Java虚拟机（Java Virtual Machine) 简称JVM Java虚拟机是一个想象中的机器,在实际的计算机上通过软件模拟来实现。Java虚拟机有自己想象中的硬件,如处理器、堆栈、寄存器等,还具有相应的指令系统。

JVM的设计目标是提供一个基于抽象规格描述的计算机模型, JVM对其实现的某些方面给出了具体的定义，特别是对Java可执行代码，即字节码(Bytecode)的格式给出了明确的规格。这一规格包括操作码和操作数的语法和数值、标识符的数值表示方式、以及Java类文件中的Java对象、常量缓冲池在JVM的存储映象。这些定义为JVM解释器开发人员提供了所需的信息和开发环境。Java的设计者希望给开发人员以随心所欲使用Java的自由。

JVM定义了控制Java代码解释执行和具体实现的五种规格，它们是：

JVM指令系统 ，JVM寄存器 ，JVM栈结构，JVM碎片回收堆 ，JVM存储区

 

 

          需要一个图：3-1  java 虚拟机描述图

 

Dalvik 虚拟机

Dalvik是Google公司自己设计用于Android平台的Java虚拟机。Dalvik虚拟机是Google等厂商合作开发的Android移动设备平台的核心组成部分之一。它可以支持已转换为 .dex（即Dalvik Executable）格式的Java应用程序的运行，.dex格式是专为Dalvik设计的一种压缩格式，适合内存和处理器速度有限的系统。Dalvik 经过优化，允许在有限的内存中同时运行多个虚拟机的实例，并且每一个Dalvik 应用作为一个独立的Linux 进程执行。独立的进程可以防止在虚拟机崩溃的时候所有程序都被关闭。

Dalvik 和标准Java 虚拟机(JVM)首要差别

　　Dalvik 基于寄存器，而 JVM 基于栈。基于寄存器的虚拟机对于更大的程序来说，在它们编译的时候，花费的时间更短。

　　

Dalvik 和Java 运行环境的区别

　　1：Dalvik主要是完成对象生命周期管理，堆栈管理，线程管理，安全和异常管理，以及垃圾回收等等重要功能。

　　2：Dalvik负责进程隔离和线程管理，每一个Android应用在底层都会对应一个独立的Dalvik虚拟机实例，其代码在虚拟机的解释下得以执行。

　　3：不同于Java虚拟机运行java字节码，Dalvik虚拟机运行的是其专有的文件格式Dex

　　4:dex文件格式可以减少整体文件尺寸，提高I/o操作的类查找速度。

　　5:odex是为了在运行过程中进一步提高性能，对dex文件的进一步优化。

　　6：所有的Android应用的线程都对应一个Linux线程，虚拟机因而可以更多的依赖操作系统的线程调度和管理机制

　　7：有一个特殊的虚拟机进程Zygote，他是虚拟机实例的孵化器。它在系统启动的时候就会产生，它会完成虚拟机的初始化，库的加载，预制类库和初始化的操作。如果系统需要一个新的虚拟机实例，它会迅速复制自身，以最快的数据提供给系统。对于一些只读的系统库，所有虚拟机实例都和Zygote共享一块内存区域。

 

 

 

 

Java虚拟机的局限性

 

 JVM 很好的解决java的可移植性问题，使得java软件可以在不同的硬件平台下运行，所以我们说java的可移植性并不是java语言的移植性有多么的好，而是JVM的可移植性，只要不同的硬件平台下可以运行JVM，那么java软件就可以运行。

但是JVM不是万能的，毕竟它只是一个模拟环境，对于一些外围的硬件就很难模拟，从JVM五种规格中我们可以看出，JVM只是模拟了一部分的寄存器，栈结构，JVM储存器，这些都是软件运行的基础硬件结构。

对于像android手机这样的平台，有很多的外围设备在软件层是需要操作的，如wifi，蓝牙，触摸屏，重力感应，键盘等，如果直接通过java语言操作是很难实现的，JVM无法模拟这么多的硬件。

JNI是Java Native Interface的缩写，中文为JAVA本地调用。从Java1.1开始，Java Native Interface(JNI)标准成为java平台的一部分，它允许Java代码和其他语言写的代码进行交互。JNI一开始是为了本地已编译语言，尤其是C和C++而设计的，但是它并不妨碍你使用其他语言，只要调用约定受支持就可以了。使用java与本地已编译的代码交互，通常会丧失平台可移植性。但是，有些情况下这样做是可以接受的，甚至是必须的，比如，使用一些旧的库，与硬件、操作系统进行交互，或者为了提高程序的性能。JNI标准至少保证本地代码能工作在任何Java虚拟机实现下。

 

               需要一个图：3-2  JNI描述图

 

 

 

JNI 桥梁作用

 

JNI 在java和c/c++中交互经常使用，c/c++语言是编译性的语言，编译性语言是把源程序编译成目标机器代码，目标机器代码可以直接在适合的机器上执行，所以它们可以直接编写操作硬件设备的代码，运行速度要比java代码快，缺点是编译成目标机器码后代码的可移植性不是太好。

Java语言和 c/c++ 语言从语法的角度去看，最大的区别就是数据类型的区别，例如：java中 string数据类型，但c/c++中使用 char * 代替，java 代码调用c/c++代码必然会存在参数的传递，所以JNI的一个重要职责是数据类型转换。

 

 

 

需要一个图：3-3  JNI桥梁作用图

 

从图可知，JNI作为接口提供的是机制而不是策略

如果说机制是一种框架，那么，策略就是填充框架的一个个具体实体。机制提供的是一种开放而宽松的环境，而策略就是在这个环境下赖以生存的生命个体

java 只关注JNI的接口作用（机制）

c/c++ 实现JNI的功能（策略）

 

 

3.2 JNI基础语法

 

  

 

3.2.1  JNI数据类型

 

基础数据类型定义：

 

typedef unsigned char   jboolean;      

typedef signed char     jbyte;         

typedef unsigned short  jchar;         

typedef short           jshort;        

typedef int             jint;          

typedef long long       jlong;         

typedef float           jfloat;        

typedef double          jdouble;       

typedef jint            jsize;

 

                 表 3-1 JNI基础数据类型与java数据类型的对应关系

 

Java Language Type	JNI Type
boolean	jboolean
byte	jbyte
char	jchar
short	jshort
int	jint
long	jlong
float	jfloat
double	jdouble

 

               

jsize 整数类型用于描述主要指数和大小

 

引用类型：

 

引用类型在C中定义，所有其它 JNI 引用类型都被定义为与 jobject 一样，都是void*。

 

 

typedef void*           jobject;

typedef jobject         jclass;

typedef jobject         jstring;

typedef jobject         jarray;

typedef jarray          jobjectArray;

typedef jarray          jbooleanArray;

typedef jarray          jbyteArray;

typedef jarray          jcharArray;

typedef jarray          jshortArray;

typedef jarray          jintArray;

typedef jarray          jlongArray;

typedef jarray          jfloatArray;

typedef jarray          jdoubleArray;

typedef jobject         jthrowable;

typedef jobject         jweak;

 

 

 引用类型在C++中定义，JNI 引入了虚构类以加强子类关系

 

 

class _jobject {};

class _jclass : public _jobject {};

class _jstring : public _jobject {};

class _jarray : public _jobject {};

class _jobjectArray : public _jarray {};

class _jbooleanArray : public _jarray {};

class _jbyteArray : public _jarray {};

class _jcharArray : public _jarray {};

class _jshortArray : public _jarray {};

class _jintArray : public _jarray {};

class _jlongArray : public _jarray {};

class _jfloatArray : public _jarray {};

class _jdoubleArray : public _jarray {};

class _jthrowable : public _jobject {};

