我正在UNIX中编写一个C++程序，以生成一个共享库，该库将使用JNI在java中调用。这个C++程序必须读取UNIX框中的一个文件，然后必须将其转换为jbyteArray(JNI数据类型)，以便JAVA可以使用它。
我将C++中的文件读取为char*，但无法转换为jbyteArray。请帮帮它。
代码如下：：
#include <iostream>
#include <fstream>
#include <stdio.h>
#include "com_sp_dll_NativeMethods.h" // this header file was generated by java
using namespace std;
JNIEXPORT void JNICALL Java_HelloWorld_displayMessage(JNIEnv *env, jobject obj)
{
printf("Hello World!n");
}
JNIEXPORT jbyteArray JNICALL Java_com_sp_dll_NativeMethods_getFile(JNIEnv *env, jobject obj)
{
ifstream fl("/home/rkannan/myFile.txt");
fl.seekg(0, ios::end );
size_t len = fl.tellg();
char *ret = new char[len];
fl.seekg(0, ios::beg);
fl.read(ret, len);
fl.close();
int i = 0;
jbyte *a1 = null;
while(ret[i] != ' '){
cout<<ret[i];
al[i] = ret[i];
i++;
}
jbyteArray result = env->NewByteArray( len);
env->SetByteArrayRegion( result, 0, len, (const jbyte*) ret );
delete[] ret;
return result;
}
错误如下
bash-3.00$ g++ -I /usr/jdk/instances/jdk1.5.0/include -I /usr/jdk/instances/jdk1.5.0/include/solaris -o libSample.so -shared com_sp_dll_NativeMethods.cpp
Text relocation remains referenced
against symbol offset in file
std::__ioinit 0x550 /var/tmp//ccKCiEKq.o
std::__ioinit 0x554 /var/tmp//ccKCiEKq.o
std::__ioinit 0x588 /var/tmp//ccKCiEKq.o
std::__ioinit 0x58c /var/tmp//ccKCiEKq.o
.rodata (section) 0x204 /var/tmp//ccKCiEKq.o
.rodata (section) 0x208 /var/tmp//ccKCiEKq.o
.rodata (section) 0x244 /var/tmp//ccKCiEKq.o
.rodata (section) 0x248 /var/tmp//ccKCiEKq.o
.rodata (section) 0x2f4 /var/tmp//ccKCiEKq.o
.rodata (section) 0x2f8 /var/tmp//ccKCiEKq.o
std::fpos<__mbstate_t>::operator long long() const0x348 /var/tmp//ccKCiEKq.o
std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char)0x400 /var/tmp//ccKCiEKq.o
std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)0x2cc /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::is_open()0x260 /var/tmp//ccKCiEKq.o
std::basic_istream<char, std::char_traits<char> >::read(char*, int)0x39c /var/tmp//ccKCiEKq.o
JNIEnv_::SetByteArrayRegion(_jbyteArray*, int, int, signed char const*)0x468 /var/tmp//ccKCiEKq.o
operator new[](unsigned int) 0x364 /var/tmp//ccKCiEKq.o
std::basic_istream<char, std::char_traits<char> >::seekg(long long, std::_Ios_Seekdir)0x31c /var/tmp//ccKCiEKq.o
std::basic_istream<char, std::char_traits<char> >::seekg(long long, std::_Ios_Seekdir)0x384 /var/tmp//ccKCiEKq.o
std::basic_istream<char, std::char_traits<char> >& std::operator>><char, std::char_traits<char> >(std::basic_istream<char, std::char_traits<char> >&, char*)0x2b4 /var/tmp//ccKCiEKq.o
printf 0x20c /var/tmp//ccKCiEKq.o
JNIEnv_::NewByteArray(int) 0x444 /var/tmp//ccKCiEKq.o
std::ios_base::Init::Init() 0x558 /var/tmp//ccKCiEKq.o
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::size() const0x14 /var/tmp//ccKCiEKq.o
std::cout 0x2c0 /var/tmp//ccKCiEKq.o
std::cout 0x2c4 /var/tmp//ccKCiEKq.o
std::cout 0x3f4 /var/tmp//ccKCiEKq.o
std::cout 0x3f8 /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::basic_ifstream()0x234 /var/tmp//ccKCiEKq.o
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned int) const0x9c /var/tmp//ccKCiEKq.o
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned int) const0x128 /var/tmp//ccKCiEKq.o
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned int) const0x184 /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::open(char const*, std::_Ios_Openmode)0x250 /var/tmp//ccKCiEKq.o
std::ios_base::Init::~Init() 0x590 /var/tmp//ccKCiEKq.o
std::basic_ios<char, std::char_traits<char> >::eof() const0x288 /var/tmp//ccKCiEKq.o
unsigned int const& std::min<unsigned int>(unsigned int const&, unsigned int const&)0x44 /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::~basic_ifstream()0x49c /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::~basic_ifstream()0x4ac /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::~basic_ifstream()0x4d4 /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::~basic_ifstream()0x4f8 /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::close()0x2e4 /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::close()0x3ac /var/tmp//ccKCiEKq.o
std::basic_ifstream<char, std::char_traits<char> >::basic_ifstream(char const*, std::_Ios_Openmode)0x300 /var/tmp//ccKCiEKq.o
operator delete[](void*) 0x484 /var/tmp//ccKCiEKq.o
std::basic_istream<char, std::char_traits<char> >::tellg() 0x334 /var/tmp//ccKCiEKq.o
_Unwind_Resume 0x508 /var/tmp//ccKCiEKq.o
ld: fatal: relocations remain against allocatable but non-writable sections
collect2: ld returned 1 exit status
您似乎没有为数组设置任何字节数据。事实上，当jbyte被typedef为char时，您可以直接在setByteArrayRegion中设置您的char数组，如下所示：
env->SetByteArrayRegion( result, 0, 100, ret );
编辑：此外，假设al[i]应该是a1[i]，你正在做一些非常危险的事情，因为你没有为a1分配空间。基本上，按照我上面的建议做意味着你可以摆脱整个循环。另外，当你完成C++数组时，不要忘记删除它(即将它复制到jByteArray中)！
JNIEXPORT jbyteArray JNICALL Java_com_sp_dll_NativeMethods_getFile
(JNIEnv *env, jobject obj)
{
ifstream fl("/home/rkannan/myFile.txt");
fl.seekg(0, ios::end );
size_t len = fl.tellg();
char *ret = new char[len];
fl.seekg(0, ios::beg);
fl.read(ret, len);
fl.close();
jbyteArray result = env->NewByteArray( len);
env->SetByteArrayRegion( result, 0, len, (const jbyte*)ret );
delete[] ret;
return result;
}