JS FA调用Java PA机制
使用兼容JS的类Web开发范式的方舟开发框架提供了JS FA（Feature Ability）调用Java PA（Particle Ability）的机制，该机制提供了一种通道来传递方法调用、处理数据返回以及订阅事件上。
当前提供Ability和Internal Ability两种调用方式。
- Ability：拥有独立的Ability生命周期，FA使用远端进程通信拉起并请求PA服务，适用于基本服务供多FA调用或者服务在后台独立运行的场景。
- Internal Ability：与FA共进程，采用内部函数调用的方式和FA进行通信，适用于对服务响应时延要求较高的场景。该方式下PA不支持其他FA访问调用。
对于Internal Ability调用方式的开发，可以使用工具自动生成代码（自动生成下篇文章详解），提高开发效率。
JS端与Java端通过bundleName和abilityName来进行关联。在系统收到JS调用请求后，根据开发者在JS接口中设置的参数来选择对应的处理方式。开发者在onRemoteRequest()中实现PA提供的业务逻辑。
FA调用PA接口
FA端提供以下三个JS接口：
- FeatureAbility.callAbility(OBJECT)：调用PA能力。
- FeatureAbility.subscribeAbilityEvent(OBJECT, Function)：订阅PA能力。
- FeatureAbility.unsubscribeAbilityEvent(OBJECT)：取消订阅PA能力。
PA端提供以下两类接口：
- IRemoteObject.onRemoteRequest(int, MessageParcel, MessageParcel, MessageOption)：Ability调用方式，FA使用远端进程通信拉起并请求PA服务。
- AceInternalAbility.AceInternalAbilityHandler.onRemoteRequest(int, MessageParcel, MessageParcel, MessageOption)：Internal Ability调用方式，采用内部函数调用的方式和FA进行通信。
FA调用PA常见问题
- callAbility返回报错："Internal ability not register."
返回该错误说明JS接口调用请求未在系统中找到对应的InternalAbilityHandler进行处理，因此需要检查以下几点是否正确执行：
- 在AceAbility继承类中对AceInternalAbility继承类执行了register方法，具体注册可参考Internal Ability的示例代码。
- JS侧填写的bundleName和abilityName与AceInternalAbility继承类构造函数中填写的名称保持相同，大小写敏感。
- 检查JS端填写的abilityType（0：Ability; 1：Internal Ability），确保没有将AbilityType缺省或误填写为Ability方式。
Ability和Internal Ability是两种不同的FA调用PA的方式。
Ability和InternalAbility差异项
| 差异项 | Ability | InternalAbility |
|---|---|---|
| JS端（abilityType） | 0 | 1 |
| 是否需要在config.json的abilities中为PA添加声明 | 需要（有独立的生命周期） | 不需要（和FA共生命周期） |
| 是否需要在FA中注册 | 不需要 | 需要 |
| 继承的类 | ohos.aafwk.ability.Ability | ohos.ace.ability.AceInternalAbility |
| 是否允许被其他FA访问调用 | 是 | 否 |
- FeatureAbility.callAbility中syncOption参数说明：
- 对于JS FA侧，返回的结果都是Promise对象，因此无论该参数取何值，都采用异步方式等待PA侧响应。
- 对于JAVA PA侧，在Internal Ability方式下收到FA的请求后，根据该参数的取值来选择：通过同步的方式获取结果后返回；或者异步执行PA逻辑，获取结果后使用remoteObject.sendRequest的方式将结果返回FA。
- 使用await方式调用时IDE编译报错，需引入babel-runtime/regenerator。
示例参考
JS端调用FeatureAbility接口，传入两个Number参数，Java端接收后返回两个数的和。
JS FA应用的JS模块(entry/src/main)的典型开发目录结构如下：
- FA JavaScript端
使用Internal Ability方式时，需要将对应的action.abilityType值改为ABILITY_TYPE_INTERNAL。
// abilityType: 0-Ability; 1-Internal Ability
const ABILITY_TYPE_EXTERNAL = 0;
const ABILITY_TYPE_INTERNAL = 1;
// syncOption(Optional, default sync): 0-Sync; 1-Async
const ACTION_SYNC = 0;
const ACTION_ASYNC = 1;
const ACTION_MESSAGE_CODE_PLUS = 1001;
export default {plus: async function() {var actionData = {};actionData.firstNum = 1024;actionData.secondNum = 2048;var action = {};action.bundleName = 'com.example.hiaceservice';action.abilityName = 'com.example.hiaceservice.ComputeServiceAbility';action.messageCode = ACTION_MESSAGE_CODE_PLUS;action.data = actionData;action.abilityType = ABILITY_TYPE_EXTERNAL;action.syncOption = ACTION_SYNC;var result = await FeatureAbility.callAbility(action);var ret = JSON.parse(result);if (ret.code == 0) {console.info('plus result is:' + JSON.stringify(ret.abilityResult));} else {console.error('plus error code:' + JSON.stringify(ret.code));}}
}- PA端（Ability方式）
在java目录下新建一个Service Ability，文件命名为ComputeServiceAbility.java
package com.example.hiaceservice;// ohos相关接口包
import ohos.aafwk.ability.Ability;
import ohos.aafwk.content.Intent;
import ohos.hiviewdfx.HiLog;
import ohos.hiviewdfx.HiLogLabel;
import ohos.rpc.IRemoteBroker;
import ohos.rpc.IRemoteObject;
import ohos.rpc.RemoteObject;
import ohos.rpc.MessageParcel;
import ohos.rpc.MessageOption;
import ohos.utils.zson.ZSONObject;import java.util.HashMap;
import java.util.Map;public class ComputeServiceAbility extends Ability {// 定义日志标签private static final HiLogLabel LABEL = new HiLogLabel(HiLog.LOG_APP, 0, "MY_TAG");private MyRemote remote = new MyRemote();// FA在请求PA服务时会调用Ability.connectAbility连接PA，连接成功后，需要在onConnect返回一个remote对象，供FA向PA发送消息@Overrideprotected IRemoteObject onConnect(Intent intent) {super.onConnect(intent);return remote.asObject();}class MyRemote extends RemoteObject implements IRemoteBroker {private static final int SUCCESS = 0;private static final int ERROR = 1;private static final int PLUS = 1001; MyRemote() {super("MyService_MyRemote");}@Overridepublic boolean onRemoteRequest(int code, MessageParcel data, MessageParcel reply, MessageOption option) {switch (code) {case PLUS: {String