利用 Rust 语言编写 Java JNI 实现 - ToB企服应用市场:ToB评测及商务社交产业平台

$ /opt/adoptopenjdk-21.0.2+13/bin/java -version
openjdk version "21.0.2" 2024-01-16 LTS
OpenJDK Runtime Environment Temurin-21.0.2+13 (build 21.0.2+13-LTS)
OpenJDK 64-Bit Server VM Temurin-21.0.2+13 (build 21.0.2+13-LTS, mixed mode, sharing)

复制代码

$ rustup --version
rustup 1.27.0 (bbb9276d2 2024-03-08)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.76.0 (07dca489a 2024-02-04)`

复制代码

$ curl -s "https://get.sdkman.io" | bash

复制代码

$ sdk install gradle

复制代码

$ gradle --version
------------------------------------------------------------
Gradle 8.7
------------------------------------------------------------
Build time: 2024-03-22 15:52:46 UTC
Revision: 650af14d7653aa949fce5e886e685efc9cf97c10
Kotlin: 1.9.22
Groovy: 3.0.17
Ant: Apache Ant(TM) version 1.10.13 compiled on January 4 2023
JVM: 17.0.10 (Oracle Corporation 17.0.10+11-LTS-240)
OS: Linux 6.8.2-zen2-1-zen amd64

复制代码

$ mkdir rust-jni-demo
$ cd rust-jni-demo

复制代码

$ mkdir java
$ cd java

复制代码

$ gradle init --use-defaults --type java-application

复制代码

/*
* This source file was generated by the Gradle 'init' task
*/
package top.srcres.apps.rustjnidemo;
import java.io.File;
import java.nio.file.Path;
public class App {
static void loadRustLibrary() {
System.out.println(System.getProperty("java.library.path"));
System.loadLibrary("rust_jni_demo");
}
static native String hello(String input);
public static void main(String[] args) {
loadRustLibrary();
String output = hello("string from Java");
System.out.println(output);
}
}

复制代码

val generateJniHeaders: Task by tasks.creating {
val jniHeaderDir = file("src/main/generated/jni")
group = "build"
dependsOn(tasks.getByName("compileJava"))
inputs.dir("src/main/java")
outputs.dir(jniHeaderDir)
doLast {
val javaHome = Jvm.current().javaHome
val javap = javaHome.resolve("bin").walk().firstOrNull { it.name.startsWith("javap") }?.absolutePath ?: error("javap not found")
val javac = javaHome.resolve("bin").walk().firstOrNull { it.name.startsWith("javac") }?.absolutePath ?: error("javac not found")
val buildDir = file("build/classes/java/main")
val tmpDir = file("build/tmp/jvmJni").apply { mkdirs() }
val bodyExtractingRegex = """^.+\Rpublic \w* ?class ([^\s]+).*\{\R((?s:.+))\}\R$""".toRegex()
val nativeMethodExtractingRegex = """.*\bnative\b.*""".toRegex()
println("Beginning to generate JNI headers.")
println("javaHome is ${javaHome.absolutePath}")
println("javap is $javap")
println("javac is $javac")
buildDir.walkTopDown()
.filter { "META" !in it.absolutePath }
.forEach { file ->
if (!file.isFile) return@forEach
val output = ByteArrayOutputStream().use {
project.exec {
commandLine(javap, "-private", "-cp", buildDir.absolutePath, file.absolutePath)
standardOutput = it
}.assertNormalExitValue()
it.toString()
}
val (qualifiedName, methodInfo) = bodyExtractingRegex.find(output)?.destructured ?: return@forEach
val lastDot = qualifiedName.lastIndexOf('.')
val packageName = qualifiedName.substring(0, lastDot)
val className = qualifiedName.substring(lastDot+1, qualifiedName.length)
val nativeMethods =
nativeMethodExtractingRegex.findAll(methodInfo).mapNotNull { it.groups }.flatMap { it.asSequence().mapNotNull { group -> group?.value } }.toList()
if (nativeMethods.isEmpty()) return@forEach
val source = buildString {
appendln("package $packageName;")
appendln("public class $className {")
for (method in nativeMethods) {
if ("()" in method) appendln(method)
else {
val updatedMethod = StringBuilder(method).apply {
var count = 0
var i = 0
while (i < length) {
if (this[i] == ',' || this[i] == ')') insert(i, " arg${count++}".also { i += it.length + 1 })
else i++
}
}
appendln(updatedMethod)
}
}
appendln("}")
}
val outputFile = tmpDir.resolve(packageName.replace(".", "/")).apply { mkdirs() }.resolve("$className.java").apply { delete() }.apply { createNewFile() }
outputFile.writeText(source)
println("Generating for ${outputFile.absolutePath} into ${jniHeaderDir.absolutePath}")
project.exec {
commandLine(javac, "-h", jniHeaderDir.absolutePath, outputFile.absolutePath)
}.assertNormalExitValue()
}
}
}

复制代码

/*
* Class: top_srcres_apps_rustjnidemo_App
* Method: hello
* Signature: (Ljava/lang/String;)Ljava/lang/String;
*/
JNIEXPORT jstring JNICALL Java_top_srcres_apps_rustjnidemo_App_hello
(JNIEnv *, jclass, jstring);

复制代码

$ mkdir rust
$ cargo new --name rust-jni-demo rust

复制代码

[dependencies]
jni = "0.21.1"
[lib]
crate-type = ["cdylib"]

