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Posted to dev@velocity.apache.org by ge...@apache.org on 2002/03/23 14:30:59 UTC
cvs commit: jakarta-velocity/src/java/org/apache/velocity/util/introspection MethodMap.java
geirm 02/03/23 05:30:58
Modified: src/java/org/apache/velocity/util/introspection
MethodMap.java
Log:
Attila's patch for doing correct overloaded method selection, replacing my
wacky hack :)
Revision Changes Path
1.14 +468 -361 jakarta-velocity/src/java/org/apache/velocity/util/introspection/MethodMap.java
Index: MethodMap.java
===================================================================
RCS file: /home/cvs/jakarta-velocity/src/java/org/apache/velocity/util/introspection/MethodMap.java,v
retrieving revision 1.13
retrieving revision 1.14
diff -u -r1.13 -r1.14
--- MethodMap.java 27 Nov 2001 00:40:46 -0000 1.13
+++ MethodMap.java 23 Mar 2002 13:30:57 -0000 1.14
@@ -1,376 +1,483 @@
-package org.apache.velocity.util.introspection;
-
-/*
- * The Apache Software License, Version 1.1
- *
- * Copyright (c) 2001 The Apache Software Foundation. All rights
- * reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * 3. The end-user documentation included with the redistribution, if
- * any, must include the following acknowlegement:
- * "This product includes software developed by the
- * Apache Software Foundation (http://www.apache.org/)."
- * Alternately, this acknowlegement may appear in the software itself,
- * if and wherever such third-party acknowlegements normally appear.
- *
- * 4. The names "The Jakarta Project", "Velocity", and "Apache Software
- * Foundation" must not be used to endorse or promote products derived
- * from this software without prior written permission. For written
- * permission, please contact apache@apache.org.
- *
- * 5. Products derived from this software may not be called "Apache"
- * nor may "Apache" appear in their names without prior written
- * permission of the Apache Group.
- *
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
- * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
- * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- * ====================================================================
- *
- * This software consists of voluntary contributions made by many
- * individuals on behalf of the Apache Software Foundation. For more
- * information on the Apache Software Foundation, please see
- * <http://www.apache.org/>.
- */
-
-import java.util.List;
-import java.util.ArrayList;
-import java.util.Map;
-import java.util.Hashtable;
-
-import java.lang.reflect.Method;
-
-/**
- *
- * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
- * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
- * @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a>
- * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
- * @version $Id: MethodMap.java,v 1.13 2001/11/27 00:40:46 geirm Exp $
- */
-public class MethodMap
+package org.apache.velocity.util.introspection;
+
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2001 The Apache Software Foundation. All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ * any, must include the following acknowlegement:
+ * "This product includes software developed by the
+ * Apache Software Foundation (http://www.apache.org/)."
+ * Alternately, this acknowlegement may appear in the software itself,
+ * if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Velocity", and "Apache Software
+ * Foundation" must not be used to endorse or promote products derived
+ * from this software without prior written permission. For written
+ * permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ * nor may "Apache" appear in their names without prior written
+ * permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation. For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.Set;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Hashtable;
+
+import java.lang.reflect.Method;
+
+/**
+ *
+ * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
+ * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
+ * @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a>
+ * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
+ * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a>
+ * @version $Id: MethodMap.java,v 1.14 2002/03/23 13:30:57 geirm Exp $
+ */
+public class MethodMap
{
- /**
- * Keep track of all methods with the same name.
- */
- Map methodByNameMap = new Hashtable();
-
- /**
- * Add a method to a list of methods by name.
- * For a particular class we are keeping track
- * of all the methods with the same name.
- */
- public void add(Method method)
- {
- String methodName = method.getName();
-
- List l = (List) methodByNameMap.get( methodName );
-
- if ( l == null)
- {
- l = new ArrayList();
- methodByNameMap.put(methodName, l);
- }
-
- l.add(method);
-
- return;
- }
-
- /**
- * Return a list of methods with the same name.
- *
- * @param String key
- * @return List list of methods
- */
- public List get(String key)
- {
- return (List) methodByNameMap.get(key);
- }
-
- /**
- * <p>
- * Find a method. Attempts to find the
- * most appropriate method using the
- * sense of 'specificity'.
- * </p>
- *
- * <p>
- * This turns out to be a relatively rare case
- * where this is needed - however, functionality
- * like this is needed. This may not be the
- * optimum approach, but it works.
- * </p>
- *
- * @param String name of method
- * @param Object[] params
- * @return Method
- */
- public Method find(String methodName, Object[] params)
- throws AmbiguousException
- {
- List methodList = (List) methodByNameMap.get(methodName);
-
- if (methodList == null)
- {
- return null;
- }
+ private static final int MORE_SPECIFIC = 0;
+ private static final int LESS_SPECIFIC = 1;
+ private static final int INCOMPARABLE = 2;
+
+ /**
+ * Keep track of all methods with the same name.
+ */
+ Map methodByNameMap = new Hashtable();
+
+ /**
+ * Add a method to a list of methods by name.
+ * For a particular class we are keeping track
+ * of all the methods with the same name.
+ */
+ public void add(Method method)
+ {
+ String methodName = method.getName();
+
+ List l = get( methodName );
+
+ if ( l == null)
+ {
+ l = new ArrayList();
+ methodByNameMap.put(methodName, l);
+ }
+
+ l.add(method);
+
+ return;
+ }
+
+ /**
+ * Return a list of methods with the same name.
