Android native get signature (cpp)

Signature.cpp

#include <jni.h>
#include <string>

extern "C"
JNIEXPORT jstring JNICALL
Java_me_axaygadekar_security_NativeSecurity_getSignatureFromJNI(JNIEnv *env, jclass nativeSecurityClass,
                                                     jobject context) {

    // --------------- PackageManager
    // context object class
    jclass contextClass = env->GetObjectClass(context);
    //  package manager method id
    jmethodID getPackageManagerMethodId = env->GetMethodID(contextClass, "getPackageManager",
                                                           "()Landroid/content/pm/PackageManager;");
    // package manager object
    jobject packageManagerObject = env->CallObjectMethod(context, getPackageManagerMethodId);

    // --------------- getting package name
    // get package name method id
    jmethodID getPackageNameMethodId = env->GetMethodID(contextClass, "getPackageName",
                                                        "()Ljava/lang/String;");
    // get package name
    jstring packageName = (jstring) env->CallObjectMethod(context, getPackageNameMethodId);

    // --------------- getting package info
    // package manager class
    jclass packageManagerClass = env->GetObjectClass(packageManagerObject);
    // get package info method id
    jmethodID getPackageInfoMethodId = env->GetMethodID(packageManagerClass, "getPackageInfo",
                                                        "(Ljava/lang/String;I)Landroid/content/pm/PackageInfo;");
    jint flags = 0x00000040;
    jobject packageInfo = env->CallObjectMethod(packageManagerObject, getPackageInfoMethodId,
                                                packageName, flags);

    // --------------- getting signatures
    // get package info class
    jclass packageInfoClass = env->GetObjectClass(packageInfo);
    // get field id
    jfieldID signaturesFieldId = env->GetFieldID(packageInfoClass, "signatures",
                                                 "[Landroid/content/pm/Signature;");
    // get signatures objects
    jobject signaturesObject = env->GetObjectField(packageInfo, signaturesFieldId);
    jobjectArray signatures = reinterpret_cast<jobjectArray>(signaturesObject);

    // --------------- getting signatures 0
    // get signature
    jobject signature = env->GetObjectArrayElement(signatures, 0);
    jclass signatureClass = env->GetObjectClass(signature);
    jmethodID toCharsStringMethodId = env->GetMethodID(signatureClass, "toCharsString",
                                                       "()Ljava/lang/String;");
    jobject ts = env->CallObjectMethod(signature, toCharsStringMethodId);
    return reinterpret_cast<jstring>(ts);

}