Dependency Injection

[John Hendrikx]

Hi,

I wrote my own DI framework, and byte code manipulation is not a 
requirement to do DI. The basic functionality is provided with 
reflection only. Most frameworks should be doing exactly that.

Byte code manipulation is only a requirement when the same can't be 
achieved by using a JDK interface based proxy. If there is no suitable 
interface that can be proxied in such a way, then the only option left 
is to create a dynamic subclass.  This is often done for injecting 
scoped dependencies in a dependency with a different scope (ie, a 
request scoped dependency injected into a singleton requires the request 
scoped dependency to be proxied).  Other features that may require byte 
code manipulation are assisted injection, wrappers, AOP, etc.

--John

------ Original Message ------
>From "Red IO" <redio.development at gmail.com>
To "amber-dev" <amber-dev at openjdk.org>
Date 20/02/2023 18:59:43
Subject Dependency Injection

>Reason/Background:
>I was building a server application (in java) designed around the 
>mediator pattern and dependency injection inspired by a c# server 
>application tutorial. So I was researching but every dependency 
>injection framework was relying on bytecode manipulation to do the 
>injection.
>For background I really dislike bytecode manipulation for production 
>code.
>So I researched what the jdk provides and what not. I discovered that 
>the jdk provides service loading capabilities in form of the 
>ServiceLoader api. But it is pretty barebones only allowing creation of 
>service implementations providing a no-args constructor.
>
>Idea:
>I thought that this could be expanded to allow loading of services that 
>depend on other services (In form of constructor parameters) that can 
>be loaded with associated ServiceLoaders.
>So I coded a small test wrapper for ServiceLoader that does the 
>injection of known services.
>I used MethodHandles to create factory handles that use the associated 
>loaders to fill in the constructor and in that way avoided bytecode 
>manipulation.
>
>Suggestion:
>I was wondering if this concept would be interesting to incorporate 
>into the jdk as an expansion of the ServiceLoader api.
>
>Great regards
>RedIODev
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