Allow customization of SpEL method resolution

This change introduces a protected ReflectiveMethodResolver#getMethods,
allowing subclasses to specify additional static methods not
declared directly on the type being evaluated. These methods then become
candidates for filtering by any registered MethodFilters and ultimately
become available within for use within SpEL expressions.

Issue: SPR-9038

org.springframework.expression/src/test/java/org/springframework/expression/spel/SpringEL300Tests.java

@@ -17,8 +17,10 @@
 package org.springframework.expression.spel;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 
 import java.lang.reflect.Field;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
@@ -38,6 +40,7 @@ import org.springframework.expression.EvaluationException;
 import org.springframework.expression.Expression;
 import org.springframework.expression.ExpressionParser;
 import org.springframework.expression.MethodExecutor;
+import org.springframework.expression.MethodResolver;
 import org.springframework.expression.ParserContext;
 import org.springframework.expression.PropertyAccessor;
 import org.springframework.expression.TypedValue;
@@ -1137,6 +1140,41 @@ public class SpringEL300Tests extends ExpressionTestCase {
 		public Map<String, String> getFourthContext() {return fourthContext;}
 	}
 
+	/**
+	 * Test the ability to subclass the ReflectiveMethodResolver and change how it
+	 * determines the set of methods for a type.
+	 */
+	@Test
+	public void testCustomStaticFunctions_SPR9038() {
+		try {
+			ExpressionParser parser = new SpelExpressionParser();
+			StandardEvaluationContext context = new StandardEvaluationContext();
+			List<MethodResolver> methodResolvers = new ArrayList<MethodResolver>();
+			methodResolvers.add(new ReflectiveMethodResolver() {
+				@Override
+				protected Method[] getMethods(Class<?> type) {
+					try {
+						return new Method[] {
+								Integer.class.getDeclaredMethod("parseInt", new Class[] {
+										String.class, Integer.TYPE }) };
+					} catch (NoSuchMethodException e1) {
+						return new Method[0];
+					}
+				}
+			});
+
+			context.setMethodResolvers(methodResolvers);
+			org.springframework.expression.Expression expression =
+					parser.parseExpression("parseInt('-FF', 16)");
+
+			Integer result = expression.getValue(context, "", Integer.class);
+			assertEquals("Equal assertion failed: ", -255, result.intValue());
+		} catch (Exception e) {
+			e.printStackTrace();
+			fail("Unexpected exception: "+e.toString());
+		}
+	}
+
 }