A built-in JavaScript (JS) service is a JS service that is installed with the webOS OSE platform at build time.
Downloadable vs. Built-In
In webOS OSE, apps and services can be classified into two types based on how they are installed on the target device.
Downloadable apps/services are installed by the appinstalld service. The appinstalld service creates webOS configurations based on files created by developers. (such as trust level) Developers can modify only certain parts of the app/service settings.
Built-in apps/services are built and installed by developers. Developers can customize app/service’s configurations to suit their needs.
This tutorial shows a step-by-step guide for creating a built-in JS service from scratch.
Note In this section, there are a lot of contents about modifying recipe files. For more about the recipe files, refer to the Yocto Project Reference Manual.
This section briefly explains the sample codes used in this tutorial.
com.example.service.js.bb
com.example.service.js.bb
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#Copyright (c) 2020-2022LGElectronics, Inc.
SUMMARY="JS Service Sample"AUTHOR="Author's name <Author's e-mail>"LICENSE="Apache-2.0"LIC_FILES_CHKSUM="file://${COMMON_LICENSE_DIR}/Apache-2.0;md5=89aea4e17d99a7cacdbeed46a0096b10"WEBOS_VERSION="0.0.1"PR="r0"inheritwebos_componentinheritwebos_submissionsinheritwebos_cmakeinheritwebos_system_busFILES:${PN}+="${webos_servicesdir}/${PN}/*"
A brief explanation of the above file:
Line (1~6): Basic descriptions of the component.
Line (8): The version of the component. Every webOS component must contain this.
Line (9): Revision version of the recipe. Each recipe requires a counter to track its modification history. Make sure that you increment the version when you edit the recipe, unless you only change the value of the WEBOS_VERSION field or comments.
Line (11~14): Inherits from other classes.
Line (11): Inherits common functions of webOS. For all components of webOS, this entry is required.
Line (12): Inherits webos_submissions to check the version information set correctly. This field is required if you develop your component on a local repository.
Line (13): Instructs OpenEmbedded that the component uses CMake for configuration, which is the preferred choice for webOS components.
Line (14): Inherits webos_system_bus to register component as a service and install LS2 configuration files.
Line (14): Appends the list of files and directories that are placed in a package. Adds the files under /usr/palm/service/com.example.service.js directory for packaging.
webos-local.conf
webos-local.conf
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INHERIT += "externalsrc"
EXTERNALSRC:pn-<SERVICE ID> = "<PATH TO THE SERVICE DIRECTORY>/"
EXTERNALSRC_BUILD:pn-<SERVICE ID> = "<PATH TO THE SERVICE DIRECTORY>/build/"
PR:append:pn-<SERVICE ID> =".local0"
A brief explanation of the above file:
Line (1): Inherits the externalsrc.bbclass file.
Line (2): Specifies the path to the service directory.
<SERVICE ID>: The service ID specified in the CMakeLists.txt file.
<PATH TO THE SERVICE DIRECTORY>: The root directory of the service where the CMakeLists.txt file is located. You must use the absolute path.
Line (3): Specifies the build directory. The build directory is located under the service directory.
Line (4): The revision for local source builds. This line is optional.
file/sysbus/*
These files are related to Access Control Group (ACG). See Security Guide.
CMakeLists.txt
CMake is a tool for supporting cross-platform build. Developers configure prerequisites and build steps in CMakeLists.txt, and then CMake reads this file, creates the build system, and builds the project.
cmake_minimum_required(VERSION2.8.7)project(com.example.service.jsNONE)set(CMAKE_BUILD_TYPEDebug)include(webOS/webOS)webos_modules_init(163)webos_component(001)set(INSTALL_DIR${WEBOS_INSTALL_WEBOS_SERVICESDIR}/${CMAKE_PROJECT_NAME})#install necessary files to destination directory
install(DIRECTORY.DESTINATION${INSTALL_DIR}USE_SOURCE_PERMISSIONSPATTERN"*~"EXCLUDEPATTERN"CMake*"EXCLUDEPATTERN"build*"EXCLUDEPATTERN"oe-*"EXCLUDEPATTERN"*.lock"EXCLUDEPATTERN"*.in"EXCLUDEPATTERN"files"EXCLUDEPATTERN"README.md"EXCLUDE)webos_build_system_bus_files()
A brief explanation of the above file:
Line (1): Sets the minimum required version of CMake for a project.
Line (2): Sets a name for the project. The second value (NONE) disables all checks for any programming language.
Line (5): Includes webOS modules for the build.
Line (7): Specifies the “cmake-modules-webos” version.
Line (8): Specifies webos_component with the component version to use webOS variables for the standard system paths. It commonly follows three digit versioning scheme.
Line (10): Sets a path to install the app. WEBOS_INSTALL_WEBOS_APPLICATIONSDIR is set to /usr/palm/applications/ by default.
Line (12~21): Installs required files to INSTALL_DIR on the target device. Excludes the files that do not need to be installed on the target device.
Line (23): Installs the LS2 configuration files (/files/sysbus) to the target.
This file provides overall information about the service.
Caution
If the README.md file is missing, a build error occurs.
Make sure the ‘Summary’ section is a single line. Even any whitespace at the line above the ‘Description’ section is considered a part of the summary and can cause the build to fail.
Summary
-------
js service sample
Description
-----------
js service sample
How to Build on Linux
---------------------
## Dependencies
Below are the tools and libraries (and their minimum versions) required to build sample program:
* cmake (version required by cmake-modules-webos)
## Building
$ cd build-webos
$ source oe-init-build-env
$ bitbake com.example.service.js
Copyright and License Information
=================================
Unless otherwise specified, all content, including all source code files and
documentation files in this repository are:
Copyright (c) 2020 LG Electronics, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
SPDX-License-Identifier: Apache-2.0
var Service = require('webos-service');
// Register com.example.service.js
var service =new Service("com.example.service.js");
// A method that always returns the same value
service.register("hello", function(message) {
console.log("[com.example.service.js]", "SERVICE_METHOD_CALLED:hello");
message.respond({
answer:"Hello, JS Service!!" });
});
// Call another service
service.register("time", function(message) {
service.call("luna://com.webos.service.systemservice/clock/getTime", {}, function(m2) {
console.log("[com.example.service.js]", "SERVICE_METHOD_CALLED:com.webos.service.systemservice/clock/getTime");
const response ="You appear to have your UTC set to: "+ m2.payload.utc;
message.respond({message: response});
});
});
A brief explanation of the above file:
Line(1): Loads the webos-service module.
Line(4): Registers the service.
Line(7~12): Registers the hello method that responds to a request with a “Hello, JS Service!!” message
Line(15~21): Registers the time method. This method gets the value of UTC information from the response received by calling com.webos.service.systemservice/clock/getTime method.
