从活动目录中的组中删除用户

我正在尝试从活动目录中的组中删除某些用户列表。在执行此操作时,我发现以下异常/错误:

下面是我用来创建到Active Directory的连接的代码。

Hashtable<String, Object> objEnvironment;
objEnvironment = new Hashtable<String, Object>(11);
objEnvironment.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
objEnvironment.put(Context.PROVIDER_URL,  "LDAPS://<domain>:636");
objEnvironment.put(Context.SECURITY_AUTHENTICATION, "simple");
objEnvironment.put(Context.SECURITY_PRINCIPAL, <username>);
objEnvironment.put(Context.SECURITY_CREDENTIALS, <password>);
System.setProperty("javax.net.ssl.trustStore", <certificates store path>));
this.objLDAPContext = new InitialLdapContext(objEnvironment, null);

以及删除组

Connection objActiveDirectory;
ModificationItem objModificationItem[];
objModificationItem = new ModificationItem[1];
objModificationItem[0]= new ModificationItem(LdapContext.REMOVE_ATTRIBUTE, new BasicAttribute("member", <user e-mail>));
objActiveDirectory = new Connection("LDAPS://<domain>:636"), <username>, <password>);
objActiveDirectory.getContext().modifyAttributes(<group distinguishedname>, objModificationItem);
objActiveDirectory.close();

你知道我该如何面对这个问题吗?