READERNAME ExceptionHandler.java
From RifidiWiki
This class should extend GenericExceptionHandler. This page goes through each of the four methods in GenericExceptionHandler and describes in detail what each one does and how it should be implemented. The first three methods must be implemented by the class that extends it, and the last class may (and probably should be) implemented by the subclass.
Contents
CommandNotFoundError
This exception is thrown in the CommandAdapter if a command is sent to the reader that is not defined in the reader.xml
public abstract ArrayList<Object> commandNotFoundError(ArrayList<Object> arg, CommandObject obj);
Arguments
- arg - The incoming command
- obj - The incoming command object
Return Value
An array of objects where the first object in the array is a message to be sent back to the client.
Reference Implementation
This is the commandNotFoundError in the alien reader
public ArrayList<Object> commandNotFoundError(ArrayList<Object> arg, CommandObject obj) { String message = ""; for (Object i : arg) { message += i.toString(); } message = "Error 1: Command not understood" + message; ArrayList<Object> returnValue = new ArrayList<Object>(); returnValue.add(message); return returnValue; }
InvalidCommandError
This exception is thrown in the CommandAdapter if a command is in the reader.xml but does has and invalid argument.
public abstract ArrayList<Object> invalidCommandError(ArrayList<Object> arg, String value, CommandObject obj);
Arguments
- arg - The incoming command
- obj - The incoming command object
Return Value
An array of objects where the first object in the array is a message to be sent back to the client.
Reference Implementation
See the above implementation for the commandNotFound. The handling of this error will likely be the same, but the message might be slightly different.
MalformedMessageError
Tiis exception is thrown in the CommandAdapter if a command is in the reader.xml but is missing a required argument
public abstract ArrayList<Object> malformedMessageError(ArrayList<Object> arg, CommandObject obj);
Arguments
- arg - The incoming command
- obj - The incoming command object
Return Value
An array of objects where the first object in the array is a message to be sent back to the client.
Reference Implementation
See the above implementation for the commandNotFound. The handling of this error will likely be the same, but the message might be slightly different.
MethodInvocationError
This exception is thrown in the CommandAdapter if something goes wrong in the handler method while executing a command. It often happens if there is a null pointer exception thrown somewhere in the handler method. While it is not required to implement this method, it is a good idea to do so, so that a proper error message can be sent back to the reader if something like that happens
public CommandObject methodInvocationError(ArrayList<Object> arg,CommandObject obj)
Arguments
- arg - The incoming command
- obj - The incoming command object
Return Value
An array of objects where the first object in the array is a message to be sent back to the client.
Reference Implementation
This is a reference implementation from the LLRPExceptionHandler. The ErrorMessage object is an LLRP specific message that the reader is required to send back to the client if an error happens.
public CommandObject methodInvocationError(ArrayList<Object> arg, CommandObject obj) { ErrorMessage em = new ErrorMessage(); LLRPStatus llrpstat = new LLRPStatus(); llrpstat.setErrorCode((short) 100); char[] c = obj.getCurrentQueryName().toCharArray(); byte[] com = new byte[c.length]; for (int i = 0; i < c.length; i++) { com[i] = (byte) c[i]; } llrpstat.setErrorDescription("Internal error in Rifidi " + "when processing a message of type " + LLRPUtilities.calculateMessageNumber(com) + " Please report error at " + "rifidi sourceforge page"); em.setLLRPStatusParam(llrpstat); obj.getReturnValue().add(em); return obj; }