java環境下呼叫VC++編寫的動態連結庫檔案

一，開發平臺：

MyEclipse 6.0，VC++6.0

二，JNI基礎知識：

JNI(java native interface)，JAVA本地介面呼叫，目的是為了JAVA可以呼叫本地程式。

三，互動過程：

1，建立java類。例如，建立一個RSA加密解密的類：

package zkxx.ctais2.client.common; public class RsaEncrypt { /** * @param args */ public native String GetKeys(); public native String Encrypt(String source,String PublicKey); public native String Decrypt(String cipher,String PrivateKey); static { System.loadLibrary("RSAEncrypt"); } public static void main(String[] args) { } }

2，生成C++語言的標頭檔案：

1）注意：利用javah工具生成標頭檔案需要注意，類的包結構，和class檔案儲存的路徑。

例如：本地class檔案儲存路徑：E:/lclai/lclai/src/

包結構應為：E:/lclai/lclai/src/com/org/lclai

RsaEncrypt.java應該存放在包路徑下。

2）CMD命令提示符下進入E:/lclai/lclai/src/com/org/lclai路徑

輸入命令：javac RsaEncrypt.java

回車。

把生成的class檔案拷貝到路徑E:/lclai/lclai/src/

CMD命令提示符下進入E:/lclai/lclai/src/

輸入命令：javah -classpath E:/lclai/lclai/src -jni com.org.lclai.RsaEncrypt

回車。

在路徑E:/lclai/lclai/src/便會生成以包結構和類名結合的標頭檔案。

3，編寫cpp檔案

cpp檔案頭需要包含剛剛生成的.h檔案，此外還需要包含jni.h.

// RSAEncrypt.cpp : Defines the initialization routines for the DLL. // #include "stdafx.h" #include "RSAEncrypt.h" #include "CryptoPP32.h" #include "zkxx_ctais2_client_common_RsaEncrypt.h" #include "jni.h" #ifdef _DEBUG #define new DEBUG_NEW #undef THIS_FILE static char THIS_FILE[] = __FILE__; #endif // // Note! // // If this DLL is dynamically linked against the MFC // DLLs, any functions exported from this DLL which // call into MFC must have the AFX_MANAGE_STATE macro // added at the very beginning of the function. // // For example: // // extern "C" BOOL PASCAL EXPORT ExportedFunction() // { // AFX_MANAGE_STATE(AfxGetStaticModuleState()); // // normal function body here // } // // It is very important that this macro appear in each // function, prior to any calls into MFC. This means that // it must appear as the first statement within the // function, even before any object variable declarations // as their constructors may generate calls into the MFC // DLL. // // Please see MFC Technical Notes 33 and 58 for additional // details. // ///////////////////////////////////////////////////////////////////////////// // CRSAEncryptApp extern "C" __declspec(dllexport) char* RSAGenKeys() { char*result=""; CRSAEncryptApp rsa; result=rsa.GenKeys(); return result; } extern "C" __declspec(dllexport) char* RSAEncrypt(char *publickey, char *source) { char*result=""; CRSAEncryptApp rsa; result=rsa.Encrypt(publickey,source); return result; } extern "C" __declspec(dllexport) char* RSADecrypt(char *privatekey, char *cipher) { char*result=""; CRSAEncryptApp rsa; result=rsa.Decrypt(privatekey,cipher); return result; } BEGIN_MESSAGE_MAP(CRSAEncryptApp, CWinApp) //{{AFX_MSG_MAP(CRSAEncryptApp) // NOTE - the ClassWizard will add and remove mapping macros here. // DO NOT EDIT what you see in these blocks of generated code! //}}AFX_MSG_MAP END_MESSAGE_MAP() ///////////////////////////////////////////////////////////////////////////// // CRSAEncryptApp construction CRSAEncryptApp::CRSAEncryptApp() { // TODO: add construction code here, // Place all significant initialization in InitInstance } ///////////////////////////////////////////////////////////////////////////// // The one and only CRSAEncryptApp object CRSAEncryptApp theApp; char* CRSAEncryptApp::GenKeys() { // 生成公鑰和私鑰字串 char* charPriv; char* charPub; CString temp1,temp2; char* result="err"; CString publickey,privatekey; bool IsOk=CryptoPP32::RSAES_PKCS_GenKeyStrings(&charPriv, &charPub); if(IsOk) { publickey=charPub; privatekey=charPriv; temp1=publickey+"##"+privatekey; result=temp1.GetBuffer(temp1.GetLength()); } return result; } char* CRSAEncryptApp::Encrypt(char *publickey, char *source) { //講明文加密，返回密文 char*cipher=""; char* result="err"; bool IsOk=CryptoPP32::RSAES_PKCS_EncryptString(publickey,source,&cipher); if(IsOk) { //AfxMessageBox(cipher); result=cipher; } return result; } char* CRSAEncryptApp::Decrypt(char *privatekey, char *cipher) { //解密密文，返回明文 char*plain=""; char*result="err"; bool IsOk=CryptoPP32::RSAES_PKCS_DecryptString(privatekey,cipher,&plain); if(IsOk) { //AfxMessageBox(plain); result=plain; } return result; } //-------------------------------------------------------------------------- // static char* jstringTostring(JNIEnv* env, jstring jstr) { char* rtn = NULL; jclass clsstring = env->FindClass("java/lang/String"); jstring strencode = env->NewStringUTF("utf-8"); jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B"); jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode); jsize alen = env->GetArrayLength(barr); jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE); if (alen > 0) { rtn = (char*)malloc(alen + 1); memcpy(rtn, ba, alen); rtn[alen] = 0; } env->ReleaseByteArrayElements(barr, ba, 0); return rtn; } static jstring stoJstring(JNIEnv* env, const char* pat) { jclass strClass = env->FindClass("Ljava/lang/String;"); jmethodID ctorID = env->GetMethodID( strClass, "<init>", "([BLjava/lang/String;)V"); jbyteArray bytes = env->NewByteArray(strlen(pat)); env->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat); jstring encoding = env->NewStringUTF("utf-8"); return (jstring)env->NewObject(strClass, ctorID, bytes, encoding); } JNIEXPORT jstring JNICALL Java_com_org_lclai_RsaEncrypt_GetKeys (JNIEnv *env, jobject jo) { jstring result; CRSAEncryptApp rsa; //CString res; char*res=""; res=rsa.GenKeys(); result=env->NewStringUTF(res); return result; } JNIEXPORT jstring JNICALL Java_com_org_lclai_RsaEncrypt_Encrypt (JNIEnv *env, jobject jo, jstring publickey, jstring source) { jstring result; CRSAEncryptApp rsa; char* pubkey=""; char* sour=""; pubkey=jstringTostring(env,publickey); sour=jstringTostring(env,source); char*cipher=rsa.Encrypt(pubkey,sour); result=stoJstring(env,cipher); return result; } JNIEXPORT jstring JNICALL Java_com_org_lclai_RsaEncrypt_Decrypt (JNIEnv *env, jobject jo, jstring privatekey , jstring cipher) { jstring result; CRSAEncryptApp rsa; char* privkey=""; char* ciphertext=""; privkey=jstringTostring(env,privatekey); ciphertext=jstringTostring(env,cipher); char*plain=rsa.Decrypt(privkey,ciphertext); result=stoJstring(env,plain); return result; }