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Ant example source code file (JavaClassHelper.java)

This example Ant source code file (JavaClassHelper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Ant tags/keywords

bytearrayinputstream, bytearrayinputstream, classparser, classparser, constantvalue, field, io, ioexception, javaclass, javaclasshelper, ls, string, string, stringbuffer, stringbuffer

The JavaClassHelper.java source code

/*
 *  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.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;

// CheckStyle:HideUtilityClassConstructorCheck OFF - bc
/**
 * Helper class that filters constants from a Java Class
 *
 */
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
     *
     * @param bytes the class as a array of bytes
     * @return a StringBuffer contains the name=value pairs
     * @exception IOException if an error occurs
     */
    public static 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;
    }
}

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