 

typedef _jobject*       jobject;

typedef _jclass*        jclass;

typedef _jstring*       jstring;

typedef _jarray*        jarray;

typedef _jobjectArray*  jobjectArray;

typedef _jbooleanArray* jbooleanArray;

typedef _jbyteArray*    jbyteArray;

typedef _jcharArray*    jcharArray;

typedef _jshortArray*   jshortArray;

typedef _jintArray*     jintArray;

typedef _jlongArray*    jlongArray;

typedef _jfloatArray*   jfloatArray;

typedef _jdoubleArray*  jdoubleArray;

typedef _jthrowable*    jthrowable;

typedef _jobject*       jweak;

 

 

 

 

                   图 3-4 JNI 引用类型与java类对应关系

 

 

 

不透明类型（opaque data structure）：

 

不透明类型是一种数据类型，它隐藏了内部的结构，可以利用typedef声明这样一个类型，但是无法预知空间的大小，也不希望开发者把它重新转化成C的数据类型，不透明类型原则是：

 1）无法预知该类型的空间大小

 2）不要强制转化成c的数据类型

 3）编程时要保证在该类型实际存储空间和格式发生变化时代码不受影响。

 

JNI中不透明类型使用的比较常见

 

域 ID 和方法 ID 常规的 C 指针类型：

struct _jfieldID;
typedef struct _jfieldID *jfieldID;

struct _jmethodID;
typedef struct _jmethodID *jmethodID;

 

 

域 ID 和方法 ID 没有定义实际的存储空间的大小，域 ID 主要用来储存java端的变量地址，方法 ID主要用来储存java端的方法地址，JNI端存储java端的方法和变量的作用是，使得C/C++端代码可以访问到java端的代码，这样java和c/c++的代码的交互可以双向进行，c/c++代码可以把底层产生的事件发送给java应用层

 

 

                     需要一个图 3-5 JNI与java交互关系图

 

 

3.2.2  JNI 常用数据结构

 

JNI复合型的类型jvalue，它能够表达所有的简单和引用类型。

   typedef union jvalue {

    jboolean    z;

    jbyte       b;

    jchar       c;

    jshort      s;

    jint        i;

    jlong       j;

    jfloat      f;

    jdouble     d;

    jobject     l;

} jvalue;

 

 

 

Java 和 C 函数的映射表数组

 

typedef struct {

    const char* name;

    const char* signature;

    void*       fnPtr;

} JNINativeMethod;

 

第一个变量name是Java中函数的名字。

第二个变量signature，用字符串是描述了函数的参数和返回值

第三个变量fnPtr是函数指针，指向C函数。

 

JNI 使用 Java 虚拟机的类型签名表述。

                表 3-2 JVM类型签名

类型签名	Java 类型
Z	boolean
B	byte
C	char
S	short
I	int
J	long
F	float
D	double
L	fully-qualified-class（全限定的类）
[	[]
[I	int[]
[F	float[]
[B	byte[]
[C	char[]
[S	short[]
[D	double[]
[J	long[]
[Z	boolean[]

 

                    

例如，Java 方法：

char fun (int n, String s, int[] value);

具有以下类型签名：

(ILjava/lang/String;[I)C

如果Java函数的参数是class，则以"L"开头，以";"结尾中间是用"/" 隔开的包及类名

如果JAVA函数参数位于一个嵌入类，则用$作为类名间的分隔符。

例如 "(Ljava/lang/String;Landroid/os/OutClass$InnerClass;)Z"

 

 

  

JNIEnv 定义为结构体JNINativeInterface，定义如下：

 

 

C中定义：

typedef const struct JNINativeInterface* JNIEnv;

 

JNINativeInterface 结构体成员变量为很多的函数指针，我们可以看看其定义的函数指针：

 

struct JNINativeInterface {

    void*       reserved0;

    void*       reserved1;

    void*       reserved2;

    void*       reserved3;

 

    jint        (*GetVersion)(JNIEnv *);

 

    jclass      (*DefineClass)(JNIEnv*, const char*, jobject, const jbyte*,

                        jsize);

    jclass      (*FindClass)(JNIEnv*, const char*);

 

    jmethodID   (*FromReflectedMethod)(JNIEnv*, jobject);

    jfieldID    (*FromReflectedField)(JNIEnv*, jobject);

   

    jobject     (*ToReflectedMethod)(JNIEnv*, jclass, jmethodID, jboolean);

 

    jclass      (*GetSuperclass)(JNIEnv*, jclass);

    jboolean    (*IsAssignableFrom)(JNIEnv*, jclass, jclass);

 

   

    jobject     (*ToReflectedField)(JNIEnv*, jclass, jfieldID, jboolean);

 

    jint        (*Throw)(JNIEnv*, jthrowable);

    jint        (*ThrowNew)(JNIEnv *, jclass, const char *);

    jthrowable  (*ExceptionOccurred)(JNIEnv*);

    void        (*ExceptionDescribe)(JNIEnv*);

    void        (*ExceptionClear)(JNIEnv*);

    void        (*FatalError)(JNIEnv*, const char*);

 

    jint        (*PushLocalFrame)(JNIEnv*, jint);

    jobject     (*PopLocalFrame)(JNIEnv*, jobject);

 

    jobject     (*NewGlobalRef)(JNIEnv*, jobject);

    void        (*DeleteGlobalRef)(JNIEnv*, jobject);

    void        (*DeleteLocalRef)(JNIEnv*, jobject);

    jboolean    (*IsSameObject)(JNIEnv*, jobject, jobject);

 

    jobject     (*NewLocalRef)(JNIEnv*, jobject);

    jint        (*EnsureLocalCapacity)(JNIEnv*, jint);

 

    jobject     (*AllocObject)(JNIEnv*, jclass);

    jobject     (*NewObject)(JNIEnv*, jclass, jmethodID, ...);

    jobject     (*NewObjectV)(JNIEnv*, jclass, jmethodID, va_list);

    jobject     (*NewObjectA)(JNIEnv*, jclass, jmethodID, jvalue*);

 

    jclass      (*GetObjectClass)(JNIEnv*, jobject);

    jboolean    (*IsInstanceOf)(JNIEnv*, jobject, jclass);

    jmethodID   (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);

 

    jobject     (*CallObjectMethod)(JNIEnv*, jobject, jmethodID, ...);

    jobject     (*CallObjectMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jobject     (*CallObjectMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jboolean    (*CallBooleanMethod)(JNIEnv*, jobject, jmethodID, ...);

    jboolean    (*CallBooleanMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jboolean    (*CallBooleanMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jbyte       (*CallByteMethod)(JNIEnv*, jobject, jmethodID, ...);

    jbyte       (*CallByteMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jbyte       (*CallByteMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jchar       (*CallCharMethod)(JNIEnv*, jobject, jmethodID, ...);

    jchar       (*CallCharMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jchar       (*CallCharMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jshort      (*CallShortMethod)(JNIEnv*, jobject, jmethodID, ...);

    jshort      (*CallShortMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jshort      (*CallShortMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jint        (*CallIntMethod)(JNIEnv*, jobject, jmethodID, ...);

    jint        (*CallIntMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jint        (*CallIntMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jlong       (*CallLongMethod)(JNIEnv*, jobject, jmethodID, ...);

    jlong       (*CallLongMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jlong       (*CallLongMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jfloat      (*CallFloatMethod)(JNIEnv*, jobject, jmethodID, ...);

    jfloat      (*CallFloatMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jfloat      (*CallFloatMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    jdouble     (*CallDoubleMethod)(JNIEnv*, jobject, jmethodID, ...);

    jdouble     (*CallDoubleMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    jdouble     (*CallDoubleMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

    void        (*CallVoidMethod)(JNIEnv*, jobject, jmethodID, ...);

    void        (*CallVoidMethodV)(JNIEnv*, jobject, jmethodID, va_list);

    void        (*CallVoidMethodA)(JNIEnv*, jobject, jmethodID, jvalue*);