+ *
+ * @param String key
+ * @return List list of methods
+ */
+ public List get(String key)
+ {
+ return (List) methodByNameMap.get(key);
+ }
+
+ /**
+ * <p>
+ * Find a method. Attempts to find the
+ * most specific applicable method using the
+ * algorithm described in the JLS section
+ * 15.12.2 (with the exception that it can't
+ * distinguish a primitive type argument from
+ * an object type argument, since in reflection
+ * primitive type arguments are represented by
+ * their object counterparts, so for an argument of
+ * type (say) java.lang.Integer, it will not be able
+ * to decide between a method that takes int and a
+ * method that takes java.lang.Integer as a parameter.
+ * </p>
+ *
+ * <p>
+ * This turns out to be a relatively rare case
+ * where this is needed - however, functionality
+ * like this is needed.
+ * </p>
+ *
+ * @param methodName name of method
+ * @param args the actual arguments with which the method is called
+ * @return the most specific applicable method, or null if no
+ * method is applicable.
+ * @throws AmbiguousException if there is more than one maximally
+ * specific applicable method
+ */
+ public Method find(String methodName, Object[] args)
+ throws AmbiguousException
+ {
+ List methodList = get(methodName);
+
+ if (methodList == null)
+ {
+ return null;
+ }
+
+ int l = args.length;
+ Class[] classes = new Class[l];
+
+ for(int i = 0; i < l; ++i)
+ {
+ Object arg = args[i];
+ // A null argument is always treated as being a generic Object.
+ classes[i] =
+ arg == null ? java.lang.Object.class : arg.getClass();
+ }
+
+ return getMostSpecific(methodList, classes);
+ }
+
+ /**
+ * simple distinguishable exception, used when
+ * we run across ambiguous overloading
+ */
+ public static class AmbiguousException extends Exception
+ {
+ }
+
+
+ private static Method getMostSpecific(List methods, Class[] classes)
+ throws AmbiguousException
+ {
+ LinkedList applicables = getApplicables(methods, classes);
+
+ if(applicables.isEmpty())
+ {
+ return null;
+ }
+
+ if(applicables.size() == 1)
+ {
+ return (Method)applicables.getFirst();
+ }
- Class[] parameterTypes = null;
- Method method = null;
+ /*
+ * This list will contain the maximally specific methods. Hopefully at
+ * the end of the below loop, the list will contain exactly one method,
+ * (the most specific method) otherwise we have ambiguity.
+ */
+
+ LinkedList maximals = new LinkedList();
- int numMethods = methodList.size();
-
- int bestDistance = -2;
- Method bestMethod = null;
- Twonk bestTwonk = null;
- boolean ambiguous = false;
-
- for (int i = 0; i < numMethods; i++)
- {
- method = (Method) methodList.get(i);
- parameterTypes = method.getParameterTypes();
-
- /*
- * The methods we are trying to compare must
- * the same number of arguments.
- */
+ for (Iterator applicable = applicables.iterator();
+ applicable.hasNext();)
+ {
+ Method app = (Method) applicable.next();
+ Class[] appArgs = app.getParameterTypes();
+ boolean lessSpecific = false;
+
+ for (Iterator maximal = maximals.iterator();
+ !lessSpecific && maximal.hasNext();)
+ {
+ Method max = (Method) maximal.next();
- if (parameterTypes.length == params.length)
- {
- /*
- * use the calling parameters as the baseline
- * and calculate the 'distance' from the parameters
- * to the method args. This will be useful when
- * determining specificity
- */
-
- Twonk twonk = calcDistance( params, parameterTypes );
-
- if (twonk != null )
+ switch(moreSpecific(appArgs, max.getParameterTypes()))
{
- /*
- * if we don't have anything yet, take it
- */
-
- if ( bestTwonk == null )
- {
- bestTwonk = twonk;
- bestMethod = method;
- }
- else
- {
+ case MORE_SPECIFIC:
+ {
/*
- * now see which is more specific, this current
- * versus what we think of as the best candidate
+ * This method is more specific than the previously
+ * known maximally specific, so remove the old maximum.
*/
-
- int val = twonk.moreSpecific( bestTwonk );
-
- //System.out.println("Val = " + val + " for " + method + " vs " + bestMethod );
-
- if( val == 0)
- {
- /*
- * this means that the parameters 'crossed'
- * therefore, it's ambiguous because one is as
- * good as the other
- */
- ambiguous = true;
- }
- else if ( val == 1)
- {
- /*
- * the current method is clearly more
- * specific than the current best, so
- * we take the current we are testing
- * and clear the ambiguity flag
- */
- ambiguous = false;
- bestTwonk = twonk;
- bestMethod = method;
- }
- }
- }
-
+
+ maximal.remove();
+ break;
+ }
+
+ case LESS_SPECIFIC:
+ {
+ /*
+ * This method is less specific than some of the
+ * currently known maximally specific methods, so we
+ * won't add it into the set of maximally specific
+ * methods
+ */
+
+ lessSpecific = true;
+ break;
+ }
+ }
}
+
+ if(!lessSpecific)
+ {
+ maximals.addLast(app);
+ }
}
-
- /*
- * if ambiguous is true, it means we couldn't decide
- * so inform the caller...
- */
-
- if ( ambiguous )
- {
- throw new AmbiguousException();
+
+ if(maximals.size() > 1)
+ {
+ // We have more than one maximally specific method
+ throw new AmbiguousException();
+ }
+
+ return (Method)maximals.getFirst();
+ }
+
+ /**
+ * Determines which method signature (represented by a class array) is more
+ * specific. This defines a partial ordering on the method signatures.
