385 lines
12 KiB
Java
385 lines
12 KiB
Java
/* Statement.java
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Copyright (C) 2004, 2005, 2006, 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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/**
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* <p>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.</p>
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*
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* @author Jerry Quinn (jlquinn@optonline.net)
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* @author Robert Schuster (robertschuster@fsfe.org)
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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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private Object target;
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private String methodName;
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private Object[] arguments;
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/**
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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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*/
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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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}
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/**
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* Execute the statement.
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*
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* <p>Finds the specified method in the target object and calls it with
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* the arguments given in the constructor.</p>
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*
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* <p>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.</p>
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*
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* <p>Execute performs some special handling for methods and
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* parameters:
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* <ul>
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* <li>Static methods can be executed by providing the class as a
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* target.</li>
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*
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* <li>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 :-)</li>
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*
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* <li>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.</li>
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*
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* <li>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.</li>
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* </ul>
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* </p>
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*
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* <p>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.</p>
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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.
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* <p>For example, if <code>c</code> is <code>Integer</code>,
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* <code>Integer.TYPE</code> is returned.</p>
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*/
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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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/** Returns <code>true</code> if all args can be assigned to
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* <code>params</code>, <code>false</code> otherwise.
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*
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* <p>Arrays are guaranteed to be the same length.</p>
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*/
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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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// Argument types are derived from argument values. If one of them was
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// null then we cannot deduce its type. However null can be assigned to
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// any type.
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if (args[i] == null)
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continue;
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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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* Returns <code>true</code> if the method arguments in first are
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* more specific than the method arguments in second, i.e. all
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* arguments in <code>first</code> can be assigned to those in
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* <code>second</code>.
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*
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* <p>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.</p>
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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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// Retrieve type or use null if the argument is null. The null argument
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// type is later used in compatible().
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for (int i = 0; i < args.length; i++)
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argTypes[i] = (args[i] != null) ? args[i].getClass() : null;
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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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if (ptypes.length != args.length)
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continue;
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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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// 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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if (ctor == null)
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{
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ctor = ctors[i];
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continue;
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}
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Class mptypes[] = ctor.getParameterTypes();
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if (moreSpecific(ptypes, mptypes))
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ctor = ctors[i];
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}
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if (ctor == null)
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throw new InstantiationException("No matching constructor for statement " + toString());
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return ctor.newInstance(args);
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}
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Method methods[] = klazz.getMethods();
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for (int i = 0; i < methods.length; i++)
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{
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// Skip methods with wrong name or number of args.
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if (!methods[i].getName().equals(methodName))
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continue;
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Class ptypes[] = methods[i].getParameterTypes();
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if (ptypes.length != args.length)
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continue;
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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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// 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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if (method == null)
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{
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method = methods[i];
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continue;
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}
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Class mptypes[] = method.getParameterTypes();
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if (moreSpecific(ptypes, mptypes))
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method = methods[i];
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}
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if (method == null)
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throw new NoSuchMethodException("No matching method for statement " + toString());
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// If we were calling Class.forName(String) we intercept and call the
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// forName-variant that allows a ClassLoader argument. We take the
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// system classloader (aka application classloader) here to make sure
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// that application defined classes can be resolved. If we would not
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// do that the Class.forName implementation would use the class loader
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// of java.beans.Statement which is <null> and cannot resolve application
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// defined classes.
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if (method.equals(
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Class.class.getMethod("forName", new Class[] { String.class })))
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return Class.forName(
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(String) args[0], true, ClassLoader.getSystemClassLoader());
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try {
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return method.invoke(target, args);
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} catch(IllegalArgumentException iae){
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System.err.println("method: " + method);
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for(int i=0;i<args.length;i++){
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System.err.println("args[" + i + "]: " + args[i]);
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}
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throw iae;
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}
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}
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/** Return the statement arguments. */
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public Object[] getArguments() { return arguments; }
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/** Return the statement method name. */
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public String getMethodName() { return methodName; }
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/** Return the statement object. */
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public Object getTarget() { return target; }
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/**
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* Returns a string representation of this <code>Statement</code>.
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*
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* @return A string representation of this <code>Statement</code>.
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*/
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public String toString()
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{
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StringBuffer result = new StringBuffer();
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String targetName;
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if (target != null)
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targetName = target.getClass().getSimpleName();
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else
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targetName = "null";
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result.append(targetName);
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result.append(".");
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result.append(methodName);
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result.append("(");
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String sep = "";
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for (int i = 0; i < arguments.length; i++)
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{
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result.append(sep);
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result.append(
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( arguments[i] == null ) ? "null" :
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( arguments[i] instanceof String ) ? "\"" + arguments[i] + "\"" :
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arguments[i].getClass().getSimpleName());
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sep = ", ";
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}
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result.append(");");
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return result.toString();
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}
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}
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