try-with-resources / use / multiple resources

Question

I\'m using a Java-API which heavily uses the Autoclosable-Interface and thus in Java try-with-resources. However in Java you can specify

Answer 1

Yet another approach for this:

val CloseableContext = ThreadLocal>()

inline fun scopeDef(inScope: () -> Unit) {
    val oldContext = CloseableContext.get()

    val currentContext = mutableListOf()

    CloseableContext.set(currentContext)

    try {
        inScope()
    }
    finally {
        for(i in (currentContext.size - 1) downTo 0) {
            try {
                currentContext[i].close()
            }
            catch(e: Exception) {
                // TODO: Record as suppressed exception
            }
        }
        CloseableContext.set(oldContext)
    }
}

fun  autoClose(resource: T): T {
    CloseableContext.get()?.add(resource) ?: throw IllegalStateException(
            "Calling autoClose outside of scopeDef is forbidden")

    return resource
}

Usage:

class Close1(val name: String): AutoCloseable {
    override fun close() {
        println("close $name")
    }
}

fun main(args : Array) {
    scopeDef {
        val c1 = autoClose(Close1("1"))

        scopeDef {
            val c3 = autoClose(Close1("3"))
        }

        val c2 = autoClose(Close1(c1.name + "+1"))

    }
}

Output:

close 3
close 1+1
close 1