import sun.security.provider.certpath.CertStoreHelper; //导入依赖的package包/类
/**
 * Loads CRLs from a source. This method is also called in JarSigner.
 * @param src the source, which means System.in if null, or a URI,
 *        or a bare file path name
 */
public static Collection<? extends CRL> loadCRLs(String src) throws Exception {
    InputStream in = null;
    URI uri = null;
    if (src == null) {
        in = System.in;
    } else {
        try {
            uri = new URI(src);
            if (uri.getScheme().equals("ldap")) {
                // No input stream for LDAP
            } else {
                in = uri.toURL().openStream();
            }
        } catch (Exception e) {
            try {
                in = new FileInputStream(src);
            } catch (Exception e2) {
                if (uri == null || uri.getScheme() == null) {
                    throw e2;   // More likely a bare file path
                } else {
                    throw e;    // More likely a protocol or network problem
                }
            }
        }
    }
    if (in != null) {
        try {
            // Read the full stream before feeding to X509Factory,
            // otherwise, keytool -gencrl | keytool -printcrl
            // might not work properly, since -gencrl is slow
            // and there's no data in the pipe at the beginning.
            ByteArrayOutputStream bout = new ByteArrayOutputStream();
            byte[] b = new byte[4096];
            while (true) {
                int len = in.read(b);
                if (len < 0) break;
                bout.write(b, 0, len);
            }
            return CertificateFactory.getInstance("X509").generateCRLs(
                    new ByteArrayInputStream(bout.toByteArray()));
        } finally {
            if (in != System.in) {
                in.close();
            }
        }
    } else {    // must be LDAP, and uri is not null
        // Lazily load LDAPCertStoreHelper if present
        CertStoreHelper helper = CertStoreHelper.getInstance("LDAP");
        String path = uri.getPath();
        if (path.charAt(0) == '/') path = path.substring(1);
        CertStore s = helper.getCertStore(uri);
        X509CRLSelector sel =
                helper.wrap(new X509CRLSelector(), null, path);
        return s.getCRLs(sel);
    }
}