The practice of using cache to speed up the JVM method calling process in Golang.-Golang-php.cn

The practice of using cache to accelerate the JVM method calling process in Golang

With the development of Internet technology, Java, as an excellent development language, is widely used in various fields. With the gradual popularization of concepts such as microservices and cloud computing, the requirements for the performance and efficiency of Java programs are becoming higher and higher. Among them, JVM method calling is a very important part of the Java program and one of the important factors affecting Java performance. So how to use caching to speed up the JVM method calling process in Golang? The specific practical methods will be introduced below.

What is JVM method call

JVM method call, that is, Java virtual machine method call, means that when a method is called in a Java program, the JVM will call the method according to the method name and method. Information such as a signature transfers control to the method. In the JVM, method calls are divided into two types: static method calls and instance method calls. For static method calls, the caller will directly give the class name and method signature of the method. For instance method calls, the caller needs to first create an object through the new instruction and then call the object's method.

The principle of calling JVM methods in Golang

To call JVM methods in Golang, the Cgo method is usually used, that is, the interaction between Golang and C language is used to fulfill. Cgo is the standard mechanism in Golang for calling C language libraries. It can specify the C language header file and library file path through #pragma cgo, and then import C language functions through import "C".

When calling JVM methods, you need to use JNI (Java Native Interface) to interact with the Java runtime. JNI is a set of C language interfaces provided by Java, which allows C programs to call methods in Java programs. Specifically, you need to define the method in Golang as a C language function, then call the method in Java through JNI, and finally pass the result back to Golang. This process requires some complex data type conversion and other operations, and requires certain basic knowledge of C language and JNI.

The practice of using caching to accelerate the JVM method calling process

In order to improve the speed and efficiency of JVM method calling, caching can be used to accelerate it. Specifically, C language objects needed when calling JVM methods can be cached to avoid re-creating and destroying each method call. Here is an example:

package jvm

/*
#cgo CFLAGS: -I/usr/local/java/include -I/usr/local/java/include/linux
#cgo LDFLAGS: -L/usr/local/java/jre/lib/amd64/server -ljvm
#include <stdlib.h>
#include <jni.h>
*/
import "C"
import (
    "sync"
)

// 缓存C语言对象
var cache = &sync.Map{}

// 获取class对象
func getClass(className string, jvm JavaVM) (jclass, error) {
    cName := C.CString(className)
    defer C.free(unsafe.Pointer(cName))

    // 先从缓存中获取
    if cClass, ok := cache.Load(cName); ok {
        return cClass.(jclass), nil
    }

    // 调用JNI创建class对象
    jniEnv, err := jvm.GetEnv()
    if err != nil {
        return nil, err
    }
    cClass, err := jniEnv.FindClass(cName)
    if err != nil {
        return nil, err
    }

    // 将对象放入缓存
    cache.Store(cName, cClass)

    return cClass, nil
}

// 调用实例方法
func InvokeMethod(jvm JavaVM, className string, methodName string, methodSignature string, objObj ObjObject, args ...interface{}) (interface{}, error) {
    // 获取class对象和method id
    cClass, err := getClass(className, jvm)
    if err != nil {
        return nil, err
    }
    cMethodName := C.CString(methodName)
    defer C.free(unsafe.Pointer(cMethodName))
    cMethodSignature := C.CString(methodSignature)
    defer C.free(unsafe.Pointer(cMethodSignature))
    jniEnv, err := jvm.GetEnv()
    if err != nil {
        return nil, err
    }
    methodID, err := jniEnv.GetMethodID(cClass, cMethodName, cMethodSignature)
    if err != nil {
        return nil, err
    }

    // 将参数转化为jvalue结构体
    jValue, err := convertArgs(jniEnv, args...)
    if err != nil {
        return nil, err
    }

    // 调用JNI方法
    result, err := jniEnv.CallObjectMethodV(objObj, methodID, jValue)
    if err != nil {
        return nil, err
    }

    // 将结果转化为interface{}类型
    return convertResult(jniEnv, result), nil
}

// 转换参数
func convertArgs(env *C.JNIEnv, args ...interface{}) ([]C.jvalue, error) {
    jValues := make([]C.jvalue, len(args))
    for i, arg := range args {
        switch arg.(type) {
        case int:
            jValues[i].i = C.jint(arg.(int))
        case int64:
            jValues[i].j = C.jlong(arg.(int64))
        case float64:
            jValues[i].d = C.jdouble(arg.(float64))
        case bool:
            jValues[i].z = C.jboolean(arg.(bool))
        case string:
            cStr := C.CString(arg.(string))
            defer C.free(unsafe.Pointer(cStr))
            jValues[i].l = C.jobject(unsafe.Pointer(env.NewStringUTF(cStr)))
        default:
            return nil, fmt.Errorf("Unsupported arg type: %T", arg)
        }
    }
    return jValues, nil
}

// 转换结果
func convertResult(env *C.JNIEnv, result jobject) interface{} {
    className, err := jni.GetObjectClassName(env, result)
    if err != nil {
        return nil
    }

    switch className {
    case "java/lang/String":
        return convertToString(env, result)
    case "java/lang/Integer":
        return convertToInt(env, result)
    case "java/lang/Long":
        return convertToLong(env, result)
    case "java/lang/Double":
        return convertToDouble(env, result)
    case "java/lang/Boolean":
        return convertToBool(env, result)
    case "java/lang/Object":
        return convertToObject(env, result)
    default:
        return result
    }
}

// 将结果转化为string
func convertToString(env *C.JNIEnv, result jobject) string {
    cStr := env.GetStringUTFChars((*C.jstring)(unsafe.Pointer(result)), nil)
    defer env.ReleaseStringUTFChars((*C.jstring)(unsafe.Pointer(result)), cStr)
    return C.GoString(cStr)
}

// 将结果转化为int
func convertToInt(env *C.JNIEnv, result jobject) int {
    return int(env.CallIntMethod(result, env.GetMethodID(env.FindClass("java/lang/Integer"), "intValue", "()I")))
}

// 将结果转化为long
func convertToLong(env *C.JNIEnv, result jobject) int64 {
    return int64(env.CallLongMethod(result, env.GetMethodID(env.FindClass("java/lang/Long"), "longValue", "()J")))
}

// 将结果转化为double
func convertToDouble(env *C.JNIEnv, result jobject) float64 {
    return float64(env.CallDoubleMethod(result, env.GetMethodID(env.FindClass("java/lang/Double"), "doubleValue", "()D")))
}

// 将结果转化为bool
func convertToBool(env *C.JNIEnv, result jobject) bool {
    return env.CallBooleanMethod(result, env.GetMethodID(env.FindClass("java/lang/Boolean"), "booleanValue", "()Z"))
}

// 将结果转化为object
func convertToObject(env *C.JNIEnv, result jobject) interface{} {
    return result
}

Copy after login

In the above code, we use Go's sync.Map to implement caching. When calling the getClass method, first search for the corresponding class object in the cache. If it already exists, return it directly. Otherwise, call JNI to create a new class object and put it in the cache. This can avoid re-creating the class object every time the method is called, thereby improving the calling efficiency.

In addition, it should be noted that in actual implementation, cache expiration and cache cleaning issues also need to be considered to ensure the effectiveness and stability of the cache.

Summary

The above is the practical method of using cache to speed up the JVM method calling process. Through caching, you can avoid re-creating class objects every time a method is called, thereby improving the performance and efficiency of Java programs. However, in actual applications, it is necessary to select an appropriate caching strategy based on specific business scenarios and implementation details to achieve optimal performance and effects.

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