Java example source code file (CheckModifiers.java)

This example Java source code file (CheckModifiers.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

classnotfoundexception, default, error, integer, ioexception, objectinputstream, objectoutputstream, objectstreamfield, serializable, string, testclass1, testclass2, testclass3, testclass4

The CheckModifiers.java Java example source code

/*
 * Copyright (c) 1999, 2010, 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 4214888
 * @clean CheckModifiers TestClass1 TestClass2
 * @build CheckModifiers
 * @run main CheckModifiers
 * @summary Make sure that serialpersistentFields data member is used to
 *          represent tyhe serializable fields only if it has the modfiers
 *          static, final, private and the type is ObjectStreamField.
 *          No need to check for static, as ObjectStreamField class is not
 *          serializable.
 *
 */

import java.io.*;
class TestClass1 implements Serializable {
    // Missing the "final" modifier
    private static ObjectStreamField[] serialPersistentFields = {
        new ObjectStreamField("field1", Integer.class),
        new ObjectStreamField("field2", Double.TYPE),
    };

    Integer field1;
    double field2;
    int field3;
    String field4;

    public TestClass1(Integer f1, double f2, int f3, String f4) {
        field1 = f1;
        field2 = f2;
        field3 = f3;
        field4 = f4;
    }

    private void readObject(ObjectInputStream ois)
        throws IOException, ClassNotFoundException {
        ObjectInputStream.GetField pfields = ois.readFields();

        field1 = (Integer) pfields.get("field1", new Integer(100));
        field2 = pfields.get("field2", 99.99);

        /* These fields must be present in the stream */
        try {
            field3 = pfields.get("field3", 99);
            System.out.println("Passes test 1a");
        } catch(IllegalArgumentException e) {
            throw new Error("data field: field3 not in the persistent stream");
        }
        try {
            field4 = (String) pfields.get("field4", "Default string");
            System.out.println("Passes test 1b");
        } catch(IllegalArgumentException e) {
            throw new Error("data field: field4 not in the persistent stream");
        }
    }
};


class TestClass2 implements Serializable {
    // public instead of private
    public static final ObjectStreamField[] serialPersistentFields = {
        new ObjectStreamField("field1", Integer.class),
        new ObjectStreamField("field2", Double.TYPE),
    };

    Integer field1;
    double field2;
    int field3;
    String field4;

    public TestClass2(Integer f1, double f2, int f3, String f4) {
        field1 = f1;
        field2 = f2;
        field3 = f3;
        field4 = f4;
    }

    private void readObject(ObjectInputStream ois)
        throws IOException, ClassNotFoundException {
        ObjectInputStream.GetField pfields = ois.readFields();

        field1 = (Integer) pfields.get("field1", new Integer(100));
        field2 = pfields.get("field2", 99.99);

        /* These fields must be present in the stream */
        try {
            field3 = pfields.get("field3", 99);
            System.out.println("Passes test 2a");
        } catch(IllegalArgumentException e) {
            throw new Error("data field: field3 not in the persistent stream");
        }
        try {
            field4 = (String) pfields.get("field4", "Default string");
            System.out.println("Passes test 2b");
        } catch(IllegalArgumentException e) {
            throw new Error("data field: field4 not in the persistent stream");
        }
    }
};

class TestClass3 implements Serializable{
    // Not of type ObjectStreamField
    private final String[] serialPersistentFields =  {"Foo","Foobar"};;
    Integer field1;
    double field2;
    int field3;
    String field4;

    public TestClass3(Integer f1, double f2, int f3, String f4) {
        field1 = f1;
        field2 = f2;
        field3 = f3;
        field4 = f4;
    }

    private void readObject(ObjectInputStream ois)
        throws IOException, ClassNotFoundException {
        ObjectInputStream.GetField pfields = ois.readFields();

        field1 = (Integer) pfields.get("field1", new Integer(100));
        field2 = pfields.get("field2", 99.99);
        field3 = pfields.get("field3", 99);
        field4 = (String) pfields.get("field4", "Default string");

        try {
            String[] tserialPersistentFields =
                (String[])pfields.get("serialPersistentFields", null);
            System.out.println("Passes test 3");
        } catch(IllegalArgumentException e) {
            throw new Error("non-static field:  " +
                "serialPersistentFields must be in the persistent stream");
        }
    }
};

class TestClass4 implements Serializable {
    // Correct format
    private static final ObjectStreamField[] serialPersistentFields = {
        new ObjectStreamField("field1", Integer.class),
        new ObjectStreamField("field2", Double.TYPE),
    };

    Integer field1;
    double field2;
    int field3;
    String field4;

    public TestClass4(Integer f1, double f2, int f3, String f4) {
        field1 = f1;
        field2 = f2;
        field3 = f3;
        field4 = f4;
    }

    private void readObject(ObjectInputStream ois)
        throws IOException, ClassNotFoundException {
        ObjectInputStream.GetField pfields = ois.readFields();

        field1 = (Integer) pfields.get("field1", new Integer(100));
        field2 = pfields.get("field2", 99.99);

        try {
            field3 = pfields.get("field3", 99);
            throw new Error("data field: field3 in the persistent stream");
        } catch(IllegalArgumentException e) {
            System.out.println("Passes test 4a");
        }
        try {
            field4 = (String) pfields.get("field4", "Default string");
            throw new Error("data field: field4 in the persistent stream");
        } catch(IllegalArgumentException e) {
            System.out.println("Passes test 4b");
        }
    }
};

public class CheckModifiers {
    public static void main(String[] args)
        throws ClassNotFoundException, IOException{
        TestClass1 tc1 = new TestClass1(new Integer(100), 25.56, 2000,
            new String("Test modifiers of serialPersistentFields"));

        TestClass2 tc2 = new TestClass2(new Integer(100), 25.56, 2000,
            new String("Test modifiers of serialPersistentFields"));

        TestClass3 tc3 = new TestClass3(new Integer(100), 25.56, 2000,
            new String("Test Type of serialPersistentFields"));

        TestClass4 tc4 = new TestClass4(new Integer(100), 25.56, 2000,
            new String("Test modifiers of serialPersistentFields"));


        FileOutputStream fos = new FileOutputStream("fields.ser");
        try {
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            System.out.println("Writing obj 1");
            oos.writeObject(tc1);
            System.out.println("Writing obj 2");
            oos.writeObject(tc2);
            System.out.println("Writing obj 3");
            oos.writeObject(tc3);
            System.out.println("Writing obj 4");
            oos.writeObject(tc4);
            oos.flush();
        } finally {
            fos.close();
        }

        FileInputStream fis = new FileInputStream("fields.ser");
        try {
            ObjectInputStream ois = new ObjectInputStream(fis);
            System.out.println("Test modifiers for serialPeristentFields ");
            System.out.println("---------------------------------------- ");
            System.out.println("Declaration missing final modifier");
            ois.readObject();
            System.out.println();
            System.out.println("Declaration with public instead of private access");
            ois.readObject();
            System.out.println();
            System.out.println("Declaration with different type");
            ois.readObject();
            System.out.println();
            System.out.println("Declaration as in specification");
            ois.readObject();
        } finally {
            fis.close();
        }
    }
};