Android Service后台进程守护

来源：互联网发布：linux打印行号编辑：程序博客网时间：2024/05/18 01:21
看了很多资料，说是在android java层实现服务自启动，但是亲测，无论怎么做都达不到自启动。
后面看了网上一些资料，从linux层面着手，感觉可行，不过很多资料都采用轮询的方法去启动服务，个人感觉轮询从耗电等各方面考虑并不是最优方案，因为如果可以检测到服务挂了然后直接启动服务可能更节省性能，而android本身提供了这样的机制，service死掉后会调用生命周期中的onDestroy进行销毁。因此，我们就可以通过这样的方法在依靠linux下孤立的子进程存活的情况下去调用启动服务命令。
基本流程：
父进程fork后产生孤立的子进程A, A启动服务进程s, s发现自己将要销毁时依靠A进程调用启动s的命令。
c关键代码：
#include <stdio.h>#include <string.h>#include <jni.h>#include <unistd.h>#include <stdlib.h>#include <sys/resource.h>#include <dirent.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <sys/wait.h>#include <pthread.h>#define PROC_DIRECTORY "/proc/"#define CASE_SENSITIVE    1#define CASE_INSENSITIVE  0#define EXACT_MATCH       1#define INEXACT_MATCH     0#define MAX_LINE_LEN 5#include <android/log.h>#define  TAG    "daemon"#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,TAG,__VA_ARGS__)#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, TAG, __VA_ARGS__)#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG,__VA_ARGS__)#define LOG "Helper"void thread(char* srvname) {    check_and_restart_service(srvname);}char* a;char* srvn;/** * srvname  服务名 * sd 之前创建子进程的pid写入的文件路径 */int start(int argc, char* srvname, char* sd) {    pthread_t id;    int ret;    struct rlimit r;    srvn = srvname;    /**     * 第一次fork的作用是让shell认为本条命令已经终止，不用挂在终端输入上。     * 还有一个作用是为后面setsid服务。setsid的调用者不能是进程组组长(group leader)。     * 此时父进程是进程组组长。     */    int pid = fork();    LOGI("fork pid: %d", pid);    if (pid < 0) {        LOGI("first fork() error pid %d,so exit", pid);        exit(0);    } else if (pid != 0) {        LOGI("first fork(): I'am father pid=%d", getpid());        //exit(0);    } else { //  第一个子进程        umask(0); //使用umask修改文件的屏蔽字，为文件赋予跟多的权限，因为继承来的文件可能某些权限被屏蔽，从而失去某些功能，如读写        int pid = fork();        if (pid == 0) { // 第二个子进程            FILE  *fp;            sprintf(sd,"%s/pid",sd);            if((fp=fopen(sd,"a"))==NULL) {//打开文件 没有就创建                LOGI("%s文件还未创建!",sd);                ftruncate(fp, 0);                lseek(fp, 0, SEEK_SET);            }            fclose(fp);            fp=fopen(sd,"rw");            if(fp>0){                char buff1[6];                int p = 0;                memset(buff1,0,sizeof(buff1));                fseek(fp,0,SEEK_SET);                fgets(buff1,6,fp);  //读取一行                LOGI("读取的进程号：%s",buff1);                if(strlen(buff1)>1){ // 有值                    kill(atoi(buff1), SIGTERM);                    LOGI("杀死进程，pid=%d",atoi(buff1));                }            }            fclose(fp);            fp=fopen(sd,"w");            char buff[100];            int k = 3;            if(fp>0){                sprintf(buff,"%lu",getpid());                fprintf(fp,"%s\n",buff); // 把进程号写入文件                LOGI("写入。。。。。");            }            fclose(fp);            fflush(fp);            LOGI("step 2 I'am child-child pid=%d", getpid());            //step 4:修改进程工作目录为根目录，chdir(“/”).            chdir("/");            LOGI("after step 4 ...11133.", "");            //step 5:关闭不需要的从父进程继承过来的文件描述符。            LOGI("after step 5 ...1111.", "");            umask(0);            // 关闭不必要的文件描述符            close(STDIN_FILENO);            close(STDOUT_FILENO);            close(STDERR_FILENO);            ret = pthread_create(&id, NULL, (void *) thread, srvname);            LOGI("after step 5 ....222", "");            if (ret != 0) {                printf("Create pthread error!