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jlechner |
/* java.beans.Statement
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Copyright (C) 2004, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.beans;
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import java.lang.reflect.Array;
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import java.lang.reflect.Constructor;
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import java.lang.reflect.Method;
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import java.util.HashMap;
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import java.util.WeakHashMap;
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/**
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* class Statement
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*
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* A Statement captures the execution of an object method. It stores
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* the object, the method to call, and the arguments to the method and
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* provides the ability to execute the method on the object, using the
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* provided arguments.
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*
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* @since 1.4
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*/
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public class Statement
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{
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/** Nested map for the relation between a class, its instances and their
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* names.
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*/
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private static HashMap classMaps = new HashMap();
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private Object target;
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private String methodName;
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private Object[] arguments;
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// One or the other of these will get a value after execute is
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// called once, but not both.
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private transient Method method;
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private transient Constructor ctor;
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/**
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* <p>Constructs a statement representing the invocation of
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* object.methodName(arg[0], arg[1], ...);</p>
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*
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* <p>If the argument array is null it is replaced with an
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* array of zero length.</p>
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*
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* @param target The object to invoke the method on.
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* @param methodName The object method to invoke.
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* @param arguments An array of arguments to pass to the method.
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*/
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public Statement(Object target, String methodName, Object[] arguments)
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{
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this.target = target;
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this.methodName = methodName;
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this.arguments = (arguments != null) ? arguments : new Object[0];
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storeTargetName(target);
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}
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/** Creates a name for the target instance or does nothing if the object's
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* name is already known. This makes sure that there *is* a name for every
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* target instance.
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*/
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private static synchronized void storeTargetName(Object obj)
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{
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Class klass = obj.getClass();
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WeakHashMap names = (WeakHashMap) classMaps.get(klass);
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if ( names == null )
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{
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names = new WeakHashMap();
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names.put(obj,
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( klass == String.class ? ("\"" + obj + "\"") :
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(klass.getName() + names.size()) ));
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classMaps.put(klass, names);
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return;
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}
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String targetName = (String) names.get(obj);
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if ( targetName == null )
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{
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names.put(obj,
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( klass == String.class ? ("\"" + obj + "\"") :
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(klass.getName() + names.size()) ));
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}
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// Nothing to do. The given object was already stored.
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}
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/**
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* Execute the statement.
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*
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* Finds the specified method in the target object and calls it with
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* the arguments given in the constructor.
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*
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* The most specific method according to the JLS(15.11) is used when
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* there are multiple methods with the same name.
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*
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* Execute performs some special handling for methods and
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* parameters:
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*
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* Static methods can be executed by providing the class as a
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* target.
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*
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* The method name new is reserved to call the constructor
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* new() will construct an object and return it. Not useful unless
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* an expression :-)
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*
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* If the target is an array, get and set as defined in
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* java.util.List are recognized as valid methods and mapped to the
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* methods of the same name in java.lang.reflect.Array.
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*
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* The native datatype wrappers Boolean, Byte, Character, Double,
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* Float, Integer, Long, and Short will map to methods that have
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* native datatypes as parameters, in the same way as Method.invoke.
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* However, these wrappers also select methods that actually take
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* the wrapper type as an argument.
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*
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* The Sun spec doesn't deal with overloading between int and
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* Integer carefully. If there are two methods, one that takes an
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* Integer and the other taking an int, the method chosen is not
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* specified, and can depend on the order in which the methods are
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* declared in the source file.
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*
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* @throws Exception if an exception occurs while locating or
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* invoking the method.
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*/
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public void execute() throws Exception
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{
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doExecute();
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}
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private static Class wrappers[] =
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{
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Boolean.class, Byte.class, Character.class, Double.class, Float.class,
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Integer.class, Long.class, Short.class
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};
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private static Class natives[] =
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{
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Boolean.TYPE, Byte.TYPE, Character.TYPE, Double.TYPE, Float.TYPE,
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Integer.TYPE, Long.TYPE, Short.TYPE
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};
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// Given a wrapper class, return the native class for it. For
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// example, if c is Integer, Integer.TYPE is returned.
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private Class unwrap(Class c)
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{
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for (int i = 0; i < wrappers.length; i++)
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if (c == wrappers[i])
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return natives[i];
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return null;
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}
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// Return true if all args can be assigned to params, false
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// otherwise. Arrays are guaranteed to be the same length.
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private boolean compatible(Class[] params, Class[] args)
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{
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for (int i = 0; i < params.length; i++)
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{
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// Treat Integer like int if appropriate
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Class nativeType = unwrap(args[i]);
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if (nativeType != null && params[i].isPrimitive()
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&& params[i].isAssignableFrom(nativeType))
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continue;
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if (params[i].isAssignableFrom(args[i]))
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continue;
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return false;
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}
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return true;
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}
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/**
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* Return true if the method arguments in first are more specific
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* than the method arguments in second, i.e. all args in first can
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* be assigned to those in second.
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*
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* A method is more specific if all parameters can also be fed to
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* the less specific method, because, e.g. the less specific method
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* accepts a base class of the equivalent argument for the more
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* specific one.