+ * @param c1 first signature to compare
+ * @param c2 second signature to compare
+ * @return MORE_SPECIFIC if c1 is more specific than c2, LESS_SPECIFIC if
+ * c1 is less specific than c2, INCOMPARABLE if they are incomparable.
+ */
+ private static int moreSpecific(Class[] c1, Class[] c2)
+ {
+ boolean c1MoreSpecific = false;
+ boolean c2MoreSpecific = false;
+
+ for(int i = 0; i < c1.length; ++i)
+ {
+ if(c1[i] != c2[i])
+ {
+ c1MoreSpecific =
+ c1MoreSpecific ||
+ isStrictMethodInvocationConvertible(c2[i], c1[i]);
+ c2MoreSpecific =
+ c2MoreSpecific ||
+ isStrictMethodInvocationConvertible(c1[i], c2[i]);
+ }
}
-
- return bestMethod;
- }
-
- /**
- * Calculates the distance, expressed as a vector of inheritance
- * steps, between the calling args and the method args.
- * There still is an issue re interfaces...
- */
- private Twonk calcDistance( Object[] set, Class[] base )
- {
- if ( set.length != base.length)
- return null;
-
- Twonk twonk = new Twonk( set.length );
-
- int distance = 0;
-
- for (int i = 0; i < set.length; i++)
- {
- /*
- * can I get from here to there?
- */
-
- Class setclass = set[i].getClass();
-
- if ( !base[i].isAssignableFrom( set[i].getClass() ))
- return null;
-
- /*
- * ok, I can. How many steps?
- */
-
- Class c = setclass;
-
- while( c != null)
- {
+
+ if(c1MoreSpecific)
+ {
+ if(c2MoreSpecific)
+ {
/*
- * is this a valid step?
+ * Incomparable due to cross-assignable arguments (i.e.
+ * foo(String, Object) vs. foo(Object, String))
*/
-
- if ( !base[i].isAssignableFrom( c ) )
- {
- /*
- * it stopped being assignable - therefore we are looking at
- * an interface as our target, so move back one step
- * from the distance as the stop wasn't valid
- */
- break;
- }
-
- if( base[i].equals( c ) )
- {
- /*
- * we are equal, so no need to move forward
- */
-
- break;
- }
-
- c = c.getSuperclass();
- twonk.distance++;
- twonk.vec[i]++;
+
+ return INCOMPARABLE;
}
- }
-
- return twonk;
- }
-
- /**
- * simple distinguishable exception, used when
- * we run across ambiguous overloading
- */
- public class AmbiguousException extends Exception
- {
- }
-
- /**
- * little class to hold 'distance' information
- * for calling params, as well as determine
- * specificity
- */
- private class Twonk
- {
- public int distance;
- public int[] vec;
-
- public Twonk( int size )
- {
- vec = new int[size];
+
+ return MORE_SPECIFIC;
}
-
- public int moreSpecific( Twonk other )
- {
- if (other.vec.length != vec.length )
- return -1;
-
- boolean low = false;
- boolean high = false;
-
- for (int i = 0; i < vec.length; i++)
- {
- if ( vec[i] > other.vec[i])
- {
- high = true;
- }
- else if (vec[i] < other.vec[i] )
- {
- low = true;
- }
- }
-
- /*
- * this is a 'crossing' - meaning that
- * we saw the parameter 'slopes' cross
- * this means ambiguity
- */
-
- if (high && low)
- return 0;
-
- /*
- * we saw that all args were 'high', meaning
- * that the other method is more specific so
- * we are less
- */
-
- if( high && !low)
- return -1;
-
- /*
- * we saw that all points were lower, therefore
- * we are more specific
- */
-
- if( !high && low )
- return 1;
-
- /*
- * the remainder, neither high or low
- * means we are the same. This really can't
- * happen, as it implies the same args, right?
- */
-
- return 1;
+
+ if(c2MoreSpecific)
+ {
+ return LESS_SPECIFIC;
+ }
+
+ /*
+ * Incomparable due to non-related arguments (i.e.
+ * foo(Runnable) vs. foo(Serializable))
+ */
+
+ return INCOMPARABLE;
+ }
+
+ /**
+ * Returns all methods that are applicable to actual argument types.
+ * @param methods list of all candidate methods
+ * @param classes the actual types of the arguments
+ * @return a list that contains only applicable methods (number of
+ * formal and actual arguments matches, and argument types are assignable
+ * to formal types through a method invocation conversion).
+ */
+ private static LinkedList getApplicables(List methods, Class[] classes)
+ {
+ LinkedList list = new LinkedList();
+
+ for (Iterator imethod = methods.iterator(); imethod.hasNext();)
+ {
+ Method method = (Method) imethod.next();
+
+ if(isApplicable(method, classes))
+ {
+ list.add(method);
+ }
+
+ }
+ return list;
+ }
+
+ /**
+ * Returns true if the supplied method is applicable to actual
+ * argument types.
+ */
+ private static boolean isApplicable(Method method, Class[] classes)
+ {
+ Class[] methodArgs = method.getParameterTypes();
+
+ if(methodArgs.length != classes.length)
+ {
+ return false;
+ }
+
+ for(int i = 0; i < classes.length; ++i)
+ {
+ if(!isMethodInvocationConvertible(methodArgs[i], classes[i]))
+ {
+ return false;
+ }
}
- }
-}
+
+ return true;
+ }
+
+ /**
+ * Determines whether a type represented by a class object is
+ * convertible to another type represented by a class object using a
+ * method invocation conversion, treating object types of primitive
+ * types as if they were primitive types (that is, a Boolean actual
+ * parameter type matches boolean primitive formal type). This behavior
+ * is because this method is used to determine applicable methods for
+ * an actual parameter list, and primitive types are represented by
+ * their object duals in reflective method calls.
