Support JSR-305 annotations on endpoint methods

Update `OperationMethodParameter` to additionally support JSR-305 based
`@Nullable` annotations.

Closes gh-24647

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/invoke/reflect/OperationMethodParameter.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -18,8 +18,14 @@ package org.springframework.boot.actuate.endpoint.invoke.reflect;
 
 import java.lang.reflect.Parameter;
 
+import javax.annotation.Nonnull;
+import javax.annotation.meta.When;
+
 import org.springframework.boot.actuate.endpoint.invoke.OperationParameter;
+import org.springframework.core.annotation.MergedAnnotation;
+import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.lang.Nullable;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -29,6 +35,8 @@ import org.springframework.util.ObjectUtils;
  */
 class OperationMethodParameter implements OperationParameter {
 
+	private static final boolean jsr305Present = ClassUtils.isPresent("javax.annotation.Nonnull", null);
+
 	private final String name;
 
 	private final Parameter parameter;
@@ -55,7 +63,10 @@ class OperationMethodParameter implements OperationParameter {
 
 	@Override
 	public boolean isMandatory() {
-		return ObjectUtils.isEmpty(this.parameter.getAnnotationsByType(Nullable.class));
+		if (!ObjectUtils.isEmpty(this.parameter.getAnnotationsByType(Nullable.class))) {
+			return false;
+		}
+		return (jsr305Present) ? new Jsr305().isMandatory(this.parameter) : true;
 	}
 
 	@Override
@@ -63,4 +74,13 @@ class OperationMethodParameter implements OperationParameter {
 		return this.name + " of type " + this.parameter.getType().getName();
 	}
 
+	private static class Jsr305 {
+
+		boolean isMandatory(Parameter parameter) {
+			MergedAnnotation<Nonnull> annotation = MergedAnnotations.from(parameter).get(Nonnull.class);
+			return !annotation.isPresent() || annotation.getEnum("when", When.class) == When.ALWAYS;
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/invoke/reflect/OperationMethodParameterTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -16,8 +16,14 @@
 
 package org.springframework.boot.actuate.endpoint.invoke.reflect;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.lang.reflect.Method;
 
+import javax.annotation.Nonnull;
+import javax.annotation.meta.TypeQualifier;
+import javax.annotation.meta.When;
+
 import org.junit.jupiter.api.Test;
 
 import org.springframework.lang.Nullable;
@@ -32,29 +38,48 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 class OperationMethodParameterTests {
 
-	private Method method = ReflectionUtils.findMethod(getClass(), "example", String.class, String.class);
+	private Method example = ReflectionUtils.findMethod(getClass(), "example", String.class, String.class);
+
+	private Method exampleJsr305 = ReflectionUtils.findMethod(getClass(), "exampleJsr305", String.class, String.class);
+
+	private Method exampleMetaJsr305 = ReflectionUtils.findMethod(getClass(), "exampleMetaJsr305", String.class,
+			String.class);
 
 	@Test
 	void getNameShouldReturnName() {
-		OperationMethodParameter parameter = new OperationMethodParameter("name", this.method.getParameters()[0]);
+		OperationMethodParameter parameter = new OperationMethodParameter("name", this.example.getParameters()[0]);
 		assertThat(parameter.getName()).isEqualTo("name");
 	}
 
 	@Test
 	void getTypeShouldReturnType() {
-		OperationMethodParameter parameter = new OperationMethodParameter("name", this.method.getParameters()[0]);
+		OperationMethodParameter parameter = new OperationMethodParameter("name", this.example.getParameters()[0]);
 		assertThat(parameter.getType()).isEqualTo(String.class);
 	}
 
 	@Test
 	void isMandatoryWhenNoAnnotationShouldReturnTrue() {
-		OperationMethodParameter parameter = new OperationMethodParameter("name", this.method.getParameters()[0]);
+		OperationMethodParameter parameter = new OperationMethodParameter("name", this.example.getParameters()[0]);
 		assertThat(parameter.isMandatory()).isTrue();
 	}
 
 	@Test
 	void isMandatoryWhenNullableAnnotationShouldReturnFalse() {
-		OperationMethodParameter parameter = new OperationMethodParameter("name", this.method.getParameters()[1]);
+		OperationMethodParameter parameter = new OperationMethodParameter("name", this.example.getParameters()[1]);
+		assertThat(parameter.isMandatory()).isFalse();
+	}
+
+	@Test
+	void isMandatoryWhenJsrNullableAnnotationShouldReturnFalse() {
+		OperationMethodParameter parameter = new OperationMethodParameter("name",
+				this.exampleJsr305.getParameters()[1]);
+		assertThat(parameter.isMandatory()).isFalse();
+	}
+
+	@Test
+	void isMandatoryWhenJsrMetaNullableAnnotationShouldReturnFalse() {
+		OperationMethodParameter parameter = new OperationMethodParameter("name",
+				this.exampleMetaJsr305.getParameters()[1]);
 		assertThat(parameter.isMandatory()).isFalse();
 	}
 
@@ -62,4 +87,19 @@ class OperationMethodParameterTests {
 
 	}
 
+	void exampleJsr305(String one, @javax.annotation.Nullable String two) {
+
+	}
+
+	void exampleMetaJsr305(String one, @MetaNullable String two) {
+
+	}
+
+	@TypeQualifier
+	@Retention(RetentionPolicy.RUNTIME)
+	@Nonnull(when = When.MAYBE)
+	@interface MetaNullable {
+
+	}
+
 }