Initial revision

From-SVN: r102074

libjava/classpath/java/beans/Statement.java

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+/* java.beans.Statement
+   Copyright (C) 2004 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.beans;
+
+import java.lang.reflect.Array;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+
+/**
+ * class Statement
+ *
+ * A Statement captures the execution of an object method.  It stores
+ * the object, the method to call, and the arguments to the method and
+ * provides the ability to execute the method on the object, using the
+ * provided arguments.
+ *
+ * @since 1.4
+ */
+public class Statement
+{
+  private Object target;
+  private String methodName;
+  private Object[] arguments;
+
+  // One or the other of these will get a value after execute is
+  // called once, but not both.
+  private transient Method method;
+  private transient Constructor ctor;
+
+  /**
+   * Constructs a statement representing the invocation of
+   * object.methodName(arg[0], arg[1], ...);
+   *
+   * @param target The object to invoke the method on.
+   * @param methodName The object method to invoke.
+   * @param arguments An array of arguments to pass to the method.
+   */
+  public Statement(Object target, String methodName, Object[] arguments)
+  {
+    this.target = target;
+    this.methodName = methodName;
+    this.arguments = arguments;
+  }
+
+  /**
+   * Execute the statement.
+   *
+   * Finds the specified method in the target object and calls it with
+   * the arguments given in the constructor.
+   *
+   * The most specific method according to the JLS(15.11) is used when
+   * there are multiple methods with the same name.
+   *
+   * Execute performs some special handling for methods and
+   * parameters:
+   *
+   * Static methods can be executed by providing the class as a
+   * target.
+   *
+   * The method name new is reserved to call the constructor 
+   * new() will construct an object and return it.  Not useful unless
+   * an expression :-)
+   *
+   * If the target is an array, get and set as defined in
+   * java.util.List are recognized as valid methods and mapped to the
+   * methods of the same name in java.lang.reflect.Array.
+   *
+   * The native datatype wrappers Boolean, Byte, Character, Double,
+   * Float, Integer, Long, and Short will map to methods that have
+   * native datatypes as parameters, in the same way as Method.invoke.
+   * However, these wrappers also select methods that actually take
+   * the wrapper type as an argument.
+   *
+   * The Sun spec doesn't deal with overloading between int and
+   * Integer carefully.  If there are two methods, one that takes an
+   * Integer and the other taking an int, the method chosen is not
+   * specified, and can depend on the order in which the methods are
+   * declared in the source file.
+   *
+   * @throws Exception if an exception occurs while locating or
+   * 		       invoking the method.
+   */
+  public void execute() throws Exception
+  {
+    doExecute();
+  }
+  
+  private static Class wrappers[] = 
+    {
+      Boolean.class, Byte.class, Character.class, Double.class, Float.class,
+      Integer.class, Long.class, Short.class
+    };
+
+  private static Class natives[] = 
+    {
+      Boolean.TYPE, Byte.TYPE, Character.TYPE, Double.TYPE, Float.TYPE,
+      Integer.TYPE, Long.TYPE, Short.TYPE
+    };
+
+  // Given a wrapper class, return the native class for it.  For
+  // example, if c is Integer, Integer.TYPE is returned.
+  private Class unwrap(Class c)
+  {
+    for (int i = 0; i < wrappers.length; i++)
+      if (c == wrappers[i])
+	return natives[i];
+    return null;
+  }
+
+  // Return true if all args can be assigned to params, false
+  // otherwise.  Arrays are guaranteed to be the same length.
+  private boolean compatible(Class[] params, Class[] args)
+  {
+    for (int i = 0; i < params.length; i++)
+      {
+	// Treat Integer like int if appropriate
+	Class nativeType = unwrap(args[i]);
+	if (nativeType != null && params[i].isPrimitive()
+	    && params[i].isAssignableFrom(nativeType))
+	  continue;
+	if (params[i].isAssignableFrom(args[i]))
+	  continue;
+
+	return false;
+      }
+    return true;
+  }
+
+  /**
+   * Return true if the method arguments in first are more specific
+   * than the method arguments in second, i.e. all args in first can
+   * be assigned to those in second.
+   *
+   * A method is more specific if all parameters can also be fed to
+   * the less specific method, because, e.g. the less specific method
+   * accepts a base class of the equivalent argument for the more
+   * specific one.
+   *
