SPR-6764: filtering strategy for SpEL method invocation

org.springframework.expression/src/main/java/org/springframework/expression/MethodFilter.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2002-2009 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.expression;
+
+import java.lang.reflect.Method;
+import java.util.List;
+
+/**
+ * MethodFilter instances allow SpEL users to fine tune the behaviour of the method resolution
+ * process.  Method resolution (which translates from a method name in an expression to a real
+ * method to invoke) will normally retrieve candidate methods for invocation via a simple call 
+ * to 'Class.getMethods()' and will choose the first one that is suitable for the 
+ * input parameters.  By registering a MethodFilter the user can receive a callback 
+ * and change the methods that will be considered suitable.
+ * 
+ * @author Andy Clement
+ * @since 3.0.1
+ */
+public interface MethodFilter {
+
+	/**
+	 * Called by the method resolver to allow the SpEL user to organize the list of candidate 
+	 * methods that may be invoked.  The filter can remove methods that should not be 
+	 * considered candidates and it may sort the results.  The resolver will then search 
+	 * through the methods as returned from the filter when looking for a suitable 
+	 * candidate to invoke.
+	 * 
+	 * @param methods the full list of methods the resolver was going to choose from
+	 * @return a possible subset of input methods that may be sorted by order of relevance
+	 */
+	List<Method> filter(List<Method> methods);
+	
+}

org.springframework.expression/src/main/java/org/springframework/expression/spel/support/ReflectiveMethodResolver.java

@@ -17,16 +17,23 @@
 package org.springframework.expression.spel.support;
 
 import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 import org.springframework.expression.AccessException;
 import org.springframework.expression.EvaluationContext;
 import org.springframework.expression.EvaluationException;
 import org.springframework.expression.MethodExecutor;
+import org.springframework.expression.MethodFilter;
 import org.springframework.expression.MethodResolver;
 import org.springframework.expression.TypeConverter;
 import org.springframework.expression.spel.SpelEvaluationException;
 import org.springframework.expression.spel.SpelMessage;
 
+
+
 /**
  * A method resolver that uses reflection to locate the method that should be invoked
  * 
@@ -35,6 +42,11 @@ import org.springframework.expression.spel.SpelMessage;
  */
 public class ReflectiveMethodResolver implements MethodResolver {
 
+	private static Method[] NO_METHODS = new Method[0];
+
+	private Map<Class<?>,MethodFilter> filters = null;
+
+	
 	/**
 	 * Locate a method on a type. There are three kinds of match that might occur:
 	 * <ol>
@@ -49,6 +61,23 @@ public class ReflectiveMethodResolver implements MethodResolver {
 			TypeConverter typeConverter = context.getTypeConverter();
 			Class<?> type = (targetObject instanceof Class ? (Class<?>) targetObject : targetObject.getClass());
 			Method[] methods = type.getMethods();
+			
+			// If a filter is registered for this type, call it
+			MethodFilter methodfilter = (filters==null?null:filters.get(type));
+			if (methodfilter!=null) {
+			    List<Method> methodsForFiltering = new ArrayList<Method>();
+			    for (Method method: methods) {
+			    	methodsForFiltering.add(method);
+			    }
+				List<Method> methodsFiltered = methodfilter.filter(methodsForFiltering);
+				if (methodsFiltered == null || methodsFiltered.size()==0) {
+					methods = NO_METHODS;
+				}
+				else {
+					methods = methodsFiltered.toArray(new Method[methodsFiltered.size()]);
+				}
+			}
+			
 			Method closeMatch = null;
 			int[] argsToConvert = null;
 			boolean multipleOptions = false;
@@ -101,4 +130,16 @@ public class ReflectiveMethodResolver implements MethodResolver {
 		}
 	}
 
+	public void registerMethodFilter(Class<?> type, MethodFilter filter) {
+		if (filters==null) {
+			filters = new HashMap<Class<?>,MethodFilter>();
+		}
+		if (filter==null) {
+			filters.remove(type);
+		}
+		else {
+			filters.put(type,filter);
+		}
+	}
+
 }

org.springframework.expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java

@@ -25,6 +25,7 @@ import java.util.Map;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.expression.ConstructorResolver;
 import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.MethodFilter;
 import org.springframework.expression.MethodResolver;
 import org.springframework.expression.OperatorOverloader;
 import org.springframework.expression.PropertyAccessor;
@@ -50,6 +51,8 @@ public class StandardEvaluationContext implements EvaluationContext {
 	private List<ConstructorResolver> constructorResolvers;
 
 	private List<MethodResolver> methodResolvers;
+	
+	private ReflectiveMethodResolver reflectiveMethodResolver;
 
 	private List<PropertyAccessor> propertyAccessors;
 