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*
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* @param first a <code>Class[]</code> value
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* @param second a <code>Class[]</code> value
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* @return a <code>boolean</code> value
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*/
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private boolean moreSpecific(Class[] first, Class[] second)
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{
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for (int j=0; j < first.length; j++)
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{
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if (second[j].isAssignableFrom(first[j]))
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continue;
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return false;
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}
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return true;
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}
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final Object doExecute() throws Exception
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{
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Class klazz = (target instanceof Class)
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? (Class) target : target.getClass();
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Object args[] = (arguments == null) ? new Object[0] : arguments;
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Class argTypes[] = new Class[args.length];
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for (int i = 0; i < args.length; i++)
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argTypes[i] = args[i].getClass();
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if (target.getClass().isArray())
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{
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// FIXME: invoke may have to be used. For now, cast to Number
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// and hope for the best. If caller didn't behave, we go boom
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// and throw the exception.
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if (methodName.equals("get") && argTypes.length == 1)
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return Array.get(target, ((Number)args[0]).intValue());
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if (methodName.equals("set") && argTypes.length == 2)
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{
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Object obj = Array.get(target, ((Number)args[0]).intValue());
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Array.set(target, ((Number)args[0]).intValue(), args[1]);
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return obj;
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}
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throw new NoSuchMethodException("No matching method for statement " + toString());
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}
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// If we already cached the method, just use it.
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if (method != null)
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return method.invoke(target, args);
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else if (ctor != null)
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return ctor.newInstance(args);
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// Find a matching method to call. JDK seems to go through all
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// this to find the method to call.
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// if method name or length don't match, skip
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// Need to go through each arg
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// If arg is wrapper - check if method arg is matchable builtin
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// or same type or super
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// - check that method arg is same or super
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if (methodName.equals("new") && target instanceof Class)
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{
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Constructor ctors[] = klazz.getConstructors();
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for (int i = 0; i < ctors.length; i++)
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{
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// Skip methods with wrong number of args.
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Class ptypes[] = ctors[i].getParameterTypes();
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283 |
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if (ptypes.length != args.length)
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continue;
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286 |
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// Check if method matches
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if (!compatible(ptypes, argTypes))
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continue;
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290 |
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// Use method[i] if it is more specific.
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// FIXME: should this check both directions and throw if
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// neither is more specific?
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293 |
|
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if (ctor == null)
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{
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ctor = ctors[i];
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continue;
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297 |
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}
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298 |
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Class mptypes[] = ctor.getParameterTypes();
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299 |
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if (moreSpecific(ptypes, mptypes))
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ctor = ctors[i];
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301 |
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}
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302 |
|
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if (ctor == null)
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303 |
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throw new InstantiationException("No matching constructor for statement " + toString());
|
304 |
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return ctor.newInstance(args);
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305 |
|
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}
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306 |
|
|
|
307 |
|
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Method methods[] = klazz.getMethods();
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308 |
|
|
|
309 |
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for (int i = 0; i < methods.length; i++)
|
310 |
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{
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311 |
|
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// Skip methods with wrong name or number of args.
|
312 |
|
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if (!methods[i].getName().equals(methodName))
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313 |
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continue;
|
314 |
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Class ptypes[] = methods[i].getParameterTypes();
|
315 |
|
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if (ptypes.length != args.length)
|
316 |
|
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continue;
|
317 |
|
|
|
318 |
|
|
// Check if method matches
|
319 |
|
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if (!compatible(ptypes, argTypes))
|
320 |
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continue;
|
321 |
|
|
|
322 |
|
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// Use method[i] if it is more specific.
|
323 |
|
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// FIXME: should this check both directions and throw if
|
324 |
|
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// neither is more specific?
|
325 |
|
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if (method == null)
|
326 |
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{
|
327 |
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method = methods[i];
|
328 |
|
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continue;
|
329 |
|
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}
|
330 |
|
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Class mptypes[] = method.getParameterTypes();
|
331 |
|
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if (moreSpecific(ptypes, mptypes))
|
332 |
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method = methods[i];
|
333 |
|
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}
|
334 |
|
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if (method == null)
|
335 |
|
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throw new NoSuchMethodException("No matching method for statement " + toString());
|
336 |
|
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return method.invoke(target, args);
|
337 |
|
|
}
|
338 |
|
|
|
339 |
|
|
|
340 |
|
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|
341 |
|
|
/** Return the statement arguments. */
|
342 |
|
|
public Object[] getArguments() { return arguments; }
|
343 |
|
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|
344 |
|
|
/** Return the statement method name. */
|
345 |
|
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public String getMethodName() { return methodName; }
|
346 |
|
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|
347 |
|
|
/** Return the statement object. */
|
348 |
|
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public Object getTarget() { return target; }
|
349 |
|
|
|
350 |
|
|
/** Return a string representation. */
|
351 |
|
|
public String toString()
|
352 |
|
|
{
|
353 |
|
|
StringBuffer result = new StringBuffer();
|
354 |
|
|
|
355 |
|
|
Class klass = target.getClass();
|
356 |
|
|
|
357 |
|
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result.append( ((WeakHashMap) classMaps.get(klass)).get(target));
|
358 |
|
|
result.append(".");
|
359 |
|
|
result.append(methodName);
|
360 |
|
|
result.append("(");
|
361 |
|
|
|
362 |
|
|
String sep = "";
|
363 |
|
|
for (int i = 0; i < arguments.length; i++)
|
364 |
|
|
{
|
365 |
|
|
result.append(sep);
|
366 |
|
|
result.append(arguments[i].getClass().getName());
|
367 |
|
|
sep = ", ";
|
368 |
|
|
}
|
369 |
|
|
result.append(")");
|
370 |
|
|
|
371 |
|
|
return result.toString();
|
372 |
|
|
}
|
373 |
|
|
}
|