HttpURLConnection.java 文件源码

/**
 *  if the caller has a URLPermission for connecting to the
 *  given URL, then return a SocketPermission which permits
 *  access to that destination. Return null otherwise. The permission
 *  is cached in a field (which can only be changed by redirects)
 */
SocketPermission URLtoSocketPermission(URL url) throws IOException {

    if (socketPermission != null) {
        return socketPermission;
    }

    SecurityManager sm = System.getSecurityManager();

    if (sm == null) {
        return null;
    }

    // the permission, which we might grant

    SocketPermission newPerm = new SocketPermission(
        getHostAndPort(url), "connect"
    );

    String actions = getRequestMethod()+":" +
            getUserSetHeaders().getHeaderNamesInList();

    String urlstring = url.getProtocol() + "://" + url.getAuthority()
            + url.getPath();

    URLPermission p = new URLPermission(urlstring, actions);
    try {
        sm.checkPermission(p);
        socketPermission = newPerm;
        return socketPermission;
    } catch (SecurityException e) {
        // fall thru
    }
    return null;
}