获取或显示在提供的 Callback 中请求的信息。

为了获取或显示请求的信息，handle 方法实现检查传入的 Callback 对象的实例.下面提供的例子是对 handle 方法实现的示范。此例子代码只用来作为指导。为了简单起见，省去了很多细节(包括适当的错误处理)。

public void handle(Callback[] callbacks)

throws IOException, UnsupportedCallbackException {

for (int i = 0; i < callbacks.length; i++) {

if (callbacks[i] instanceof TextOutputCallback) {

// display the message according to the specified type

TextOutputCallback toc = (TextOutputCallback)callbacks[i];

switch (toc.getMessageType()) {

case TextOutputCallback.INFORMATION:

System.out.println(toc.getMessage());

break;

case TextOutputCallback.ERROR:

System.out.println("ERROR: " + toc.getMessage());

break;

case TextOutputCallback.WARNING:

System.out.println("WARNING: " + toc.getMessage());

break;

default:

throw new IOException("Unsupported message type: " +

toc.getMessageType());

}

} else if (callbacks[i] instanceof NameCallback) {

// prompt the user for a username

NameCallback nc = (NameCallback)callbacks[i];

// ignore the provided defaultName

System.err.print(nc.getPrompt());

System.err.flush();

nc.setName((new BufferedReader

(new InputStreamReader(System.in))).readLine());

} else if (callbacks[i] instanceof PasswordCallback) {

// prompt the user for sensitive information

PasswordCallback pc = (PasswordCallback)callbacks[i];

System.err.print(pc.getPrompt());

System.err.flush();

pc.setPassword(readPassword(System.in));

} else {

throw new UnsupportedCallbackException

(callbacks[i], "Unrecognized Callback");

}

}

}

// Reads user password from given input stream.

private char[] readPassword(InputStream in) throws IOException {

// insert code to read a user password from the input stream

}