Exception when instanciating JarLauncher from spring-boot-starter-web

[arnaultbonafos]

I attempt to use a SpringApplication started from spring-boot-starter-web packaged jar file, from within an existing Plugin architecture.

For that I do :

Class<?> starterclass = Class.forName("org.springframework.boot.loader.launch.JarLauncher", true, jarloader);

Then when I want to invoke the "launch" method I get the following exception:

Caused by: java.lang.IllegalStateException: java.net.MalformedURLException: unknown protocol: nested
        at org.springframework.boot.loader.net.protocol.jar.JarUrlConnection.<clinit>(JarUrlConnection.java:67)
        ... 30 more
Caused by: java.net.MalformedURLException: unknown protocol: nested
        at java.base/java.net.URL.<init>(URL.java:779)
        at java.base/java.net.URL.<init>(URL.java:654)
        at java.base/java.net.URL.<init>(URL.java:590)
        at java.base/java.net.JarURLConnection.parseSpecs(JarURLConnection.java:176)
        at java.base/java.net.JarURLConnection.<init>(JarURLConnection.java:158)
        at org.springframework.boot.loader.net.protocol.jar.JarUrlConnection.<init>(JarUrlConnection.java:92)
        at org.springframework.boot.loader.net.protocol.jar.JarUrlConnection.<clinit>(JarUrlConnection.java:64)
        ... 30 more

I have looked at the Code around JarUrlConnection:64, and a static initializer throws the IllegalException.
I suspect a bug but it could be that I doing something wrong.

[philwebb]

There's not really enough information to tell what's going on, but I suspect your comment about "packaged jar file, from within an existing Plugin architecture" might be key. The uber jars aren't really designed to work outside of java -jar. At a guess, I would say that org.springframework.boot.loader.net.protocol.Handlers.register() hasn't been called or the classes it references aren't on your main classpath.

If you'd like us to spend some more time investigating, please take the time to provide a complete minimal sample (something that we can unzip or git clone, build, and deploy) that reproduces the problem.