前言

我会在小专栏和简书一起分享。
最近在忙其他事情，今天想起JNI做加解密不错，于是我调查了一下AES使用JNI实现，试验过程发现用C或者C++出了很多问题，于是发现有人使用一种巧妙的方式，用Java做加解密，只是把加解密的Key放在SO库中，这里我要讲的就是这种方式。

正文

新建java类

public class AESjni {
    public static native String myEncrypt(String str);
    public static native String myDecrypt(String str);
}

还是使用我们的Tools工具生成.h文件

#include "com_crayfish_ndkproject_AESjni.h"
#include <stdlib.h>
const char *DES_KEY = "12345678912345678912345678912345";
/*
* Class:     com_jzp_myapplication_JniUtils
* Method:    getString
* Signature: ()Ljava/lang/String;
*/
JNIEXPORT jstring JNICALL Java_com_crayfish_ndkproject_AESjni_myEncrypt
        (JNIEnv *env, jclass jclass1, jstring jstr)
{
    if (jstr == NULL) {
        return NULL;
    }
    jstring key;
    jstring result;
    jclass AESencrypt;
    jmethodID mid;

    AESencrypt = (*env)->FindClass(env, "com/crayfish/ndkproject/AESjni");
    if (NULL == AESencrypt) {
        return NULL;
    }
    mid = (*env)->GetStaticMethodID(env, AESencrypt, "encrypt",
                                    "(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;");
    if (NULL == mid) {
        (*env)->DeleteLocalRef(env, AESencrypt);
        return NULL;
    }
    key = (*env)->NewStringUTF(env, DES_KEY);
    result = (*env)->CallStaticObjectMethod(env, AESencrypt, mid, key, jstr);
    (*env)->DeleteLocalRef(env, AESencrypt);
    (*env)->DeleteLocalRef(env, key);
    return result;
}

JNIEXPORT jstring JNICALL Java_com_crayfish_ndkproject_AESjni_myDecrypt
        (JNIEnv *env, jclass jclass1, jstring jstr)
{
    if (jstr == NULL) {
        return NULL;
    }
    jstring key;
    jstring result;
    jclass AESencrypt;
    jmethodID mid;

    AESencrypt = (*env)->FindClass(env, "com/crayfish/ndkproject/AESjni");
    if (NULL == AESencrypt) {
        return NULL;
    }
    mid = (*env)->GetStaticMethodID(env, AESencrypt, "decrypt",
                                    "(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;");
    if (NULL == mid) {
        (*env)->DeleteLocalRef(env, AESencrypt);
        return NULL;
    }
    key = (*env)->NewStringUTF(env, DES_KEY);
    result = (*env)->CallStaticObjectMethod(env, AESencrypt, mid, key, jstr);
    (*env)->DeleteLocalRef(env, AESencrypt);
    (*env)->DeleteLocalRef(env, key);
    return result;
}

看到c代码中有读取java类中encrypt和decrypt两个方法了吧，我们把它们补上，这里就是真正的加解密逻辑。

    public static String encrypt(String key,String palinText) throws Exception{
        //加密
        return "";
    }
    public static String decrypt(String key,String palinText) throws Exception{
        //解密
        return "";
    }

记得配置Android.mk和build.gradle

include $(CLEAR_VARS)
LOCAL_MODULE := AESjni
LOCAL_SRC_FILES := aesjni.c
include $(BUILD_SHARED_LIBRARY)

ndk{
      moduleName "AESjni"        //生成的so名字
      //abiFilters "armeabi", "armeabi-v7a", "x86"  //输出指定三种abi体系结构下的so库。目前可有可无。
        }

结尾

今天的内容很简单，到这就结束了。