Load multiple web applications/clients from within a standalone @SpringBootApplication not working

Hi!

I am currently trying to load an additional web application during the startup of a standalone @SpringBootApplication. I'm running into several problems but one of them is as I run the Java application from within Eclipse, I get a lot of exceptions getting thrown at me by the embedded Tomcat server (see full output log).

I am not sure why I can do about this and I'm stuck for quite a while now for such a "simple" task. I have a related question on stackoverflow if you want to take a look at it.

I have the web application as a WAR file inside the standalone as a resource. As the application starts/loads I want to take this resource and move/copy it to the server-home directory. From there I want to call Tomcat#addWebapp - and like I said - I was able to make this work for the final standalone jar but I'm not able to run this in Eclipse which means I cannot debug the actual server code.

In the end it's boiling down to these few lines of code:

@SpringBootApplication
public class Server {

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

    @Bean
    public EmbeddedServletContainerFactory servletContainerFactory() {

        return new TomcatEmbeddedServletContainerFactory() {

            @Override
            protected TomcatEmbeddedServletContainer getTomcatEmbeddedServletContainer(Tomcat tomcat) {

                String appHome = System.getProperty(Environment.APP_HOME);
                String targetFileName = "web-0.0.1-SNAPSHOT.war";
                InputStream resourceAsStream = getClass().getClassLoader().getResourceAsStream(targetFileName);

                File target = new File(Paths.get(appHome, targetFileName).toString());

                try {

                    java.nio.file.Files.copy(resourceAsStream, target.getAbsoluteFile().toPath(), StandardCopyOption.REPLACE_EXISTING);

                    tomcat.addWebapp("/web", target.getAbsolutePath());

                } catch (ServletException ex) {
                    throw new IllegalStateException("Failed to add webapp", ex);
                } catch (Exception e) {
                    throw new IllegalStateException("Failed to add webapp", e);
                }
                
                return super.getTomcatEmbeddedServletContainer(tomcat);
            }
        };
    }

}

Can anybody tell me how I can do this?

[wilkinsona]

Looking at the log your other war file is using Jasper (I assume it's got some JSPs in it) and you haven't got Jasper on the classpath. What's in your pom.xml/build.gradle?

Hi @wilkinsona!

Well, there's not much actually - it's just a naked web client. I thought - since this is getting loaded by the built-in Tomcat - all required dependencies are going to be available at that point.

<?xml version="1.0"?>
<project
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
  xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.ema.server</groupId>
    <artifactId>ema-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
  </parent>

  <artifactId>web</artifactId>
  <packaging>war</packaging>
  <name>web Maven Webapp</name>
  <url>http://maven.apache.org</url>

  <dependencies>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>

  </dependencies>

  <build>
    <finalName>web</finalName>
  </build>

</project>

There's not a lot to it, you can take a look at the web module here if you want. However, you think adding Jasper dependencies to the war file would solve this issue? That would be great actually ...

[wilkinsona]

However, you think adding Jasper dependencies to the war file would solve this issue? That would be great actually ...

No, not to the war, but to the Spring Boot application that's running the embedded Tomcat to which you are deploying the war.

@wilkinsona Ok, okay I thought that his would be already included - I don't understand - why isn't that already available? Or is this due to my kind of "special" architecture that I'm currently going with? I currently have a servermodule that's just gluing together the rest-api and via a tricky maven build loads the web client into the final spring application.

Do you know which dependency I have to load in order to support the embedded Tomcat?

[wilkinsona]

org.apache.tomcat.embed:tomcat-embed-jasper

GitHub issues aren't really the right place for this sort of thing. It looks like you are seeking some general guidance rather than reporting a bug. If adding the Jasper dependency doesn't fix the problem, then please either provide a small sample that reproduces the problem you are seeing or ask another question on Stack Overflow (things seem to have moved on beyond the related question you linked to above).

@wilkinsona Well, I've already tried to include this as a dependency

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
    <version>9.0.0.M15</version>
</dependency>

but it does not work. The core issue is that it does not seem to be possible for a standalone to simply add a web application to its build-in Tomcat and on stackoverflow no one could give me a concrete answer to this issue or how to solve it. That is why I went on github because I thought it's either not possible or somebody here can tell me how I can do this.

I am not sure if what I do is meant to be. Usually the WAR file that gets compiled to the standalone JAR contains also the web application. In my scenario I have sourced out the web client into another Maven module and I try to include it into the standalone. I am not sure if this is supported by Spring at all actually.

[wilkinsona]

Well, I've already tried to include this as a dependency but it does not work

Why are you using 9.0.0.M15? Spring Boot uses Tomcat 8.5. Also, "it does not work" tells me almost nothing. In what way doesn't it work? What happened?

The core issue is that it does not seem to be possible for a standalone to simply add a web application to its build-in Tomcat

That is absolutely possible (although unusual). Your question on Stack Overflow already links to a question and answer telling you how to do it. You've said in your question of Stack Overflow that "it appears that such a war file must either be located somewhere in the file system". That's correct, but your description above shows that you've already figured out how to extract the war from the fat jar and deploy it. As far as I can tell, you know the answer to your Stack Overflow question.

In my scenario I have sourced out the web client into another Maven module and I try to include it into the standalone

Sorry, I don't understand this. What's a "web client" in this context? A war typically isn't a web client.

I am not sure if this is supported by Spring at all actually.

It's not really a question of what Spring (Boot) supports as it has very little to do with it. It's a question of what Tomcat supports and it definitely supports deploying a war file.

This issue isn't really making any progress. Sorry, but I don't have the time to try and guess exactly what it is that you're trying to do or what might have happened when all you say is that "it doesn't work". I'll ask one last time: please provide a sample that reproduces the problem you're facing or ask another question on Stack Overflow. If you can't or won't spend the time doing that then I can't justify spending any more time looking at this.