#1653 - Tighten contracts for parameter values in MethodLinkBuilderFactory.linkTo(…).

If a parameter array is given to MethodLinkBuilderFactory.linkTo(…) methods, we now verify its correct length in correspondence to the method given. If no parameters are given at all, we automatically create a parameter value array of the required length.

src/main/java/org/springframework/hateoas/server/MethodLinkBuilderFactory.java

@@ -30,7 +30,8 @@ public interface MethodLinkBuilderFactory<T extends LinkBuilder> extends LinkBui
 
 	/**
 	 * Returns a {@link LinkBuilder} pointing to the URI mapped to the given {@link Method} and expanding this mapping
-	 * using the given parameters.
+	 * using the given parameters. The number of parameter values has to match the length of the given method's expected
+	 * parameters.
 	 *
 	 * @param method must not be {@literal null}.
 	 * @param parameters
@@ -40,7 +41,8 @@ public interface MethodLinkBuilderFactory<T extends LinkBuilder> extends LinkBui
 
 	/**
 	 * Returns a {@link LinkBuilder} pointing to the URI mapped to the given {@link Method} assuming it was invoked on an
-	 * object of the given type.
+	 * object of the given type. The number of parameter values has to match the length of the given method's expected
+	 * parameters.
 	 *
 	 * @param type must not be {@literal null}.
 	 * @param method must not be {@literal null}.

src/main/java/org/springframework/hateoas/server/mvc/WebMvcLinkBuilder.java

@@ -136,6 +136,12 @@ public class WebMvcLinkBuilder extends TemplateVariableAwareLinkBuilderSupport<W
 		Assert.notNull(method, "Method must not be null!");
 		Assert.notNull(parameters, "Parameters must not be null!");
 
+		int expected = method.getParameterTypes().length;
+		int given = parameters.length;
+
+		Assert.isTrue(expected == given,
+				() -> String.format("Incorrect number of parameter values given. Expected %s, got %s!", expected, given));
+
 		return linkTo(DummyInvocationUtils.getLastInvocationAware(controller, method, parameters));
 	}
 

src/main/java/org/springframework/hateoas/server/mvc/WebMvcLinkBuilderFactory.java

@@ -99,6 +99,15 @@ public class WebMvcLinkBuilderFactory implements MethodLinkBuilderFactory<WebMvc
 		return WebMvcLinkBuilder.linkTo(controller, parameters);
 	}
 
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.hateoas.MethodLinkBuilderFactory#linkTo(java.lang.reflect.Method, java.lang.Object[])
+	 */
+	@Override
+	public WebMvcLinkBuilder linkTo(Method method, Object... parameters) {
+		return WebMvcLinkBuilder.linkTo(method, parameters);
+	}
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.hateoas.MethodLinkBuilderFactory#linkTo(java.lang.Class, java.lang.reflect.Method, java.lang.Object[])
@@ -139,15 +148,6 @@ public class WebMvcLinkBuilderFactory implements MethodLinkBuilderFactory<WebMvc
 		}, builderFactory, getConversionService());
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.hateoas.MethodLinkBuilderFactory#linkTo(java.lang.reflect.Method, java.lang.Object[])
-	 */
-	@Override
-	public WebMvcLinkBuilder linkTo(Method method, Object... parameters) {
-		return WebMvcLinkBuilder.linkTo(method, parameters);
-	}
-
 	private static Supplier<ConversionService> getConversionService() {
 
 		return () -> {

src/test/java/org/springframework/hateoas/server/mvc/WebMvcLinkBuilderUnitTest.java

@@ -26,6 +26,7 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.stream.Stream;
 
+import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.Test;
 import org.springframework.hateoas.IanaLinkRelations;
 import org.springframework.hateoas.Link;
@@ -669,6 +670,19 @@ class WebMvcLinkBuilderUnitTest extends TestUtils {
 		assertThat(linkTo(method, new Object[] { null }).withSelfRel().getHref()).endsWith("?id={id}");
 	}
 
+	@Test // #1653
+	void buildsLinkWithoutParameterValuesGiven() throws Exception {
+
+		Method method = ControllerWithMethods.class.getDeclaredMethod("myMethod", Object.class);
+
+		Stream.<ThrowingCallable> of( //
+				() -> linkTo(method, new Object[0]), //
+				() -> linkTo(ControllerWithMethods.class, method, new Object[0]) //
+		) //
+				.map(assertThatIllegalArgumentException()::isThrownBy) //
+				.forEach(it -> it.withMessageContaining("Expected 1, got 0"));
+	}
+
 	private static UriComponents toComponents(Link link) {
 		return UriComponentsBuilder.fromUriString(link.expand().getHref()).build();
 	}