MD5 算法（Android，IOS，JNI C++，Java）

1、Android 写法

/**
     * MD5加密算法
     *
     * @param val 需要加密的字符串
     * @return
     * @throws NoSuchAlgorithmException
     */
public static String getMD5(String val) {
        try {
            MessageDigest bmd5 = MessageDigest.getInstance("MD5");
            bmd5.update(val.getBytes());
            int i;
            StringBuffer buf = new StringBuffer();
            byte[] b = bmd5.digest();
            for (int offset = 0; offset < b.length; offset++) {
                i = b[offset];
                if (i < 0)
                    i += 256;
                if (i < 16)
                    buf.append("0");
                buf.append(Integer.toHexString(i));
            }
            return buf.toString();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return "";
    }

2、Java写法

 /** 
     * md5或者sha-1加密 
     *  
     * @param inputText 
     *            要加密的内容 
     * @param algorithmName 
     *            加密算法名称：md5或者sha-1，不区分大小写 
     * @return 
     */  
    private static String encrypt(String inputText, String algorithmName) {
        try {  
            MessageDigest m = MessageDigest.getInstance(algorithmName);
            m.update(inputText.getBytes("UTF8"));  
            byte s[] = m.digest();  
            // m.digest(inputText.getBytes("UTF8"));  
            return hex(s);  
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();  
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();  
        }  
        return "";  
    }  
    // 返回十六进制字符串  
    private static String hex(byte[] arr) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < arr.length; ++i) {  
            sb.append(Integer.toHexString((arr[i] & 0xFF) | 0x100).substring(1, 3));
        }  
        return sb.toString();  
    }

3、IOS写法

+ (NSString *)md5:(NSString *)str{
    const char *cStr = [str UTF8String];
    unsigned char result[32];
    CC_MD5( cStr, strlen(cStr), result );
    return [NSString stringWithFormat:
            @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
            result[0],result[1],result[2],result[3],
            result[4],result[5],result[6],result[7],
            result[8],result[9],result[10],result[11],
            result[12],result[13],result[14],result[15],
            result[16], result[17],result[18], result[19],
            result[20], result[21],result[22], result[23],
            result[24], result[25],result[26], result[27],
            result[28], result[29],result[30], result[31]];
}

4、Android JNI 方法

#include "md5.h"
#include <jni.h>
#include <stdlib.h>
#include <string>
void ByteToHexStr(const char *source, char *dest, int sourceLen) {
    short i;
    char highByte, lowByte;
    for (i = 0; i < sourceLen; i++) {
        highByte = source[i] >> 4;
        lowByte = source[i] & 0x0f;
        highByte += 0x30;
        if (highByte > 0x39) {
            dest[i * 2] = highByte + 0x07;
        } else {
            dest[i * 2] = highByte;
        }
        lowByte += 0x30;
        if (lowByte > 0x39) {
            dest[i * 2 + 1] = lowByte + 0x07;
        } else {
            dest[i * 2 + 1] = lowByte;
        }
    }
}
//转成小写字符
void MyToLower(char *s){
    int len=strlen(s);
    for(int i=0;i<len;i++){
        if(s[i]>='A'&&s[i]<='Z'){
            //s[i]=tolower(s[i]);
            s[i]+=32;//+32转换为小写，-32为大写
            //s[i]=s[i]-'A'+'a';
        }
    }
}
// byte数组转MD5字符串
extern "C"
jstring ToMd5(JNIEnv *env, jbyteArray source) {
    // MessageDigest类
    jclass classMessageDigest = env->FindClass("java/security/MessageDigest");
    // MessageDigest.getInstance()静态方法
    jmethodID midGetInstance = env->GetStaticMethodID(classMessageDigest, "getInstance",
                                                      "(Ljava/lang/String;)Ljava/security/MessageDigest;");
    // MessageDigest object
    jobject objMessageDigest = env->CallStaticObjectMethod(classMessageDigest, midGetInstance,
                                                           env->NewStringUTF("md5"));
    // update方法，这个函数的返回值是void，写V
    jmethodID midUpdate = env->GetMethodID(classMessageDigest, "update", "([B)V");
    env->CallVoidMethod(objMessageDigest, midUpdate, source);
    // digest方法
    jmethodID midDigest = env->GetMethodID(classMessageDigest, "digest", "()[B");
    jbyteArray objArraySign = (jbyteArray) env->CallObjectMethod(objMessageDigest, midDigest);
    jsize intArrayLength = env->GetArrayLength(objArraySign);
    jbyte *byte_array_elements = env->GetByteArrayElements(objArraySign, NULL);
    size_t length = (size_t) intArrayLength * 2 + 1;
    char *char_result = (char *) malloc(length);
    memset(char_result, 0, length);
    // 将byte数组转换成16进制字符串，发现这里不用强转，jbyte和unsigned char应该字节数是一样的
    ByteToHexStr((const char *) byte_array_elements, char_result, intArrayLength);
    // 在末尾补\0
    *(char_result + intArrayLength * 2) = '\0';
    //如果需要转小写，请添加这个方法
    //MyToLower(char_result);
    jstring stringResult = env->NewStringUTF(char_result);
    // release
    env->ReleaseByteArrayElements(objArraySign, byte_array_elements, JNI_ABORT);
    // 释放指针使用free
    free(char_result);
    env->DeleteLocalRef(classMessageDigest);
    env->DeleteLocalRef(objMessageDigest);
    return stringResult;
}