public static String sendPost(String url, String param) {
PrintWriter out = null;
BufferedReader in = null;
String result = "";
try {
URL realUrl = new URL(url);
// 打開和URL之間的連接
URLConnection conn = realUrl.openConnection();

// 第二次發送post，設置cookie與第一次獲取到的值相同
if (cookieStore != null) {
conn.setRequestProperty("Cookie", "JSESSIONID="
+ cookieStore.getCookies().get(0).getValue());
}

// 設置通用的請求屬性
conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("connection", "Keep-Alive");
conn.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");

// 發送POST請求必須設置如下兩行

conn.setDoOutput(true);
conn.setDoInput(true);
// 獲取URLConnection對象對應的輸出流

out = new PrintWriter(conn.getOutputStream());
// 發送請求參數

out.print(param);
// flush輸出流的緩沖

out.flush();
// 定義BufferedReader輸入流來讀取URL的響應

in = new BufferedReader(
new InputStreamReader(conn.getInputStream()));

// 第一次登陸，設置cookie
if (cookieStore == null) {
String cookieValue = conn.getHeaderField("Set-Cookie");

String sessionId = cookieValue.substring(0,
cookieValue.indexOf(";"));
// System.out.println("cookie value:" + sessionId);

cookieStore = new BasicCookieStore();
BasicClientCookie cookie = new BasicClientCookie("JSESSIONID",
sessionId.split("=")[1]);
cookie.setVersion(0);
cookie.setDomain("domain");
cookie.setPath("/xxx");
cookieStore.addCookie(cookie);
}

String line;
while ((line = in.readLine()) != null) {
result += line;
}
} catch (Exception e) {
System.out.println("發送 POST 請求出現異常！" + e);
}
// 使用finally塊來關閉輸出流、輸入流

finally {
try {
if (out != null) {
out.close();
}
if (in != null) {
in.close();
}
} catch (IOException ex) {
System.out.println("發送 POST 請求出現異常！" + ex);
}
}
return result;
}

模擬post提交，保持session不變