├── .gitignore
├── README.md
├── lib-rust
    ├── Cargo.toml
    └── src
    │   └── lib.rs
└── use-java
    ├── libdummymath.dylib
    ├── pom.xml
    └── src
        └── main
            └── java
                └── ch
                    └── frankel
                        └── blog
                            └── rust
                                └── Main.java


/.gitignore:
--------------------------------------------------------------------------------
1 | .idea
2 | *.iml
3 | target
4 | Cargo.lock
5 | 


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
 1 | # How to call rust from java
 2 | 
 3 | 
 4 | ## Building rust
 5 | 
 6 | Ensure you have maven and rust installed. 
 7 | 
 8 | For example on macos with apple silicon: 
 9 | 
10 | ```bash
11 | cd lib-rust
12 | rustup target add x86_64-apple-darwin
13 | cargo build --target x86_64-apple-darwin
14 | cp target/x86_64-apple-darwin/debug/libdummymath.dylib ../use-java/
15 | ```
16 | 
17 | You can adjust this for you platform, but what this does is install the x86_64 builder and build a rust binary for x86_64. The binary will be loaded by the `use-java` code. 
18 | 
19 | ## Building and running from java
20 | 
21 | ```bash
22 | cd ../use-java
23 | mvn package
24 | ```
25 | 
26 | You can then run the Main class from your IDE or from the command line. 
27 | 
28 | This will load the libdummymath.dylib and call the rust code. 
29 | 
30 | 
31 | 
32 | 
33 | 


--------------------------------------------------------------------------------
/lib-rust/Cargo.toml:
--------------------------------------------------------------------------------
 1 | [package]
 2 | name = "dummymath"
 3 | version = "0.1.0"
 4 | authors = ["Nicolas Frankel <nicolas@frankel.ch>"]
 5 | edition = "2018"
 6 | 
 7 | [dependencies]
 8 | jni = "0.19.0"
 9 | 
10 | [lib]
11 | crate_type = ["cdylib"]
12 | 


--------------------------------------------------------------------------------
/lib-rust/src/lib.rs:
--------------------------------------------------------------------------------
 1 | use jni::JNIEnv;
 2 | use jni::sys::jint;
 3 | use jni::objects::JObject;
 4 | 
 5 | #[no_mangle]
 6 | pub extern "system" fn Java_ch_frankel_blog_rust_Main_doubleRust(_env: JNIEnv, _obj: JObject, x: jint) -> jint {
 7 |     x * 2
 8 | }
 9 | 
10 | #[no_mangle]
11 | pub extern "system" fn Java_ch_frankel_blog_rust_Main_timesRust(env: JNIEnv, obj: JObject, x: jint) -> jint {
12 |     let state = env.get_field(obj, "state", "I");
13 |     state.unwrap().i().unwrap() * x
14 | }
15 | 


--------------------------------------------------------------------------------
/use-java/libdummymath.dylib:
--------------------------------------------------------------------------------
https://raw.githubusercontent.com/ajavageek/rust-jvm/737216dd1089a049a2a87c615ad7914b515fae25/use-java/libdummymath.dylib


--------------------------------------------------------------------------------
/use-java/pom.xml:
--------------------------------------------------------------------------------
 1 | <?xml version="1.0" encoding="UTF-8"?>
 2 | <project xmlns="http://maven.apache.org/POM/4.0.0"
 3 |          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4 |          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 5 |     <modelVersion>4.0.0</modelVersion>
 6 |     <groupId>ch.frankel.blog</groupId>
 7 |     <artifactId>use-java</artifactId>
 8 |     <version>1.0-SNAPSHOT</version>
 9 |     <properties>
10 |         <maven.compiler.source>11</maven.compiler.source>
11 |         <maven.compiler.target>${maven.compiler.source}</maven.compiler.target>
12 |         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
13 |     </properties>
14 |     <build>
15 |         <plugins>
16 |             <plugin>
17 |                 <artifactId>maven-compiler-plugin</artifactId>
18 |                 <version>3.8.1</version>
19 |                 <configuration>
20 |                     <compilerArgs>
21 |                         <arg>-h</arg>
22 |                         <arg>target/headers</arg>
23 |                     </compilerArgs>
24 |                 </configuration>
25 |             </plugin>
26 |         </plugins>
27 |     </build>
28 | </project>
29 | 


--------------------------------------------------------------------------------
/use-java/src/main/java/ch/frankel/blog/rust/Main.java:
--------------------------------------------------------------------------------
 1 | package ch.frankel.blog.rust;
 2 | 
 3 | public class Main {
 4 | 
 5 |     private int state;
 6 | 
 7 |     static {
 8 |         System.loadLibrary("dummymath");
 9 |     }
10 | 
11 |     public Main(int state) {
12 |         this.state = state;
13 |     }
14 | 
15 |     public Main() {
16 |         this(-1);
17 |     }
18 | 
19 |     public static void main(String[] args) {
20 |         args = new String[2];
21 |         args[0] = "double";
22 |         args[1] = "2";
23 |         if (args.length == 0) {
24 |             throw new IllegalArgumentException("You must provide a method and its parameters");
25 |         }
26 |         var arg = args[0];
27 |         switch (arg) {
28 |             case "double":
29 |                 double_(args);
30 |                 break;
31 |             case "times":
32 |                 times(args);
33 |                 break;
34 |         }
35 |     }
36 | 
37 |     public static void double_(String[] args) {
38 |         if (args.length < 2) {
39 |             throw new IllegalArgumentException("You must provide an int parameter");
40 |         }
41 |         try {
42 |             var arg = Integer.parseInt(args[1]);
43 |             var result = new Main().doubleRust(arg);
44 |             System.out.println(arg + "x2 = " + result);
45 |         } catch (NumberFormatException e) {
46 |             throw new IllegalArgumentException("Argument must be an int");
47 |         }
48 |     }
49 | 
50 |     public static void times(String[] args) {
51 |         if (args.length < 3) {
52 |             throw new IllegalArgumentException("You must provide two int parameters");
53 |         }
54 |         try {
55 |             var arg1 = Integer.parseInt(args[1]);
56 |             var arg2 = Integer.parseInt(args[2]);
57 |             var result = new Main(arg1).timesRust(arg2);
58 |             System.out.println(arg1 + "x" + arg2 + " = " + result);
59 |         } catch (NumberFormatException e) {
60 |             throw new IllegalArgumentException("Arguments must be ints");
61 |         }
62 |     }
63 | 
64 |     public native int doubleRust(int input);
65 |     public native int timesRust(int input);
66 | }
67 | 


--------------------------------------------------------------------------------