2 unstable releases
0.3.0 | Oct 20, 2024 |
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0.1.0 | Oct 6, 2024 |
#630 in Rust patterns
317 downloads per month
67KB
1K
SLoC
EZ JNI
Closing the gap between Java and Rust. Check out the documentation page.
lib.rs
:
EZ JNI
This library helps with creating Rust libraries or programs that can use Java code or be used by Java code.
If you are not familiar with the Java Native Interface, take a look at the JNI bindings.
Using Java from Rust
The call!
macro is used to call Java methods.
Specify the name of the method, as well as the Class if it is a static method
, or the object (within parenthesis) the method belongs to.
Then pass in parameters by specifying the Java Type, and the value (within parenthesis).
The call will handle null
return values and thrown exceptions
if you use Option
or Result
(respectively) as the return type.
The new!
macro can create new Object by calling the constructor.
Specify the Class of the object you want to construct, and pass specify the parameters.
You can also handle exceptions
by using throws
after the parameters and specifying an error type.
The syntax is very similar to call!
.
Using Rust from Java
A Rust or C function that can be called from Java must be named in a specific way
and have a similar signature as the method on the Java side
(see the JNI doc for more details).
The jni_fn!
macro takes a Rust function (with Java Types instead of Rust types)
and makes it into one that can be called from Java.
These jni_fns
are exported in the binary and serve as entrypoints to Rust from Java.
The idea is similar to how Rust library crates have functions and types that are exported and used by other Rust packages.
Android and printing
Using the regular std::print
(or any of its variants) will not work in Android
because it seems that stdout and stderr redirect to /dev/null
(for some reason).
To get around this, replace those macros with the ones in this crate,
which will call the right method to print in Android.
use ez_jni::{println, eprintln};
The downside is that the macro requires env
to be a variable/argument that the macro can access,
so you will only be able to print from functions that have the env
passed into them.
Dependencies
~2–13MB
~99K SLoC