鴻蒙開發(fā)實(shí)戰(zhàn)：【系統(tǒng)服務(wù)管理部件】

簡(jiǎn)介

samgr組件是OpenHarmony的核心組件，提供OpenHarmony系統(tǒng)服務(wù)啟動(dòng)、注冊(cè)、查詢等功能。

系統(tǒng)架構(gòu)

圖 1 系統(tǒng)服務(wù)管理系統(tǒng)架構(gòu)圖

說明

1. samgr服務(wù)接收到sa框架層發(fā)送的注冊(cè)消息，會(huì)在本地緩存中存入系統(tǒng)服務(wù)相關(guān)信息。

   int32_t SystemAbilityManager::AddSystemAbility(int32_t systemAbilityId, const sptr< IRemoteObject >& ability,
       const SAExtraProp& extraProp)
   {
       if (!CheckInputSysAbilityId(systemAbilityId) || ability == nullptr) {
           HILOGE("AddSystemAbilityExtra input params is invalid.");
           return ERR_INVALID_VALUE;
       }
       {
           unique_lock< shared_mutex > writeLock(abilityMapLock_);
           auto saSize = abilityMap_.size();
           if (saSize >= MAX_SERVICES) {
               HILOGE("map size error, (Has been greater than %zu)", saSize);
               return ERR_INVALID_VALUE;
           }
           SAInfo saInfo;
           saInfo.remoteObj = ability;
           saInfo.isDistributed = extraProp.isDistributed;
           saInfo.capability = extraProp.capability;
           saInfo.permission = Str16ToStr8(extraProp.permission);
           abilityMap_[systemAbilityId] = std::move(saInfo);
           HILOGI("insert %{public}d. size : %{public}zu", systemAbilityId, abilityMap_.size());
       }
       RemoveCheckLoadedMsg(systemAbilityId);
       if (abilityDeath_ != nullptr) {
           ability- >AddDeathRecipient(abilityDeath_);
       }
   
       u16string strName = Str8ToStr16(to_string(systemAbilityId));
       if (extraProp.isDistributed && dBinderService_ != nullptr) {
           dBinderService_- >RegisterRemoteProxy(strName, systemAbilityId);
           HILOGD("AddSystemAbility RegisterRemoteProxy, serviceId is %{public}d", systemAbilityId);
       }
       if (systemAbilityId == SOFTBUS_SERVER_SA_ID && !isDbinderStart_) {
           if (dBinderService_ != nullptr && rpcCallbackImp_ != nullptr) {
               bool ret = dBinderService_- >StartDBinderService(rpcCallbackImp_);
               HILOGI("start result is %{public}s", ret ? "succeed" : "fail");
               isDbinderStart_ = true;
           }
       }
       SendSystemAbilityAddedMsg(systemAbilityId, ability);
       return ERR_OK;
   }
   

2. 對(duì)于本地服務(wù)而言，samgr服務(wù)接收到sa框架層發(fā)送的獲取消息，會(huì)通過服務(wù)id，查找到對(duì)應(yīng)服務(wù)的代理對(duì)象，然后返回給sa框架。

   sptr< IRemoteObject > SystemAbilityManager::CheckSystemAbility(int32_t systemAbilityId)
   {
       if (!CheckInputSysAbilityId(systemAbilityId)) {
           HILOGW("CheckSystemAbility CheckSystemAbility invalid!");
           return nullptr;
       }
   
       shared_lock< shared_mutex > readLock(abilityMapLock_);
       auto iter = abilityMap_.find(systemAbilityId);
       if (iter != abilityMap_.end()) {
           HILOGI("found service : %{public}d.", systemAbilityId);
           return iter- >second.remoteObj;
       }
       HILOGI("NOT found service : %{public}d", systemAbilityId);
       return nullptr;
   }
   

3. 動(dòng)態(tài)加載系統(tǒng)服務(wù)進(jìn)程及SystemAbility, 系統(tǒng)進(jìn)程無需開機(jī)啟動(dòng)，而是在SystemAbility被訪問的時(shí)候按需拉起，并加載指定SystemAbility。
   3.1 繼承SystemAbilityLoadCallbackStub類，并覆寫OnLoadSystemAbilitySuccess(int32_t systemAbilityId, const sptr& remoteObject)、OnLoadSystemAbilityFail(int32_t systemAbilityId)方法。

   class OnDemandLoadCallback : public SystemAbilityLoadCallbackStub {
   public:
       void OnLoadSystemAbilitySuccess(int32_t systemAbilityId, const sptr< IRemoteObject >& remoteObject) override;
       void OnLoadSystemAbilityFail(int32_t systemAbilityId) override;
   };
   
   void OnDemandLoadCallback::OnLoadSystemAbilitySuccess(int32_t systemAbilityId,
       const sptr< IRemoteObject >& remoteObject) // systemAbilityId為指定加載的SAID，remoteObject為指定systemAbility的代理對(duì)象
   {
       cout < < "OnLoadSystemAbilitySuccess systemAbilityId:" < < systemAbilityId < < " IRemoteObject result:" < <
           ((remoteObject != nullptr) ? "succeed" : "failed") < < endl;
   }
   
   void OnDemandLoadCallback::OnLoadSystemAbilityFail(int32_t systemAbilityId) // systemAbilityId為指定加載的SAID
   {
       cout < < "OnLoadSystemAbilityFail systemAbilityId:" < < systemAbilityId < < endl;
   }
   

   3.2 調(diào)用samgr提供的動(dòng)態(tài)加載接口LoadSystemAbility(int32_t systemAbilityId, const sptr& callback)。

   // 構(gòu)造步驟1的SystemAbilityLoadCallbackStub子類的實(shí)例
   sptr< OnDemandLoadCallback > loadCallback_ = new OnDemandLoadCallback();
   // 調(diào)用LoadSystemAbility方法
   sptr< ISystemAbilityManager > sm = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
   if (sm == nullptr) {
       cout < < "GetSystemAbilityManager samgr object null!" < < endl;
       return;
   }
   int32_t result = sm- >LoadSystemAbility(systemAbilityId, loadCallback_);
   if (result != ERR_OK) {
       cout < < "systemAbilityId:" < < systemAbilityId < < " load failed, result code:" < < result < < endl;
       return;
   }
   

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說明：
1.LoadSystemAbility方法調(diào)用成功后，指定SystemAbility加載成功后會(huì)觸發(fā)回調(diào)OnLoadSystemAbilitySuccess，加載失敗觸發(fā)回調(diào)OnLoadSystemAbilityFail。
2.動(dòng)態(tài)加載的進(jìn)程cfg文件不能配置為開機(jī)啟動(dòng)，需指定"ondemand" : true, 示例如下:

{
  "services" : [{
          "name" : "listen_test",
          "path" : ["/system/bin/sa_main", "/system/profile/listen_test.json"],
          "ondemand" : true,
          "uid" : "system",
          "gid" : ["system", "shell"]
      }   
  ]
}

3.LoadSystemAbility方法適用于動(dòng)態(tài)加載場(chǎng)景，其他獲取SystemAbility場(chǎng)景建議使用CheckSystemAbility方法。
4.cfg里進(jìn)程名稱需要與SA的配置json文件里進(jìn)程名保持一致

審核編輯 黃宇