在哪里可以找到“ j_security_check”？

它是Servlet
API
的一部分，并内置在servletcontainer中。在您的情况下，它内置在Tomcat中。更具体地说，

org.apache.catalina.authenticator.FormAuthenticator

227        // Is this the action request from the login page?228        boolean loginAction =229 requestURI.startsWith(contextPath) &&230 requestURI.endsWith(Constants.FORM_ACTION);231232        // No -- Save this request and redirect to the form login page233        if (!loginAction) {234 session = request.getSessionInternal(true);235 if (log.isDebugEnabled())236     log.debug("Save request in session '" + session.getIdInternal() + "'");237 try {238     saveRequest(request, session);239 } catch (IOException ioe) {240     log.debug("Request body too big to save during authentication");241     response.sendError(HttpServletResponse.SC_FORBIDDEN,242  sm.getString("authenticator.requestBodyTooBig"));243     return (false);244 }245 forwardToLoginPage(request, response, config);246 return (false);247        }248249        // Yes -- Validate the specified credentials and redirect250        // to the error page if they are not correct251        Realm realm = context.getRealm();252        if (characterEncoding != null) {253 request.setCharacterEncoding(characterEncoding);254        }255        String username = request.getParameter(Constants.FORM_USERNAME);256        String password = request.getParameter(Constants.FORM_PASSWORD);257        if (log.isDebugEnabled())258 log.debug("Authenticating username '" + username + "'");259        principal = realm.authenticate(username, password);260        if (principal == null) {261 forwardToErrorPage(request, response, config);262 return (false);263        }

该

Constants.FORM_ACTION

/j_security_check

至于被锁定的具体问题，只需确保提供正确的用户名和密码即可。用户数据库通常由领域配置。