mirror of git://gcc.gnu.org/git/gcc.git
139 lines
4.5 KiB
Java
139 lines
4.5 KiB
Java
/* java.beans.Expression
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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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/**
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* <p>An Expression captures the execution of an object method
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* that returns a value.</p>
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*
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* <p>It stores an object, the method to call, and the arguments to pass to
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* the method.</p>
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*
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* <p>While this class can generally be used to describe method calls it is
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* part of the XML serialization API.</p>
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*
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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 Expression extends Statement
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{
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// This is a placeholder to indicate that value hasn't been set
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// yet;
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private static final Object UNSET = new Object();
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// The value to return. This is equal to unset until getValue is called.
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private Object value;
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/**
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* Constructor Constructs an Expression representing the invocation of
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* object.methodName(arg[0], arg[1], ...); However, it will never be executed.
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* Instead, value will always be returned.
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*
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* @param value
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* The value to return.
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* @param target
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* The object to invoke the method on.
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* @param methodName
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* The object method to invoke.
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* @param arguments
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* An array of arguments to pass to the method.
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*/
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public Expression(Object value, Object target, String methodName,
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Object[] arguments)
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{
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super(target, methodName, arguments);
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this.value = value;
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}
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/**
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* Constructor Constructs an Expression representing the invocation of
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* object.methodName(arg[0], arg[1], ...);
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*
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* @param target
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* The object to invoke the method on.
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* @param methodName
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* The object method to invoke.
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* @param arguments
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* An array of arguments to pass to the method.
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*/
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public Expression(Object target, String methodName, Object[] arguments)
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{
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super(target, methodName, arguments);
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this.value = UNSET;
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}
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/**
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* Return the result of executing the method. If the cached value has not yet
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* been set, the method is executed in the same way as Statement.execute(),
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* except that the value is cached, and then returned. If the value has been
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* set, it is returned without executing the method again.
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*
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* @return the result of executing the method.
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* @exception Exception
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* if an error occurs
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*/
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public Object getValue() throws Exception
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{
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if (value == UNSET)
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value = doExecute();
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return value;
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}
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/**
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* Set the cached value to be returned by getValue()
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*
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* @param value
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* the value to cache and return.
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*/
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public void setValue(Object value)
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{
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this.value = value;
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}
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/**
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* Return a string representation of this expression.
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*/
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public String toString()
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{
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String result = super.toString();
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if (value != UNSET)
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return value.getClass().getName() + "=" + result;
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return result;
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}
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}
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