复制代码

use jni::JNIEnv;
use jni::objects::{JClass, JObject, JString, JValue};
use jni::sys::{jint, jlong, jstring};
use std::thread;
use std::time::Duration;
fn create_rust_string(src: &str) -> String {
format!("Rust-created string, {}", src)
}
#[allow(non_snake_case)]
#[no_mangle]
pub extern "system" fn Java_top_srcres_apps_rustjnidemo_App_hello<'a>(
mut env: JNIEnv<'a>,
_: JClass<'a>,
input: JString<'a>
) -> jstring {
let input: String = env.get_string(&input).expect("Failed to get Java string.").into();
let output = env.new_string(create_rust_string(&input)).expect("Failed to create Rust string.");
output.into_raw()
}

复制代码

$ cargo build --release

复制代码

application {
// Define the main class for the application.
mainClass = "top.srcres.apps.rustjnidemo.App"
applicationDefaultJvmArgs = listOf(
"-Djava.library.path=../../rust/target/release/"
)
}

复制代码

Rust-created string, string from Java

复制代码

static int testInt;
static String testString;
static String testStringFromRust;
static native String hello(String input);
static native int helloInt(int input);
static native int helloFromTestIntField();
static native String helloFromTestStringField();
static native void modifyTestStringFromRust(String input);
static String callFromRust(String input) {
System.out.println("Method callFromRust was invoked!");
return "Java-side received: " + input;
}
static native String actCallFromRust(String input);
static native void delayInRust(long timeMillis);

复制代码

public static void main(String[] args) {
loadRustLibrary();
String output = hello("string from Java");
System.out.println(output);
int outputInt = helloInt(114514);
System.out.println(outputInt);
testInt = 514;
System.out.println(helloFromTestIntField());
testString = "String static field from Java";
System.out.println(helloFromTestStringField());
modifyTestStringFromRust("string from Java #2");
System.out.println(testStringFromRust);
System.out.println("actCallFromRust result: " + actCallFromRust("string from Java #3"));
System.out.println("Delay in Rust for 2 seconds...");
delayInRust(2000);
System.out.println("Delay done.");
}

复制代码

#[allow(non_snake_case)]
#[no_mangle]
pub extern "system" fn Java_top_srcres_apps_rustjnidemo_App_helloInt<'a>(
_: JNIEnv<'a>,
_: JClass<'a>,
input: jint
) -> jint {
input + 1919810
}
#[allow(non_snake_case)]
#[no_mangle]
pub extern "system" fn Java_top_srcres_apps_rustjnidemo_App_helloFromTestIntField<'a>(
mut env: JNIEnv<'a>,
class: JClass<'a>
) -> jint {
let testInt = env.get_static_field(&class, "testInt", "I")
.expect("Failed to get static field testInt")
.i()
.expect("Failed to convert testInt into jint");
testInt + 114
}
#[allow(non_snake_case)]
#[no_mangle]
pub extern "system" fn Java_top_srcres_apps_rustjnidemo_App_helloFromTestStringField<'a>(
mut env: JNIEnv<'a>,
class: JClass<'a>
) -> jstring {
let testStringObj = env.get_static_field(&class, "testString", "Ljava/lang/String;")
.expect("Failed to get static field testString")
.l()
.expect("Failed to convert testString into JObject");
let testString: String = env.get_string(&JString::from(testStringObj))
.expect("Failed to get the value of testString")
.into();
let output = env.new_string(create_rust_string(&testString)).expect("Failed to create Rust string.");
output.into_raw()
}
#[allow(non_snake_case)]
#[no_mangle]
pub extern "system" fn Java_top_srcres_apps_rustjnidemo_App_modifyTestStringFromRust<'a>(
mut env: JNIEnv<'a>,
class: JClass<'a>,
input: JString<'a>
) {
let inputStr: String = env.get_string(&input).expect("Failed to receive the argument: input").into();
let testStringFromRust = env.new_string(create_rust_string(&inputStr)).expect("Failed to create Rust string.");
let testStringFromRustObj = JObject::from(testStringFromRust);
let testStringFromRustId = env.get_static_field_id(&class, "testStringFromRust", "Ljava/lang/String;")
.expect("Failed to get the ID of static field testStringFromRust");
env.set_static_field(&class, &testStringFromRustId, JValue::from(&testStringFromRustObj))
.expect("Failed to set static field testStringFromRust");
}
#[allow(non_snake_case)]
#[no_mangle]
pub extern "system" fn Java_top_srcres_apps_rustjnidemo_App_actCallFromRust<'a>(
mut env: JNIEnv<'a>,
class: JClass<'a>,
input: JString<'a>
) -> jstring {
let inputStr: String = env.get_string(&input).expect("Failed to receive the argument: input").into();
let testStringFromRust = env.new_string(create_rust_string(&inputStr)).expect("Failed to create Rust string.");
let testStringFromRustObj = JObject::from(testStringFromRust);
let callFromRustResult = env.call_static_method(&class, "callFromRust", "(Ljava/lang/String;)Ljava/lang/String;", &[JValue::from(&testStringFromRustObj)])
.expect("Failed to invoke static method callFromRust");
let callFromRustResultObj = callFromRustResult.l().expect("Failed to convert the method result into JObject.");
JString::from(callFromRustResultObj).into_raw()
}
#[allow(non_snake_case)]
#[no_mangle]
pub extern "system" fn Java_top_srcres_apps_rustjnidemo_App_delayInRust<'a>(
_: JNIEnv<'a>,
_: JClass<'a>,
input: jlong
) {
let inputU = u64::try_from(input).expect("Attempting to call delayInRust with negative millisecond duration.");
thread::sleep(Duration::from_millis(inputU));
}

复制代码

../../rust/target/release/
Rust-created string, string from Java
2034324
628
Rust-created string, String static field from Java
Rust-created string, string from Java #2
Method callFromRust was invoked!
actCallFromRust result: Java-side received: Rust-created string, string from Java #3
Delay in Rust for 2 seconds...
Delay done.

复制代码