 

    jobject     (*CallNonvirtualObjectMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jobject     (*CallNonvirtualObjectMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jobject     (*CallNonvirtualObjectMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    jboolean    (*CallNonvirtualBooleanMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jboolean    (*CallNonvirtualBooleanMethodV)(JNIEnv*, jobject, jclass,

                         jmethodID, va_list);

    jboolean    (*CallNonvirtualBooleanMethodA)(JNIEnv*, jobject, jclass,

                         jmethodID, jvalue*);

    jbyte       (*CallNonvirtualByteMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jbyte       (*CallNonvirtualByteMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jbyte       (*CallNonvirtualByteMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    jchar       (*CallNonvirtualCharMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jchar       (*CallNonvirtualCharMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jchar       (*CallNonvirtualCharMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    jshort      (*CallNonvirtualShortMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jshort      (*CallNonvirtualShortMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jshort      (*CallNonvirtualShortMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    jint        (*CallNonvirtualIntMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jint        (*CallNonvirtualIntMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jint        (*CallNonvirtualIntMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    jlong       (*CallNonvirtualLongMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jlong       (*CallNonvirtualLongMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jlong       (*CallNonvirtualLongMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    jfloat      (*CallNonvirtualFloatMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jfloat      (*CallNonvirtualFloatMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jfloat      (*CallNonvirtualFloatMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    jdouble     (*CallNonvirtualDoubleMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    jdouble     (*CallNonvirtualDoubleMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    jdouble     (*CallNonvirtualDoubleMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

    void        (*CallNonvirtualVoidMethod)(JNIEnv*, jobject, jclass,

                        jmethodID, ...);

    void        (*CallNonvirtualVoidMethodV)(JNIEnv*, jobject, jclass,

                        jmethodID, va_list);

    void        (*CallNonvirtualVoidMethodA)(JNIEnv*, jobject, jclass,

                        jmethodID, jvalue*);

 

    jfieldID    (*GetFieldID)(JNIEnv*, jclass, const char*, const char*);

 

    jobject     (*GetObjectField)(JNIEnv*, jobject, jfieldID);

    jboolean    (*GetBooleanField)(JNIEnv*, jobject, jfieldID);

    jbyte       (*GetByteField)(JNIEnv*, jobject, jfieldID);

    jchar       (*GetCharField)(JNIEnv*, jobject, jfieldID);

    jshort      (*GetShortField)(JNIEnv*, jobject, jfieldID);

    jint        (*GetIntField)(JNIEnv*, jobject, jfieldID);

    jlong       (*GetLongField)(JNIEnv*, jobject, jfieldID);

    jfloat      (*GetFloatField)(JNIEnv*, jobject, jfieldID);

    jdouble     (*GetDoubleField)(JNIEnv*, jobject, jfieldID);

 

    void        (*SetObjectField)(JNIEnv*, jobject, jfieldID, jobject);

    void        (*SetBooleanField)(JNIEnv*, jobject, jfieldID, jboolean);

    void        (*SetByteField)(JNIEnv*, jobject, jfieldID, jbyte);

    void        (*SetCharField)(JNIEnv*, jobject, jfieldID, jchar);

    void        (*SetShortField)(JNIEnv*, jobject, jfieldID, jshort);

    void        (*SetIntField)(JNIEnv*, jobject, jfieldID, jint);

    void        (*SetLongField)(JNIEnv*, jobject, jfieldID, jlong);

    void        (*SetFloatField)(JNIEnv*, jobject, jfieldID, jfloat);

    void        (*SetDoubleField)(JNIEnv*, jobject, jfieldID, jdouble);

 

    jmethodID   (*GetStaticMethodID)(JNIEnv*, jclass, const char*, const char*);

 

    jobject     (*CallStaticObjectMethod)(JNIEnv*, jclass, jmethodID, ...);

    jobject     (*CallStaticObjectMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jobject     (*CallStaticObjectMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    jboolean    (*CallStaticBooleanMethod)(JNIEnv*, jclass, jmethodID, ...);

    jboolean    (*CallStaticBooleanMethodV)(JNIEnv*, jclass, jmethodID,

                        va_list);

    jboolean    (*CallStaticBooleanMethodA)(JNIEnv*, jclass, jmethodID,

                        jvalue*);

    jbyte       (*CallStaticByteMethod)(JNIEnv*, jclass, jmethodID, ...);

    jbyte       (*CallStaticByteMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jbyte       (*CallStaticByteMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    jchar       (*CallStaticCharMethod)(JNIEnv*, jclass, jmethodID, ...);

    jchar       (*CallStaticCharMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jchar       (*CallStaticCharMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    jshort      (*CallStaticShortMethod)(JNIEnv*, jclass, jmethodID, ...);

    jshort      (*CallStaticShortMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jshort      (*CallStaticShortMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    jint        (*CallStaticIntMethod)(JNIEnv*, jclass, jmethodID, ...);

    jint        (*CallStaticIntMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jint        (*CallStaticIntMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    jlong       (*CallStaticLongMethod)(JNIEnv*, jclass, jmethodID, ...);

    jlong       (*CallStaticLongMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jlong       (*CallStaticLongMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    jfloat      (*CallStaticFloatMethod)(JNIEnv*, jclass, jmethodID, ...);

    jfloat      (*CallStaticFloatMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jfloat      (*CallStaticFloatMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    jdouble     (*CallStaticDoubleMethod)(JNIEnv*, jclass, jmethodID, ...);

    jdouble     (*CallStaticDoubleMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    jdouble     (*CallStaticDoubleMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

    void        (*CallStaticVoidMethod)(JNIEnv*, jclass, jmethodID, ...);

    void        (*CallStaticVoidMethodV)(JNIEnv*, jclass, jmethodID, va_list);

    void        (*CallStaticVoidMethodA)(JNIEnv*, jclass, jmethodID, jvalue*);

 

    jfieldID    (*GetStaticFieldID)(JNIEnv*, jclass, const char*,

                        const char*);

 

    jobject     (*GetStaticObjectField)(JNIEnv*, jclass, jfieldID);

    jboolean    (*GetStaticBooleanField)(JNIEnv*, jclass, jfieldID);

    jbyte       (*GetStaticByteField)(JNIEnv*, jclass, jfieldID);

    jchar       (*GetStaticCharField)(JNIEnv*, jclass, jfieldID);

    jshort      (*GetStaticShortField)(JNIEnv*, jclass, jfieldID);

    jint        (*GetStaticIntField)(JNIEnv*, jclass, jfieldID);

    jlong       (*GetStaticLongField)(JNIEnv*, jclass, jfieldID);

    jfloat      (*GetStaticFloatField)(JNIEnv*, jclass, jfieldID);

    jdouble     (*GetStaticDoubleField)(JNIEnv*, jclass, jfieldID);

