开发J2ME联网应用程序[1]

作者：mingjava  文章来源：http://www.j2medev.com/Article/ShowArticle.asp?ArticleID=14

尽管目前的无线网络不够理想，手机联网还是给我们开发人员不小的震撼的。毕竟这真的是件神奇的事情，不是吗？本文将讲述如何应用J2ME平台中的通用联网框架开发联网的应用程序。

     首先，必须说明一点：MIDP中规定，任何移动信息设备都必须提供通过http协议的支持，而像其他的通信方式例如socket是设备相关的。有些手机会支持，有些则不支持。这里只大概的说明一下http协议相关的内容，如果不了解这个方面的知识请参考http协议。在javax.microedition.io里面是大量的接口，只有一个connector类，当然在midp2.0里面添加了对push技术的支持，这个留做以后讲。connector类提供的最重要的方法是open()方法，它的返回值为Connection，你可以对他进行转换得到你需要的类型，比如我们以http协议访问服务器。
void postViaHttpConnection(String url) throws IOException {
        HttpConnection c = null;
        InputStream is = null;
        OutputStream os = null;
        int rc;

        try {
            c = (HttpConnection)Connector.open(url);

            // Set the request method and headers
            c.setRequestMethod(HttpConnection.POST);
            c.setRequestProperty("If-Modified-Since",
                "29 Oct 1999 19:43:31 GMT");
            c.setRequestProperty("User-Agent",
                "Profile/MIDP-2.0 Configuration/CLDC-1.0");
            c.setRequestProperty("Content-Language", "en-US");

            // Getting the output stream may flush the headers
            os = c.openOutputStream();
            os.write("LIST games\n".getBytes());
            os.flush();           // Optional, getResponseCode will flush

            // Getting the response code will open the connection,
            // send the request, and read the HTTP response headers.
            // The headers are stored until requested.
            rc = c.getResponseCode();
            if (rc != HttpConnection.HTTP_OK) {
                throw new IOException("HTTP response code: " + rc);
            }

            is = c.openInputStream();

            // Get the ContentType
            String type = c.getType();
            processType(type);

            // Get the length and process the data
            int len = (int)c.getLength();
            if (len > 0) {
                 int actual = 0;
                 int bytesread = 0 ;
                 byte[] data = new byte[len];
                 while ((bytesread != len) && (actual != -1)) {
                    actual = is.read(data, bytesread, len - bytesread);
                    bytesread += actual;
                 }
  &nbs