利用JNI进行对象操作

       在JNI原理及实现中，只是实现了一个Helloworld。

        回忆一下JNI的实现步骤：

     1.编写native声明的JAVA类;

     2.使用javac命令编译所编写的java类;

     3.使用Javah生成JNI头文件.h;

     4.编写本地方法实现方法;

     5.生成动态库;(如果方法实现是cpp写的话就一定要用g++来编译)

     6.在java中调用。

    下面的一个例子是C\C++与Java之间进行对象的操作。

1.创建Student类

/*
* FileName:Student.java
* Description:Class Student
* */
package pojo;

public class Student {
private int id;
private String name;
public Student(){}
public Student(int _id,String _name)
{
this.id=_id;
this.name=_name;
}
public void setId(int _id)
{
this.id=_id;
}
public void setName(String _name)
{
this.name=_name;
}
public int getId()
{
return id;
}
public String getName()
{
return name;
}
public String toString()
{
return "Name:"+name+" id:"+id;
}
}

2.创建主调类

/*
* FileName:JniMain.java
* Description:Main class
* */
package pojo;

public class JniMain {

static{
System.loadLibrary("studentbean");
}
public static native void sayHello();
public native int getId();
public native void setId(int i);
public native void setName(String _name);
public native Student getStudent();
public static void main(String[] args) {
// TODO Auto-generated method stub
JniMain test=new JniMain();
test.setId(101);
test.setName("Rose");
Student tmp=test.getStudent();
System.out.println("Id:"+tmp.getId());
System.out.println("Name:"+tmp.getName());
test.sayHello();
}

}

3.编译java，生成.h

sudo javac pojo/JniMain.java pojo/Student.java

javah -classpath . -jni pojo.JniMain

4.根据.h文件写函数实现

创建pojo_JniMain.cpp

#include"pojo_JniMain.h"
#include <iostream>
#include <stdio.h>
using namespace std;
int id=1;
jobject student;
jstring name;
JNIEXPORT void JNICALL Java_pojo_JniMain_sayHello
(JNIEnv *evn, jclass cla)
{
printf("shit~\n");
}
JNIEXPORT jint JNICALL Java_pojo_JniMain_getId
(JNIEnv *evn, jobject thiz)
{
return id;
}
JNIEXPORT void JNICALL Java_pojo_JniMain_setId
(JNIEnv *evn, jobject thiz, jint ji)
{
id=ji;
}
JNIEXPORT void JNICALL Java_pojo_JniMain_setName
(JNIEnv *env, jobject thiz, jstring _name)
{
//name=env->GetStringUTFChars(_name, 0);
jclass studentClass = env->FindClass("pojo/Student");
jmethodID studentMethod = env->GetMethodID(studentClass,"<init>","()V");
jfieldID mId = env->GetFieldID(studentClass,"id","I");
jfieldID mstudentName = env->GetFieldID(studentClass,"name","Ljava/lang/String;");
jobject studentObject = env->NewObject(studentClass,studentMethod);
env->SetObjectField(studentObject,mstudentName,_name);
env->SetIntField(studentObject,mId,id);
student = studentObject;
}
JNIEXPORT jobject JNICALL Java_pojo_JniMain_getStudent
(JNIEnv *env, jobject thiz)
{
return student;
}

5.编译动态库

sudo g++ -shared -I /usr/local/lib/jdk1.6.0_29/include/ -I /usr/local/lib/jdk1.6.0_29/include/linux/ pojo_JniMain.cpp -o libstudentbean.so

6.运行

结果如下：



参考： Java JNI由浅入深(包括：Java和C++互传ArrayList泛型对象参数)-http://blog.csdn.net/u_xtian/article/details/6033963