mailconnection.java

J2ME程序设计实例教程的源码

import javax.microedition.io.SocketConnection;
import javax.microedition.io.Connector;
import java.io.;

/**
 * 该类实现了到邮件服务器的连接，提供了send、receive等方法。
 */
public class MailConnection {
    //
    private static final byte CR = 0x0D;    //回车
    private static final byte LF = 0x0A;    //换行
    private static final byte[] CRLF = {CR, LF};
    private SocketConnection socket;        //套接字
    private OutputStream os;        
    private InputStream is;
    private byte[] buffer = new byte[128];  //读取数据的缓冲区
    
    //构造方法，创建一个到host:port的套接字连接
    public MailConnection(String host, int port) throws IOException {
        socket = (SocketConnection)Connector.open("socket://" + host + ":" + port);
        os = socket.openOutputStream();
        is = socket.openInputStream();
    }
    
    //关闭连接
    public void close() throws IOException {
        if(socket != null) {
            socket.close();
            socket = null;
        }
    }
    
    //检测是否连接到服务器
    public boolean isConnection() {
        return socket != null;
    }
    
    //发送字符串s到服务器
    public void send(String s) throws IOException {
        byte[] bytes = s.getBytes();
        int len = bytes.length;
        if(len == 0) {
            os.write(CRLF, 0, 2);
        }
        else {
            int i = 0;
            int j = i;
            while(i < len) {
                while(j<len && bytes[j] != CR && bytes[j] != LF) {
                    j++;
                }
                
                os.write(bytes, i, j-i);
                os.write(CRLF, 0, 2);
                
                if(j < len-1 && bytes[j] == CR && bytes[j+1] == LF) {
                    j++;
                }
                i = ++j;
            }
        }
    }
    
    //接收服务器返回的字符串，字符串以CRLF为结束标志。
    public String receive() throws IOException {
        boolean stop = false;
        int n = -1;
        StringBuffer result = new StringBuffer();
        while(!stop) {
            int count = 0;
            while(true) {
                n = is.read(buffer, count, 1);  //读取一个字节
                if(n == -1) {   //
                    try {
                        close();    //关闭连接
                    }
                    catch(IOException ioe) {
                        //
                    }
                    throw new IOException("连接已经关闭");
                }
                else if(n == 0) {
                    Thread.yield();//暂停当前线程，其他线程获得执行的机会。
                }
                else {  //
                    byte b = buffer[count];
                    if(b == CR) {
                        //忽略CR
                    }
                    else if(b == LF) {  //遇到结束标志，停止读取数据
                        stop = true;
                        break;
                    }
                    else {  
                        count++;    //接收读取的字节
                        if(count>=buffer.length) {  //缓冲区满
                            break;
                        }
                    }
                }
            }
            result.append(new String(buffer, 0, count));
        }
        
        return result.toString();
    }
}