几周前我开始使用JNI从C++调用Java类,而今天我遇到了一种特殊情况。我是C++的新手(虽然熟悉Java),所以这可能是一个n00b错误。我在Java中有这个名为IntArray.java的类,并且我在C++中创建了另一个名为IntArrayProxy的类(拆分为.h和.cpp文件),以便通过JNI访问它的方法。我还有另一个名为IntArrayProxyTest.cpp的源文件,它测试IntArrayProxy方法。c0000005在C++中使用JNI时出现异常(访问冲突)
在IntArrayProxy中,我使用了包含Java类实例的数据成员jobject * intArrayObject,并将其传递给IntArrayProxy类的每个方法。我的问题是,当我将它用作指针(jobject *)时,插入(使用插入)一些整数并更改其中一些(使用setElement)后,当我使用相同的size()方法两次时,可执行文件创建崩溃给我一个c0000005异常(访问冲突)。
我注意到的第一件事是,如果我使用正常的jobject(而不是jobject *),那么根本没有问题,而第二个是当我尝试调用第二个非void方法时发生异常。 insert()和setElement(int,int)都是无效的,所以我可以根据需要多次调用它们。我尝试了几乎所有的非void方法,并且每次尝试调用两个非void方法时抛出同样的异常。
我以为可能指针改变了,所以我试图在每种方法中打印jobject *,但它保持不变。我在论坛中发现的第二个解释是,也许对象被破坏了,但我不知道如何检查它以及为什么会发生这种情况。我花了整整一天的搜索和调试,但没有运气。
我认为这并不重要,但我在Win7(64位)上使用最新的(32位)minGW编译器。我也使用32位jvm.dll。我正在使用命令行进行编译(g ++ -I“C:\ Program Files(x86)\ Java \ jdk1.6.0_26 \ include”-I“C:\ Program Files(x86)\ Java \ jdk1.6.0 _26 \ include \ win32“IntArrayProxy.cpp IntArrayProxyTest.cpp -L”C:\ Users \ jEOPARd \ Desktop \ Creta \ JNI samples“-ljvm -o IntArrayProxyTest.exe)
希望有人能帮助我!
Thanx提前!!
Kostis
IntArray.java
package SortIntArray;
public class IntArray {
private int[] arrayOfInt;
private int cursor;
private static final int CAPACITY = 5;
public IntArray() {
arrayOfInt = new int[CAPACITY];
cursor = 0;
}
public void insert(int n) {
if (isFull()) {
System.out.println("Inserting in a full array!");
} else {
arrayOfInt[cursor++] = n;
}
}
public int removeLast() {
if (isEmpty()) {
System.out.println("Removing from an empty array!");
return -666;
} else {
return arrayOfInt[--cursor];
}
}
private boolean isEmpty() {
return cursor <= 0;
}
private boolean isFull() {
return cursor >= CAPACITY;
}
public String toString() {
if (isEmpty()) {
return "Empty Array";
}
String s = Integer.toString(arrayOfInt[0]);
for (int i = 1; i < cursor; i++) {
s += ", " + Integer.toString(arrayOfInt[i]);
}
return s;
}
public int size() {
return cursor;
}
public int getElement(int pos) {
return arrayOfInt[pos];
}
public void setElement(int pos, int newElement) {
arrayOfInt[pos] = newElement;
}
}
IntArrayProxy.h
#ifndef INTARRAYPROXY_H
#define INTARRAYPROXY_H
#include <jni.h>
using namespace std;
class IntArrayProxy {
JNIEnv *env;
jclass intArrayClass;
jobject *intArrayObject; //giati oxi pointer?
