javax.servlet
Class UnavailableException
public class 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.
Servlet | getServlet()- As of Java Servlet API 2.2, with no replacement.
|
int | getUnavailableSeconds()- Returns the number of seconds the servlet expects to
be temporarily unavailable.
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boolean | isPermanent()-
Returns a
boolean indicating
whether the servlet is permanently unavailable.
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UnavailableException
public UnavailableException(String msg)
Constructs a new exception with a descriptive
message indicating that the servlet is permanently
unavailable.
msg - a String specifying the
descriptive message
UnavailableException
public UnavailableException(String msg,
int seconds) Constructs a new exception with a descriptive message
indicating that the servlet is temporarily unavailable
and giving an estimate of how long it will be unavailable.
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 estimate
UnavailableException
public UnavailableException(int seconds,
Servlet servlet,
String msg)As of Java Servlet API 2.2, use 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.
UnavailableException
public UnavailableException(Servlet servlet,
String msg)As of Java Servlet API 2.2, use UnavailableException(String) instead.
servlet - the Servlet instance that is
unavailablemsg - a String specifying the
descriptive message
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