Add more @Nullable parameters based on null usage

Issue: SPR-15540

spring-test/src/main/java/org/springframework/mock/web/MockAsyncContext.java

@@ -30,6 +30,7 @@ import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.springframework.beans.BeanUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.util.WebUtils;
 
@@ -91,7 +92,7 @@ public class MockAsyncContext implements AsyncContext {
 	}
 
 	@Override
-	public void dispatch(ServletContext context, String path) {
+	public void dispatch(@Nullable ServletContext context, String path) {
 		this.dispatchedPath = path;
 		for (Runnable r : this.dispatchHandlers) {
 			r.run();

spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -873,7 +873,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 	}
 
 	@Override
-	public AsyncContext startAsync(ServletRequest request, ServletResponse response) {
+	public AsyncContext startAsync(ServletRequest request, @Nullable ServletResponse response) {
 		Assert.state(this.asyncSupported, "Async not supported");
 		this.asyncStarted = true;
 		this.asyncContext = new MockAsyncContext(request, response);
@@ -1088,7 +1088,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 		return this.method;
 	}
 
-	public void setPathInfo(String pathInfo) {
+	public void setPathInfo(@Nullable String pathInfo) {
 		this.pathInfo = pathInfo;
 	}
 

spring-test/src/main/java/org/springframework/test/web/servlet/setup/StubWebApplicationContext.java

@@ -303,7 +303,7 @@ class StubWebApplicationContext implements WebApplicationContext {
 	//---------------------------------------------------------------------
 
 	@Override
-	public String getMessage(String code, @Nullable Object args[], String defaultMessage, Locale locale) {
+	public String getMessage(String code, @Nullable Object args[], @Nullable String defaultMessage, Locale locale) {
 		return this.messageSource.getMessage(code, args, defaultMessage, locale);
 	}
 
@@ -400,13 +400,13 @@ class StubWebApplicationContext implements WebApplicationContext {
 		}
 
 		@Override
-		public Object resolveDependency(DependencyDescriptor descriptor, String requestingBeanName) {
+		public Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName) {
 			throw new UnsupportedOperationException("Dependency resolution not supported");
 		}
 
 		@Override
 		public Object resolveDependency(DependencyDescriptor descriptor, String requestingBeanName,
-				Set<String> autowiredBeanNames, TypeConverter typeConverter) {
+				@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) {
 			throw new UnsupportedOperationException("Dependency resolution not supported");
 		}