使用jni.h在C++中编译java方法时出现构建错误

Build error when compiling java methods in C++ using jni.h

本文关键字：方法 错误 构建 java 编译 jni C++ 使用      更新时间：2023-10-16

我正在Visual Studio C++环境中尝试从Java类运行一些方法。我得到了一个与CreateJavaVM相关的错误。

你能帮我找到解决办法吗？

我做了以下步骤。

步骤1:JDK 1.6安装在以下路径下：C:\Program Files\Java下面有两个子目录：jdk1.6.0_45，jre6

步骤2:编写一个简单的java程序。

public class Sample2
{
public static int intMethod(int n)
{
return n*n;
}
public static boolean booleanMethod(boolean bool) 
{
return !bool;
}
}

步骤3:编译java代码：

javac Sample2.java

步骤4:创建Visual Studio C++程序。Visual C++CLR控制台应用程序。

第5步：添加其他依赖项。(jvm.lib和jvm.dll)a) 选择项目->属性->链接器->输入->其他依赖项：jvm.libb) 选择项目->属性->链接器->输入->延迟加载的Dlls:jvm.dll

步骤6:添加包含目录a) 选择项目->属性->配置属性->C/C++->常规->其他包含目录：C:\Program Files\Java\jdk1.6.0_45\lib；C： \Program Files\Java\jdk1.6.0_45\include\win32；C： \Program Files\Java\jdk1.6.0_45\包括

步骤7:编写C++代码以运行java方法。

#include "stdafx.h"
#include "jni.h"
#include <jni_md.h>
using namespace System;
int main(array<System::String ^> ^args)
{
JavaVM *jvm;   /* denotes a Java VM */
JNIEnv *env;  /* pointer to native method interface */
jint square;
jboolean not;
JavaVMInitArgs vm_args; /* JDK/JRE 6 VM initialization arguments */
JavaVMOption *options = new JavaVMOption[1];
options[0].optionString = "-Djava.class.path=C:\JavaCode";  
vm_args.version = JNI_VERSION_1_6;
vm_args.options = options;
vm_args.nOptions = 1;
vm_args.ignoreUnrecognized = false;
int res = JNI_CreateJavaVM(&jvm, (void **)&env, &vm_args);
jclass cls = env->FindClass("Sample2");
jmethodID mid = env->GetStaticMethodID(cls, "staticInt", "(I)I");
env->CallStaticVoidMethod(cls, mid,10);
if(cls !=0)
{   
mid = env->GetStaticMethodID(cls,"intMethod","(I)I");    
if(mid !=0)
{  
square = env->CallStaticIntMethod(cls, mid, 5);       
printf("Result of intMethod: %dn", square);
}
mid = env->GetStaticMethodID(cls, "booleanMethod", "(Z)Z");
if(mid !=0)
{ 
not = env->CallStaticBooleanMethod(cls, mid, 1);
printf("Result of booleanMethod: %dn", not);
}
}
jvm->DestroyJavaVM();
Console::Read();
return 0;
}

步骤8:当我构建项目时，我得到了以下错误：

1>------ Build started: Project: 1, Configuration: Debug Win32 ------
1>LINK : warning LNK4199: /DELAYLOAD:jvm.dll ignored; no imports found from jvm.dll
1>1.obj : warning LNK4248: unresolved typeref token (0100000F) for '_jmethodID'; image may not run
1>1.obj : error LNK2028: unresolved token (0A000016) "extern "C" long __stdcall JNI_CreateJavaVM(struct JavaVM_ * *,void * *,void *)" (?JNI_CreateJavaVM@@$$J212YGJPAPAUJavaVM_@@PAPAXPAX@Z) referenced in function "int __clrcall main(cli::array<class System::String ^ >^)" (?main@@$$HYMHP$01AP$AAVString@System@@@Z)
1>1.obj : error LNK2019: unresolved external symbol "extern "C" long __stdcall JNI_CreateJavaVM(struct JavaVM_ * *,void * *,void *)" (?JNI_CreateJavaVM@@$$J212YGJPAPAUJavaVM_@@PAPAXPAX@Z) referenced in function "int __clrcall main(cli::array<class System::String ^ >^)" (?main@@$$HYMHP$01AP$AAVString@System@@@Z)
1>C:UserstveluppillaiDesktopTest11Debug1.exe : fatal error LNK1120: 2 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

有人能帮我解决这个错误吗？

JNI_CreateJavaVM是在jni.h中定义的，所以我猜测您的链接器找不到jni.h。实际上，我把那个文件和jni_md.h和我的源代码放在了我的项目目录中。

请注意，jni.h包括jni_md.h，因此在源代码中包含#include <jni_md.h>是多余的。

所以，我解决了这个错误。以下是正在使用的C++代码。

// 1.cpp : main project file.
#include "stdafx.h"
#include "jni.h"
#include <windows.h>
using namespace System;

int CallJava()
{
JavaVM *jvm;   /* denotes a Java VM */
JNIEnv *env;  /* pointer to native method interface */
jint square;
jboolean not;
JavaVMInitArgs vm_args; /* JDK/JRE 6 VM initialization arguments */
JavaVMOption *options = new JavaVMOption[1];
options[0].optionString = "-Djava.class.path=C:\JavaCode";  
vm_args.version = JNI_VERSION_1_6;
vm_args.options = options;
vm_args.nOptions = 1;
vm_args.ignoreUnrecognized = false;
HINSTANCE hinstLib;  
hinstLib = LoadLibrary(TEXT("C:\Program Files\Java\jdk1.6.0_45\jre\bin\server\jvm.dll"));
if(hinstLib==0)
{
printf("Error");
}
if(hinstLib!= NULL)
{
typedef jint (JNICALL *PtrCreateJavaVM)(JavaVM **, void **, void *);
PtrCreateJavaVM ptrCreateJavaVM =  (PtrCreateJavaVM)GetProcAddress(hinstLib,"JNI_CreateJavaVM");
int res = ptrCreateJavaVM(&jvm, (void**)&env, &vm_args);
jclass cls = env->FindClass("Sample2");
jmethodID mid;   
if(cls !=0)
{   
mid = env->GetStaticMethodID(cls,"intMethod","(I)I");
if(mid !=0)
{  
square = env->CallStaticIntMethod(cls, mid, 5);       
printf("Result of intMethod: %dn", square);
}
mid = env->GetStaticMethodID(cls, "booleanMethod", "(Z)Z");
if(mid !=0)
{ 
not = env->CallStaticBooleanMethod(cls, mid, 1);
printf("Result of booleanMethod: %dn", not);
}
}
jvm->DestroyJavaVM();
}
else
{
printf("Library is NULL");
}
Console::Read();
return 0;
}
int main(array<System::String ^> ^args)
{
CallJava();
Console::Read();
return 0;
}
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