dataStr = data.readString();RequestParam param = new RequestParam();try { param = ZSONObject.stringToClass(dataStr, RequestParam.class);} catch (RuntimeException e) { HiLog.error(LABEL, "convert failed.");}// 返回结果当前仅支持String，对于复杂结构可以序列化为ZSON字符串上报Map<String, Object> result = new HashMap<String, Object>();result.put("code", SUCCESS);result.put("abilityResult", param.getFirstNum() + param.getSecondNum());reply.writeString(ZSONObject.toZSONString(result));break;}default: {Map<String, Object> result = new HashMap<String, Object>();result.put("abilityError", ERROR);reply.writeString(ZSONObject.toZSONString(result));return false;}}return true;}@Overridepublic IRemoteObject asObject() {return this;}}
}请求参数代码：
RequestParam.java
public class RequestParam {private int firstNum;private int secondNum;public int getFirstNum() {return firstNum;}public void setFirstNum(int firstNum) {this.firstNum = firstNum;}public int getSecondNum() {return secondNum;}public void setSecondNum(int secondNum) {this.secondNum = secondNum;}
}PA端（Internal Ability方式）
在java目录下新建一个Service Ability，文件命名为ComputeInternalAbility.java
package com.example.hiaceservice;// ohos相关接口包
import ohos.ace.ability.AceInternalAbility;
import ohos.app.AbilityContext;
import ohos.hiviewdfx.HiLog;
import ohos.hiviewdfx.HiLogLabel;
import ohos.rpc.IRemoteObject;
import ohos.rpc.MessageOption;
import ohos.rpc.MessageParcel;
import ohos.rpc.RemoteException;
import ohos.utils.zson.ZSONObject;import java.util.HashMap;
import java.util.Map;public class ComputeInternalAbility extends AceInternalAbility {private static final String BUNDLE_NAME = "com.example.hiaceservice";private static final String ABILITY_NAME = "com.example.hiaceservice.ComputeInternalAbility";private static final int SUCCESS = 0;private static final int ERROR = 1;private static final int PLUS = 1001;// 定义日志标签private static final HiLogLabel LABEL = new HiLogLabel(HiLog.LOG_APP, 0, "MY_TAG");private static ComputeInternalAbility instance;private AbilityContext abilityContext;// 如果多个Ability实例都需要注册当前InternalAbility实例，需要更改构造函数，设定自己的bundleName和abilityNamepublic ComputeInternalAbility() {super(BUNDLE_NAME, ABILITY_NAME);}public boolean onRemoteRequest(int code, MessageParcel data, MessageParcel reply, MessageOption option) {switch (code) {case PLUS: {String dataStr = data.readString();RequestParam param = new RequestParam();try { param = ZSONObject.stringToClass(dataStr, RequestParam.class);} catch (RuntimeException e) { HiLog.error(LABEL, "convert failed.");}// 返回结果当前仅支持String，对于复杂结构可以序列化为ZSON字符串上报Map<String, Object> result = new HashMap<String, Object>();result.put("code", SUCCESS);result.put("abilityResult", param.getFirstNum() + param.getSecondNum());// SYNCif (option.getFlags() == MessageOption.TF_SYNC) {reply.writeString(ZSONObject.toZSONString(result));} else {// ASYNCMessageParcel responseData = MessageParcel.obtain();responseData.writeString(ZSONObject.toZSONString(result));IRemoteObject remoteReply = reply.readRemoteObject();try {remoteReply.sendRequest(0, responseData, MessageParcel.obtain(), new MessageOption());} catch (RemoteException exception) {return false;} finally {responseData.reclaim();}}break;}default: {Map<String, Object> result = new HashMap<String, Object>();result.put("abilityError", ERROR);reply.writeString(ZSONObject.toZSONString(result));return false;}}return true;}/*** Internal ability 注册接口。*/public static void register(AbilityContext abilityContext) {instance = new ComputeInternalAbility();instance.onRegister(abilityContext);}private void onRegister(AbilityContext abilityContext) {this.abilityContext = abilityContext;this.setInternalAbilityHandler((code, data, reply, option) -> {return this.onRemoteRequest(code, data, reply, option);});}/*** Internal ability 注销接口。*/public static void unregister() {instance.onUnregister();}private void onUnregister() {abilityContext = null;this.setInternalAbilityHandler(null);}
}Internal Ability注册：修改继承AceAbility工程中的代码
public class MainAbility extends AceAbility {@Overridepublic void onStart(Intent intent) {// 注册, 如果需要在Page初始化(onInit或之前)时调用AceInternalAbility的能力，注册操作需要在super.onStart之前进行ComputeInternalAbility.register(this);...super.onStart(intent);}@Override public void onStop() {// 注销ComputeInternalAbility.unregister(); super.onStop();}
}
