Testing streaming abort error handling in Tomcat and Spring Boot

AbortedStreamingDemo.java

package demo;

import org.apache.catalina.startup.Tomcat;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;

@SpringBootApplication
@RestController
public class AbortedStreamingDemo {

    static void respond(HttpServletResponse resp) throws IOException {
        resp.setStatus(200);
        resp.setHeader("Content-Disposition", "attachment");
        resp.setContentType("application/octet-stream");
        var out = resp.getOutputStream();
        out.flush();
        if (true) throw new RuntimeException("simulated error");
        // status is already sent here, can't change it!
    }

    static class DemoServlet extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            respond(resp);
        }
    }

    @GetMapping("/controller")
    void serve(HttpServletResponse resp) throws IOException {
        respond(resp);
    }

    @Bean
    ServletRegistrationBean<HttpServlet> demoServletServletRegistrationBean() {
        return new ServletRegistrationBean<>(new DemoServlet(), "/servlet");
    }

    static class SpringApp {
        public static void main(String[] args) {
            SpringApplication.run(AbortedStreamingDemo.class, args);
        }
    }

    static class TomcatApp {
        public static void main(String[] args) throws Exception {
            var tomcat = new Tomcat();
            tomcat.setPort(8080);
            tomcat.addContext("", new File(".").getAbsolutePath());
            tomcat.addServlet("", "demo", new DemoServlet()).addMapping("/servlet");
            tomcat.getConnector(); // FFS
            tomcat.start();
            tomcat.getServer().await();
        }
    }

}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.5.2</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>11</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
  </dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

With tomcat the response to curl -iv --raw http://localhost:8080/servlet is an error as expected:

curl: (18) transfer closed with outstanding read data remaining

But in Spring Boot both endpoints respond with terminal "0":

<
0

* Connection #0 to host localhost left intact