J2ME 調用 Web Service 實戰：JSR 172 (JAX-RPC) 完整流程

背景

JSR 172 為 J2ME 提供 **JAX-RPC 子集** (Stub-based 調用) + **SAX/StAX 解析器**，支援 SOAP 1.1 over HTTP/HTTPS。需 MIDP 2.0 + CLDC 1.1 + 設備廠商實現 (WTK 2.2+ 內建，S60 3rd/FP1+ 真機支援)。

架構選型

JSR 172 完整流程 (以用戶登錄為例)

1. 獲取 WSDL

https://example.com/ws/auth?wsdl

2. 生成 Stub (WTK wscompile / Ant 任務)

wscompile -gen:client -d generated -classpath %WTK_HOME%\lib\j2mews.jar -f:wsi -features:documentliteral config.xml

config.xml 指定 WSDL 位置、包名、服務名。生成：AuthService_Stub、AuthServiceIF、序列化器類。

3. MIDlet 調用代碼

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.xml.rpc.*;
import java.rmi.*;
import generated.*;

public class WSLoginMidlet extends MIDlet implements CommandListener {
    private Display display;
    private Form form;
    private TextField tfUser, tfPass;
    private Command cmdLogin, cmdExit;
    private AuthServiceIF service;

    public WSLoginMidlet() {
        display = Display.getDisplay(this);
        form = new Form("WebService 登錄");
        tfUser = new TextField("用戶名", "", 20, TextField.ANY);
        tfPass = new TextField("密碼", "", 20, TextField.PASSWORD);
        cmdLogin = new Command("登錄", Command.OK, 1);
        cmdExit = new Command("退出", Command.EXIT, 1);
        form.append(tfUser); form.append(tfPass);
        form.addCommand(cmdLogin); form.addCommand(cmdExit);
        form.setCommandListener(this);

        // 初始化 Stub (耗時操作，放線程)
        new Thread(() -> {
            try {
                AuthService_Stub stub = new AuthService_Stub();
                stub._setProperty(Stub.ENDPOINT_ADDRESS_PROPERTY,
                    "https://example.com/ws/auth");
                service = stub;
            } catch (Exception e) { e.printStackTrace(); }
        }).start();
    }

    protected void startApp() { display.setCurrent(form); }
    protected void pauseApp() {}
    protected void destroyApp(boolean u) {}

    public void commandAction(Command c, Displayable d) {
        if (c == cmdExit) { notifyDestroyed(); return; }
        if (c == cmdLogin) { new Thread(this::doLogin).start(); }
    }

    private void doLogin() {
        if (service == null) { showAlert("服務未就緒"); return; }
        try {
            String token = service.login(tfUser.getString(), tfPass.getString());
            // token 非空即成功
            showAlert("登錄成功", "Token: " + token);
        } catch (RemoteException e) {
            showAlert("網絡錯誤", e.getMessage());
        } catch (Exception e) {
            showAlert("異常", e.toString());
        }
    }

    private void showAlert(String title, String msg) {
        Alert a = new Alert(title, msg, null, AlertType.INFO);
        a.setTimeout(Alert.FOREVER);
        display.setCurrent(a, form);
    }
    private void showAlert(String msg) { showAlert("提示", msg); }
}

4. 打包與部署

• 將生成的 generated/ 所有類複製進專案 src/。
• 專案屬性 → API Selection → 勾選 J2ME Web Services (JSR 172)。
• ProGuard 配置保留 Stub：-keep class generated.** { *; }。
• 構建 JAD/JAR → OTA 部署真機測試。

常見坑點與對策

現代啟示

JSR 172 的 **Stub 生成、序列化映射、異步調用** 模式直接映射到現代：

• Android: Retrofit + OkHttp + Moshi/Gson (介面定義 + 註解生成實現)
• iOS: URLSession + Codable / Alamofire
• 跨平台: gRPC (Protobuf) / GraphQL (Apollo) / tRPC

核心思想不變：**契約優先、代碼生成、類型安全、網絡細節封裝**。