/*

 * Copyright (c) 2003, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 */

package javax.sql.rowset.serial;

import java.io.*;

import java.lang.reflect.*;

import java.util.Arrays;

import java.util.Vector;

import javax.sql.rowset.RowSetWarning;

/**

 * A serializable mapping in the Java programming language of an SQL

 * <code>JAVA_OBJECT</code> value. Assuming the Java object

 * implements the <code>Serializable</code> interface, this class simply wraps the

 * serialization process.

 * <P>

 * If however, the serialization is not possible because

 * the Java object is not immediately serializable, this class will

 * attempt to serialize all non-static members to permit the object

 * state to be serialized.

 * Static or transient fields cannot be serialized; an attempt to serialize

 * them will result in a <code>SerialException</code> object being thrown.

 *

 * @author Jonathan Bruce

 */

public class SerialJavaObject implements Serializable, Cloneable {

    /**

     * Placeholder for object to be serialized.

     */

    private Object obj;

   /**

    * Placeholder for all fields in the <code>JavaObject</code> being serialized.

    */

    private transient Field[] fields;

    /**

     * Constructor for <code>SerialJavaObject</code> helper class.

     * <p>

     *

     * @param obj the Java <code>Object</code> to be serialized

     * @throws SerialException if the object is found not to be serializable

     */

    public SerialJavaObject(Object obj) throws SerialException {

        // if any static fields are found, an exception

        // should be thrown

        // get Class. Object instance should always be available

        Class<?> c = obj.getClass();

        // determine if object implements Serializable i/f

        if (!(obj instanceof java.io.Serializable)) {

            setWarning(new RowSetWarning("Warning, the object passed to the constructor does not implement Serializable"));

        }

        // can only determine public fields (obviously). If

        // any of these are static, this should invalidate

        // the action of attempting to persist these fields

        // in a serialized form

        fields = c.getFields();

        if (hasStaticFields(fields)) {

            throw new SerialException("Located static fields in " +

                "object instance. Cannot serialize");

        }

        this.obj = obj;

    }

    /**

     * Returns an <code>Object</code> that is a copy of this <code>SerialJavaObject</code>

     * object.

     *

     * @return a copy of this <code>SerialJavaObject</code> object as an

     *         <code>Object</code> in the Java programming language

     * @throws SerialException if the instance is corrupt

     */

    public Object getObject() throws SerialException {

        return this.obj;

    }

    /**

     * Returns an array of <code>Field</code> objects that contains each

     * field of the object that this helper class is serializing.

     *

     * @return an array of <code>Field</code> objects

     * @throws SerialException if an error is encountered accessing

     * the serialized object

     */

    public Field[] getFields() throws SerialException {

        if (fields != null) {

            Class<?> c = this.obj.getClass();

            return c.getFields();

        } else {

            throw new SerialException("SerialJavaObject does not contain" +

                " a serialized object instance");

        }

    }

    /**

     * The identifier that assists in the serialization of this

     * <code>SerialJavaObject</code> object.

     */

    static final long serialVersionUID = -1465795139032831023L;

    /**

     * A container for the warnings issued on this <code>SerialJavaObject</code>

     * object. When there are multiple warnings, each warning is chained to the

     * previous warning.

     */

    Vector<RowSetWarning> chain;

    /**

     * Compares this SerialJavaObject to the specified object.

     * The result is {@code true} if and only if the argument

     * is not {@code null} and is a {@code SerialJavaObject}

     * object that is identical to this object

     *

     * @param  o The object to compare this {@code SerialJavaObject} against

     *

     * @return  {@code true} if the given object represents a {@code SerialJavaObject}

     *          equivalent to this SerialJavaObject, {@code false} otherwise

     *

     */

    public boolean equals(Object o) {

        if (this == o) {

            return true;

        }

        if (o instanceof SerialJavaObject) {

            SerialJavaObject sjo = (SerialJavaObject) o;

            return obj.equals(sjo.obj);

        }

        return false;

    }

    /**

     * Returns a hash code for this SerialJavaObject. The hash code for a

     * {@code SerialJavaObject} object is taken as the hash code of

     * the {@code Object} it stores

     *

     * @return  a hash code value for this object.

     */

    public int hashCode() {

        return 31 + obj.hashCode();

    }

    /**

     * Returns a clone of this {@code SerialJavaObject}.

     *

     * @return  a clone of this SerialJavaObject

     */

    public Object clone() {

        try {

            SerialJavaObject sjo = (SerialJavaObject) super.clone();

            sjo.fields = Arrays.copyOf(fields, fields.length);

            if (chain != null)

                sjo.chain = new Vector<>(chain);

            return sjo;

        } catch (CloneNotSupportedException ex) {

            // this shouldn't happen, since we are Cloneable

            throw new InternalError();

        }

    }

    /**

     * Registers the given warning.

     */

    private void setWarning(RowSetWarning e) {

        if (chain == null) {

            chain = new Vector<>();

        }

        chain.add(e);

    }

    /**

     * readObject is called to restore the state of the {@code SerialJavaObject}

     * from a stream.

     */

    private void readObject(ObjectInputStream s)

            throws IOException, ClassNotFoundException {

        ObjectInputStream.GetField fields1 = s.readFields();

        @SuppressWarnings("unchecked")

        Vector<RowSetWarning> tmp = (Vector<RowSetWarning>)fields1.get("chain", null);

        if (tmp != null)

            chain = new Vector<>(tmp);

        obj = fields1.get("obj", null);

        if (obj != null) {

            fields = obj.getClass().getFields();

            if(hasStaticFields(fields))

                throw new IOException("Located static fields in " +

                "object instance. Cannot serialize");

        } else {

            throw new IOException("Object cannot be null!");

        }

    }

    /**

     * writeObject is called to save the state of the {@code SerialJavaObject}

     * to a stream.

     */

    private void writeObject(ObjectOutputStream s)

            throws IOException {

        ObjectOutputStream.PutField fields = s.putFields();

        fields.put("obj", obj);

        fields.put("chain", chain);

        s.writeFields();

    }

    /*

     * Check to see if there are any Static Fields in this object

     */

    private static boolean hasStaticFields(Field[] fields) {

        for (Field field : fields) {

            if ( field.getModifiers() == Modifier.STATIC) {

                return true;

            }

        }

        return false;

    }

}