SWF-443 - Enhance MethodInvoker to allow type conversion on a method result.

spring-binding/src/main/java/org/springframework/binding/method/MethodInvoker.java

@@ -26,17 +26,18 @@ import org.springframework.core.style.StylerUtils;
 import org.springframework.util.CachingMapDecorator;
 
 /**
- * A helper for invoking typed methods on abritrary objects, with support for argument value type conversion from values
- * retrieved from a argument attribute source.
+ * A helper for invoking typed methods on arbitrary objects, with support for argument value type conversion from values
+ * retrieved from an argument attribute source, and conversion of the result to a desired type.
  * 
  * @author Keith Donald
+ * @author Jeremy Grelle
  */
 public class MethodInvoker {
 
 	private static final Log logger = LogFactory.getLog(MethodInvoker.class);
 
 	/**
-	 * Conversion service for converting arguments to the neccessary type if required.
+	 * Conversion service for converting arguments to the necessary type if required.
 	 */
 	private ConversionService conversionService = new DefaultConversionService();
 
@@ -90,7 +91,7 @@ public class MethodInvoker {
 						+ StylerUtils.style(arguments) + " on bean [" + bean + "]");
 
 			}
-			Object returnValue = method.invoke(bean, arguments);
+			Object returnValue = applyTypeConversion(method.invoke(bean, arguments), signature.getDesiredResultType());
 			if (logger.isDebugEnabled()) {
 				logger.debug("Invoked method with signature [" + key + "] returned value [" + returnValue + "]");
 			}
@@ -103,16 +104,16 @@ public class MethodInvoker {
 	}
 
 	/**
-	 * Apply type conversion on the event parameter if neccessary
+	 * Apply type conversion on the supplied value
 	 * 
-	 * @param parameterValue the raw argument value
-	 * @param targetType the target type for the matching method argument
-	 * @return the converted method argument
+	 * @param value the raw value to be converted
+	 * @param targetType the target type for the conversion
+	 * @return the converted result
 	 */
-	protected Object applyTypeConversion(Object parameterValue, Class targetType) {
-		if (parameterValue == null || targetType == null) {
-			return parameterValue;
+	protected Object applyTypeConversion(Object value, Class targetType) {
+		if (value == null || targetType == null) {
+			return value;
 		}
-		return conversionService.getConversionExecutor(parameterValue.getClass(), targetType).execute(parameterValue);
+		return conversionService.getConversionExecutor(value.getClass(), targetType).execute(value);
 	}
 }

spring-binding/src/main/java/org/springframework/binding/method/MethodSignature.java

@@ -24,6 +24,7 @@ import org.springframework.util.Assert;
  * {@link MethodInvoker method invoker attempt}.
  * 
  * @author Keith Donald
+ * @author Jeremy Grelle
  */
 public class MethodSignature {
 
@@ -37,12 +38,17 @@ public class MethodSignature {
 	 */
 	private Parameters parameters;
 
+	/**
+	 * The desired result type of the method invocation
+	 */
+	private Class desiredResultType;
+
 	/**
 	 * Creates a method signature with no parameters.
 	 * @param methodName the name of the method
 	 */
 	public MethodSignature(String methodName) {
-		this(methodName, Parameters.NONE);
+		this(methodName, Parameters.NONE, null);
 	}
 
 	/**
@@ -51,19 +57,21 @@ public class MethodSignature {
 	 * @param parameter the method parameter
 	 */
 	public MethodSignature(String methodName, Parameter parameter) {
-		this(methodName, new Parameters(parameter));
+		this(methodName, new Parameters(parameter), null);
 	}
 
 	/**
 	 * Creates a method signature with a list of parameters.
 	 * @param methodName the name of the method
 	 * @param parameters the method parameters
+	 * @param desiredResultType the desired result type of the method invocation
 	 */
-	public MethodSignature(String methodName, Parameters parameters) {
+	public MethodSignature(String methodName, Parameters parameters, Class desiredResultType) {
 		Assert.notNull(methodName, "The method name is required");
 		Assert.notNull(parameters, "The parameters are required");
 		this.methodName = methodName;
 		this.parameters = parameters;
+		this.desiredResultType = desiredResultType;
 	}
 
 	/**
@@ -80,6 +88,14 @@ public class MethodSignature {
 		return parameters;
 	}
 
+	/**
+	 * Returns the desired result type of the method invocation
+	 * @return the desired result type
+	 */
+	public Class getDesiredResultType() {
+		return desiredResultType;
+	}
+
 	public boolean equals(Object obj) {
 		if (!(obj instanceof MethodSignature)) {
 			return false;

spring-binding/src/test/java/org/springframework/binding/method/MethodInvokerTests.java

@@ -23,6 +23,7 @@ import org.springframework.binding.expression.support.StaticExpression;
  * Unit tests for {@link org.springframework.binding.method.MethodInvoker}.
  * 
  * @author Erwin Vervaet
+ * @author Jeremy Grelle
  */
 public class MethodInvokerTests extends TestCase {
 
@@ -55,17 +56,23 @@ public class MethodInvokerTests extends TestCase {
 		Parameters parameters = new Parameters();
 		Bean bean = new Bean();
 		parameters.add(new Parameter(Bean.class, new StaticExpression(bean)));
-		MethodSignature method = new MethodSignature("testBeanArg", parameters);
+		MethodSignature method = new MethodSignature("testBeanArg", parameters, null);
 		assertSame(bean, methodInvoker.invoke(method, new TestObject(), null));
 	}
 
 	public void testPrimitiveArg() {
 		Parameters parameters = new Parameters();
 		parameters.add(new Parameter(Boolean.class, new StaticExpression(Boolean.TRUE)));
-		MethodSignature method = new MethodSignature("testPrimitiveArg", parameters);
+		MethodSignature method = new MethodSignature("testPrimitiveArg", parameters, null);
 		assertEquals(Boolean.TRUE, methodInvoker.invoke(method, new TestObject(), null));
 	}
 
+	public void testResultConversion() {
+		Parameters parameters = Parameters.NONE;
+		MethodSignature method = new MethodSignature("testConvertResult", parameters, Class.class);
+		assertEquals(Object.class, methodInvoker.invoke(method, new TestObject(), null));
+	}
+
 	private static class TestObject {
 
 		public void test() {
@@ -76,6 +83,10 @@ public class MethodInvokerTests extends TestCase {
 			return bean;
 		}
 
+		public String testConvertResult() {
+			return "java.lang.Object";
+		}
+
 		public boolean testPrimitiveArg(boolean primitive) {
 			return primitive;
 		}