+ *
+ * @param formal the formal parameter type to which the actual
+ * parameter type should be convertible
+ * @param actual the actual parameter type.
+ * @return true if either formal type is assignable from actual type,
+ * or formal is a primitive type and actual is its corresponding object
+ * type or an object type of a primitive type that can be converted to
+ * the formal type.
+ */
+ private static boolean isMethodInvocationConvertible(Class formal,
+ Class actual)
+ {
+ /*
+ * Check for identity or widening reference conversion
+ */
+
+ if(formal.isAssignableFrom(actual))
+ {
+ return true;
+ }
+
+ /*
+ * Check for boxing with widening primitive conversion. Note that
+ * actual parameters are never primitives.
+ */
+
+ if(formal.isPrimitive())
+ {
+ if(formal == Boolean.TYPE && actual == Boolean.class)
+ return true;
+ if(formal == Character.TYPE && actual == Character.class)
+ return true;
+ if(formal == Byte.TYPE && actual == Byte.class)
+ return true;
+ if(formal == Short.TYPE &&
+ (actual == Short.class || actual == Byte.class))
+ return true;
+ if(formal == Integer.TYPE &&
+ (actual == Integer.class || actual == Short.class ||
+ actual == Byte.class))
+ return true;
+ if(formal == Long.TYPE &&
+ (actual == Long.class || actual == Integer.class ||
+ actual == Short.class || actual == Byte.class))
+ return true;
+ if(formal == Float.TYPE &&
+ (actual == Float.class || actual == Long.class ||
+ actual == Integer.class || actual == Short.class ||
+ actual == Byte.class))
+ return true;
+ if(formal == Double.TYPE &&
+ (actual == Double.class || actual == Float.class ||
+ actual == Long.class || actual == Integer.class ||
+ actual == Short.class || actual == Byte.class))
+ return true;
+ }
+ return false;
+ }
+
+ /**
+ * Determines whether a type represented by a class object is
+ * convertible to another type represented by a class object using a
+ * method invocation conversion, without matching object and primitive
+ * types. This method is used to determine the more specific type when
+ * comparing signatures of methods.
+ *
+ * @param formal the formal parameter type to which the actual
+ * parameter type should be convertible
+ * @param actual the actual parameter type.
+ * @return true if either formal type is assignable from actual type,
+ * or formal and actual are both primitive types and actual can be
+ * subject to widening conversion to formal.
+ */
+ private static boolean isStrictMethodInvocationConvertible(Class formal,
+ Class actual)
+ {
+ /*
+ * Check for identity or widening reference conversion
+ */
+ if(formal.isAssignableFrom(actual))
+ {
+ return true;
+ }
+
+ /*
+ * Check for widening primitive conversion.
+ */
+
+ if(formal.isPrimitive())
+ {
+ if(formal == Short.TYPE && (actual == Byte.TYPE))
+ return true;
+ if(formal == Integer.TYPE &&
+ (actual == Short.TYPE || actual == Byte.TYPE))
+ return true;
+ if(formal == Long.TYPE &&
+ (actual == Integer.TYPE || actual == Short.TYPE ||
+ actual == Byte.TYPE))
+ return true;
+ if(formal == Float.TYPE &&
+ (actual == Long.TYPE || actual == Integer.TYPE ||
+ actual == Short.TYPE || actual == Byte.TYPE))
+ return true;
+ if(formal == Double.TYPE &&
+ (actual == Float.TYPE || actual == Long.TYPE ||
+ actual == Integer.TYPE || actual == Short.TYPE ||
+ actual == Byte.TYPE))
+ return true;
+ }
+ return false;
+ }
+}
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Re: cvs commit:
jakarta-velocity/src/java/org/apache/velocity/util/introspection
MethodMap.java
Posted by "Geir Magnusson Jr." <ge...@earthlink.net>.
On 3/25/02 12:05 PM, "Daniel Rall" <dl...@finemaltcoding.com> wrote:
> Will this be in RC2, or was 1.3 branched?
>
1.3 was branched.
--
Geir Magnusson Jr. geirm@optonline.net
System and Software Consulting
"They that can give up essential liberty to obtain a little temporary safety
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Re: cvs commit: jakarta-velocity/src/java/org/apache/velocity/util/introspection MethodMap.java
Posted by Daniel Rall <dl...@finemaltcoding.com>.
Will this be in RC2, or was 1.3 branched?
geirm@apache.org writes:
> geirm 02/03/23 05:30:58
>
> Modified: src/java/org/apache/velocity/util/introspection
> MethodMap.java
> Log:
> Attila's patch for doing correct overloaded method selection, replacing my
> wacky hack :)
>
> Revision Changes Path
> 1.14 +468 -361 jakarta-velocity/src/java/org/apache/velocity/util/introspection/MethodMap.java
>
> Index: MethodMap.java
> ===================================================================
> RCS file: /home/cvs/jakarta-velocity/src/java/org/apache/velocity/util/introspection/MethodMap.java,v
> retrieving revision 1.13
> retrieving revision 1.14
> diff -u -r1.13 -r1.14
> --- MethodMap.java 27 Nov 2001 00:40:46 -0000 1.13
> +++ MethodMap.java 23 Mar 2002 13:30:57 -0000 1.14
> @@ -1,376 +1,483 @@
> -package org.apache.velocity.util.introspection;
> -
> -/*
> - * The Apache Software License, Version 1.1
> - *
> - * Copyright (c) 2001 The Apache Software Foundation. All rights
> - * reserved.