+   * @param first a <code>Class[]</code> value
+   * @param second a <code>Class[]</code> value
+   * @return a <code>boolean</code> value
+   */
+  private boolean moreSpecific(Class[] first, Class[] second)
+  {
+    for (int j=0; j < first.length; j++)
+      {
+	if (second[j].isAssignableFrom(first[j]))
+	  continue;
+	return false;
+      }
+    return true;
+  }
+
+  final Object doExecute() throws Exception
+  {
+    Class klazz = (target instanceof Class)
+	? (Class) target : target.getClass();
+    Object args[] = (arguments == null) ? new Object[0] : arguments;
+    Class argTypes[] = new Class[args.length];
+    for (int i = 0; i < args.length; i++)
+      argTypes[i] = args[i].getClass();
+
+    if (target.getClass().isArray())
+      {
+	// FIXME: invoke may have to be used.  For now, cast to Number
+	// and hope for the best.  If caller didn't behave, we go boom
+	// and throw the exception.
+	if (methodName.equals("get") && argTypes.length == 1)
+	  return Array.get(target, ((Number)args[0]).intValue());
+	if (methodName.equals("set") && argTypes.length == 2)
+	  {
+	    Object obj = Array.get(target, ((Number)args[0]).intValue());
+	    Array.set(target, ((Number)args[0]).intValue(), args[1]);
+	    return obj;
+	  }
+	throw new NoSuchMethodException("No matching method for statement " + toString());
+      }
+
+    // If we already cached the method, just use it.
+    if (method != null)
+      return method.invoke(target, args);
+    else if (ctor != null)
+      return ctor.newInstance(args);
+
+    // Find a matching method to call.  JDK seems to go through all
+    // this to find the method to call.
+
+    // if method name or length don't match, skip
+    // Need to go through each arg
+    // If arg is wrapper - check if method arg is matchable builtin
+    //  or same type or super
+    //  - check that method arg is same or super
+
+    if (methodName.equals("new") && target instanceof Class)
+      {
+	Constructor ctors[] = klazz.getConstructors();
+	for (int i = 0; i < ctors.length; i++)
+	  {
+	    // Skip methods with wrong number of args.
+	    Class ptypes[] = ctors[i].getParameterTypes();
+	    System.out.println("ptypeslen = " + ptypes.length);
+	    System.out.println("ptypes = " + ptypes);
+	    System.out.println("ctor = " + ctors[i].getName());
+	    for (int j=0; j < ptypes.length; j++) {
+	      System.out.println("param = " + ptypes[i].getName());
+     
+	    }
+	      
+	    
+	    if (ptypes.length != args.length)
+	      continue;
+
+	    // Check if method matches
+	    if (!compatible(ptypes, argTypes))
+	      continue;
+
+	    // Use method[i] if it is more specific. 
+	    // FIXME: should this check both directions and throw if
+	    // neither is more specific?
+	    if (ctor == null)
+	      {
+		ctor = ctors[i];
+		continue;
+	      }
+	    Class mptypes[] = ctor.getParameterTypes();
+	    if (moreSpecific(ptypes, mptypes))
+	      ctor = ctors[i];
+	  }
+	if (ctor == null)
+	  throw new InstantiationException("No matching constructor for statement " + toString());
+	return ctor.newInstance(args);
+      }
+
+    Method methods[] = klazz.getMethods();
+
+    for (int i = 0; i < methods.length; i++)
+      {
+	// Skip methods with wrong name or number of args.
+	if (!methods[i].getName().equals(methodName))
+	  continue;
+	Class ptypes[] = methods[i].getParameterTypes();
+	if (ptypes.length != args.length)
+	  continue;
+
+	// Check if method matches
+	if (!compatible(ptypes, argTypes))
+	  continue;
+
+	// Use method[i] if it is more specific. 
+	// FIXME: should this check both directions and throw if
+	// neither is more specific?
+	if (method == null)
+	  {
+	    method = methods[i];
+	    continue;
+	  }
+	Class mptypes[] = method.getParameterTypes();
+	if (moreSpecific(ptypes, mptypes))
+	  method = methods[i];
+      }
+    if (method == null)
+      throw new NoSuchMethodException("No matching method for statement " + toString());
+    return method.invoke(target, args);
+  }
+
+  
+
+  /** Return the statement arguments. */
+  public Object[] getArguments() { return arguments; }
+
+  /** Return the statement method name. */
+  public String getMethodName() { return methodName; }
+
+  /** Return the statement object. */
+  public Object getTarget() { return target; }
+
+  /** Return a string representation. */
+  public String toString()
+  {
+    String result = target.getClass().getName() + "." + methodName + "(";
+    String sep = "";
+    for (int i = 0; i < arguments.length; i++)
+      {
+	result = result + sep + arguments[i].getClass().getName();
+	sep = ", ";
+      }
+    result = result + ")";
+    return result;
+  }
+}