Github user mikezaccardo commented on a diff in the pull request:
https://github.com/apache/incubator-brooklyn/pull/714#discussion_r33174619
--- Diff: core/src/main/java/brooklyn/util/flags/MethodCoercions.java ---
@@ -0,0 +1,183 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 brooklyn.util.flags;
+
+import brooklyn.util.exceptions.Exceptions;
+import brooklyn.util.guava.Maybe;
+import com.google.common.base.Optional;
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
+import com.google.common.reflect.TypeToken;
+
+import javax.annotation.Nullable;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Type;
+import java.util.Arrays;
+import java.util.List;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * A way of binding a loosely-specified method call into a strongly-typed
Java method call.
+ */
+public class MethodCoercions {
+
+ /**
+ * Returns a predicate that matches a method with the given name, and
a single parameter that
+ * {@link brooklyn.util.flags.TypeCoercions#tryCoerce(Object,
com.google.common.reflect.TypeToken)} can process
+ * from the given argument.
+ *
+ * @param methodName name of the method
+ * @param argument argument that is intended to be given
+ * @return a predicate that will match a compatible method
+ */
+ public static Predicate<Method> matchSingleParameterMethod(final
String methodName, final Object argument) {
+ checkNotNull(methodName, "methodName");
+ checkNotNull(argument, "argument");
+
+ return new Predicate<Method>() {
+ @Override
+ public boolean apply(@Nullable Method input) {
+ if (input == null) return false;
+ if (!input.getName().equals(methodName)) return false;
+ Type[] parameterTypes = input.getGenericParameterTypes();
+ return parameterTypes.length == 1
+ && TypeCoercions.tryCoerce(argument,
TypeToken.of(parameterTypes[0])).isPresentAndNonNull();
+
+ }
+ };
+ }
+
+ /**
+ * Tries to find a single-parameter method with a parameter compatible
with (can be coerced to) the argument, and
+ * invokes it.
+ *
+ * @param instance the object to invoke the method on
+ * @param methodName the name of the method to invoke
+ * @param argument the argument to the method's parameter.
+ * @return the result of the method call, or {@link
brooklyn.util.guava.Maybe#absent()} if method could not be matched.
+ */
+ public static Maybe<?> tryFindAndInvokeSingleParameterMethod(final
Object instance, final String methodName, final Object argument) {
+ Class<?> clazz = instance.getClass();
+ Iterable<Method> methods = Arrays.asList(clazz.getMethods());
+ Optional<Method> matchingMethod = Iterables.tryFind(methods,
matchSingleParameterMethod(methodName, argument));
+ if (matchingMethod.isPresent()) {
+ Method method = matchingMethod.get();
+ try {
+ Type paramType = method.getGenericParameterTypes()[0];
+ Object coercedArgument = TypeCoercions.coerce(argument,
TypeToken.of(paramType));
+ return Maybe.of(method.invoke(instance, coercedArgument));
+ } catch (IllegalAccessException | InvocationTargetException e)
{
+ throw Exceptions.propagate(e);
+ }
+ } else {
+ return Maybe.absent();
+ }
+ }
+
+ /**
+ * Returns a predicate that matches a method with the given name, and
parameters that
+ * {@link brooklyn.util.flags.TypeCoercions#tryCoerce(Object,
com.google.common.reflect.TypeToken)} can process
+ * from the given list of arguments.
+ *
+ * @param methodName name of the method
+ * @param arguments arguments that is intended to be given
+ * @return a predicate that will match a compatible method
+ */
+ public static Predicate<Method> matchMultiParameterMethod(final String
methodName, final List<?> arguments) {
+ checkNotNull(methodName, "methodName");
+ checkNotNull(arguments, "arguments");
+
+ return new Predicate<Method>() {
+ @Override
+ public boolean apply(@Nullable Method input) {
+ if (input == null) return false;
+ if (!input.getName().equals(methodName)) return false;
+ int numOptionParams = arguments.size();
+ Type[] parameterTypes = input.getGenericParameterTypes();
+ if (parameterTypes.length != numOptionParams) return false;
+
+ for (int paramCount = 0; paramCount < numOptionParams;
paramCount++) {
+ if (!TypeCoercions.tryCoerce(((List)
arguments).get(paramCount),
+
TypeToken.of(parameterTypes[paramCount])).isPresentAndNonNull()) return false;
+ }
+ return true;
+ }
+ };
+ }
+
+ /**
+ * Tries to find a multiple-parameter method with each parameter
compatible with (can be coerced to) the
+ * corresponding argument, and invokes it.
+ *
+ * @param instance the object to invoke the method on
+ * @param methodName the name of the method to invoke
+ * @param argument a list of the arguments to the method's parameters.
+ * @return the result of the method call, or {@link
brooklyn.util.guava.Maybe#absent()} if method could not be matched.
+ */
+ public static Maybe<?> tryFindAndInvokeMultiParameterMethod(final
Object instance, final String methodName, final List<?> arguments) {
+ Class<?> clazz = instance.getClass();
+ Iterable<Method> methods = Arrays.asList(clazz.getMethods());
+ Optional<Method> matchingMethod = Iterables.tryFind(methods,
matchMultiParameterMethod(methodName, arguments));
+ if (matchingMethod.isPresent()) {
+ Method method = matchingMethod.get();
+ try {
+ int numOptionParams = ((List)arguments).size();
+ Object[] coercedArguments = new Object[numOptionParams];
+ for (int paramCount = 0; paramCount < numOptionParams;
paramCount++) {
+ Object argument = arguments.get(paramCount);
+ Type paramType =
method.getGenericParameterTypes()[paramCount];
+ coercedArguments[paramCount] =
TypeCoercions.coerce(argument, TypeToken.of(paramType));
+ }
+ return Maybe.of(method.invoke(instance, coercedArguments));
+ } catch (IllegalAccessException | InvocationTargetException e)
{
+ throw Exceptions.propagate(e);
+ }
+ } else {
+ return Maybe.absent();
+ }
+ }
+
+ /**
+ * Tries to find a method with each parameter compatible with (can be
coerced to) the corresponding argument, and invokes it.
+ *
+ * @param instance the object to invoke the method on
+ * @param methodName the name of the method to invoke
+ * @param argument a list of the arguments to the method's parameters,
or a single argument for a single-parameter method.
+ * @return the result of the method call, or {@link
brooklyn.util.guava.Maybe#absent()} if method could not be matched.
+ */
+ public static Maybe<?> tryFindAndInvokeBestMatchingMethod(final Object
instance, final String methodName, final Object argument) {
+ if (argument instanceof List) {
+ List<?> arguments = (List<?>) argument;
+
+ // ambiguous case: we can't tell if the user is using the
multi-parameter syntax, or the single-parameter
+ // syntax for a method which takes a List parameter. So we try
one, then fall back to the other.
+
+ Maybe<?> maybe =
tryFindAndInvokeMultiParameterMethod(instance, methodName, arguments);
+ if (maybe.isAbsent())
--- End diff --
Personal preference: I like the conciseness of a ternary, so I would do
something like:
`return (maybe.isPresent()) ? maybe :
tryFindAndInvokeSingleParameterMethod(instance, methodName, argument);`
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