/* * Copyright (c) 2000, 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.  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 java.beans; import com.sun.beans.finder.PersistenceDelegateFinder; import java.util.HashMap;import java.util.IdentityHashMap;import java.util.Map; /** * An <code>Encoder</code> is a class which can be used to create * files or streams that encode the state of a collection of * JavaBeans in terms of their public APIs. The <code>Encoder</code>, * in conjunction with its persistence delegates, is responsible for * breaking the object graph down into a series of <code>Statements</code>s * and <code>Expression</code>s which can be used to create it. * A subclass typically provides a syntax for these expressions * using some human readable form - like Java source code or XML. * * @since 1.4 * * @author Philip Milne */ public class Encoder {    private final PersistenceDelegateFinder finder = new PersistenceDelegateFinder();    private Map bindings = new IdentityHashMap();    private ExceptionListener exceptionListener;    boolean executeStatements = true;    private Map attributes;     /**     * Write the specified object to the output stream.     * The serialized form will denote a series of     * expressions, the combined effect of which will create     * an equivalent object when the input stream is read.     * By default, the object is assumed to be a <em>JavaBean</em>     * with a nullary constructor, whose state is defined by     * the matching pairs of "setter" and "getter" methods     * returned by the Introspector.     *     * @param o The object to be written to the stream.     *     * @see XMLDecoder#readObject     */    protected void writeObject(Object o) {        if (o == this) {            return;        }        PersistenceDelegate info = getPersistenceDelegate(o == null ? null : o.getClass());        info.writeObject(o, this);    }     /**     * Sets the exception handler for this stream to <code>exceptionListener</code>.     * The exception handler is notified when this stream catches recoverable     * exceptions.     *     * @param exceptionListener The exception handler for this stream;     *       if <code>null</code> the default exception listener will be used.     *     * @see #getExceptionListener     */    public void setExceptionListener(ExceptionListener exceptionListener) {        this.exceptionListener = exceptionListener;    }     /**     * Gets the exception handler for this stream.     *     * @return The exception handler for this stream;     *    Will return the default exception listener if this has not explicitly been set.     *     * @see #setExceptionListener     */    public ExceptionListener getExceptionListener() {        return (exceptionListener != null) ? exceptionListener : Statement.defaultExceptionListener;    }     Object getValue(Expression exp) {        try {            return (exp == null) ? null : exp.getValue();        }        catch (Exception e) {            getExceptionListener().exceptionThrown(e);            throw new RuntimeException("failed to evaluate: " + exp.toString());        }    }     /**     * Returns the persistence delegate for the given type.     * The persistence delegate is calculated by applying     * the following rules in order:     * <ol>     * <li>     * If a persistence delegate is associated with the given type     * by using the {@link #setPersistenceDelegate} method     * it is returned.     * <li>     * A persistence delegate is then looked up by the name     * composed of the the fully qualified name of the given type     * and the "PersistenceDelegate" postfix.     * For example, a persistence delegate for the {@code Bean} class     * should be named {@code BeanPersistenceDelegate}     * and located in the same package.     * <pre>     * public class Bean { ... }     * public class BeanPersistenceDelegate { ... }</pre>     * The instance of the {@code BeanPersistenceDelegate} class     * is returned for the {@code Bean} class.     * <li>     * If the type is {@code null},     * a shared internal persistence delegate is returned     * that encodes {@code null} value.     * <li>     * If the type is a {@code enum} declaration,     * a shared internal persistence delegate is returned     * that encodes constants of this enumeration     * by their names.     * <li>     * If the type is a primitive type or the corresponding wrapper,     * a shared internal persistence delegate is returned     * that encodes values of the given type.     * <li>     * If the type is an array,     * a shared internal persistence delegate is returned     * that encodes an array of the appropriate type and length,     * and each of its elements as if they are properties.     * <li>     * If the type is a proxy,     * a shared internal persistence delegate is returned     * that encodes a proxy instance by using     * the {@link java.lang.reflect.Proxy#newProxyInstance} method.     * <li>     * If the {@link BeanInfo} for this type has a {@link BeanDescriptor}     * which defined a "persistenceDelegate" attribute,     * the value of this named attribute is returned.     * <li>     * In all other cases the default persistence delegate is returned.     * The default persistence delegate assumes the type is a <em>JavaBean</em>,     * implying that it has a default constructor and that its state     * may be characterized by the matching pairs of "setter" and "getter"     * methods returned by the {@link Introspector} class.     * The default constructor is the constructor with the greatest number     * of parameters that has the {@link ConstructorProperties} annotation.     * If none of the constructors has the {@code ConstructorProperties} annotation,     * then the nullary constructor (constructor with no parameters) will be used.     * For example, in the following code fragment, the nullary constructor     * for the {@code Foo} class will be used,     * while the two-parameter constructor     * for the {@code Bar} class will be used.     * <pre>     * public class Foo {     *     public Foo() { ... }     *     public Foo(int x) { ... }     * }     * public class Bar {     *     public Bar() { ... }     *     &#64;ConstructorProperties({"x"})     *     public Bar(int x) { ... }     *     &#64;ConstructorProperties({"x", "y"})     *     public Bar(int x, int y) { ... }     * }</pre>     * </ol>     *     * @param type  the class of the objects     * @return the persistence delegate for the given type     *     * @see #setPersistenceDelegate     * @see java.beans.Introspector#getBeanInfo     * @see java.beans.BeanInfo#getBeanDescriptor     */    public PersistenceDelegate getPersistenceDelegate(Class<?> type) {        PersistenceDelegate pd = this.finder.find(type);        return (pd != null) ? pd : MetaData.getPersistenceDelegate(type);    }     /**     * Associates the specified persistence delegate with the given type.     *     * @param type  the class of objects that the specified persistence delegate applies to     * @param delegate  the persistence delegate for instances of the given type     *     * @see #getPersistenceDelegate     * @see java.beans.Introspector#getBeanInfo     * @see java.beans.BeanInfo#getBeanDescriptor     */    public void setPersistenceDelegate(Class<?> type, PersistenceDelegate delegate) {        this.finder.register(type, delegate);    }     /**     * Removes the entry for this instance, returning the old entry.     *     * @param oldInstance The entry that should be removed.     * @return The entry that was removed.     *     * @see #get     */    public Object remove(Object oldInstance) {        Expression exp = (Expression)bindings.remove(oldInstance);        return getValue(exp);    }     /**     * Returns a tentative value for <code>oldInstance</code> in     * the environment created by this stream. A persistence     * delegate can use its <code>mutatesTo</code> method to     * determine whether this value may be initialized to     * form the equivalent object at the output or whether     * a new object must be instantiated afresh. If the     * stream has not yet seen this value, null is returned.     *     * @param  oldInstance The instance to be looked up.     * @return The object, null if the object has not been seen before.     */    public Object get(Object oldInstance) {        if (oldInstance == null || oldInstance == this ||            oldInstance.getClass() == String.class) {            return oldInstance;        }        Expression exp = (Expression)bindings.get(oldInstance);        return getValue(exp);    }     private Object writeObject1(Object oldInstance) {        Object o = get(oldInstance);        if (o == null) {            writeObject(oldInstance);            o = get(oldInstance);        }        return o;    }     private Statement cloneStatement(Statement oldExp) {        Object oldTarget = oldExp.getTarget();        Object newTarget = writeObject1(oldTarget);         Object[] oldArgs = oldExp.getArguments();        Object[] newArgs = new Object[oldArgs.length];        for (int i = 0; i < oldArgs.length; i++) {            newArgs[i] = writeObject1(oldArgs[i]);        }        Statement newExp = Statement.class.equals(oldExp.getClass())                ? new Statement(newTarget, oldExp.getMethodName(), newArgs)                : new Expression(newTarget, oldExp.getMethodName(), newArgs);        newExp.loader = oldExp.loader;        return newExp;    }     /**     * Writes statement <code>oldStm</code> to the stream.     * The <code>oldStm</code> should be written entirely     * in terms of the callers environment, i.e. the     * target and all arguments should be part of the     * object graph being written. These expressions     * represent a series of "what happened" expressions     * which tell the output stream how to produce an     * object graph like the original.     * <p>     * The implementation of this method will produce     * a second expression to represent the same expression in     * an environment that will exist when the stream is read.     * This is achieved simply by calling <code>writeObject</code>     * on the target and all the arguments and building a new     * expression with the results.     *     * @param oldStm The expression to be written to the stream.     */    public void writeStatement(Statement oldStm) {        // System.out.println("writeStatement: " + oldExp);        Statement newStm = cloneStatement(oldStm);        if (oldStm.getTarget() != this && executeStatements) {            try {                newStm.execute();            } catch (Exception e) {                getExceptionListener().exceptionThrown(new Exception("Encoder: discarding statement "                                                                     + newStm, e));            }        }    }     /**     * The implementation first checks to see if an     * expression with this value has already been written.     * If not, the expression is cloned, using     * the same procedure as <code>writeStatement</code>,     * and the value of this expression is reconciled     * with the value of the cloned expression     * by calling <code>writeObject</code>.     *     * @param oldExp The expression to be written to the stream.     */    public void writeExpression(Expression oldExp) {        // System.out.println("Encoder::writeExpression: " + oldExp);        Object oldValue = getValue(oldExp);        if (get(oldValue) != null) {            return;        }        bindings.put(oldValue, (Expression)cloneStatement(oldExp));        writeObject(oldValue);    }     void clear() {        bindings.clear();    }     // Package private method for setting an attributes table for the encoder    void setAttribute(Object key, Object value) {        if (attributes == null) {            attributes = new HashMap();        }        attributes.put(key, value);    }     Object getAttribute(Object key) {        if (attributes == null) {            return null;        }        return attributes.get(key);    }}