> - *
> - * Redistribution and use in source and binary forms, with or without
> - * modification, are permitted provided that the following conditions
> - * are met:
> - *
> - * 1. Redistributions of source code must retain the above copyright
> - * notice, this list of conditions and the following disclaimer.
> - *
> - * 2. Redistributions in binary form must reproduce the above copyright
> - * notice, this list of conditions and the following disclaimer in
> - * the documentation and/or other materials provided with the
> - * distribution.
> - *
> - * 3. The end-user documentation included with the redistribution, if
> - * any, must include the following acknowlegement:
> - * "This product includes software developed by the
> - * Apache Software Foundation (http://www.apache.org/)."
> - * Alternately, this acknowlegement may appear in the software itself,
> - * if and wherever such third-party acknowlegements normally appear.
> - *
> - * 4. The names "The Jakarta Project", "Velocity", and "Apache Software
> - * Foundation" must not be used to endorse or promote products derived
> - * from this software without prior written permission. For written
> - * permission, please contact apache@apache.org.
> - *
> - * 5. Products derived from this software may not be called "Apache"
> - * nor may "Apache" appear in their names without prior written
> - * permission of the Apache Group.
> - *
> - * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
> - * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
> - * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
> - * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
> - * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> - * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> - * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
> - * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
> - * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
> - * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
> - * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> - * SUCH DAMAGE.
> - * ====================================================================
> - *
> - * This software consists of voluntary contributions made by many
> - * individuals on behalf of the Apache Software Foundation. For more
> - * information on the Apache Software Foundation, please see
> - * <http://www.apache.org/>.
> - */
> -
> -import java.util.List;
> -import java.util.ArrayList;
> -import java.util.Map;
> -import java.util.Hashtable;
> -
> -import java.lang.reflect.Method;
> -
> -/**
> - *
> - * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
> - * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
> - * @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a>
> - * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
> - * @version $Id: MethodMap.java,v 1.13 2001/11/27 00:40:46 geirm Exp $
> - */
> -public class MethodMap
> +package org.apache.velocity.util.introspection;
> +
> +/*
> + * The Apache Software License, Version 1.1
> + *
> + * Copyright (c) 2001 The Apache Software Foundation. All rights
> + * reserved.
> + *
> + * Redistribution and use in source and binary forms, with or without
> + * modification, are permitted provided that the following conditions
> + * are met:
> + *
> + * 1. Redistributions of source code must retain the above copyright
> + * notice, this list of conditions and the following disclaimer.
> + *
> + * 2. Redistributions in binary form must reproduce the above copyright
> + * notice, this list of conditions and the following disclaimer in
> + * the documentation and/or other materials provided with the
> + * distribution.
> + *
> + * 3. The end-user documentation included with the redistribution, if
> + * any, must include the following acknowlegement:
> + * "This product includes software developed by the
> + * Apache Software Foundation (http://www.apache.org/)."
> + * Alternately, this acknowlegement may appear in the software itself,
> + * if and wherever such third-party acknowlegements normally appear.
> + *
> + * 4. The names "The Jakarta Project", "Velocity", and "Apache Software
> + * Foundation" must not be used to endorse or promote products derived
> + * from this software without prior written permission. For written
> + * permission, please contact apache@apache.org.
> + *
> + * 5. Products derived from this software may not be called "Apache"
> + * nor may "Apache" appear in their names without prior written
> + * permission of the Apache Group.
> + *
> + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
> + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
> + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
> + * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
> + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
> + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
> + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
> + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
> + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> + * SUCH DAMAGE.
> + * ====================================================================
> + *
> + * This software consists of voluntary contributions made by many
> + * individuals on behalf of the Apache Software Foundation. For more
> + * information on the Apache Software Foundation, please see
> + * <http://www.apache.org/>.
> + */
> +
> +import java.util.Iterator;
> +import java.util.List;
> +import java.util.ArrayList;
> +import java.util.LinkedList;
> +import java.util.Set;
> +import java.util.HashSet;
> +import java.util.Map;
> +import java.util.Hashtable;
> +
> +import java.lang.reflect.Method;
> +
> +/**
> + *
> + * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
> + * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
> + * @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a>
> + * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
> + * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a>
> + * @version $Id: MethodMap.java,v 1.14 2002/03/23 13:30:57 geirm Exp $
> + */
> +public class MethodMap
> {
> - /**
> - * Keep track of all methods with the same name.
> - */
> - Map methodByNameMap = new Hashtable();
> -
> - /**
> - * Add a method to a list of methods by name.
> - * For a particular class we are keeping track
> - * of all the methods with the same name.
> - */
> - public void add(Method method)
> - {
> - String methodName = method.getName();
> -
> - List l = (List) methodByNameMap.get( methodName );
> -
> - if ( l == null)
> - {
> - l = new ArrayList();
> - methodByNameMap.put(methodName, l);
> - }
> -
> - l.add(method);
> -
> - return;
> - }
> -
> - /**
> - * Return a list of methods with the same name.
> - *
> - * @param String key
> - * @return List list of methods
> - */
> - public List get(String key)
> - {
> - return (List) methodByNameMap.get(key);
> - }
> -
> - /**
> - * <p>
> - * Find a method. Attempts to find the
> - * most appropriate method using the
> - * sense of 'specificity'.
> - * </p>
> - *
> - * <p>
> - * This turns out to be a relatively rare case
> - * where this is needed - however, functionality
> - * like this is needed. This may not be the
> - * optimum approach, but it works.
