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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* particular file as subject to the "Classpath" exception as provided
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*
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* accompanied this code).
*
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package java.beans;
import com.sun.beans.finder.PersistenceDelegateFinder;
import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.Map;
/**
* An {@code Encoder} 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},
* in conjunction with its persistence delegates, is responsible for
* breaking the object graph down into a series of {@code Statement}s
* and {@code Expression}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<Object, Expression> bindings = new IdentityHashMap<>();
private ExceptionListener exceptionListener;
boolean executeStatements = true;
private Map<Object, Object> 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}.
* The exception handler is notified when this stream catches recoverable
* exceptions.
*
* @param exceptionListener The exception handler for this stream;
* if {@code null} 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 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 an {@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() { ... }
* @ConstructorProperties({"x"})
* public Bar(int x) { ... }
* @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);
if (pd == null) {
pd = MetaData.getPersistenceDelegate(type);
if (pd != null) {
this.finder.register(type, pd);
}
}
return pd;
}
/**
* 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 = bindings.remove(oldInstance);
return getValue(exp);
}
/**
* Returns a tentative value for {@code oldInstance} in
* the environment created by this stream. A persistence
* delegate can use its {@code mutatesTo} 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 = 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} to the stream.
* The {@code oldStm} 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}
* 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 "
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