JNI初体验
因为需要接入统一的安全服务，调用验证码接口，对方是使用UDP协议进行通信，并且不提供http service调用接口，没有提供客户端包，丢了一个C的协议和client包过来，本想用java socket来自己实现协议，但是协议甚至麻烦，一看就想死，无奈考虑JNI调用实现。
JAVA的定义的接口如下：
public class VerifyCoder {
static {
try {
System.loadLibrary("vc");
} catch (Exception e) {
e.printStackTrace();
}
}
public native ImageCode getCoderImage(Service[] services,int timeout,int appid,String clientIP,long uin,int type,String filename);
public native ImageCode getCoderBytes(Service[] services,int timeout,int appid,String clientIP,long uin,int type);
public native int vefiryCoder(Service[] services,int timeout,int appid,String clientIP,String code,String sig);
}
接口:
public native ImageCode getCoderImage(Service[] services,int timeout,int appid,String clientIP,long uin,int type,String filename);可用于指定文件存储参数，用于生成验证码图片，返回图片绝对路径。理论上该filename可以实用sessionid作为临时名称，或者考虑实用tmpnam生成。
接口：
public native ImageCode getCoderBytes(Service[] services,int timeout,int appid,String clientIP,long uin,int type);可用于获取验证码的二进制数据数组。
接口：
public native int vefiryCoder(Service[] services,int timeout,int appid,String clientIP,String code,String sig);主要是用签名和用户填写的验验证码进行校验，返回标志位。
利用javah VerifyCode生成头文件，如下：
#include <jni.h>
/* Header for class com_corey_verifycode_VerifyCoder */
#ifndef _Included_com_corey_verifycode_VerifyCoder
#define _Included_com_corey_verifycode_VerifyCoder
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_qq_verifycode_VerifyCoder
* Method: getCoderImage
* Signature: ([Lcom/qq/verifycode/Service;IILjava/lang/String;JILjava/lang/String;)Lcom/qq/verifycode/ImageCode;
*/
JNIEXPORT jobject JNICALL Java_com_qq_verifycode_VerifyCoder_getCoderImage
(JNIEnv *, jobject, jobjectArray, jint, jint, jstring, jlong, jint, jstring);
/*
* Class: com_qq_verifycode_VerifyCoder
* Method: getCoderBytes
* Signature: ([Lcom/corey/verifycode/Service;IILjava/lang/String;JI)Lcom/qq/verifycode/ImageCode;
*/
JNIEXPORT jobject JNICALL Java_com_qq_verifycode_VerifyCoder_getCoderBytes
(JNIEnv *, jobject, jobjectArray, jint, jint, jstring, jlong, jint);
/*
* Class: com_qq_verifycode_VerifyCoder
* Method: vefiryCoder
* Signature: ([Lcom/corey/verifycode/Service;IILjava/lang/String;Ljava/lang/String;Ljava/lang/String;)I
*/
JNIEXPORT jint JNICALL Java_com_corey_verifycode_VerifyCoder_vefiryCoder
(JNIEnv *, jobject, jobjectArray, jint, jint, jstring, jstring, jstring);
#ifdef __cplusplus
}
#endif
#endif
其中env是函数调用指针集合，提供了很多函数，jobject是this对象，后续则是参数。
数组处理：
jsize serviceLength=(env)->GetArrayLength(services);
stInit.iSvrNum = serviceLength;
for(int i=0;i<serviceLength;i++){
jobject service=(env)->GetObjectArrayElement(services,i);
jclass serviceClass=(env)->FindClass("com/qq/verifycode/Service");
jfieldID ipFieldID=(env)->GetFieldID(serviceClass,"ip","Ljava/lang/String;");
jfieldID portFieldID=(env)->GetFieldID(serviceClass,"port","I");
jint port=(env)->GetIntField(service,portFieldID);
stInit.stRemoteSvr[i].usSvrPort = port;
jstring jip=(jstring)(env)->GetObjectField(service,ipFieldID);
char* ip=(char*)(env)->GetStringUTFChars(jip,NULL);
strncpy(stInit.stRemoteSvr[i].aszIp, ip, sizeof(stInit.stRemoteSvr[i].aszIp) - 1);
env->ReleaseStringUTFChars(jip,ip);
}
java对象的构建：
jclass imageCodeClass=(env)->FindClass("com/qq/verifycode/ImageCode");
jfieldID imagePathFieldID=(env)->GetFieldID(imageCodeClass,"imagePath","Ljava/lang/String;");
jfieldID sigFieldID=(env)->GetFieldID(imageCodeClass,"sig","Ljava/lang/String;");
jmethodID construction_id=(env)->GetMethodID(imageCodeClass,"<init>","()V");
jobject imageCode = (env)->NewObject(imageCodeClass, construction_id);
java对象的字段和方法的调用：
env->SetObjectField(imageCode,imagePathFieldID,(env)->NewStringUTF(""));
env->SetObjectField(imageCode,sigFieldID,(env)->NewStringUTF("getCaptcha error"));
字符串的转换和释放：
char * clientIP =(char*)env->GetStringUTFChars(jclientIP,NULL); env->ReleaseStringUTFChars(jclientIP,clientIP);
byte数组和char数组转换：
char* data=(char*)stOut.aucPicBuffer;
jbyteArray bytes=0;
bytes=(env)->NewByteArray(stOut.usPicData);
if(bytes!=NULL){
(env)->SetByteArrayRegion(bytes,0,stOut.usPicData,(jbyte*)data);
}