Issue 1670 : InstructorCourseEnrollSaveAction failed due to null parameter

Issue 1670 : InstructorCourseEnrollSaveAction failed due to null parameter

[damith, 2014-03-13 15:32:13]

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/common...
File src/main/java/teammates/common/util/Const.java (right):

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/common...
src/main/java/teammates/common/util/Const.java:622: public static final String
NULL_POST_PARAMETER_MESSAGE = "?message=You have been redirected to this page
due to some missing data in the previous URL."
due to a possible expiry of the previous login.

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/common...
src/main/java/teammates/common/util/Const.java:623: + "<br>If you have
previously typed some data and wish to retrieve it from the previous page,
please press the back button.";
... you may use the 'Back' button of your Browser to navigate to the previous
page containing the data you typed in'.

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/ui/con...
File src/main/java/teammates/ui/controller/Action.java (right):

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/ui/con...
src/main/java/teammates/ui/controller/Action.java:123: public ActionResult
executeAndPostProcess() throws EntityDoesNotExistException,
NullPostParameterException {
You can make this exception a subclass of RuntimeException so that it doesn't
have to be declared like this everywhere.

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/ui/con...
File src/main/java/teammates/ui/controller/ControllerServlet.java (right):

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/ui/con...
src/main/java/teammates/ui/controller/ControllerServlet.java:78:
if(requestUrl.contains("instructor")) {
This check is week. It is possible that the url contains both these words.
startsWith("/instructor")?

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/ui/con...
File src/main/java/teammates/ui/controller/InstructorCourseEnrollSaveAction.java
(right):

https://codereview.appspot.com/75470043/diff/1/src/main/java/teammates/ui/con...
src/main/java/teammates/ui/controller/InstructorCourseEnrollSaveAction.java:31:
}
May be extract this to a helper method and push to parent class? 
e.g. assertPostParamNotNull(...)

[damith, 2014-03-14 00:20:27]

https://codereview.appspot.com/75470043/diff/20001/src/main/java/teammates/ui...
File src/main/java/teammates/ui/controller/LoginFilter.java (right):

https://codereview.appspot.com/75470043/diff/20001/src/main/java/teammates/ui...
src/main/java/teammates/ui/controller/LoginFilter.java:22: protected static
final Logger log = Utils.getLogger();
May be we can move the initialization to the place where it is used, to avoid
initializing it if we don't need it (i.e. most of the time)?