javax.servlet: public class: UnavailableException

javax.servlet
public class: UnavailableException [javadoc | source]

java.lang.Object
   java.lang.Throwable
      java.lang.Exception
         javax.servlet.ServletException
            javax.servlet.UnavailableException

All Implemented Interfaces:
Serializable

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.

author: Various -

version: $ - Version$

Constructor:

Constructor:
public UnavailableException(String msg) { super(msg); permanent = true; } Constructs a new exception with a descriptive message indicating that the servlet is permanently unavailable. Parameters: `msg` - a `String` specifying the descriptive message
public UnavailableException(Servlet servlet, String msg) { super(msg); this.servlet = servlet; permanent = true; } Parameters: `servlet` - the `Servlet` instance that is unavailable `msg` - a `String` specifying the descriptive message
public UnavailableException(String msg, int seconds) { super(msg); if (seconds < = 0) this.seconds = -1; else this.seconds = seconds; permanent = false; } 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` - 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
public UnavailableException(int seconds, Servlet servlet, String msg) { super(msg); this.servlet = servlet; if (seconds < = 0) this.seconds = -1; else this.seconds = seconds; permanent = false; } Parameters: `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 `servlet` - the `Servlet` that is unavailable `msg` - a `String` specifying the descriptive message, which can be written to a log file or displayed for the user.

 public UnavailableException(String msg) {
	super(msg);
	permanent = true;
}

Constructs a new exception with a descriptive message indicating that the servlet is permanently unavailable.

Parameters:

msg - a String specifying the descriptive message

 public UnavailableException(Servlet servlet,
    String msg) {
	super(msg);
	this.servlet = servlet;
	permanent = true;
}

Parameters:

servlet - the Servlet instance that is unavailable

msg - a String specifying the descriptive message

 public UnavailableException(String msg,
    int seconds) {
	super(msg);
	if (seconds < = 0)
	    this.seconds = -1;
	else
	    this.seconds = seconds;
	permanent = false;
}

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 - 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

 public UnavailableException(int seconds,
    Servlet servlet,
    String msg) {
	super(msg);
	this.servlet = servlet;
	if (seconds < = 0)
	    this.seconds = -1;
	else
	    this.seconds = seconds;
	permanent = false;
}

Parameters:

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

servlet - the Servlet that is unavailable

msg - a String specifying the descriptive message, which can be written to a log file or displayed for the user.

Method from javax.servlet.UnavailableException Summary:
getServlet, getUnavailableSeconds, isPermanent

Methods from javax.servlet.ServletException:
getRootCause

Methods from java.lang.Throwable:
fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString

Methods from java.lang.Object:
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from javax.servlet.UnavailableException Detail:
public Servlet getServlet() { return servlet; } Deprecated! `As` - of Java Servlet API 2.2, with no replacement. Returns the servlet that is reporting its unavailability.
public int getUnavailableSeconds() { return permanent ? -1 : seconds; } 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.
public boolean isPermanent() { return permanent; } Returns a `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.

Method from javax.servlet.UnavailableException Detail:

 public Servlet getServlet() {
	return servlet;
}

Deprecated! As - of Java Servlet API 2.2, with no replacement. Returns the servlet that is reporting its unavailability.

 public int getUnavailableSeconds() {
	return permanent ? -1 : seconds;
}

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.

 public boolean isPermanent() {
	return permanent;
}

boolean