Java example source code file (ReplaceStringArray.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

bytearrayoutputstream, class, classnotfoundexception, error, expected, ioexception, object, reflection, replacestringarray, serializable, string, substituteobjectinputstream, substituteobjectoutputstream

The ReplaceStringArray.java Java example source code

/*
 * Copyright (c) 1998, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/* @test
 * @bug 4099013
 * @summary Enable substitution of String and Array by ObjectStreams.
 */

import java.io.*;
import java.lang.reflect.Array;

class A implements Serializable {
    String stringA;
    String stringB;
    String stringC;
    String[] arrayOfString;

    A() {
        stringA = "hello";
        stringB = "goodbye";
        stringC = stringA;
        arrayOfString = new String[2];
        for (int i = 0; i < arrayOfString.length; i++)
            arrayOfString[i] = new String("array element " + i);
    }

    void report() {
            System.out.println("stringA = " + stringA);
            System.out.println("stringB = " + stringB);
            System.out.println("stringC = " + stringC);
            System.out.println("length of arrayOfString = " +
                               arrayOfString.length);
            for (int i = 0; i < arrayOfString.length; i++)
                System.out.println("arrayOfString[" + i + "]= " +
                                   arrayOfString[i]);
    }
}

class SubstituteObjectOutputStream extends ObjectOutputStream {
    public int numStringsReplaced = 0;
    public int numArraysCounted = 0;

    public SubstituteObjectOutputStream(OutputStream out) throws IOException {
        super(out);
        enableReplaceObject(true);
    }

    protected Object replaceObject(Object obj) throws IOException {
        if (obj instanceof String) {
            numStringsReplaced++;
            return obj + "_WriteReplaced";
        }
        if (obj.getClass().isArray()) {
            Object[] array = (Object[]) obj;
            /* Double the array.
             * Initialize new array elements with original array. */
            Class arrayComponentType = array.getClass().getComponentType();
            Object[] newarray =
                (Object[])Array.newInstance(arrayComponentType,
                                            array.length * 2);
            for (int i = 0; i < array.length; i++)
                newarray[i] = array[i];
            for (int ni = array.length; ni < 2* array.length; ni++)
                newarray[ni] = array[ni - array.length];
            numArraysCounted++;
            obj = newarray;
        }
        return obj;
    }
}

class SubstituteObjectInputStream extends ObjectInputStream {
    public int numStringsReplaced = 0;
    public int numArraysCounted = 0;

    public SubstituteObjectInputStream(InputStream in) throws IOException {
        super(in);
        enableResolveObject(true);
    }

    protected Object resolveObject(Object obj) throws IOException {
        if (obj instanceof String) {
            numStringsReplaced++;
            return obj + "_ReadResolved";
        }
        if (obj.getClass().isArray()) {
            Object[] array = (Object[])obj;

            /* Double the array.
             * Initialize new array elements with original array. */
            Class arrayComponentType = array.getClass().getComponentType();
            Object[] newarray =
                (Object[])Array.newInstance(arrayComponentType,
                                            array.length * 2);
            for (int i = 0; i < array.length; i++)
                newarray[i] = array[i];
            for (int ni = array.length; ni < 2* array.length; ni++)
                newarray[ni] = array[ni - array.length];
            numArraysCounted++;
            obj = newarray;
        }
        return obj;
    }
}

public class ReplaceStringArray {
    public static void main(String args[]) throws IOException, ClassNotFoundException {
        boolean verbose = false;
        if (args.length >= 1 && args[0].compareTo("verbose") == 0)
            verbose = true;


        A a = new A();
        if (verbose) {
            System.out.println("Value of Class A");
            a.report();
            System.out.println("");
        }


        /* Serialize object a to bytestream. */
        if (verbose) {
            System.out.println("Serialize A to SubstituteObjectOutputStream");
            System.out.println("");
        }
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        SubstituteObjectOutputStream out =   new SubstituteObjectOutputStream(baos);
        out.writeObject(a);
        out.close();
        a = null;

        /* Validate that writeReplace called by SubstituteObjectOutputStream.*/
        boolean expectedResult = (out.numStringsReplaced == 4);
        if (!expectedResult)
            throw new Error("Expected " + 4 + " strings to be replaced during serialization;" +
                            " only " + out.numStringsReplaced + " strings were replaced.");
        if (out.numArraysCounted != 1)
            throw new Error("Expected 1 array during serialization; only " +
                            out.numArraysCounted + " arrays");

        if (verbose) {
            System.out.println("DeSerialize A from SubstituteObjectInputStream");
            System.out.println("");
        }
        SubstituteObjectInputStream in =
            new SubstituteObjectInputStream(new ByteArrayInputStream(baos.toByteArray()));
        a = (A)in.readObject();
        in.close();

        /* Validate that readResolve called by SubstituteObjectInputStream.*/
        if (in.numStringsReplaced != 4)
            throw new Error("Expected 4 strings to be resolved during deserialization;" +
                            " only " + in.numStringsReplaced + " strings were resolved.");
        if (in.numArraysCounted != 1)
            throw new Error("Expected 1 array during deserialization; only " +
                            out.numArraysCounted + " arrays");
        if (a.arrayOfString.length != 8)
            throw new Error("Expected a.arrayOfString.length to be 8, observed " +
                            a.arrayOfString.length);
        if (verbose) {
            System.out.println("Value of Class A after serialize/deserialize with writeReplace/readResolve");
            a.report();
        }
    }
}