> - * </p>
> - *
> - * @param String name of method
> - * @param Object[] params
> - * @return Method
> - */
> - public Method find(String methodName, Object[] params)
> - throws AmbiguousException
> - {
> - List methodList = (List) methodByNameMap.get(methodName);
> -
> - if (methodList == null)
> - {
> - return null;
> - }
> + private static final int MORE_SPECIFIC = 0;
> + private static final int LESS_SPECIFIC = 1;
> + private static final int INCOMPARABLE = 2;
> +
> + /**
> + * Keep track of all methods with the same name.
> + */
> + Map methodByNameMap = new Hashtable();
> +
> + /**
> + * Add a method to a list of methods by name.
> + * For a particular class we are keeping track
> + * of all the methods with the same name.
> + */
> + public void add(Method method)
> + {
> + String methodName = method.getName();
> +
> + List l = get( methodName );
> +
> + if ( l == null)
> + {
> + l = new ArrayList();
> + methodByNameMap.put(methodName, l);
> + }
> +
> + l.add(method);
> +
> + return;
> + }
> +
> + /**
> + * Return a list of methods with the same name.
> + *
> + * @param String key
> + * @return List list of methods
> + */
> + public List get(String key)
> + {
> + return (List) methodByNameMap.get(key);
> + }
> +
> + /**
> + * <p>
> + * Find a method. Attempts to find the
> + * most specific applicable method using the
> + * algorithm described in the JLS section
> + * 15.12.2 (with the exception that it can't
> + * distinguish a primitive type argument from
> + * an object type argument, since in reflection
> + * primitive type arguments are represented by
> + * their object counterparts, so for an argument of
> + * type (say) java.lang.Integer, it will not be able
> + * to decide between a method that takes int and a
> + * method that takes java.lang.Integer as a parameter.
> + * </p>
> + *
> + * <p>
> + * This turns out to be a relatively rare case
> + * where this is needed - however, functionality
> + * like this is needed.
> + * </p>
> + *
> + * @param methodName name of method
> + * @param args the actual arguments with which the method is called
> + * @return the most specific applicable method, or null if no
> + * method is applicable.
> + * @throws AmbiguousException if there is more than one maximally
> + * specific applicable method
> + */
> + public Method find(String methodName, Object[] args)
> + throws AmbiguousException
> + {
> + List methodList = get(methodName);
> +
> + if (methodList == null)
> + {
> + return null;
> + }
> +
> + int l = args.length;
> + Class[] classes = new Class[l];
> +
> + for(int i = 0; i < l; ++i)
> + {
> + Object arg = args[i];
> + // A null argument is always treated as being a generic Object.
> + classes[i] =
> + arg == null ? java.lang.Object.class : arg.getClass();
> + }
> +
> + return getMostSpecific(methodList, classes);
> + }
> +
> + /**
> + * simple distinguishable exception, used when
> + * we run across ambiguous overloading
> + */
> + public static class AmbiguousException extends Exception
> + {
> + }
> +
> +
> + private static Method getMostSpecific(List methods, Class[] classes)
> + throws AmbiguousException
> + {
> + LinkedList applicables = getApplicables(methods, classes);
> +
> + if(applicables.isEmpty())
> + {
> + return null;
> + }
> +
> + if(applicables.size() == 1)
> + {
> + return (Method)applicables.getFirst();
> + }
>
> - Class[] parameterTypes = null;
> - Method method = null;
> + /*
> + * This list will contain the maximally specific methods. Hopefully at
> + * the end of the below loop, the list will contain exactly one method,
> + * (the most specific method) otherwise we have ambiguity.
> + */
> +
> + LinkedList maximals = new LinkedList();
>
> - int numMethods = methodList.size();
> -
> - int bestDistance = -2;
> - Method bestMethod = null;
> - Twonk bestTwonk = null;
> - boolean ambiguous = false;
> -
> - for (int i = 0; i < numMethods; i++)
> - {
> - method = (Method) methodList.get(i);
> - parameterTypes = method.getParameterTypes();
> -
> - /*
> - * The methods we are trying to compare must
> - * the same number of arguments.
> - */
> + for (Iterator applicable = applicables.iterator();
> + applicable.hasNext();)
> + {
> + Method app = (Method) applicable.next();
> + Class[] appArgs = app.getParameterTypes();
> + boolean lessSpecific = false;
> +
> + for (Iterator maximal = maximals.iterator();
> + !lessSpecific && maximal.hasNext();)
> + {
> + Method max = (Method) maximal.next();
>
> - if (parameterTypes.length == params.length)
> - {
> - /*
> - * use the calling parameters as the baseline
> - * and calculate the 'distance' from the parameters
> - * to the method args. This will be useful when
> - * determining specificity
> - */
> -
> - Twonk twonk = calcDistance( params, parameterTypes );
> -
> - if (twonk != null )
> + switch(moreSpecific(appArgs, max.getParameterTypes()))
> {
> - /*
> - * if we don't have anything yet, take it
> - */
> -
> - if ( bestTwonk == null )
> - {
> - bestTwonk = twonk;
> - bestMethod = method;
> - }
> - else
> - {
> + case MORE_SPECIFIC:
> + {
> /*
> - * now see which is more specific, this current
> - * versus what we think of as the best candidate
> + * This method is more specific than the previously
> + * known maximally specific, so remove the old maximum.
