Examples of usages of JSP---three popup dialog boxes

(Non-original)

Way 1:jsp Front End

<script type= "Text/javascript" language= "JavaScript" >
Alert ("You are not logged in, please log in ...");
Window.document.location.href= "userlogin.html";
</script>

Way 2:java Backstage

public void Popalert () {

Response.setcharacterencoding ("Utf-8");
PrintWriter out = Response.getwriter ();
Out.print ("<script>alert (' You are not logged in, please login ... '); window.location= ' userlogin.html ' </script> ');
Out.flush ();
Out.close ();

}

Way 3:java Backstage   +   JSP frontend

1) Java Background Code snippet

public void Popalert () {

Request.setattribute ("LoginError", "You are not logged in, please login ..."); Setting Error Properties
Request.getrequestdispatcher ("userlogin.html"). Forward (request, response);

}

2) JSP frontend code snippet

<%
String errorinfo = (string) request.getattribute ("LoginError"); Get Error properties
if (errorinfo! = null) {
%>
<script type= "Text/javascript" language= "JavaScript" >
Alert ("<%=errorInfo%>"); Pop-up error message

window.location= ' userlogin.html '; Jump to login screen
</script>
<%
}
%>

Summarize

Three ways, essentially through the JavaScript popup dialog box, prompting the user password error, when the user clicked the Alert OK button, automatically jump to the login interface userlogin.html