proposal/sandbox/filterreaders/src/main/org/apache/tools/ant/filters/util/JavaClassHelper.java

/*
 *  The Apache Software License, Version 1.1
 *
 *  Copyright (c) 2002 The Apache Software Foundation.  All rights
 *  reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *  notice, this list of conditions and the following disclaimer.
 *
 *  2. Redistributions in binary form must reproduce the above copyright
 *  notice, this list of conditions and the following disclaimer in
 *  the documentation and/or other materials provided with the
 *  distribution.
 *
 *  3. The end-user documentation included with the redistribution, if
 *  any, must include the following acknowlegement:
 *  "This product includes software developed by the
 *  Apache Software Foundation (http://www.apache.org/)."
 *  Alternately, this acknowlegement may appear in the software itself,
 *  if and wherever such third-party acknowlegements normally appear.
 *
 *  4. The names "The Jakarta Project", "Ant", and "Apache Software
 *  Foundation" must not be used to endorse or promote products derived
 *  from this software without prior written permission. For written
 *  permission, please contact apache@apache.org.
 *
 *  5. Products derived from this software may not be called "Apache"
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 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 *  ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 *  USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 *  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 *  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 *  OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 *  SUCH DAMAGE.
 *  ====================================================================
 *
 *  This software consists of voluntary contributions made by many
 *  individuals on behalf of the Apache Software Foundation.  For more
 *  information on the Apache Software Foundation, please see
 *  <http://www.apache.org/>.
 */
package org.apache.tools.ant.filters.util;

import java.io.ByteArrayInputStream;
import java.io.IOException;

import org.apache.bcel.classfile.ClassParser;
import org.apache.bcel.classfile.ConstantValue;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;

/**
 * Helper class that filters constants from a Java Class
 *
 * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
 */
public final class JavaClassHelper {

    /** System specific line separator. */
    private static final String LS = System.getProperty("line.separator");

    /**
     * Get the constants declared in a file as name=value
     */
    public static final StringBuffer getConstants(byte[] bytes)
        throws IOException {
        final StringBuffer sb = new StringBuffer();
        final ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
        final ClassParser parser = new ClassParser(bis, "");
        final JavaClass javaClass = parser.parse();
        final Field[] fields = javaClass.getFields();
        for (int i = 0; i < fields.length; i++) {
            final Field field = fields[i];
            if (field != null) {
                final ConstantValue cv = field.getConstantValue();
                if (cv != null) {
                    String cvs = cv.toString();
                    //Remove start and end quotes if field is a String
                    if (cvs.startsWith("\"") && cvs.endsWith("\"")) {
                        cvs = cvs.substring(1, cvs.length() - 1);
                    }
                    sb.append(field.getName());
                    sb.append('=');
                    sb.append(cvs);
                    sb.append(LS);
                }
            }
        }
        return sb;
    }
}