@@ -120,7 +123,7 @@ public class StandardEvaluationContext implements EvaluationContext {
 	private void ensureMethodResolversInitialized() {
 		if (this.methodResolvers == null) {
 			this.methodResolvers = new ArrayList<MethodResolver>();
-			this.methodResolvers.add(new ReflectiveMethodResolver());
+			this.methodResolvers.add(reflectiveMethodResolver=new ReflectiveMethodResolver());
 		}
 	}
 
@@ -199,4 +202,17 @@ public class StandardEvaluationContext implements EvaluationContext {
 		return this.variables.get(name);
 	}
 
+	/**
+	 * Register a MethodFilter which will be called during method resolution for the
+	 * specified type.  The MethodFilter may remove methods and/or sort the methods
+	 * which will then be used by SpEL as the candidates to look through for a match.
+	 * 
+	 * @param type the type for which the filter should be called
+	 * @param filter a MethodFilter, or NULL to deregister a filter for the type
+	 */
+	public void registerMethodFilter(Class<?> type, MethodFilter filter) {
+		ensureMethodResolversInitialized();
+		reflectiveMethodResolver.registerMethodFilter(type,filter);
+	}
+
 }

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

@@ -16,9 +16,18 @@
 
 package org.springframework.expression.spel;
 
+import java.lang.annotation.Annotation;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.List;
+
 import org.junit.Assert;
 import org.junit.Test;
 import org.springframework.expression.Expression;
+import org.springframework.expression.MethodFilter;
+import org.springframework.expression.spel.standard.SpelExpression;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.expression.spel.testresources.PlaceOfBirth;
@@ -141,7 +150,99 @@ public class MethodInvocationTests extends ExpressionTestCase {
 		}
 		// If counter is 5 then the method got called twice!
 		Assert.assertEquals(4,parser.parseExpression("counter").getValue(eContext));
-}
+	}
+	
+	@Test
+	public void testMethodFiltering_SPR6764() {
+		SpelExpressionParser parser = new SpelExpressionParser();
+		StandardEvaluationContext context = new StandardEvaluationContext();
+		context.setRootObject(new TestObject());
+		LocalFilter filter = new LocalFilter();
+		context.registerMethodFilter(TestObject.class,filter);
+		
+		// Filter will be called but not do anything, so first doit() will be invoked
+		SpelExpression expr = (SpelExpression) parser.parseExpression("doit(1)");
+		String result = expr.getValue(context,String.class);
+		Assert.assertEquals("1",result);
+		Assert.assertTrue(filter.filterCalled);
+		
+		// Filter will now remove non @Anno annotated methods
+		filter.removeIfNotAnnotated = true;
+		filter.filterCalled = false;
+		expr = (SpelExpression) parser.parseExpression("doit(1)");
+		result = expr.getValue(context,String.class);
+		Assert.assertEquals("double 1.0",result);
+		Assert.assertTrue(filter.filterCalled);
+		
+		// check not called for other types
+		filter.filterCalled=false;
+		context.setRootObject(new String("abc"));
+		expr = (SpelExpression) parser.parseExpression("charAt(0)");
+		result = expr.getValue(context,String.class);
+		Assert.assertEquals("a",result);
+		Assert.assertFalse(filter.filterCalled);
+		
+		// check de-registration works
+		filter.filterCalled = false;
+		context.registerMethodFilter(TestObject.class,null);//clear filter
+		context.setRootObject(new TestObject());
+		expr = (SpelExpression) parser.parseExpression("doit(1)");
+		result = expr.getValue(context,String.class);
+		Assert.assertEquals("1",result);
+		Assert.assertFalse(filter.filterCalled);
+	}
+	
+	// Simple filter
+	static class LocalFilter implements MethodFilter {
+		
+		public boolean removeIfNotAnnotated = false;
+		
+		public boolean filterCalled = false;
+		
+		private boolean isAnnotated(Method m) {
+			Annotation[] annos = m.getAnnotations();
+			if (annos==null) {
+				return false;
+			}
+			for (Annotation anno: annos) {
+				String s = anno.annotationType().getName();
+				if (s.endsWith("Anno")) {
+					return true;
+				}
+			}
+			return false;
+		}
+
+		public List<Method> filter(List<Method> methods) {
+			filterCalled = true;
+			List<Method> forRemoval = new ArrayList<Method>();
+			for (Method m: methods) {
+				if (removeIfNotAnnotated && !isAnnotated(m)) {
+					forRemoval.add(m);
+				}
+			}
+			for (Method m: forRemoval) {
+				methods.remove(m);
+			}
+			return methods;
+		}
+		
+	}
+	
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface Anno {}
+	
+	class TestObject {
+		public int doit(int i) {
+			return i;
+		}
+		
+		@Anno
+		public String doit(double d) {
+			return "double "+d;
+		}
+		
+	}
 
 	@Test
 	public void testVarargsInvocation01() {