Class UnavailableException
- All Implemented Interfaces:
Serializable
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.
- See Also:
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Constructor Summary
ConstructorDescriptionConstructs a new exception with a descriptive message indicating that the servlet is permanently unavailable.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. -
Method Summary
Modifier and TypeMethodDescriptionint
Returns the number of seconds the servlet expects to be temporarily unavailable.boolean
Returns aboolean
indicating whether the servlet is permanently unavailable.Methods inherited from class jakarta.servlet.ServletException
getRootCause
Methods inherited from class java.lang.Throwable
addSuppressed, fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, getSuppressed, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString
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Constructor Details
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UnavailableException
Constructs a new exception with a descriptive message indicating that the servlet is permanently unavailable.- Parameters:
msg
- aString
specifying the descriptive message
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UnavailableException
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.- Parameters:
msg
- aString
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
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Method Details
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isPermanent
public boolean isPermanent()Returns aboolean
indicating whether the servlet is permanently unavailable. If so, something is wrong with the servlet, and the system administrator must take some corrective action.- Returns:
true
if the servlet is permanently unavailable;false
if the servlet is available or temporarily unavailable
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