HttpUrlConnection

利用HttpURLConnection对象,我们可以从网络中获取网页数据.
URL url = new URL("http://www.sohu.com");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(6* 1000);//设置连接超时
if (conn.getResponseCode() != 200) throw new RuntimeException("请求url失败");
InputStream is = conn.getInputStream();//得到网络返回的输入流
String result = readData(is, "GBK");
conn.disconnect();
System.out.println(result);
//第一个参数为输入流,第二个参数为字符集编码
public static String readData(InputStream inSream, String charsetName) throws Exception{
    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int len = -1;
    while( (len = inSream.read(buffer)) != -1 ){
        outStream.write(buffer, 0, len);
    }
    byte[] data = outStream.toByteArray();
    outStream.close();
    inSream.close();
    return new String(data, charsetName);
}
利用HttpURLConnection对象,我们可以从网络中获取文件数据.
URL url = new URL("http://photocdn.sohu.com/20100125/Img269812337.jpg");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(6* 1000);
if (conn.getResponseCode() != 200) throw new RuntimeException("请求url失败");
InputStream is = conn.getInputStream();
readAsFile(is, "Img269812337.jpg");

public static void readAsFile(InputStream inSream, File file) throws Exception{
    FileOutputStream outStream = new FileOutputStream(file);
    byte[] buffer = new byte[1024];
    int len = -1;
    while( (len = inSream.read(buffer)) != -1 ){
        outStream.write(buffer, 0, len);
    }
     outStream.close();
    inSream.close();
}

利用HttpURLConnection对象,我们可以向网络发送请求参数.
String requestUrl = "http://localhost:8080/itcast/contanctmanage.do";
Map<String, String> requestParams = new HashMap<String, String>();
requestParams.put("age", "12");
requestParams.put("name", "中国");
 StringBuilder params = new StringBuilder();
for(Map.Entry<String, String> entry : requestParams.entrySet()){
    params.append(entry.getKey());
    params.append("=");
    params.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
    params.append("&");
}
if (params.length() > 0) params.deleteCharAt(params.length() - 1);
byte[] data = params.toString().getBytes();
URL realUrl = new URL(requestUrl);
HttpURLConnection conn = (HttpURLConnection) realUrl.openConnection();
conn.setDoOutput(true);//发送POST请求必须设置允许输出
conn.setUseCaches(false);//不使用Cache
conn.setRequestMethod("POST");            
conn.setRequestProperty("Connection", "Keep-Alive");//维持长连接
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Content-Length", String.valueOf(data.length));
conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
DataOutputStream outStream = new DataOutputStream(conn.getOutputStream());
outStream.write(data);
outStream.flush();
if( conn.getResponseCode() == 200 ){
        String result = readAsString(conn.getInputStream(), "UTF-8");
        outStream.close();
        System.out.println(result);
}
利用HttpURLConnection对象,我们可以向网络发送xml数据.
StringBuilder xml =  new StringBuilder();
xml.append("<?xml version=\"1.0\" encoding=\"utf-8\" ?>");
xml.append("<M1 V=10000>");
xml.append("<U I=1 D=\"N73\">中国</U>");
xml.append("</M1>");
byte[] xmlbyte = xml.toString().getBytes("UTF-8");
URL url = new URL("http://localhost:8080/itcast/contanctmanage.do?method=readxml");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(6* 1000);
conn.setDoOutput(true);//允许输出
conn.setUseCaches(false);//不使用Cache
conn.setRequestMethod("POST");            
conn.setRequestProperty("Connection", "Keep-Alive");//维持长连接
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Content-Length", String.valueOf(xmlbyte.length));
conn.setRequestProperty("Content-Type", "text/xml; charset=UTF-8");
DataOutputStream outStream = new DataOutputStream(conn.getOutputStream());
outStream.write(xmlbyte);//发送xml数据
outStream.flush();
if (conn.getResponseCode() != 200) throw new RuntimeException("请求url失败");
InputStream is = conn.getInputStream();//获取返回数据
String result = readAsString(is, "UTF-8");
outStream.close();