Java中的链接错误 [英] Link Error in Java

问题描述

我收到以下错误:

Exception in thread "main" java.lang.UnsatisfiedLinkError: model.JNIResultSet.getSpieler()[Lmodel/Spieler;
    at model.JNIResultSet.getSpieler(Native Method)
    at model.JNIResultSet.main(JNIResultSet.java:18)

我的java类如下:

package model;

public class Spieler {
private String vorname;
private String nachname;
private int trikotnummer;


public Spieler(String vorname, String nachname, int trikotnummer) {
    this.vorname = vorname;
    this.nachname = nachname;
    this.trikotnummer = trikotnummer;
}
}

和

package model;

public class JNIResultSet {

public JNIResultSet() { }

public native Spieler[] getSpieler();

static {
    System.loadLibrary("spieler");
}

public static void main(String[] args) {
    JNIResultSet jni = new JNIResultSet();
    Spieler s[] = jni.getSpieler();
    System.out.println("Laenge: " + s.length);
}


}

我的头文件如下所示:

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class model_JNIResultSet */

#ifndef _Included_model_JNIResultSet
#define _Included_model_JNIResultSet
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class:     model_JNIResultSet
* Method:    getSpieler
* Signature: ()[Lmodel/Spieler;
*/
JNIEXPORT jobjectArray JNICALL Java_model_JNIResultSet_getSpieler
(JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

最后我的C代码看起来像这样:

And finally my C code looks like that:

JNIEXPORT jobjectArray JNICALL
JAVA_model_JNIResultSet_getSpieler(JNIEnv *env, jobject obj) {

Spieler *ptr = head;
jobjectArray ret;
int i;
jclass clazz = (*env)->FindClass(env, "model/Spieler");
jmethodID mid = (*env)->GetMethodID(env, clazz, "<init>", "(III)V");
jobject object; 

ret= (*env)->NewObjectArray(env, count,
        clazz,
        NULL);

for(i = 0; i < count; i++) {
    object = (*env)->NewObject(env, clazz, mid, ptr);
    (*env)->SetObjectArrayElement(env,
            ret, i, object);
    ptr = ptr->next;
}

return ret;
}

您对解决该问题有任何建议吗?
我也不知道C代码是否正确，也许就是问题所在?

Do you have any suggestions how to fix that problem?
I also don't know if the C code is right, maybe that's the problem?

我以这种方式执行它:

cd src
javac model/JNIResultSet.java
cd ..

cd bin
javah -jni model.JNIResultSet

gcc -fPIC -o libspieler.so -shared -I/usr/java/jdk1.8.0_73/include/ SharedTable.c -lc

java -Djava.library.path=/home/pupil/workspace/JNITableV2/bin/ model.JNIResultSet

这可能是我更新了C代码的错误，但我认为这是错误的:

Probably this is the error I've updated the C code but I think it's wrong:

jclass clazz = (*env)->FindClass(env, "model/JNIResultSet");
jmethodID mid = (*env)->GetMethodID(env, clazz, "getSpieler", "()Lmodel/Spieler;");

nm -D报告:

U atoi
0000000000202088 B bss_start
00000000002020b0 B当前
w __cxa_finalize
0000000000202088 D _edata
00000000002022b8 B _end
U fclose
0000000000000ef0 T _fini
U fopen
w __gmon_start
00000000002020a8 B头
0000000000000948 T _init
0000000000000b35 T insertFirst
U _IO_getc
w _ITM_deregisterTMCloneTable
w _ITM_registerTMCloneTable
0000000000000ca2 T JAVA_model_JNIResultSet_getSpieler
w _Jv_RegisterClasses
U malloc
U memcpy
U memset
0000000000000c49 T反向
U strcpy
00000000002020c0 B字符串
吓死了

U atoi
0000000000202088 B bss_start
00000000002020b0 B current
w __cxa_finalize
0000000000202088 D _edata
00000000002022b8 B _end
U fclose
0000000000000ef0 T _fini
U fopen
w __gmon_start
00000000002020a8 B head
0000000000000948 T _init
0000000000000b35 T insertFirst
U _IO_getc
w _ITM_deregisterTMCloneTable
w _ITM_registerTMCloneTable
0000000000000ca2 T JAVA_model_JNIResultSet_getSpieler
w _Jv_RegisterClasses
U malloc
U memcpy
U memset
0000000000000c49 T reverse
U strcpy
00000000002020c0 B string
U strlen

推荐答案

getSpieler()方法可以声明为静态；您可以使用它而无需实例化 JNIResultSet 类.

getSpieler() method could be declared static; you can use it without instantiating JNIResultSet class.

mid 应该指向构造函数，而不是getSpieler()，但是<init>签名是错误的:应该使用Ljava/lang/String;Ljava/lang/String;I而不是三个int:

mid should point to the constructor, not getSpieler(), but the <init> signature is wrong: it should take Ljava/lang/String;Ljava/lang/String;I and not three ints:

jmethodID mid = (*env)->GetMethodID(env, clazz, "<init>", "(Ljava/lang/String;Ljava/lang/String;I)V");
…
jobject strVorname = (*env)->NewStringUTF(env, ptr->vorname);
jobject strNachname = (*env)->NewStringUTF(env, ptr->nachname);
object = (*env)->NewObject(env, clazz, mid, strVorname, strNachname, ptr->trikotnummer);

在继续下一步之前，请始终检查方法ID和对象是否为NULL.

Always check the method IDs and objects for NULL before proceeding to the next step.

对于不满意的链接，检查 libspieler.so 文件是否正确:运行nm -D以查看是否确实导出了JAVA_model_JNIResultSet_getSpieler.重命名JAVA_model_JNIResultSet_getSpieler到Java_model_JNIResultSet_getSpieler，完全与生成的.h文件中指示的一样.

Regarding the unsatisfied link, check that the libspieler.so file is good: run nm -D to see if JAVA_model_JNIResultSet_getSpieler is actually exported. rename JAVA_model_JNIResultSet_getSpieler to Java_model_JNIResultSet_getSpieler, exactly as indicated in the generated .h file.

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