NameSender程序片
时间:2007-05-29 yycnet.yeah.net yyc译
正如早先指出的那样，程序片必须用Java 1.0编写，使其能与绝大多数的浏览器适应。也正是由于这个原因，我们产生的类数量应尽可能地少。所以我们在这儿不考虑使用前面设计好的Dgram类，而将数据报的所有维护工作都转到代码行中进行。此外，程序片要用一个线程监视由服务器传回的响应信息，而非实现Runnable接口，用集成到程序片的一个独立线程来做这件事情。当然，这样做对代码的可读性不利，但却能产生一个单类（以及单个服务器请求）程序片：
//: NameSender.java
// An applet that sends an email address
// as a datagram, using Java 1.02.
import java.awt.*;
import java.applet.*;
import java.net.*;
import java.io.*;
public class NameSender extends Applet
implements Runnable {
private Thread pl = null;
private Button send = new Button(
"Add email address to mailing list");
private TextField t = new TextField(
"type your email address here", 40);
private String str = new String();
private Label
l = new Label(), l2 = new Label();
private DatagramSocket s;
private InetAddress hostAddress;
private byte[] buf =
new byte[NameCollector.BUFFER_SIZE];
private DatagramPacket dp =
new DatagramPacket(buf, buf.length);
private int vcount = 0;
public void init() {
setLayout(new BorderLayout());
Panel p = new Panel();
p.setLayout(new GridLayout(2, 1));
p.add(t);
p.add(send);
add("North", p);
Panel labels = new Panel();
labels.setLayout(new GridLayout(2, 1));
labels.add(l);
labels.add(l2);
add("Center", labels);
try {
// Auto-assign port number:
s = new DatagramSocket();
hostAddress = InetAddress.getByName(
getCodeBase().getHost());
} catch(UnknownHostException e) {
l.setText("Cannot find host");
} catch(SocketException e) {
l.setText("Can''t open socket");
}
l.setText("Ready to send your email address");
}
public boolean action (Event evt, Object arg) {
if(evt.target.equals(send)) {
if(pl != null) {
// pl.stop(); Deprecated in Java 1.2
Thread remove = pl;
pl = null;
remove.interrupt();
}
l2.setText("");
// Check for errors in email name:
str = t.getText().toLowerCase().trim();
if(str.indexOf('' '') != -1) {
l.setText("Spaces not allowed in name");
return true;
}
if(str.indexOf('','') != -1) {
l.setText("Commas not allowed in name");
return true;
}
if(str.indexOf(''@'') == -1) {
l.setText("Name must include ''@''");
l2.setText("");
return true;
}
if(str.indexOf(''@'') == 0) {
l.setText("Name must preceed ''@''");
l2.setText("");
return true;
}
String end =
str.substring(str.indexOf(''@''));
if(end.indexOf(''.'') == -1) {
l |
