mirror of
https://github.com/enso-org/enso.git
synced 2024-11-27 17:04:08 +03:00
99 lines
3.3 KiB
Markdown
99 lines
3.3 KiB
Markdown
---
|
|
layout: developer-doc
|
|
title: Polyglot Java
|
|
category: polyglot
|
|
tags: [polyglot, java]
|
|
order: 3
|
|
---
|
|
|
|
# Polyglot Java
|
|
|
|
This document deals with the implementation of polyglot interoperation with Java
|
|
in the runtime. Please familiarise yourself with the general operation of
|
|
[polyglot bindings](./polyglot-bindings.md).
|
|
|
|
<!-- MarkdownTOC levels="2,3" autolink="true" -->
|
|
|
|
- [Class Lookup](#class-lookup)
|
|
- [Polyglot Library System](#polyglot-library-system)
|
|
- [Polyglot Syntax System](#polyglot-syntax-system)
|
|
|
|
<!-- /MarkdownTOC -->
|
|
|
|
## Class Lookup
|
|
|
|
In order for the Enso runtime to effectively find Java objects for working with
|
|
in a polyglot fashion, it will look in the `polyglot/java` subdirectory of an
|
|
Enso project. This directory has the following requirements placed on it.
|
|
|
|
- The top level of the `java` directory should contain only `.jar` files and
|
|
directories.
|
|
- Each directory must provide a valid class-path structure, with `.class` files
|
|
at the appropriate points.
|
|
- Both `.jar` files and directories are added to the runtime class-path for
|
|
Enso, and hence be made available to Enso programs.
|
|
|
|
> The actionables for this section are:
|
|
>
|
|
> - In future, we want to expand this to support `.class` files directly, and
|
|
> maybe even compiling Java code.
|
|
|
|
## Polyglot Library System
|
|
|
|
The dynamic polyglot system is a dynamic runtime lookup for Java objects,
|
|
allowing Enso code to work with them through a runtime reflection-style
|
|
mechanism. It is comprised of the following components:
|
|
|
|
- `Java.lookup_class : Class.Path -> Maybe Class`: A function that lets users
|
|
look up a class by a given name on the runtime classpath.
|
|
- `Polyglot.instantiate : Class -> Object`: A function that lets users
|
|
instantiate a class into an object.
|
|
- A whole host of functions on the polyglot type that let you dynamically work
|
|
with object bindings.
|
|
|
|
An example can be found below:
|
|
|
|
```ruby
|
|
main =
|
|
class = Java.lookup_class "org.enso.example.TestClass"
|
|
instance = Polyglot.instantiate1 class (x -> x * 2)
|
|
method = Polyglot.get_member instance "callFunctionAndIncrement"
|
|
Polyglot.execute1 method 10
|
|
```
|
|
|
|
> The actionables for this section are:
|
|
>
|
|
> - Expand on the detail when there is time.
|
|
|
|
## Polyglot Syntax System
|
|
|
|
The static system, however, lets us do much better in terms of user experience.
|
|
Instead of having to dynamically look things up at runtime, we can instead do
|
|
the following:
|
|
|
|
- Statically resolve imports of polyglot bindings within the project to make
|
|
sure that they are available.
|
|
- Create java-compatible object entities that dynamically look up and dispatch
|
|
both static methods on classes (by name), and methods on objects (by name).
|
|
This includes the constructor and field reads.
|
|
- This invocation syntax is integrated into Enso as variadic methods, allowing
|
|
us to deal with the inter-language impedance mismatch.
|
|
- Due to different semantics of Java calls, currying and over-applying functions
|
|
are necessarily disabled for such calls, instead expecting the exact arguments
|
|
list to be passed.
|
|
|
|
An example can be found below:
|
|
|
|
```ruby
|
|
polyglot java import com.example.MyClass as MyClassJava
|
|
|
|
main =
|
|
x = MyClassJava.foo 1 2 3
|
|
inst = MyClassJava.new a b c
|
|
bar = inst.methodName x y
|
|
```
|
|
|
|
> The actionables for this section are:
|
|
>
|
|
> - Expand on the detail as the implementation becomes clear.
|