> */
> -
> - int val = twonk.moreSpecific( bestTwonk );
> -
> - //System.out.println("Val = " + val + " for " + method + " vs " + bestMethod );
> -
> - if( val == 0)
> - {
> - /*
> - * this means that the parameters 'crossed'
> - * therefore, it's ambiguous because one is as
> - * good as the other
> - */
> - ambiguous = true;
> - }
> - else if ( val == 1)
> - {
> - /*
> - * the current method is clearly more
> - * specific than the current best, so
> - * we take the current we are testing
> - * and clear the ambiguity flag
> - */
> - ambiguous = false;
> - bestTwonk = twonk;
> - bestMethod = method;
> - }
> - }
> - }
> -
> +
> + maximal.remove();
> + break;
> + }
> +
> + case LESS_SPECIFIC:
> + {
> + /*
> + * This method is less specific than some of the
> + * currently known maximally specific methods, so we
> + * won't add it into the set of maximally specific
> + * methods
> + */
> +
> + lessSpecific = true;
> + break;
> + }
> + }
> }
> +
> + if(!lessSpecific)
> + {
> + maximals.addLast(app);
> + }
> }
> -
> - /*
> - * if ambiguous is true, it means we couldn't decide
> - * so inform the caller...
> - */
> -
> - if ( ambiguous )
> - {
> - throw new AmbiguousException();
> +
> + if(maximals.size() > 1)
> + {
> + // We have more than one maximally specific method
> + throw new AmbiguousException();
> + }
> +
> + return (Method)maximals.getFirst();
> + }
> +
> + /**
> + * Determines which method signature (represented by a class array) is more
> + * specific. This defines a partial ordering on the method signatures.
> + * @param c1 first signature to compare
> + * @param c2 second signature to compare
> + * @return MORE_SPECIFIC if c1 is more specific than c2, LESS_SPECIFIC if
> + * c1 is less specific than c2, INCOMPARABLE if they are incomparable.
> + */
> + private static int moreSpecific(Class[] c1, Class[] c2)
> + {
> + boolean c1MoreSpecific = false;
> + boolean c2MoreSpecific = false;
> +
> + for(int i = 0; i < c1.length; ++i)
> + {
> + if(c1[i] != c2[i])
> + {
> + c1MoreSpecific =
> + c1MoreSpecific ||
> + isStrictMethodInvocationConvertible(c2[i], c1[i]);
> + c2MoreSpecific =
> + c2MoreSpecific ||
> + isStrictMethodInvocationConvertible(c1[i], c2[i]);
> + }
> }
> -
> - return bestMethod;
> - }
> -
> - /**
> - * Calculates the distance, expressed as a vector of inheritance
> - * steps, between the calling args and the method args.
> - * There still is an issue re interfaces...
> - */
> - private Twonk calcDistance( Object[] set, Class[] base )
> - {
> - if ( set.length != base.length)
> - return null;
> -
> - Twonk twonk = new Twonk( set.length );
> -
> - int distance = 0;
> -
> - for (int i = 0; i < set.length; i++)
> - {
> - /*
> - * can I get from here to there?
> - */
> -
> - Class setclass = set[i].getClass();
> -
> - if ( !base[i].isAssignableFrom( set[i].getClass() ))
> - return null;
> -
> - /*
> - * ok, I can. How many steps?
> - */
> -
> - Class c = setclass;
> -
> - while( c != null)
> - {
> +
> + if(c1MoreSpecific)
> + {
> + if(c2MoreSpecific)
> + {
> /*
> - * is this a valid step?
> + * Incomparable due to cross-assignable arguments (i.e.
> + * foo(String, Object) vs. foo(Object, String))
> */
> -
> - if ( !base[i].isAssignableFrom( c ) )
> - {
> - /*
> - * it stopped being assignable - therefore we are looking at
> - * an interface as our target, so move back one step
> - * from the distance as the stop wasn't valid
> - */
> - break;
> - }
> -
> - if( base[i].equals( c ) )
> - {
> - /*
> - * we are equal, so no need to move forward
> - */
> -
> - break;
> - }
> -
> - c = c.getSuperclass();
> - twonk.distance++;
> - twonk.vec[i]++;
> +
> + return INCOMPARABLE;
> }
> - }
> -
> - return twonk;
> - }
> -
> - /**
> - * simple distinguishable exception, used when
> - * we run across ambiguous overloading
> - */
> - public class AmbiguousException extends Exception
> - {
> - }
> -
> - /**
> - * little class to hold 'distance' information
> - * for calling params, as well as determine
> - * specificity
> - */
> - private class Twonk
> - {
> - public int distance;
> - public int[] vec;
> -
> - public Twonk( int size )
> - {
> - vec = new int[size];
> +
> + return MORE_SPECIFIC;
> }
> -
> - public int moreSpecific( Twonk other )
> - {
> - if (other.vec.length != vec.length )
> - return -1;
> -
> - boolean low = false;
> - boolean high = false;
> -
> - for (int i = 0; i < vec.length; i++)
> - {
> - if ( vec[i] > other.vec[i])
> - {
> - high = true;
> - }
> - else if (vec[i] < other.vec[i] )
> - {
> - low = true;
> - }
> - }
> -
> - /*
> - * this is a 'crossing' - meaning that
> - * we saw the parameter 'slopes' cross
> - * this means ambiguity
> - */
> -
> - if (high && low)
> - return 0;
> -
> - /*
> - * we saw that all args were 'high', meaning
> - * that the other method is more specific so
> - * we are less
> - */
> -
> - if( high && !low)
> - return -1;
> -
> - /*
> - * we saw that all points were lower, therefore
> - * we are more specific
> - */
> -
> - if( !high && low )
> - return 1;
> -
> - /*
> - * the remainder, neither high or low
> - * means we are the same. This really can't
> - * happen, as it implies the same args, right?