 

    void        (*SetStaticObjectField)(JNIEnv*, jclass, jfieldID, jobject);

    void        (*SetStaticBooleanField)(JNIEnv*, jclass, jfieldID, jboolean);

    void        (*SetStaticByteField)(JNIEnv*, jclass, jfieldID, jbyte);

    void        (*SetStaticCharField)(JNIEnv*, jclass, jfieldID, jchar);

    void        (*SetStaticShortField)(JNIEnv*, jclass, jfieldID, jshort);

    void        (*SetStaticIntField)(JNIEnv*, jclass, jfieldID, jint);

    void        (*SetStaticLongField)(JNIEnv*, jclass, jfieldID, jlong);

    void        (*SetStaticFloatField)(JNIEnv*, jclass, jfieldID, jfloat);

    void        (*SetStaticDoubleField)(JNIEnv*, jclass, jfieldID, jdouble);

 

    jstring     (*NewString)(JNIEnv*, const jchar*, jsize);

    jsize       (*GetStringLength)(JNIEnv*, jstring);

    const jchar* (*GetStringChars)(JNIEnv*, jstring, jboolean*);

    void        (*ReleaseStringChars)(JNIEnv*, jstring, const jchar*);

    jstring     (*NewStringUTF)(JNIEnv*, const char*);

    jsize       (*GetStringUTFLength)(JNIEnv*, jstring);

   

    const char* (*GetStringUTFChars)(JNIEnv*, jstring, jboolean*);

    void        (*ReleaseStringUTFChars)(JNIEnv*, jstring, const char*);

    jsize       (*GetArrayLength)(JNIEnv*, jarray);

    jobjectArray (*NewObjectArray)(JNIEnv*, jsize, jclass, jobject);

    jobject     (*GetObjectArrayElement)(JNIEnv*, jobjectArray, jsize);

    void        (*SetObjectArrayElement)(JNIEnv*, jobjectArray, jsize, jobject);

 

    jbooleanArray (*NewBooleanArray)(JNIEnv*, jsize);

    jbyteArray    (*NewByteArray)(JNIEnv*, jsize);

    jcharArray    (*NewCharArray)(JNIEnv*, jsize);

    jshortArray   (*NewShortArray)(JNIEnv*, jsize);

    jintArray     (*NewIntArray)(JNIEnv*, jsize);

    jlongArray    (*NewLongArray)(JNIEnv*, jsize);

    jfloatArray   (*NewFloatArray)(JNIEnv*, jsize);

    jdoubleArray  (*NewDoubleArray)(JNIEnv*, jsize);

 

    jboolean*   (*GetBooleanArrayElements)(JNIEnv*, jbooleanArray, jboolean*);

    jbyte*      (*GetByteArrayElements)(JNIEnv*, jbyteArray, jboolean*);

    jchar*      (*GetCharArrayElements)(JNIEnv*, jcharArray, jboolean*);

    jshort*     (*GetShortArrayElements)(JNIEnv*, jshortArray, jboolean*);

    jint*       (*GetIntArrayElements)(JNIEnv*, jintArray, jboolean*);

    jlong*      (*GetLongArrayElements)(JNIEnv*, jlongArray, jboolean*);

    jfloat*     (*GetFloatArrayElements)(JNIEnv*, jfloatArray, jboolean*);

    jdouble*    (*GetDoubleArrayElements)(JNIEnv*, jdoubleArray, jboolean*);

 

    void        (*ReleaseBooleanArrayElements)(JNIEnv*, jbooleanArray,

                        jboolean*, jint);

    void        (*ReleaseByteArrayElements)(JNIEnv*, jbyteArray,

                        jbyte*, jint);

    void        (*ReleaseCharArrayElements)(JNIEnv*, jcharArray,

                        jchar*, jint);

    void        (*ReleaseShortArrayElements)(JNIEnv*, jshortArray,

                        jshort*, jint);

    void        (*ReleaseIntArrayElements)(JNIEnv*, jintArray,

                        jint*, jint);

    void        (*ReleaseLongArrayElements)(JNIEnv*, jlongArray,

                        jlong*, jint);

    void        (*ReleaseFloatArrayElements)(JNIEnv*, jfloatArray,

                        jfloat*, jint);

    void        (*ReleaseDoubleArrayElements)(JNIEnv*, jdoubleArray,

                        jdouble*, jint);

 

    void        (*GetBooleanArrayRegion)(JNIEnv*, jbooleanArray,

                        jsize, jsize, jboolean*);

    void        (*GetByteArrayRegion)(JNIEnv*, jbyteArray,

                        jsize, jsize, jbyte*);

    void        (*GetCharArrayRegion)(JNIEnv*, jcharArray,

                        jsize, jsize, jchar*);

    void        (*GetShortArrayRegion)(JNIEnv*, jshortArray,

                        jsize, jsize, jshort*);

    void        (*GetIntArrayRegion)(JNIEnv*, jintArray,

                        jsize, jsize, jint*);

    void        (*GetLongArrayRegion)(JNIEnv*, jlongArray,

                        jsize, jsize, jlong*);

    void        (*GetFloatArrayRegion)(JNIEnv*, jfloatArray,

                        jsize, jsize, jfloat*);

    void        (*GetDoubleArrayRegion)(JNIEnv*, jdoubleArray,

                        jsize, jsize, jdouble*);

 

   

    void        (*SetBooleanArrayRegion)(JNIEnv*, jbooleanArray,

                        jsize, jsize, const jboolean*);

    void        (*SetByteArrayRegion)(JNIEnv*, jbyteArray,

                        jsize, jsize, const jbyte*);

    void        (*SetCharArrayRegion)(JNIEnv*, jcharArray,

                        jsize, jsize, const jchar*);

    void        (*SetShortArrayRegion)(JNIEnv*, jshortArray,

                        jsize, jsize, const jshort*);

    void        (*SetIntArrayRegion)(JNIEnv*, jintArray,

                        jsize, jsize, const jint*);

    void        (*SetLongArrayRegion)(JNIEnv*, jlongArray,

                        jsize, jsize, const jlong*);

    void        (*SetFloatArrayRegion)(JNIEnv*, jfloatArray,

                        jsize, jsize, const jfloat*);

    void        (*SetDoubleArrayRegion)(JNIEnv*, jdoubleArray,

                        jsize, jsize, const jdouble*);

 

    jint        (*RegisterNatives)(JNIEnv*, jclass, const JNINativeMethod*,

                        jint);

    jint        (*UnregisterNatives)(JNIEnv*, jclass);

    jint        (*MonitorEnter)(JNIEnv*, jobject);

    jint        (*MonitorExit)(JNIEnv*, jobject);

    jint        (*GetJavaVM)(JNIEnv*, JavaVM**);

 

    void        (*GetStringRegion)(JNIEnv*, jstring, jsize, jsize, jchar*);

    void        (*GetStringUTFRegion)(JNIEnv*, jstring, jsize, jsize, char*);

 

    void*       (*GetPrimitiveArrayCritical)(JNIEnv*, jarray, jboolean*);

    void        (*ReleasePrimitiveArrayCritical)(JNIEnv*, jarray, void*, jint);

 

    const jchar* (*GetStringCritical)(JNIEnv*, jstring, jboolean*);

    void        (*ReleaseStringCritical)(JNIEnv*, jstring, const jchar*);

 

    jweak       (*NewWeakGlobalRef)(JNIEnv*, jobject);

    void        (*DeleteWeakGlobalRef)(JNIEnv*, jweak);

 

    jboolean    (*ExceptionCheck)(JNIEnv*);

