add basic pre/post processing aka poor man's AOP

SHL-40

src/main/java/org/springframework/shell/ExecutionProcessor.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2011-2012 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.shell;
+
+import org.springframework.roo.shell.CommandMarker;
+import org.springframework.roo.shell.ParseResult;
+
+/**
+ * Extension interface allowing command provider to be called
+ * in a generic fashion just before, and right after, executing a command.
+ * 
+ * @author Costin Leau
+ */
+public interface ExecutionProcessor extends CommandMarker {
+
+	/**
+	 * Method called before invoking the target command (described by {@link ParseResult}).
+	 * Additionally, for advanced cases, the parse result itself effectively changing the invocation
+	 * calling site.
+	 * 
+	 * @param invocationContext target command context
+	 * @return the invocation target 
+	 */
+	ParseResult beforeInvocation(ParseResult invocationContext);
+
+	/**
+	 * Method called after invoking the target command (described by {@link ParseResult}).
+	 * 
+	 * @param invocationContext target command context
+	 */
+	void afterInvocation(ParseResult invocationContext);
+}

src/main/java/org/springframework/shell/SimpleExecutionStrategy.java

@@ -1,22 +1,47 @@
 package org.springframework.shell;
 
+import org.springframework.roo.shell.CommandMarker;
 import org.springframework.roo.shell.ExecutionStrategy;
 import org.springframework.roo.shell.ParseResult;
 import org.springframework.roo.support.util.Assert;
 import org.springframework.roo.support.util.ReflectionUtils;
 
+/**
+ * Simple execution strategy for invoking a target method.
+ * Supports pre/post processing to allow {@link CommandMarker}s for aop-like behavior (
+ * typically used for controlling stateful objects). 
+ * 
+ * @author Mark Pollack
+ * @author Costin Leau
+ */
 public class SimpleExecutionStrategy implements ExecutionStrategy {
 
 	private final Class<?> mutex = SimpleExecutionStrategy.class;
-	
+
 	public Object execute(ParseResult parseResult) throws RuntimeException {
 		Assert.notNull(parseResult, "Parse result required");
 		synchronized (mutex) {
 			Assert.isTrue(isReadyForCommands(), "ProcessManagerHostedExecutionStrategy not yet ready for commands");
-			return ReflectionUtils.invokeMethod(parseResult.getMethod(), parseResult.getInstance(), parseResult.getArguments());
+			Object target = parseResult.getInstance();
+			if (target instanceof ExecutionProcessor) {
+				ExecutionProcessor processor = ((ExecutionProcessor) target);
+				parseResult = processor.beforeInvocation(parseResult);
+				try {
+					return invoke(parseResult);
+				} finally {
+					processor.afterInvocation(parseResult);
+				}
+			}
+			else {
+				return invoke(parseResult);
+			}
 		}
 	}
 
+	private Object invoke(ParseResult parseResult) {
+		return ReflectionUtils.invokeMethod(parseResult.getMethod(), parseResult.getInstance(), parseResult.getArguments());
+	}
+
 	public boolean isReadyForCommands() {
 		return true;
 	}