鸿蒙开发实战：【系统服务管理部件】

简介

samgr组件是OpenHarmony的核心组件，提供OpenHarmony系统服务启动、注册、查询等功能。

系统架构

图 1 系统服务管理系统架构图

/foundation/systemabilitymgr
├── samgr
│   ├── bundle.json  # 部件描述及编译文件
│   ├── frameworks   # 框架实现存在目录
│   ├── interfaces   # 接口目录
│   ├── services     # 组件服务端目录
│   ├── test         # 测试代码存放目录
│   ├── utils        # 工具类目录

说明

samgr服务接收到sa框架层发送的注册消息，会在本地缓存中存入系统服务相关信息。

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;
}

对于本地服务而言，samgr服务接收到sa框架层发送的获取消息，会通过服务id，查找到对应服务的代理对象，然后返回给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;
}

动态加载系统服务进程及SystemAbility, 系统进程无需开机启动，而是在SystemAbility被访问的时候按需拉起，并加载指定SystemAbility。
3.1 继承SystemAbilityLoadCallbackStub类，并覆写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为指定加载的SAID，remoteObject为指定systemAbility的代理对象
{cout << "OnLoadSystemAbilitySuccess systemAbilityId:" << systemAbilityId << " IRemoteObject result:" <<((remoteObject != nullptr) ? "succeed" : "failed") << endl;
}void OnDemandLoadCallback::OnLoadSystemAbilityFail(int32_t systemAbilityId) // systemAbilityId为指定加载的SAID
{cout << "OnLoadSystemAbilityFail systemAbilityId:" << systemAbilityId << endl;
}

3.2 调用samgr提供的动态加载接口LoadSystemAbility(int32_t systemAbilityId, const sptr& callback)。

// 构造步骤1的SystemAbilityLoadCallbackStub子类的实例
sptr<OnDemandLoadCallback> loadCallback_ = new OnDemandLoadCallback();
// 调用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;
}

说明：
1.LoadSystemAbility方法调用成功后，指定SystemAbility加载成功后会触发回调OnLoadSystemAbilitySuccess，加载失败触发回调OnLoadSystemAbilityFail。
2.动态加载的进程cfg文件不能配置为开机启动，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方法适用于动态加载场景，其他获取SystemAbility场景建议使用CheckSystemAbility方法。
4.cfg里进程名称需要与SA的配置json文件里进程名保持一致

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