 

    jobject     (*NewDirectByteBuffer)(JNIEnv*, void*, jlong);

    void*       (*GetDirectBufferAddress)(JNIEnv*, jobject);

    jlong       (*GetDirectBufferCapacity)(JNIEnv*, jobject);

 

   

    jobjectRefType (*GetObjectRefType)(JNIEnv*, jobject);

}

 

C++中定义：

 

struct _JNIEnv;

typedef _JNIEnv JNIEnv;

 

_JNIEnv结构体定义依赖于JNINativeInterface，定义如下：

struct _JNIEnv {

 

    const struct JNINativeInterface* functions;

 

#if defined(__cplusplus)

 

    jint GetVersion()

    { return functions->GetVersion(this); }

 

    jclass DefineClass(const char *name, jobject loader, const jbyte* buf,

        jsize bufLen)

    { return functions->DefineClass(this, name, loader, buf, bufLen); }

 

    jclass FindClass(const char* name)

    { return functions->FindClass(this, name); }

 

    jmethodID FromReflectedMethod(jobject method)

    { return functions->FromReflectedMethod(this, method); }

 

    jfieldID FromReflectedField(jobject field)

    { return functions->FromReflectedField(this, field); }

 

    jobject ToReflectedMethod(jclass cls, jmethodID methodID, jboolean isStatic)

    { return functions->ToReflectedMethod(this, cls, methodID, isStatic); }

 

    jclass GetSuperclass(jclass clazz)

    { return functions->GetSuperclass(this, clazz); }

 

    jboolean IsAssignableFrom(jclass clazz1, jclass clazz2)

    { return functions->IsAssignableFrom(this, clazz1, clazz2); }

 

    jobject ToReflectedField(jclass cls, jfieldID fieldID, jboolean isStatic)

    { return functions->ToReflectedField(this, cls, fieldID, isStatic); }

 

    jint Throw(jthrowable obj)

    { return functions->Throw(this, obj); }

 

    jint ThrowNew(jclass clazz, const char* message)

    { return functions->ThrowNew(this, clazz, message); }

 

    jthrowable ExceptionOccurred()

    { return functions->ExceptionOccurred(this); }

 

    void ExceptionDescribe()

    { functions->ExceptionDescribe(this); }

 

    void ExceptionClear()

    { functions->ExceptionClear(this); }

 

    void FatalError(const char* msg)

    { functions->FatalError(this, msg); }

 

    jint PushLocalFrame(jint capacity)

    { return functions->PushLocalFrame(this, capacity); }

 

    jobject PopLocalFrame(jobject result)

    { return functions->PopLocalFrame(this, result); }

 

    jobject NewGlobalRef(jobject obj)

    { return functions->NewGlobalRef(this, obj); }

 

    void DeleteGlobalRef(jobject globalRef)

    { functions->DeleteGlobalRef(this, globalRef); }

 

    void DeleteLocalRef(jobject localRef)

    { functions->DeleteLocalRef(this, localRef); }

 

    jboolean IsSameObject(jobject ref1, jobject ref2)

    { return functions->IsSameObject(this, ref1, ref2); }

 

    jobject NewLocalRef(jobject ref)

    { return functions->NewLocalRef(this, ref); }

 

    jint EnsureLocalCapacity(jint capacity)

    { return functions->EnsureLocalCapacity(this, capacity); }

 

    jobject AllocObject(jclass clazz)

    { return functions->AllocObject(this, clazz); }

 

    jobject NewObject(jclass clazz, jmethodID methodID, ...)

    {

        va_list args;

        va_start(args, methodID);

        jobject result = functions->NewObjectV(this, clazz, methodID, args);

        va_end(args);

        return result;

    }

 

    jobject NewObjectV(jclass clazz, jmethodID methodID, va_list args)

    { return functions->NewObjectV(this, clazz, methodID, args); }

 

    jobject NewObjectA(jclass clazz, jmethodID methodID, jvalue* args)

    { return functions->NewObjectA(this, clazz, methodID, args); }

 

    jclass GetObjectClass(jobject obj)

    { return functions->GetObjectClass(this, obj); }

 

    jboolean IsInstanceOf(jobject obj, jclass clazz)

    { return functions->IsInstanceOf(this, obj, clazz); }

 

    jmethodID GetMethodID(jclass clazz, const char* name, const char* sig)

    { return functions->GetMethodID(this, clazz, name, sig); }

 

#define CALL_TYPE_METHOD(_jtype, _jname)                                    \

    _jtype Call##_jname##Method(jobject obj, jmethodID methodID, ...)       \

    {                                                                       \

        _jtype result;                                                      \

        va_list args;                                                       \

        va_start(args, methodID);                                           \

        result = functions->Call##_jname##MethodV(this, obj, methodID,      \

                    args);                                                  \

        va_end(args);                                                       \

        return result;                                                      \

    }

#define CALL_TYPE_METHODV(_jtype, _jname)                                   \

    _jtype Call##_jname##MethodV(jobject obj, jmethodID methodID,           \

        va_list args)                                                       \

    { return functions->Call##_jname##MethodV(this, obj, methodID, args); }

#define CALL_TYPE_METHODA(_jtype, _jname)                                   \

    _jtype Call##_jname##MethodA(jobject obj, jmethodID methodID,           \

        jvalue* args)                                                       \

    { return functions->Call##_jname##MethodA(this, obj, methodID, args); }

 

#define CALL_TYPE(_jtype, _jname)                                           \

    CALL_TYPE_METHOD(_jtype, _jname)                                        \

    CALL_TYPE_METHODV(_jtype, _jname)                                       \

    CALL_TYPE_METHODA(_jtype, _jname)

 

    CALL_TYPE(jobject, Object)

    CALL_TYPE(jboolean, Boolean)

    CALL_TYPE(jbyte, Byte)

    CALL_TYPE(jchar, Char)

    CALL_TYPE(jshort, Short)

    CALL_TYPE(jint, Int)

    CALL_TYPE(jlong, Long)

    CALL_TYPE(jfloat, Float)

    CALL_TYPE(jdouble, Double)

 

    void CallVoidMethod(jobject obj, jmethodID methodID, ...)

    {

        va_list args;

        va_start(args, methodID);

        functions->CallVoidMethodV(this, obj, methodID, args);

        va_end(args);

    }

    void CallVoidMethodV(jobject obj, jmethodID methodID, va_list args)

    { functions->CallVoidMethodV(this, obj, methodID, args); }

    void CallVoidMethodA(jobject obj, jmethodID methodID, jvalue* args)

    { functions->CallVoidMethodA(this, obj, methodID, args); }

 

#define CALL_NONVIRT_TYPE_METHOD(_jtype, _jname)                            \

    _jtype CallNonvirtual##_jname##Method(jobject obj, jclass clazz,        \

        jmethodID methodID, ...)                                            \

    {                                                                       \

        _jtype result;                                                      \

        va_list args;                                                       \

        va_start(args, methodID);                                           \

        result = functions->CallNonvirtual##_jname##MethodV(this, obj,      \

                    clazz, methodID, args);                                 \

        va_end(args);                                                       \

        return result;                                                      \

    }

#define CALL_NONVIRT_TYPE_METHODV(_jtype, _jname)                           \

    _jtype CallNonvirtual##_jname##MethodV(jobject obj, jclass clazz,       \

        jmethodID methodID, va_list args)                                   \

    { return functions->CallNonvirtual##_jname##MethodV(this, obj, clazz,   \

        methodID, args); }

#define CALL_NONVIRT_TYPE_METHODA(_jtype, _jname)                           \

    _jtype CallNonvirtual##_jname##MethodA(jobject obj, jclass clazz,       \

        jmethodID methodID, jvalue* args)                                   \

    { return functions->CallNonvirtual##_jname##MethodA(this, obj, clazz,   \

        methodID, args); }

 