public:
IntArrayProxy(JNIEnv*);
void insert(int n);
int removeLast();
string toString();
int size();
int getElement(int);
void setElement(int pos, int newElement);
jobject *getIntArrayObject();
};
#endif /* INTARRAYPROXY_H */
IntArrayProxy.cpp
#include <stdio.h>
#include <cstdlib>
#include <iostream>
using namespace std;
#include "IntArrayProxy.h"
IntArrayProxy::IntArrayProxy(JNIEnv *envir) {
env = envir;
intArrayClass = env -> FindClass("SortIntArray/IntArray");
if (intArrayClass == NULL) {
cout << "--intArrayClass = NULL\n";
exit(0);
}
jmethodID IntArrayConstructor = env->GetMethodID(intArrayClass, "<init>", "()V");
if (IntArrayConstructor == NULL) {
cout << "--IntArrayConstructor = NULL";
exit(0);
}
cout << "IntArrayProxy: Got constructor\n";
jobject obj = env -> NewObject(intArrayClass, IntArrayConstructor);
intArrayObject = &obj; // I also can't assign intArrayObject directly at the above line, I don't know why (would be glad if you could tell me)
if (*intArrayObject == NULL) {
cout << "--*intArrayObject = NULL";
exit(0);
}
cout << "IntArrayProxy: Object created\n";
}
void IntArrayProxy::insert(int n) {
jmethodID insertID = env -> GetMethodID(intArrayClass, "insert", "(I)V");
if (insertID == NULL) {
cout << "--insertID = NULL";
exit(0);
}
env -> CallVoidMethod(*intArrayObject, insertID, (jint) n);
}
int IntArrayProxy::removeLast() {
jmethodID removeLastID = env -> GetMethodID(intArrayClass, "removeLast", "()I");
if (removeLastID == NULL) {
cout << "--removeLastID = NULL";
exit(0);
}
return (int) (env -> CallIntMethod(*intArrayObject, removeLastID));
}
string IntArrayProxy::toString() {
jmethodID toStringID = env -> GetMethodID(intArrayClass, "toString", "()Ljava/lang/String;");
if (toStringID == NULL) {
cout << "--toStringID = NULL";
exit(0);
}
jstring intArrayString = (jstring) env -> CallObjectMethod(*intArrayObject, toStringID);
string s = env -> GetStringUTFChars(intArrayString, NULL);
return s;
}
int IntArrayProxy::size(){
jmethodID sizeID = env -> GetMethodID(intArrayClass, "size", "()I");
if (sizeID == NULL) {
cout << "--sizeID = NULL";
exit(0);
}
return (int) (env -> CallIntMethod(*intArrayObject, sizeID));
}
int IntArrayProxy::getElement(int pos) {
jmethodID getElementID = env -> GetMethodID(intArrayClass, "getElement", "(I)I");
if (getElementID == NULL) {
cout << "--getElementID = NULL";
exit(0);
}
return (int) env -> CallObjectMethod(*intArrayObject, getElementID, (jint) pos);
}
void IntArrayProxy::setElement(int pos, int newElement){
jmethodID setElementID = env -> GetMethodID(intArrayClass, "setElement", "(II)V");
if (setElementID == NULL) {
cout << "--setElementID = NULL";
exit(0);
}
env -> CallVoidMethod(*intArrayObject, setElementID, (jint) pos, (jint) newElement);
}
jobject *IntArrayProxy::getIntArrayObject(){
return intArrayObject;
}
IntArrayProxyTest.cpp
#include <stdio.h>
#include <jni.h>
#include <cstdlib>
#include <iostream>
using namespace std;
#include "IntArrayProxy.h"
int main() {
cout << "--Starting..\n";
JavaVM *jvm; /* denotes a Java VM */
JNIEnv *env; /* pointer to native method interface */
JavaVMInitArgs vm_args; /* JDK/JRE 6 VM initialization arguments */
JavaVMOption* options = new JavaVMOption[1];
options[0].optionString = "-Djava.class.path=C:\\Users\\jEOPARd\\Desktop\\Creta\\JNI samples\\JNI tests\\build\\classes";
vm_args.version = JNI_VERSION_1_6;
vm_args.nOptions = 1;
vm_args.options = options;
vm_args.ignoreUnrecognized = false;
/* load and initialize a Java VM, return a JNI interface
* pointer in env */
cout << "--Creating VM..\n";
JNI_CreateJavaVM(&jvm, (void **) &env, &vm_args);
cout << "--VM created successfully!!\n";
delete options;
cout << "--Finding IntArray class..\n";
IntArrayProxy *intArrayProxy = new IntArrayProxy(env);
if (env->ExceptionOccurred())
env->ExceptionDescribe();
intArrayProxy -> insert(1);
intArrayProxy -> insert(10);
intArrayProxy -> insert(3);
intArrayProxy -> insert(88);
intArrayProxy -> insert(32);
intArrayProxy ->setElement(2, 5);
intArrayProxy ->setElement(3, 7);
cout << "Size: " << intArrayProxy -> size() << endl;
cout << "Size: " << intArrayProxy -> size() << endl;
cout << "--Destroying VM..\n";
jvm->DestroyJavaVM();
cout << "--Done!!!\n";
return 0;
}
也许你可以尝试减少重现错误的代码量? –