從 MIDlet 呼叫 JSP 頁面：HTTP POST 實戰教學

HttpConnection 介面速覽

MIDP 建立在 CLDC 的 Generic Connection Framework 之上，強制支援 HTTP。所有連線均由 Connector.open(url) 建立，回傳對應介面實例。HTTP 連線可設定請求方法、Header，並開啟 I/O 串流。

HttpConnection conn = (HttpConnection) Connector.open(url);
conn.setRequestMethod(HttpConnection.POST);
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
OutputStream os = conn.openOutputStream();
InputStream is = conn.openInputStream();

JSP 伺服端範例 (today.jsp)

<%! String name; %>
<%
    name = request.getParameter("name");
    java.util.Date today = new java.util.Date();
    out.println("Got: " + name);
    out.println("Date&time: " + today);
%>

MIDlet 客戶端完整實作 (InvokeJSPMidlet)

public class InvokeJSPMidlet extends MIDlet implements CommandListener {
    private Display display;
    private TextField nameField;
    private Form form;
    private String url = "https://127.0.0.1:8080/examples/jsp/today.jsp";
    private Command callCmd = new Command("Query", Command.OK, 1);
    private Command clearCmd = new Command("Clear", Command.STOP, 1);
    private String myName;

    public InvokeJSPMidlet() {
        display = Display.getDisplay(this);
        nameField = new TextField("Name:", "", 25, TextField.ANY);
        form = new Form("Invoke JSP");
        form.append(nameField);
        form.addCommand(callCmd);
        form.addCommand(clearCmd);
        form.setCommandListener(this);
    }

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

    void invokeJSP(String url) throws IOException {
        HttpConnection c = null; InputStream is = null; OutputStream os = null;
        StringBuffer buf = new StringBuffer();
        TextBox resultBox = null;
        try {
            c = (HttpConnection) Connector.open(url);
            c.setRequestMethod(HttpConnection.POST);
            c.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            c.setRequestProperty("User-Agent", "Profile/MIDP-1.0 Configuration/CLDC-1.0");
            os = c.openOutputStream();
            os.write(("name=" + myName).getBytes());
            os.flush();
            is = c.openDataInputStream();
            int ch;
            while ((ch = is.read()) != -1) {
                buf.append((char) ch);
            }
            resultBox = new TextBox("Response", buf.toString(), 1024, 0);
            resultBox.setCommandListener(this);
        } finally {
            if (is != null) is.close();
            if (os != null) os.close();
            if (c != null) c.close();
        }
        display.setCurrent(resultBox);
    }

    public void commandAction(Command c, Displayable d) {
        if (c == clearCmd) { destroyApp(true); }
        else if (c == callCmd) {
            myName = nameField.getString();
            try { invokeJSP(url); } catch (IOException ignored) {}
        }
    }
}

關鍵點總結

• POST 請求須設定 Content-Type: application/x-www-form-urlencoded，JSP 才能用 getParameter() 取值。
• 資料以 name=value 格式寫入 OutputStream。
• 若手機瀏覽器不支援 HTML，可改用 XML 回應，MIDlet 端解析 XML 更靈活。