#define CALL_NONVIRT_TYPE(_jtype, _jname)                                   \

    CALL_NONVIRT_TYPE_METHOD(_jtype, _jname)                                \

    CALL_NONVIRT_TYPE_METHODV(_jtype, _jname)                               \

    CALL_NONVIRT_TYPE_METHODA(_jtype, _jname)

 

    CALL_NONVIRT_TYPE(jobject, Object)

    CALL_NONVIRT_TYPE(jboolean, Boolean)

    CALL_NONVIRT_TYPE(jbyte, Byte)

    CALL_NONVIRT_TYPE(jchar, Char)

    CALL_NONVIRT_TYPE(jshort, Short)

    CALL_NONVIRT_TYPE(jint, Int)

    CALL_NONVIRT_TYPE(jlong, Long)

    CALL_NONVIRT_TYPE(jfloat, Float)

    CALL_NONVIRT_TYPE(jdouble, Double)

 

    void CallNonvirtualVoidMethod(jobject obj, jclass clazz,

        jmethodID methodID, ...)

    {

        va_list args;

        va_start(args, methodID);

        functions->CallNonvirtualVoidMethodV(this, obj, clazz, methodID, args);

        va_end(args);

    }

    void CallNonvirtualVoidMethodV(jobject obj, jclass clazz,

        jmethodID methodID, va_list args)

    { functions->CallNonvirtualVoidMethodV(this, obj, clazz, methodID, args); }

    void CallNonvirtualVoidMethodA(jobject obj, jclass clazz,

        jmethodID methodID, jvalue* args)

    { functions->CallNonvirtualVoidMethodA(this, obj, clazz, methodID, args); }

 

    jfieldID GetFieldID(jclass clazz, const char* name, const char* sig)

    { return functions->GetFieldID(this, clazz, name, sig); }

 

    jobject GetObjectField(jobject obj, jfieldID fieldID)

    { return functions->GetObjectField(this, obj, fieldID); }

    jboolean GetBooleanField(jobject obj, jfieldID fieldID)

    { return functions->GetBooleanField(this, obj, fieldID); }

    jbyte GetByteField(jobject obj, jfieldID fieldID)

    { return functions->GetByteField(this, obj, fieldID); }

    jchar GetCharField(jobject obj, jfieldID fieldID)

    { return functions->GetCharField(this, obj, fieldID); }

    jshort GetShortField(jobject obj, jfieldID fieldID)

    { return functions->GetShortField(this, obj, fieldID); }

    jint GetIntField(jobject obj, jfieldID fieldID)

    { return functions->GetIntField(this, obj, fieldID); }

    jlong GetLongField(jobject obj, jfieldID fieldID)

    { return functions->GetLongField(this, obj, fieldID); }

    jfloat GetFloatField(jobject obj, jfieldID fieldID)

    { return functions->GetFloatField(this, obj, fieldID); }

    jdouble GetDoubleField(jobject obj, jfieldID fieldID)

    { return functions->GetDoubleField(this, obj, fieldID); }

 

    void SetObjectField(jobject obj, jfieldID fieldID, jobject value)

    { functions->SetObjectField(this, obj, fieldID, value); }

    void SetBooleanField(jobject obj, jfieldID fieldID, jboolean value)

    { functions->SetBooleanField(this, obj, fieldID, value); }

    void SetByteField(jobject obj, jfieldID fieldID, jbyte value)

    { functions->SetByteField(this, obj, fieldID, value); }

    void SetCharField(jobject obj, jfieldID fieldID, jchar value)

    { functions->SetCharField(this, obj, fieldID, value); }

    void SetShortField(jobject obj, jfieldID fieldID, jshort value)

    { functions->SetShortField(this, obj, fieldID, value); }

    void SetIntField(jobject obj, jfieldID fieldID, jint value)

    { functions->SetIntField(this, obj, fieldID, value); }

    void SetLongField(jobject obj, jfieldID fieldID, jlong value)

    { functions->SetLongField(this, obj, fieldID, value); }

    void SetFloatField(jobject obj, jfieldID fieldID, jfloat value)

    { functions->SetFloatField(this, obj, fieldID, value); }

    void SetDoubleField(jobject obj, jfieldID fieldID, jdouble value)

    { functions->SetDoubleField(this, obj, fieldID, value); }

 

    jmethodID GetStaticMethodID(jclass clazz, const char* name, const char* sig)

    { return functions->GetStaticMethodID(this, clazz, name, sig); }

 

#define CALL_STATIC_TYPE_METHOD(_jtype, _jname)                             \

    _jtype CallStatic##_jname##Method(jclass clazz, jmethodID methodID,     \

        ...)                                                                \

    {                                                                       \

        _jtype result;                                                      \

        va_list args;                                                       \

        va_start(args, methodID);                                           \

        result = functions->CallStatic##_jname##MethodV(this, clazz,        \

                    methodID, args);                                        \

        va_end(args);                                                       \

        return result;                                                      \

    }

#define CALL_STATIC_TYPE_METHODV(_jtype, _jname)                            \

    _jtype CallStatic##_jname##MethodV(jclass clazz, jmethodID methodID,    \

        va_list args)                                                       \

    { return functions->CallStatic##_jname##MethodV(this, clazz, methodID,  \

        args); }

#define CALL_STATIC_TYPE_METHODA(_jtype, _jname)                            \

    _jtype CallStatic##_jname##MethodA(jclass clazz, jmethodID methodID,    \

        jvalue* args)                                                       \

    { return functions->CallStatic##_jname##MethodA(this, clazz, methodID,  \

        args); }

 

#define CALL_STATIC_TYPE(_jtype, _jname)                                    \

    CALL_STATIC_TYPE_METHOD(_jtype, _jname)                                 \

    CALL_STATIC_TYPE_METHODV(_jtype, _jname)                                \

    CALL_STATIC_TYPE_METHODA(_jtype, _jname)

 

    CALL_STATIC_TYPE(jobject, Object)

    CALL_STATIC_TYPE(jboolean, Boolean)

    CALL_STATIC_TYPE(jbyte, Byte)

    CALL_STATIC_TYPE(jchar, Char)

    CALL_STATIC_TYPE(jshort, Short)

    CALL_STATIC_TYPE(jint, Int)

    CALL_STATIC_TYPE(jlong, Long)

    CALL_STATIC_TYPE(jfloat, Float)

    CALL_STATIC_TYPE(jdouble, Double)

 

    void CallStaticVoidMethod(jclass clazz, jmethodID methodID, ...)

