     * Gets the pattern string
     * 
     * @return the pattern string
     */
    public String getPattern() {
        return this.pattern;
    }

    /**
     * Validates the input against the given constraints
     * 
     * @return TRUE if valid, FALSE otherwise
     */
    protected Boolean validate(Object newValue, boolean setErrorCode) {

        if (((String) newValue).length() != ISBN_LENGTH) {
            if (setErrorCode) setErrorCode(ERR_NEED_CORRECT_LENGTH_ISBN_CODE);
            return Boolean.FALSE;
        }
        if (pattern != null && !(Pattern.matches(pattern, (String)newValue))) {
            if (setErrorCode) setErrorCode(ERR_INVALID_ISBN_CODE);
            return Boolean.FALSE;
        }
        if (!checksum(((String) newValue).toUpperCase())) {
            if (setErrorCode) setErrorCode(ERR_INVALID_ISBN_CODE);
            return Boolean.FALSE;
        }
        return Boolean.TRUE;
    }

    /**
     * Verifies the checksum of the given ISBN value 
     *  
     * @return true if checksum is valid, false otherwise
     */

    private boolean checksum(String isbn) {
        int sum = 0;
        int val;
        String numberValues = "0123456789X";

        for (int i = 0; i < isbn.length(); i++) {
            val = numberValues.indexOf(isbn.charAt(i));
            if (val >= 0) {
                if (val == 10 && (i != isbn.length() - 1)) {
                    // X in wrong position, should be only in the last place
                    return false;
                }
                sum += (10 - i) * val;
            } else {
                // invalid character
                return false;
            }
        }

        if ((sum % 11) == 0) {
            return true;
        } else {
            return false;
        }
    }
}