Class ServiceIndexGenerator

java.lang.Object

io.micronaut.aot.serviceindex.ServiceIndexGenerator

@Internal
public final class ServiceIndexGenerator
extends Object

Generates micronaut-core's service index for a packaged application: a StaticOptimizations.Loader that registers a ServiceIndex of the application's class path, so that service loading at run time does not scan META-INF/services and META-INF/micronaut.

It is meant for the Micronaut Gradle and Maven plugins and Micronaut Runner, which call generate(Request) in-process with plain paths, once the class path is final, and get class files back. It is internal to them, not an API for applications or other build tools, and may change in any release.

The index is built by the application's own micronaut-core, with its ServiceIndexBuilder, in an isolated class loader of the class path, whose parent is the platform class loader. The generated loader is emitted with the ClassFile API, verified, and then run in that micronaut-core, which must rebuild exactly the builder's index before anything is returned. No class of the application is loaded or initialised, and nothing of the caller's class path is used. It needs micronaut-core 5.3.0 or later on the class path, and stands down with an older one.

An index describes a class path that cannot change. So a caller runs it last, on the class path as it ships: after Micronaut AOT, the merging of service files, Shadow or Shade, and any other rewrite of the jars, and before a JDK AOT cache is trained. Whatever the ServiceIndexGenerator.Result.status(), the caller writes ServiceIndexGenerator.Result.entries() into the holder, replacing entries of the same name, and deletes ServiceIndexGenerator.Result.removals(): a call that generates nothing may still remove an earlier index from the holder. Callers do not run it for run tasks, tests or native images.

At run time, -Dmicronaut.service.index.enabled=false switches the index off, and -Dmicronaut.service.index.validate=true checks it against a scan of the class path.

Since:

3.2.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	ServiceIndexGenerator.Request	The class path an index is generated for: plain paths, no build tool type.
static final class	ServiceIndexGenerator.Result	The outcome of one generation: its ServiceIndexGenerator.Result.status(), one ServiceIndexGenerator.Result.message() for the caller to log, the ServiceIndexGenerator.Result.entries() to write into the holder and the ServiceIndexGenerator.Result.removals() to delete from it, which the caller applies whatever the status.
static enum	ServiceIndexGenerator.Status	What a generation did.

Method Summary

Modifier and Type	Method	Description
static ServiceIndexGenerator.Result	generate(ServiceIndexGenerator.Request request)	Generates the service index of a class path, or says why it does not.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

generate

public static ServiceIndexGenerator.Result generate(ServiceIndexGenerator.Request request)

Generates the service index of a class path, or says why it does not.

It never throws for anything about the inputs: a missing entry, an unreadable file and any failure of micronaut-core or of the emitter, Errors included, are a ServiceIndexGenerator.Result that generated nothing. Only a VirtualMachineError propagates. It keeps no state, so calls are independent of each other; before it returns, the class loaders it opened are closed and the caller's context class loader is restored.

Parameters:

request - the class path and the entry that will hold the index

Returns:

what was generated, or why nothing was