    {

        va_list args;

        va_start(args, methodID);

        functions->CallStaticVoidMethodV(this, clazz, methodID, args);

        va_end(args);

    }

    void CallStaticVoidMethodV(jclass clazz, jmethodID methodID, va_list args)

    { functions->CallStaticVoidMethodV(this, clazz, methodID, args); }

    void CallStaticVoidMethodA(jclass clazz, jmethodID methodID, jvalue* args)

    { functions->CallStaticVoidMethodA(this, clazz, methodID, args); }

 

    jfieldID GetStaticFieldID(jclass clazz, const char* name, const char* sig)

    { return functions->GetStaticFieldID(this, clazz, name, sig); }

 

    jobject GetStaticObjectField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticObjectField(this, clazz, fieldID); }

    jboolean GetStaticBooleanField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticBooleanField(this, clazz, fieldID); }

    jbyte GetStaticByteField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticByteField(this, clazz, fieldID); }

    jchar GetStaticCharField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticCharField(this, clazz, fieldID); }

    jshort GetStaticShortField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticShortField(this, clazz, fieldID); }

    jint GetStaticIntField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticIntField(this, clazz, fieldID); }

    jlong GetStaticLongField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticLongField(this, clazz, fieldID); }

    jfloat GetStaticFloatField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticFloatField(this, clazz, fieldID); }

    jdouble GetStaticDoubleField(jclass clazz, jfieldID fieldID)

    { return functions->GetStaticDoubleField(this, clazz, fieldID); }

 

    void SetStaticObjectField(jclass clazz, jfieldID fieldID, jobject value)

    { functions->SetStaticObjectField(this, clazz, fieldID, value); }

    void SetStaticBooleanField(jclass clazz, jfieldID fieldID, jboolean value)

    { functions->SetStaticBooleanField(this, clazz, fieldID, value); }

    void SetStaticByteField(jclass clazz, jfieldID fieldID, jbyte value)

    { functions->SetStaticByteField(this, clazz, fieldID, value); }

    void SetStaticCharField(jclass clazz, jfieldID fieldID, jchar value)

    { functions->SetStaticCharField(this, clazz, fieldID, value); }

    void SetStaticShortField(jclass clazz, jfieldID fieldID, jshort value)

    { functions->SetStaticShortField(this, clazz, fieldID, value); }

    void SetStaticIntField(jclass clazz, jfieldID fieldID, jint value)

    { functions->SetStaticIntField(this, clazz, fieldID, value); }

    void SetStaticLongField(jclass clazz, jfieldID fieldID, jlong value)

    { functions->SetStaticLongField(this, clazz, fieldID, value); }

    void SetStaticFloatField(jclass clazz, jfieldID fieldID, jfloat value)

    { functions->SetStaticFloatField(this, clazz, fieldID, value); }

    void SetStaticDoubleField(jclass clazz, jfieldID fieldID, jdouble value)

    { functions->SetStaticDoubleField(this, clazz, fieldID, value); }

 

    jstring NewString(const jchar* unicodeChars, jsize len)

    { return functions->NewString(this, unicodeChars, len); }

 

    jsize GetStringLength(jstring string)

    { return functions->GetStringLength(this, string); }

 

    const jchar* GetStringChars(jstring string, jboolean* isCopy)

    { return functions->GetStringChars(this, string, isCopy); }

 

    void ReleaseStringChars(jstring string, const jchar* chars)

    { functions->ReleaseStringChars(this, string, chars); }

 

    jstring NewStringUTF(const char* bytes)

    { return functions->NewStringUTF(this, bytes); }

 

    jsize GetStringUTFLength(jstring string)

    { return functions->GetStringUTFLength(this, string); }

 

    const char* GetStringUTFChars(jstring string, jboolean* isCopy)

    { return functions->GetStringUTFChars(this, string, isCopy); }

 

    void ReleaseStringUTFChars(jstring string, const char* utf)

    { functions->ReleaseStringUTFChars(this, string, utf); }

 

    jsize GetArrayLength(jarray array)

    { return functions->GetArrayLength(this, array); }

 

    jobjectArray NewObjectArray(jsize length, jclass elementClass,

        jobject initialElement)

    { return functions->NewObjectArray(this, length, elementClass,

        initialElement); }

 

    jobject GetObjectArrayElement(jobjectArray array, jsize index)

    { return functions->GetObjectArrayElement(this, array, index); }

 

    void SetObjectArrayElement(jobjectArray array, jsize index, jobject value)

    { functions->SetObjectArrayElement(this, array, index, value); }

 

    jbooleanArray NewBooleanArray(jsize length)

    { return functions->NewBooleanArray(this, length); }

    jbyteArray NewByteArray(jsize length)

    { return functions->NewByteArray(this, length); }

    jcharArray NewCharArray(jsize length)

    { return functions->NewCharArray(this, length); }

    jshortArray NewShortArray(jsize length)

    { return functions->NewShortArray(this, length); }

    jintArray NewIntArray(jsize length)

    { return functions->NewIntArray(this, length); }

    jlongArray NewLongArray(jsize length)

    { return functions->NewLongArray(this, length); }

    jfloatArray NewFloatArray(jsize length)

    { return functions->NewFloatArray(this, length); }

    jdoubleArray NewDoubleArray(jsize length)

    { return functions->NewDoubleArray(this, length); }

 

    jboolean* GetBooleanArrayElements(jbooleanArray array, jboolean* isCopy)

    { return functions->GetBooleanArrayElements(this, array, isCopy); }

    jbyte* GetByteArrayElements(jbyteArray array, jboolean* isCopy)

    { return functions->GetByteArrayElements(this, array, isCopy); }

    jchar* GetCharArrayElements(jcharArray array, jboolean* isCopy)

    { return functions->GetCharArrayElements(this, array, isCopy); }

    jshort* GetShortArrayElements(jshortArray array, jboolean* isCopy)

    { return functions->GetShortArrayElements(this, array, isCopy); }

    jint* GetIntArrayElements(jintArray array, jboolean* isCopy)

    { return functions->GetIntArrayElements(this, array, isCopy); }

    jlong* GetLongArrayElements(jlongArray array, jboolean* isCopy)

    { return functions->GetLongArrayElements(this, array, isCopy); }

    jfloat* GetFloatArrayElements(jfloatArray array, jboolean* isCopy)

    { return functions->GetFloatArrayElements(this, array, isCopy); }

    jdouble* GetDoubleArrayElements(jdoubleArray array, jboolean* isCopy)

    { return functions->GetDoubleArrayElements(this, array, isCopy); }

 

    void ReleaseBooleanArrayElements(jbooleanArray array, jboolean* elems,

        jint mode)

    { functions->ReleaseBooleanArrayElements(this, array, elems, mode); }

    void ReleaseByteArrayElements(jbyteArray array, jbyte* elems,

        jint mode)

    { functions->ReleaseByteArrayElements(this, array, elems, mode); }

    void ReleaseCharArrayElements(jcharArray array, jchar* elems,

        jint mode)

    { functions->ReleaseCharArrayElements(this, array, elems, mode); }

    void ReleaseShortArrayElements(jshortArray array, jshort* elems,

        jint mode)

    { functions->ReleaseShortArrayElements(this, array, elems, mode); }

    void ReleaseIntArrayElements(jintArray array, jint* elems,

        jint mode)

    { functions->ReleaseIntArrayElements(this, array, elems, mode); }

    void ReleaseLongArrayElements(jlongArray array, jlong* elems,

        jint mode)

    { functions->ReleaseLongArrayElements(this, array, elems, mode); }

    void ReleaseFloatArrayElements(jfloatArray array, jfloat* elems,

        jint mode)

    { functions->ReleaseFloatArrayElements(this, array, elems, mode); }

    void ReleaseDoubleArrayElements(jdoubleArray array, jdouble* elems,

        jint mode)

    { functions->ReleaseDoubleArrayElements(this, array, elems, mode); }

 

    void GetBooleanArrayRegion(jbooleanArray array, jsize start, jsize len,

        jboolean* buf)

