Add ability to pass JVM arguments to executable Java apps

[marshalhayes]

Related to an existing integration?

Yes

Existing integration

Java

Overview

AddJavaApp does not currently support passing JVM arguments to executable Java apps.

Usage example

var builder = DistributedApplication.CreateBuilder(args);

builder.AddJavaApp("app", workingDirectory: "./app",
    new JavaAppExecutableResourceOptions
    {
        ApplicationName = "app.jar",
        OtelAgentPath = "./agents",
        JvmArgs = ["-Darg=value"]
    })

The only new part here is the additional JvmArgs property.

Breaking change?

No

Alternatives

The only workaround I can think of at the moment is to build a container image for my application which sets the JVM arguments. For example:

# Dockerfile
ENV JAVA_OPTS=""
ENTRYPOINT [ "java", "$JAVA_OPTS", "-jar", "app.jar"]

// AppHost.cs
var builder = DistributedApplication.CreateBuilder(args);

builder.AddJavaApp(
    "containerapp",
    new JavaAppContainerResourceOptions
    {
        ContainerImageName = "registry/app:latest",
        OtelAgentPath = "./agents"
    })
    .WithEnvironment("JAVA_OPTS", "-Darg=value");

Additional context

No response

Help us help you

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[marshalhayes]

Here's another way to add JVM args, which is supported currently. Although, I'm not sure how I feel about it.

var builder = DistributedApplication.CreateBuilder(args);

builder.AddJavaApp("app", workingDirectory: "./app",
    new JavaAppExecutableResourceOptions
    {
        ApplicationName = "app.jar",
        OtelAgentPath = "./agents"
    })
   .WithArgs(context => context.Args.Insert(0, "-Darg=value");

It wasn't immediately obvious as a newcomer how I would do this. Given the amount of people who will likely need to set JVM args, perhaps the additional JvmArgs property still makes sense.

[aaronpowell]

The second option, using the WithArgs is probably more idiomatic from an Aspire perspective, but given we already use an options object, it's probably justifiable to extend it.

In reality, we probably should overhaul the AddJavaApp entirely so that it is more aligned with the current Aspire design, as it was one of the first so some of the patterns have evolved since then.