> - */
> -
> - return 1;
> +
> + if(c2MoreSpecific)
> + {
> + return LESS_SPECIFIC;
> + }
> +
> + /*
> + * Incomparable due to non-related arguments (i.e.
> + * foo(Runnable) vs. foo(Serializable))
> + */
> +
> + return INCOMPARABLE;
> + }
> +
> + /**
> + * Returns all methods that are applicable to actual argument types.
> + * @param methods list of all candidate methods
> + * @param classes the actual types of the arguments
> + * @return a list that contains only applicable methods (number of
> + * formal and actual arguments matches, and argument types are assignable
> + * to formal types through a method invocation conversion).
> + */
> + private static LinkedList getApplicables(List methods, Class[] classes)
> + {
> + LinkedList list = new LinkedList();
> +
> + for (Iterator imethod = methods.iterator(); imethod.hasNext();)
> + {
> + Method method = (Method) imethod.next();
> +
> + if(isApplicable(method, classes))
> + {
> + list.add(method);
> + }
> +
> + }
> + return list;
> + }
> +
> + /**
> + * Returns true if the supplied method is applicable to actual
> + * argument types.
> + */
> + private static boolean isApplicable(Method method, Class[] classes)
> + {
> + Class[] methodArgs = method.getParameterTypes();
> +
> + if(methodArgs.length != classes.length)
> + {
> + return false;
> + }
> +
> + for(int i = 0; i < classes.length; ++i)
> + {
> + if(!isMethodInvocationConvertible(methodArgs[i], classes[i]))
> + {
> + return false;
> + }
> }
> - }
> -}
> +
> + return true;
> + }
> +
> + /**
> + * Determines whether a type represented by a class object is
> + * convertible to another type represented by a class object using a
> + * method invocation conversion, treating object types of primitive
> + * types as if they were primitive types (that is, a Boolean actual
> + * parameter type matches boolean primitive formal type). This behavior
> + * is because this method is used to determine applicable methods for
> + * an actual parameter list, and primitive types are represented by
> + * their object duals in reflective method calls.
> + *
> + * @param formal the formal parameter type to which the actual
> + * parameter type should be convertible
> + * @param actual the actual parameter type.
> + * @return true if either formal type is assignable from actual type,
> + * or formal is a primitive type and actual is its corresponding object
> + * type or an object type of a primitive type that can be converted to
> + * the formal type.
> + */
> + private static boolean isMethodInvocationConvertible(Class formal,
> + Class actual)
> + {
> + /*
> + * Check for identity or widening reference conversion
> + */
> +
> + if(formal.isAssignableFrom(actual))
> + {
> + return true;
> + }
> +
> + /*
> + * Check for boxing with widening primitive conversion. Note that
> + * actual parameters are never primitives.
> + */
> +
> + if(formal.isPrimitive())
> + {
> + if(formal == Boolean.TYPE && actual == Boolean.class)
> + return true;
> + if(formal == Character.TYPE && actual == Character.class)
> + return true;
> + if(formal == Byte.TYPE && actual == Byte.class)
> + return true;
> + if(formal == Short.TYPE &&
> + (actual == Short.class || actual == Byte.class))
> + return true;
> + if(formal == Integer.TYPE &&
> + (actual == Integer.class || actual == Short.class ||
> + actual == Byte.class))
> + return true;
> + if(formal == Long.TYPE &&
> + (actual == Long.class || actual == Integer.class ||
> + actual == Short.class || actual == Byte.class))
> + return true;
> + if(formal == Float.TYPE &&
> + (actual == Float.class || actual == Long.class ||
> + actual == Integer.class || actual == Short.class ||
> + actual == Byte.class))
> + return true;
> + if(formal == Double.TYPE &&
> + (actual == Double.class || actual == Float.class ||
> + actual == Long.class || actual == Integer.class ||
> + actual == Short.class || actual == Byte.class))
> + return true;
> + }
> + return false;
> + }
> +
> + /**
> + * Determines whether a type represented by a class object is
> + * convertible to another type represented by a class object using a
> + * method invocation conversion, without matching object and primitive
> + * types. This method is used to determine the more specific type when
> + * comparing signatures of methods.
> + *
> + * @param formal the formal parameter type to which the actual
> + * parameter type should be convertible
> + * @param actual the actual parameter type.
> + * @return true if either formal type is assignable from actual type,
> + * or formal and actual are both primitive types and actual can be
> + * subject to widening conversion to formal.
> + */
> + private static boolean isStrictMethodInvocationConvertible(Class formal,
> + Class actual)
> + {
> + /*
> + * Check for identity or widening reference conversion
> + */
> + if(formal.isAssignableFrom(actual))
> + {
> + return true;
> + }
> +
> + /*
> + * Check for widening primitive conversion.
> + */
> +
> + if(formal.isPrimitive())
> + {
> + if(formal == Short.TYPE && (actual == Byte.TYPE))
> + return true;
> + if(formal == Integer.TYPE &&
> + (actual == Short.TYPE || actual == Byte.TYPE))
> + return true;
> + if(formal == Long.TYPE &&
> + (actual == Integer.TYPE || actual == Short.TYPE ||
> + actual == Byte.TYPE))
> + return true;
> + if(formal == Float.TYPE &&
> + (actual == Long.TYPE || actual == Integer.TYPE ||
> + actual == Short.TYPE || actual == Byte.TYPE))
> + return true;
> + if(formal == Double.TYPE &&
> + (actual == Float.TYPE || actual == Long.TYPE ||
> + actual == Integer.TYPE || actual == Short.TYPE ||
> + actual == Byte.TYPE))
> + return true;
> + }
> + return false;
> + }
> +}
>
>
>
>
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