JNI传递修改自定义Java Class数组数据

声明：迁移自本人CSDN博客https://blog.csdn.net/u013365635

结合前面讲的2篇关于JNI的文章，这里直接把代码贴上，主要是要知道如果传递自定义Class Array的时候，在JNI怎么处理。单独拎出来讲解，是因为和系统自带类型如long Array、String等的处理还是往往会有所区别的。可以做了写代码时迷惑时的一个参考。

自定义POJO类

package com.testjni;

public class AObject

{

    int a;

    int b;

    public int getA()

    {

        return a;

    }

    public void setA(int a)

    {

        this.a = a;

    }

    public int getB()

    {

        return b;

    }

    public void setB(int b)

    {

        this.b = b;

    }

    /**

     * {@inheritDoc}

     */

    @Override

    public String toString()

    {

        final StringBuilder sb =

            new StringBuilder("AObject").append('[').append("a=").append(a).append(",b=").append(b).append(']');

        return sb.toString();

    }

}

Java测试类

package com.testjni;

public class TestJNI

{

    public native boolean testJobjectArray(AObject[] aObjects);

    static

    {

        System.load("D:\\eclipseWebWorkSpace\\testest\\src\\com\\testjni\\libTestJNI_amd64.dll");

    }

    public static void main(String[] args)

    {

        TestJNI testJNI = new TestJNI();

        AObject[] aObjects = new AObject[3];

        for (int i = 0; i < 3; i++)

        {

            aObjects[i] = new AObject();

        }

        for (int i = 0; i < 3; i++)

        {

            System.out.println("aObjects[" + i + "]=" + aObjects[i]);

        }

        testJNI.testJobjectArray(aObjects);

        System.out.println("\n\n\nafter modified by jni");

        for (int i = 0; i < 10; i++)

        {

            System.out.println(i + "-->" + aObjects[i]);

        }

    }

}

JNI头文件com_testjni_TestJNI.h

/* DO NOT EDIT THIS FILE - it is machine generated */

#include "jni.h"

/* Header for class com_testjni_TestJNI */

#ifndef _Included_com_testjni_TestJNI

#define _Included_com_testjni_TestJNI

#ifdef __cplusplus

extern "C" {

#endif

/*

 * Class:     com_testjni_TestJNI

 * Method:    test_jobjectArray

 * Signature: ([Lcom/testjni/AObject;)Z

 */

JNIEXPORT jboolean JNICALL Java_com_testjni_TestJNI_testJobjectArray

  (JNIEnv *, jobject, jobjectArray);

#ifdef __cplusplus

}

#endif

#endif

JNI 源码文件com_testjni_TestJNI.cpp

#include <stdio.h>

#include "com_testjni_TestJNI.h"

#include "jni.h"

static const char* const AObjectClassPath = "com/testjni/AObject";

JNIEXPORT jboolean JNICALL Java_com_testjni_TestJNI_testJobjectArray(JNIEnv *env, jobject obj, jobjectArray aObjects)

{

    jint arrLen = env->GetArrayLength(aObjects);

    printf("\narrLen=%d", nArrLen);

    jclass aObjectClass = env->FindClass(AObjectClassPath);

    if (aObjectClass == NULL)

    {

    	return true;

    }

    jfieldID afield = env->GetFieldID(aObjectClass, "a", "I");

    jfieldID bfield = env->GetFieldID(aObjectClass, "b", "I");

    for (int i = 0; i < 3; i++)

    {

        jobject aObject = env->GetObjectArrayElement(aObjects, i);

        env->SetIntField(aObject, afield, i*i);

        env->SetIntField(aObject, bfield, i*(i+1));

    }

}

编译命令
cl /LD D:\eclipseWebWorkSpace\testest\src\com\testjni\com_testjni_TestJNI.cpp -o D:\eclipseWebWorkSpace\testest\src\com\testjni\libTestJNI_amd64.dll
运行结果：
before modified by jni
aObjects[0]=AObject[a=0,b=0]
aObjects[1]=AObject[a=0,b=0]
aObjects[2]=AObject[a=0,b=0]

after modified by jni
aObjects[0]=AObject[a=0,b=0]
aObjects[1]=AObject[a=1,b=2]
aObjects[2]=AObject[a=4,b=6]

arrLen=3
关键的方法就是GetObjectArrayElement，取出jobjectArray中的元素，然后对这些自定义Class对象进行操作。

巴特西

JNI传递修改自定义Java Class数组数据

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