🍃 Dependency Injection

[Spikhalskiy]

Description

Improve support and/or safety of Dependency Injection with JavaSDK.

Core objectives

Dependency Injection into Workflow instances should be strongly discouraged. It's deemed unsafe and leads to practices that create non-deterministic workflows at the end. But Temporal needs to provide alternative solutions for the common problems and goals that users are addressing with dependency injection.

Tasks

• Reuse of ActivityStubs from another workflow should produce a usable diagnostic or be allowed #746
• Support for unit testing of Workflows code #747
• Provide a way to inject options into Workflow instances #748
• Documentation page describing why in the vast majority of cases injection into workflow instances is dangerous with examples of situations when it's a legit approach and when it's not (and what alternative should be used)
• Add an example of Spring usage with Temporal samples-java#168
• Spring Boot Integration #8
• Provide a recommended way to pass configuration into workflow  #827

Related user requests / reports

• Support Spring Proxy classes marked with @Component for activities #718
• Allow passing proxy objects to registerActivitiesImplementations  #466