JNI方式遍历HashMap

extern "C"
extern "C"
JNIEXPORT jstring JNICALL
Java_com_xxx_sign_SignUtil_sign0(JNIEnv *env, jobject params) {
    // 获取HashMap类entrySet()方法ID
    jclass hashmapClass = env->FindClass("java/util/HashMap");
    jmethodID entrySetMID = env->GetMethodID(hashmapClass, "entrySet", "()Ljava/util/Set;");
    // 调用entrySet()方法获取Set对象
    jobject setObj = env->CallObjectMethod(params, entrySetMID);
    // 获取Set类中iterator()方法ID
    jclass setClass = env->FindClass("java/util/Set");
    jmethodID iteratorMID = env->GetMethodID(setClass, "iterator", "()Ljava/util/Iterator;");
    // 调用iterator()方法获取Iterator对象
    jobject iteratorObj = env->CallObjectMethod(setObj, iteratorMID);
    // 获取Iterator类中hasNext()方法ID
    // 用于while循环判断HashMap中是否还有数据
    jclass iteratorClass = env->FindClass("java/util/Iterator");
    jmethodID hasNextMID = env->GetMethodID(iteratorClass, "hasNext", "()Z");
    // 获取Iterator类中next()方法ID
    // 用于读取HashMap中的每一条数据
    jmethodID nextMID = env->GetMethodID(iteratorClass, "next", "()Ljava/lang/Object;");

    // 获取Map.Entry类中getKey()和getValue()的方法ID
    // 用于读取“K-V”键值对，注意：内部类使用$符号表示
    jclass entryClass = env->FindClass("java/util/Map$Entry");
    jmethodID getKeyMID = env->GetMethodID(entryClass, "getKey", "()Ljava/lang/Object;");
    jmethodID getValueMID = env->GetMethodID(entryClass, "getValue", "()Ljava/lang/Object;");

    //结构体整型赋值
    query_info temp;
    // 循环检测HashMap中是否还有数据
    while (env->CallBooleanMethod(iteratorObj, hasNextMID)) {
        // 读取一条数据
        jobject entryObj = env->CallObjectMethod(iteratorObj, nextMID);

        // 提取数据中key值：String类型课程名字
        jstring courseJS = (jstring) env->CallObjectMethod(entryObj, getKeyMID);
        if (courseJS == NULL)   // HashMap允许null类型
            continue;
        // jstring转C风格字符串
        const char *courseStr = env->GetStringUTFChars(courseJS, NULL);

        // 提取数据中value值：Integer类型分数，并转为int类型
        jstring scoreObj = static_cast<jstring>(env->CallObjectMethod(entryObj, getValueMID));
        if (scoreObj == NULL)
            continue;
        // jstring转C风格字符串
        const char *score = env->GetStringUTFChars(scoreObj, NULL);



        // 释放UTF字符串资源
        env->ReleaseStringUTFChars(courseJS, courseStr);
        // 释放JNI局部引用资源
        env->DeleteLocalRef(entryObj);
        env->DeleteLocalRef(courseJS);
        env->DeleteLocalRef(scoreObj);
    }
    
    // 释放JNI局部引用: jclass jobject
    env->DeleteLocalRef(hashmapClass);
    env->DeleteLocalRef(setObj);
    env->DeleteLocalRef(setClass);
    env->DeleteLocalRef(iteratorObj);
    env->DeleteLocalRef(iteratorClass);
    env->DeleteLocalRef(entryClass);
    
    return env->NewStringUTF("");
}