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.
| Modifier and Type | Field and Description |
|---|---|
| private boolean | permanent
Does this need an admin action? |
| private int | seconds
Estimate of how long the resource will be unavaile. |
| private Servlet | servlet
What is unavailable |
| Access | Constructor and Description |
|---|---|
| public | UnavailableException(Servlet
the servlet, String Servlet instance that is unavailablea msg)String specifying the descriptive message
Deprecated
As of Java Servlet API 2.2, use
UnavailableException(String) instead.
|
| public | UnavailableException(int
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 seconds, Servlet the servlet, String Servlet that is unavailablea msg)String specifying the descriptive
message, which can be written to a log file or displayed for
the user.
Deprecated
As of Java Servlet API 2.2, use
UnavailableException(String, int) instead.
|
| public | UnavailableException(String
a msg)String specifying the descriptive messageConstructs a new exception with a descriptive message indicating that the servlet is permanently unavailable. |
| public | UnavailableException(String
a msg, int String specifying the descriptive
message, which can be written to a log file or displayed for
the user.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 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. |
| Modifier and Type | Method and Description |
|---|---|
| public Servlet | Returns: theServlet object that is
throwing the UnavailableException
Deprecated
As of Java Servlet API 2.2, with no replacement.
Returns the servlet that is reporting its unavailability.
|
| public int | Returns: an integer specifying the number of seconds the servlet will be temporarily unavailable, or a negative number if the servlet is permanently unavailable or cannot make an estimateReturns the number of seconds the servlet expects to be temporarily unavailable. |
| public boolean | Returns: true if the servlet is
permanently unavailable; false
if the servlet is available or temporarily unavailableReturns a |
| permanent | back to summary |
|---|---|
| private boolean permanent Does this need an admin action? | |
| seconds | back to summary |
|---|---|
| private int seconds Estimate of how long the resource will be unavaile. | |
| servlet | back to summary |
|---|---|
| private Servlet servlet What is unavailable | |
| UnavailableException | back to summary |
|---|---|
| public UnavailableException(Servlet servlet, String msg)
Deprecated As of Java Servlet API 2.2, use | |
| UnavailableException | back to summary |
|---|---|
| public UnavailableException(int seconds, Servlet servlet, String msg)
Deprecated As of Java Servlet API 2.2, use
| |
| UnavailableException | back to summary |
|---|---|
| public UnavailableException(String msg) Constructs a new exception with a descriptive message indicating that the servlet is permanently unavailable.
| |
| UnavailableException | back to summary |
|---|---|
| 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
| |
| getServlet | back to summary |
|---|---|
| public Servlet getServlet()
Deprecated As of Java Servlet API 2.2, with no replacement. Returns the servlet that is reporting its unavailability.
| |
| getUnavailableSeconds | back to summary |
|---|---|
| public int getUnavailableSeconds() Returns the number of seconds the servlet expects to be temporarily unavailable. 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.
| |
| isPermanent | back to summary |
|---|---|
| public boolean isPermanent() Returns a
| |