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首页 > 解决方案 > 如何使用 Java GraalVM 在 Java 代码和嵌入式 WASM 代码之间将字符串作为参数传递和返回值

java - 如何使用 Java GraalVM 在 Java 代码和嵌入式 WASM 代码之间将字符串作为参数传递和返回值

问题描述

我想将一个字符串作为参数从 Java 代码传递给 WASM 代码，并将一个字符串从 WASM 代码返回给 Java。遵循GraalVM WASM 参考并没有显示如何做到这一点。

编译成的 Rust 示例代码example.wasm：

#[no_mangle]
pub extern fn main() -> *const u8 {
    "Hello world!".as_ptr()
}

使用 GraalVM 多语言 API 嵌入 WASM 的 Java 代码：

byte[] binary = readBytes("example.wasm");
Context.Builder contextBuilder = Context.newBuilder("wasm");
Source.Builder sourceBuilder = Source.newBuilder("wasm", ByteSequence.create(binary), "example");
Source source = sourceBuilder.build();
Context context = contextBuilder.build();

context.eval(source);

Value mainFunction = context.getBindings("wasm").getMember("main").getMember("main");
System.out.println("Returned: " + mainFunction.execute());

但是，在运行此程序时会打印以下内容：

Returned: 1048641

我希望这能打印出来Returned: Hello world!

尝试mainFunction.execute().asString()投掷

Exception in thread "main" java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:108)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:58)
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88)
Caused by: java.lang.ClassCastException: Cannot convert '1048641'(language: Java, type: java.lang.Integer) to Java type 'java.lang.String' using Value.asString(): Invalid coercion. You can ensure that the value can be converted using Value.isString().
    at org.graalvm.truffle/com.oracle.truffle.polyglot.PolyglotEngineException.classCast(PolyglotEngineException.java:154)
    at org.graalvm.truffle/com.oracle.truffle.polyglot.PolyglotValue.cannotConvert(PolyglotValue.java:1261)
    at org.graalvm.truffle/com.oracle.truffle.polyglot.PolyglotValue.invalidCastPrimitive(PolyglotValue.java:686)
    at org.graalvm.truffle/com.oracle.truffle.polyglot.PolyglotValue.asStringUnsupported(PolyglotValue.java:658)
    at org.graalvm.truffle/com.oracle.truffle.polyglot.PolyglotValue.asString(PolyglotValue.java:649)
    at org.graalvm.truffle/com.oracle.truffle.polyglot.PolyglotValue$PrimitiveValue.asString(PolyglotValue.java:4016)
    at org.graalvm.sdk/org.graalvm.polyglot.Value.asString(Value.java:952)
    at org.example.wasmhost.WasmHostApplication.main(WasmHostApplication.java:63)
    ... 8 more

我的Java是：

$ java -version
openjdk version "11.0.11" 2021-04-20
OpenJDK Runtime Environment GraalVM CE 21.1.0 (build 11.0.11+8-jvmci-21.1-b05)
OpenJDK 64-Bit Server VM GraalVM CE 21.1.0 (build 11.0.11+8-jvmci-21.1-b05, mixed mode, sharing)

标签： javarustwebassemblygraalvm

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