Clarify implicit mappings and welcome file behaviour

[glassfishrobot]

Consider the following:
*.do is mapped to a servlet
welcome files are index.jsp, index.do

The intention is that the index.jsp page should be used if present and index.do (which always maps to the servlet) used if it is not. However, a strict reading of the servlet spec requires that a 404 is returned in index.jsp is not present .

[glassfishrobot]

@glassfishrobot Commented
Reported by markt_asf

[glassfishrobot]

@glassfishrobot Commented
gregwilkins said:
The problem with this mechanism is that it was designed (and named) for welcome files. This has been somewhat subverted to allow for welcome servlets - ie if *.jsp is mapped to a servlet, then you get this 404 issue.

I believe the solution is to have a separate welcome servlet configuration, that would allow index.do to be attempted even though there is not a index.do file that exists.

[glassfishrobot]

@glassfishrobot Commented
This issue was imported from java.net JIRA SERVLET_SPEC-20

[glassfishrobot]

• Issue Imported From: https://github.com/javaee/servlet-spec/issues/20
• Original Issue Raised By:@glassfishrobot
• Original Issue Assigned To: @glassfishrobot

[markt-asf]

How about something along the lines of the following (it is an expanded version of Greg's prior proposal):

Define a new <welcome-servlet> element. It is a sub-element of <welcome-files>. Update <welcome-files> to allow any combination of <welcome-file> and <welcome-servlet>.

<welcome-files> entries are processed in order. The first valid entry found is used.

For a <welcome-file> element to be considered valid, the file defined by the element must exist at the directory defined by the request URI. If the element is considered valid, the request URI is updated to be the request URI with the entry appended and and the new request URI is mapped to a servlet using standard Servlet mapping rules. This will typically result in a mapping to the default servlet but may result in a mapping to other servlets such as the JSP servlet.

For a <welcome-servlet> element to be considered valid the request URI with the entry appended must map to a servlet other than the default servlet. If the element is considered valid, the request URI is updated to be the request URI with the entry appended and the new request URI is mapped to a servlet using standard Servlet mapping rules.

The end result is very similar to the current specified behaviour but with a key difference for JSP files. Consider the following list of welcome files:

<welcome-file>index.jsp</welcome-file>
<welcome-file>index.do</welcome-file>

and a request to a directory that contains neither index.jsp nor index.do.

With the current specification, the first pass of the welcome files will not find a match as no files match. On the second pass, index.jsp will match the JSP servlet so the request will be mapped resulting in a 404.

With the new approach the files would be specified as:

<welcome-file>index.jsp</welcome-file>
<welcome-servlet>index.do</welcome-servlet>

The first entry will not be matched since the directory does not contain an index.jsp. The second entry will match, assuming a servlet is mapped to *.do.

The requirement for two separate passes of the welcome files - one for files and one for servlets - will be removed.

[janbartel]

@markt-asf could you clarify how this proposal works if pre-compiled jsps are used? In this case, it is not necessary for the file to exist, but there will be a servlet mapping for the file location.