java.lang.Object | +--java.lang.Throwable | +--java.lang.Exception | +--javax.servlet.ServletException | +--javax.servlet.UnavailableException
Defines an exception that a servlet or filter throws to indicate that it is permanently or temporarily unavailable.
When a servlet or filter is permanently unavailable, something is wrong with it, and it cannot handle requests until some action is taken. For example, a servlet might be configured incorrectly, or a filter's state may be corrupted. The component should log both the error and the corrective action that is needed.
A servlet or filter is temporarily unavailable if it cannot handle requests momentarily due to some system-wide problem. For example, a third-tier server might not be accessible, or there may be insufficient memory or disk storage to handle requests. A system administrator may need to take corrective action.
Servlet containers can safely treat both types of unavailable exceptions in the same way. However, treating temporary unavailability effectively makes the servlet container more robust. Specifically, the servlet container might block requests to the servlet or filter for a period of time suggested by the exception, rather than rejecting them until the servlet container restarts.
UnavailableException(int seconds,
Servlet servlet,
java.lang.String msg)
UnavailableException(String, int) instead.
UnavailableException(Servlet servlet,
java.lang.String msg)
UnavailableException(String) instead.
UnavailableException(java.lang.String msg)
UnavailableException(java.lang.String msg,
int seconds)
Servlet
getServlet()
int
getUnavailableSeconds()
fillInStackTrace,
getLocalizedMessage,
getMessage,
printStackTrace,
printStackTrace,
printStackTrace,
toString
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
wait,
wait,
wait
public UnavailableException(Servlet servlet, java.lang.String msg)
UnavailableException(String) instead.
servlet - the Servlet instance that is
unavailablemsg - a String specifying the
descriptive messagepublic UnavailableException(int seconds, Servlet servlet, java.lang.String msg)
UnavailableException(String, int) instead.
seconds - an integer specifying the number of seconds
the servlet expects to be unavailable; if
zero or negative, indicates that the servlet
can't make an estimateservlet - the Servlet that is unavailablemsg - a String specifying the descriptive
message, which can be written to a log file or
displayed for the user.public UnavailableException(java.lang.String msg)
msg - a String specifying the
descriptive messagepublic UnavailableException(java.lang.String msg, int seconds)
In some cases, the servlet cannot make an estimate. For
example, the servlet might know that a server it needs is
not running, but not be able to report how long it will take
to be restored to functionality. This can be indicated with
a negative or zero value for the seconds argument.
msg - a String specifying the
descriptive message, which can be written
to a log file or displayed for the user.seconds - an integer specifying the number of seconds
the servlet expects to be unavailable; if
zero or negative, indicates that the servlet
can't make an estimatepublic boolean isPermanent()
boolean indicating
whether the servlet is permanently unavailable.
If so, something is wrong with the servlet, and the
system administrator must take some corrective action.true if the servlet is
permanently unavailable; false
if the servlet is available or temporarily
unavailablepublic Servlet getServlet()
Servlet object that is
throwing the UnavailableExceptionpublic int getUnavailableSeconds()
If this method returns a negative number, the servlet is permanently unavailable or cannot provide an estimate of how long it will be unavailable. No effort is made to correct for the time elapsed since the exception was first reported.