Introduced DefaultParameterNameDiscoverer which checks JDK 8's standard reflection first and then falls back to ASM-based debug symbol analysis

Also, StandardReflectionParameterNameDiscoverer calls "Parameter.isNamePresent()" now to return null (and pass on to the next discoverer) if no JDK 8 parameters are available. Note that this requires OpenJDK 8 b100 or higher to compile now.

Issue: SPR-10532

spring-core/src/main/java/org/springframework/core/DefaultParameterNameDiscoverer.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2002-2013 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.core;
+
+/**
+ * Default implementation of the {@link ParameterNameDiscoverer} strategy interface,
+ * using the Java 8 standard reflection mechanism (if available), and falling back
+ * to the ASM-based {@link LocalVariableTableParameterNameDiscoverer} for checking
+ * debug information in the class file.
+ *
+ * <p>Further discoverers may be added through {@link #addDiscoverer(ParameterNameDiscoverer)}.
+ *
+ * @author Juergen Hoeller
+ * @since 4.0
+ * @see StandardReflectionParameterNameDiscoverer
+ * @see LocalVariableTableParameterNameDiscoverer
+ */
+public class DefaultParameterNameDiscoverer extends PrioritizedParameterNameDiscoverer {
+
+	private static final boolean standardReflectionAvailable =
+			(JdkVersion.getMajorJavaVersion() >= JdkVersion.JAVA_18);
+
+
+	public DefaultParameterNameDiscoverer() {
+		if (standardReflectionAvailable) {
+			addDiscoverer(new StandardReflectionParameterNameDiscoverer());
+		}
+		addDiscoverer(new LocalVariableTableParameterNameDiscoverer());
+	}
+
+}

spring-core/src/main/java/org/springframework/core/StandardReflectionParameterNameDiscoverer.java

@@ -20,6 +20,8 @@ import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
 import java.lang.reflect.Parameter;
 
+import org.springframework.util.ClassUtils;
+
 /**
  * {@link ParameterNameDiscoverer} implementation which uses JDK 8's
  * reflection facilities for introspecting parameter names.
@@ -35,7 +37,11 @@ public class StandardReflectionParameterNameDiscoverer implements ParameterNameD
 		Parameter[] parameters = method.getParameters();
 		String[] parameterNames = new String[parameters.length];
 		for (int i = 0; i < parameters.length; i++) {
-			parameterNames[i] = parameters[i].getName();
+			Parameter param = parameters[i];
+			if (!param.isNamePresent()) {
+				return null;
+			}
+			parameterNames[i] = param.getName();
 		}
 		return parameterNames;
 	}
@@ -45,7 +51,11 @@ public class StandardReflectionParameterNameDiscoverer implements ParameterNameD
 		Parameter[] parameters = ctor.getParameters();
 		String[] parameterNames = new String[parameters.length];
 		for (int i = 0; i < parameters.length; i++) {
-			parameterNames[i] = parameters[i].getName();
+			Parameter param = parameters[i];
+			if (!param.isNamePresent()) {
+				return null;
+			}
+			parameterNames[i] = param.getName();
 		}
 		return parameterNames;
 	}