    { functions->GetBooleanArrayRegion(this, array, start, len, buf); }

    void GetByteArrayRegion(jbyteArray array, jsize start, jsize len,

        jbyte* buf)

    { functions->GetByteArrayRegion(this, array, start, len, buf); }

    void GetCharArrayRegion(jcharArray array, jsize start, jsize len,

        jchar* buf)

    { functions->GetCharArrayRegion(this, array, start, len, buf); }

    void GetShortArrayRegion(jshortArray array, jsize start, jsize len,

        jshort* buf)

    { functions->GetShortArrayRegion(this, array, start, len, buf); }

    void GetIntArrayRegion(jintArray array, jsize start, jsize len,

        jint* buf)

    { functions->GetIntArrayRegion(this, array, start, len, buf); }

    void GetLongArrayRegion(jlongArray array, jsize start, jsize len,

        jlong* buf)

    { functions->GetLongArrayRegion(this, array, start, len, buf); }

    void GetFloatArrayRegion(jfloatArray array, jsize start, jsize len,

        jfloat* buf)

    { functions->GetFloatArrayRegion(this, array, start, len, buf); }

    void GetDoubleArrayRegion(jdoubleArray array, jsize start, jsize len,

        jdouble* buf)

    { functions->GetDoubleArrayRegion(this, array, start, len, buf); }

 

    void SetBooleanArrayRegion(jbooleanArray array, jsize start, jsize len,

        const jboolean* buf)

    { functions->SetBooleanArrayRegion(this, array, start, len, buf); }

    void SetByteArrayRegion(jbyteArray array, jsize start, jsize len,

        const jbyte* buf)

    { functions->SetByteArrayRegion(this, array, start, len, buf); }

    void SetCharArrayRegion(jcharArray array, jsize start, jsize len,

        const jchar* buf)

    { functions->SetCharArrayRegion(this, array, start, len, buf); }

    void SetShortArrayRegion(jshortArray array, jsize start, jsize len,

        const jshort* buf)

    { functions->SetShortArrayRegion(this, array, start, len, buf); }

    void SetIntArrayRegion(jintArray array, jsize start, jsize len,

        const jint* buf)

    { functions->SetIntArrayRegion(this, array, start, len, buf); }

    void SetLongArrayRegion(jlongArray array, jsize start, jsize len,

        const jlong* buf)

    { functions->SetLongArrayRegion(this, array, start, len, buf); }

    void SetFloatArrayRegion(jfloatArray array, jsize start, jsize len,

        const jfloat* buf)

    { functions->SetFloatArrayRegion(this, array, start, len, buf); }

    void SetDoubleArrayRegion(jdoubleArray array, jsize start, jsize len,

        const jdouble* buf)

    { functions->SetDoubleArrayRegion(this, array, start, len, buf); }

 

    jint RegisterNatives(jclass clazz, const JNINativeMethod* methods,

        jint nMethods)

    { return functions->RegisterNatives(this, clazz, methods, nMethods); }

 

    jint UnregisterNatives(jclass clazz)

    { return functions->UnregisterNatives(this, clazz); }

 

    jint MonitorEnter(jobject obj)

    { return functions->MonitorEnter(this, obj); }

 

    jint MonitorExit(jobject obj)

    { return functions->MonitorExit(this, obj); }

 

    jint GetJavaVM(JavaVM** vm)

    { return functions->GetJavaVM(this, vm); }

 

    void GetStringRegion(jstring str, jsize start, jsize len, jchar* buf)

    { functions->GetStringRegion(this, str, start, len, buf); }

 

    void GetStringUTFRegion(jstring str, jsize start, jsize len, char* buf)

    { return functions->GetStringUTFRegion(this, str, start, len, buf); }

 

    void* GetPrimitiveArrayCritical(jarray array, jboolean* isCopy)

    { return functions->GetPrimitiveArrayCritical(this, array, isCopy); }

 

    void ReleasePrimitiveArrayCritical(jarray array, void* carray, jint mode)

    { functions->ReleasePrimitiveArrayCritical(this, array, carray, mode); }

 

    const jchar* GetStringCritical(jstring string, jboolean* isCopy)

    { return functions->GetStringCritical(this, string, isCopy); }

 

    void ReleaseStringCritical(jstring string, const jchar* carray)

    { functions->ReleaseStringCritical(this, string, carray); }

 

    jweak NewWeakGlobalRef(jobject obj)

    { return functions->NewWeakGlobalRef(this, obj); }

 

    void DeleteWeakGlobalRef(jweak obj)

    { functions->DeleteWeakGlobalRef(this, obj); }

 

    jboolean ExceptionCheck()

    { return functions->ExceptionCheck(this); }

 

    jobject NewDirectByteBuffer(void* address, jlong capacity)

    { return functions->NewDirectByteBuffer(this, address, capacity); }

 

    void* GetDirectBufferAddress(jobject buf)

    { return functions->GetDirectBufferAddress(this, buf); }

 

    jlong GetDirectBufferCapacity(jobject buf)

    { return functions->GetDirectBufferCapacity(this, buf); }

 

   

    jobjectRefType GetObjectRefType(jobject obj)

    { return functions->GetObjectRefType(this, obj); }

#endif

};

 

JVM负责从Java Stack转入C/C++ Native Stack。当Java进入JNI调用，除了函数本身的参数,会多出两个参数：JNIEnv指针和jobject指针。
JNIEnv指针是JVM创建的，用于Native的c/c++方法操纵Java执行栈中的数据，比如Java类, Java 方法等。

从c/c++两种定义上看，C++将JNINativeInterface封装到_JNIEnv中，由于C语言并不支持对象的概念，所以C语法中需要把env作为第一个参数传入，类似于C++的隐式参数this指针

JVM 从java Stack转入C/C++ Native Stack时，都会使用JNIEnv指针进行参数传递，c/c++在JNI层对JNIEnv定义不同，就产生两种调用方式，如下：

c语法：

jsize len = (*env)->GetArrayLength(env,array);

c++语法：

jsize len =env->GetArrayLength(array);

 

 

JNIEnv有几个设计的原则：

第一、JNIEnv指针被设计成了Thread Local Storage(TLS)变量，也就是说每一个Thread, JNIEnv变量都有独立的Copy。这样做的原因主要是考虑到：由于JVM要运行在多个平台（除了主流的Windows,Linux等平台),JNI内部实现很多要依赖到TLS， 为了减少对TLS的依赖，所有TLS based的，数据都会存放于JNIEnv中。这样相当于只依赖一个TLS based的变量JNIEnv。由于JNIEnv指针是TLS的，所以你不能把Thead#1使用的JNIEnv传给Thread#2使用。

第二、JNIEnv中定义了一组函数指针，c/c++ Native程序是通过这些函数指针操纵Java数据。这样设计的好处是：你的c/c++ 程序不需要依赖

任何函数库，或者DLL。由于JVM可能由不同的厂商实现，不同厂商有自己不同的JNI实现，如果要求这些厂商暴露约定好的一些头文件和库，这不是灵活的设计。

而且使用函数指针表的另外一个好处是： JVM可以根据启动参数动态替换JNI实现。比如：类似于C库，JNI实现为了性能起见，并没有对调用者

传入的参数进行检查。但是在调试阶段，也许这种检查是很必要的，帮助你尽早发现BUG。例如如果你使用IBM JDK，你可以指定JVM参数–Xcheck:jni，告诉JVM使用带检查的JNI实现。

http://harmony.apache.org/subcomponents/drlvm/doxygen/vmcore/html/struct_j_n_i_native_interface__.html（参考）