\n");                exit(1);            }            int stdfd = open ("/dev/null", O_RDWR);            dup2(stdfd, STDOUT_FILENO);            dup2(stdfd, STDERR_FILENO);        } else {            exit(0);        }    }    return 0;}/** * 执行命令 */void ExecuteCommandWithPopen(char* command, char* out_result,                             int resultBufferSize) {    FILE * fp;    out_result[resultBufferSize - 1] = '\0';    fp = popen(command, "r");    if (fp) {        fgets(out_result, resultBufferSize - 1, fp);        out_result[resultBufferSize - 1] = '\0';        pclose(fp);    } else {        LOGI("popen null,so exit");        exit(0);    }}/** * 检测服务，如果不存在服务则启动. * 通过am命令启动一个laucher服务,由laucher服务负责进行主服务的检测,laucher服务在检测后自动退出 */void check_and_restart_service(char* service) {    LOGI("current process pid=",getpid());    char cmdline[200];    sprintf(cmdline, "am startservice --user 0 -n %s", service);    char tmp[200];    sprintf(tmp, "cmd=%s", cmdline);    ExecuteCommandWithPopen(cmdline, tmp, 200);    LOGI( tmp, LOG);}jstring stoJstring(JNIEnv* env, const char* pat) {    jclass strClass = (*env)->FindClass(env, "Ljava/lang/String;");    jmethodID ctorID = (*env)->GetMethodID(env, strClass, "<init>",                                           "([BLjava/lang/String;)V");    jbyteArray bytes = (*env)->NewByteArray(env, strlen(pat));    (*env)->SetByteArrayRegion(env, bytes, 0, strlen(pat), (jbyte*) pat);    jstring encoding = (*env)->NewStringUTF(env, "utf-8");    return (jstring)(*env)->NewObject(env, strClass, ctorID, bytes, encoding);}/** * 判断是否是数字 */int IsNumeric(const char* ccharptr_CharacterList) {    //LOGI("IsNumeric: test.cpp/main: argc=%d",ccharptr_CharacterList);    for (; *ccharptr_CharacterList; ccharptr_CharacterList++)        if (*ccharptr_CharacterList < '0' || *ccharptr_CharacterList > '9')            return 0; // false    return 1; // true}//intCaseSensitive=0大小写不敏感int strcmp_Wrapper(const char *s1, const char *s2, int intCaseSensitive) {    if (intCaseSensitive)        return !strcmp(s1, s2);    else        return !strcasecmp(s1, s2);}//intCaseSensitive=0大小写不敏感int strstr_Wrapper(const char* haystack, const char* needle,                   int intCaseSensitive) {    if (intCaseSensitive)        return (int) strstr(haystack, needle);    else        return (int) strcasestr(haystack, needle);}/** * 通过进程名称获取pid */pid_t GetPIDbyName_implements(const char* cchrptr_ProcessName,                              int intCaseSensitiveness, int intExactMatch) {    char chrarry_CommandLinePath[100];    char chrarry_NameOfProcess[300];    char* chrptr_StringToCompare = NULL;    pid_t pid_ProcessIdentifier = (pid_t) - 1;    struct dirent* de_DirEntity = NULL;    DIR* dir_proc = NULL;    int (*CompareFunction)(const char*, const char*, int);    if (intExactMatch)        CompareFunction = &strcmp_Wrapper;    else        CompareFunction = &strstr_Wrapper;    dir_proc = opendir(PROC_DIRECTORY);    if (dir_proc == NULL) {        perror("Couldn't open the " PROC_DIRECTORY " directory");        return (pid_t) - 2;    }    while ((de_DirEntity = readdir(dir_proc))) {        if (de_DirEntity->d_type == DT_DIR) {            if (IsNumeric(de_DirEntity->d_name)) {                strcpy(chrarry_CommandLinePath, PROC_DIRECTORY);                strcat(chrarry_CommandLinePath, de_DirEntity->d_name);                strcat(chrarry_CommandLinePath, "/cmdline");                FILE* fd_CmdLineFile = fopen(chrarry_CommandLinePath, "rt"); //open the file for reading text                if (fd_CmdLineFile) {                    LOGI("chrarry_NameOfProcess %s", chrarry_NameOfProcess);                    fscanf(fd_CmdLineFile, "%s", chrarry_NameOfProcess); //read from /proc/<NR>/cmdline                    fclose(fd_CmdLineFile); //close the file prior to exiting the routine                    chrptr_StringToCompare = chrarry_NameOfProcess;                    if (CompareFunction(chrptr_StringToCompare,                                        cchrptr_ProcessName, intCaseSensitiveness)) {                        pid_ProcessIdentifier = (pid_t) atoi(                                de_DirEntity->d_name);                        