OpenHarmony系统服务的核心组件

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

目录

/foundation/distributedschedule
├── 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

1. 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& ability,
    const SAExtraProp& extraProp)
{
    if (!CheckInputSysAbilityId(systemAbilityId) || ability == nullptr) {
        HILOGE("AddSystemAbilityExtra input params is invalid.");
        return ERR_INVALID_VALUE;
    }
    {
        unique_lock 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. 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 SystemAbilityManager::CheckSystemAbility(int32_t systemAbilityId)
{
    if (!CheckInputSysAbilityId(systemAbilityId)) {
        HILOGW("CheckSystemAbility CheckSystemAbility invalid!");
        return nullptr;
    }

    shared_lock 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. 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& remoteObject) override;
    void OnLoadSystemAbilityFail(int32_t systemAbilityId) override;
};

void OnDemandLoadCallback::OnLoadSystemAbilitySuccess(int32_t systemAbilityId,
    const sptr& 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 loadCallback_ = new OnDemandLoadCallback();
// 调用LoadSystemAbility方法
sptr 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.xml"],
        "ondemand" : true,
        "uid" : "system",
        "gid" : ["system", "shell"]
        }
    ]
}