LOGI("processName=%d, pid=%d",cchrptr_ProcessName,pid_ProcessIdentifier);                        closedir(dir_proc);                        return pid_ProcessIdentifier;                    }                }            }        }    }    LOGI("processName=%d, pid=%d",cchrptr_ProcessName,pid_ProcessIdentifier);    closedir(dir_proc);    return pid_ProcessIdentifier;}/** * 检测服务，如果不存在服务则启动 */void check_and_restart_activity(char* service) {    char cmdline[200];    sprintf(cmdline, "am start -n %s", service);    char tmp[200];    sprintf(tmp, "cmd=%s", cmdline);    ExecuteCommandWithPopen(cmdline, tmp, 200);    LOGI( tmp, LOG);}/** * 返回ABI给Java */jstring Java_com_daemonprocess_fork_NativeRuntime_stringFromJNI(JNIEnv* env, jobject thiz) {#if defined(__arm__)#if defined(__ARM_ARCH_7A__)    #if defined(__ARM_NEON__)            #define ABI "armeabi-v7a/NEON"         #else            #define ABI "armeabi-v7a"         #endif#else#define ABI "armeabi"#endif#elif defined(__i386__)    #define ABI "x86"   #elif defined(__mips__)      #define ABI "mips"   #else      #define ABI "unknown"#endif    return (*env)->NewStringUTF(env,                                "Hello from JNI !  Compiled with ABI " ABI ".");}/** * jstring 转 String */char* jstringTostring(JNIEnv* env, jstring jstr) {    char* rtn = NULL;    jclass clsstring = (*env)->FindClass(env, "java/lang/String");    jstring strencode = (*env)->NewStringUTF(env, "utf-8");    jmethodID mid = (*env)->GetMethodID(env, clsstring, "getBytes",                                        "(Ljava/lang/String;)[B");    jbyteArray barr = (jbyteArray)(*env)->CallObjectMethod(env, jstr, mid,                                                           strencode);    jsize alen = (*env)->GetArrayLength(env, barr);    jbyte* ba = (*env)->GetByteArrayElements(env, barr, JNI_FALSE);    if (alen > 0) {        rtn = (char*) malloc(alen + 1);        memcpy(rtn, ba, alen);        rtn[alen] = 0;    }    (*env)->ReleaseByteArrayElements(env, barr, ba, 0);    return rtn;}/** * 查找进程 */pid_t JNICALL Java_com_daemonprocess_fork_NativeRuntime_findProcess(JNIEnv* env,jobject thiz, jstring cchrptr_ProcessName) {    char * rtn = jstringTostring(env, cchrptr_ProcessName);    LOGI("Java_com_daemonprocess_fork_NativeRuntime_findProcess run....ProcessName:%s", rtn);    //return 1;    return GetPIDbyName_implements(rtn, 0, 0); //大小写不敏感 sub串匹配}/** * 启动Service */void Java_com_daemonprocess_fork_NativeRuntime_startService(JNIEnv* env, jobject thiz,jstring cchrptr_ProcessName, jstring sdpath) {    char * rtn = jstringTostring(env, cchrptr_ProcessName); // 得到进程名称    char * sd = jstringTostring(env, sdpath);    LOGI("Java_com_daemonprocess_fork_NativeRuntime_startService run....ProcessName:%s", rtn);    a = rtn;    start(1, rtn, sd);}/** * 关闭Service */JNIEXPORT jint JNICALL Java_com_daemonprocess_fork_NativeRuntime_stopService(JNIEnv* env, jobject thiz) {    LOGI("========exit", "");    exit(0);}/** * service已经断开，重启服务 */JNIEXPORT void JNICALL Java_com_daemonprocess_fork_NativeRuntime_serviceHasDisconnection(JNIEnv* env, jobject thiz){if(srvn != NULL){LOGI("========serviceHasDisconnection serviceprocess--%s", srvn);check_and_restart_service(srvn);}}/** * 启动Activity */void Java_com_daemonprocess_fork_NativeRuntime_startActivity(JNIEnv* env, jobject thiz,jstring activityName) {    char * rtn = jstringTostring(env, activityName);    LOGI("check_and_restart_activity run....activityName:%s", rtn);    check_and_restart_activity(rtn);}JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {    JNIEnv* env = NULL;    jint result = -1;    if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {    return result;    }    LOGI("JNI_OnLoad ......");    return JNI_VERSION_1_4;}
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