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Notes of things to consider for the next major Tomcat release (probably 8.0.x
but possibly 7.1.x).
1. Refactor the TLD parsing. TLDs are currently parsed twice. Once by Catalina
looking for listeners and once by Jasper.
- Complete
2. Refactor the XML parsing (org.apache.tomcat.util.xml ?) to remove duplicate
XML parsing code in Catalina and Jasper such as the entity resolvers used
for validation.
- Complete
3. TLDs may have a many to many relationship between URIs and TLD files. This
can result in the same TLD file being parsed many times. Refactor the
TldLocationCache to cache the parsed nodes (will need to check for changes
to TLD files).
- Complete
4. TLD files should be included in the dependencies for JSP and Tag files.
- Complete
5. Run the unused code detector and remove everything that isn't currently used.
Add deprecation markers for the removed code to Tomcat 7.0.x
- Complete
6. Change the default URIEncoding on the connector to UTF-8.
- Complete
7. Rip out all the JNDI code in resource handling and replace it with straight
URLs (File or WAR).
- Complete
kkolinko: I think this proposal goes too far. There are several
separate issues. There are:
a) Internal API to define resources
- BaseDirContext implementing aliases and resource jars,
and there will be overlays in Servlet 3.1
- StandardContext.setResources() allowing an arbitrary DirContext
implementation via <Resources> element.
- Too many ways to configure it.
b) Internal API to lookup resources
- DirContext interface
- Unnecessary objects, e.g. NamingException instead of null.
- Too many methods. Name vs. String. list() vs. listBindings().
- Limited API. As a workaround, there are non-standard methods that
are implemented on BaseDirContext instead, e.g. getRealPath(),
- All caching (ProxyDirContext) and aliases handling is
performed on the root level only.
Once I do a lookup that returns a DirContext, further lookups on it
will bypass the caching and aliases.
c) WebappClassLoader and its interaction with resources
WebappClassLoader uses DirContext API to access resources (classes,
Note that it has to construct a classpath for Java compiler called by
Jasper. The compiler cannot operate on a DirContext and needs access
to actual files and JARs.
- There are problems with access to classes and JAR files in
non-unpacked WARs.
It is resolved by unzipping the files into the working directory (in
Note that DirContext is not notified of this copying.
StandardJarScanner does not know of those copies either.
- There are problems when the classes directory is served from
multiple locations
It seems to be worked around by adding the path of the alternative
classes directory to virtualClasspath of VirtualWebappLoader (as shown
by example in config/context.html#Virtual_webapp), but it is likely
that I miss something.
- antiJARLocking support in WebappClassLoader creates copies of
resources, but does not notify the DirContext.
- WebappClassLoader.jarFiles is used to track JAR files and keep them
open. These might be useful when looking for resources in those files.
These might be useful for StandardJarScanner.
d) StandardJarScanner
- It essentially scans the same JARs as accessed by WebappClassLoader.
It might be better to access them via WebappClassLoader rather that
through Servlet API methods.
The scanner is used by Jasper as well, so there are some concerns to
keep the components independent.
e) URL returned by ServletContext.getResource()
- Uniform URL space. Both files and directories can be represented,
hiding details of aliases, resource jars, etc.
- It hides implementation details.
- Permissions can be expressed as JndiPermission. They do not depend
on context version number.
- Accessing a resource through such URL leverages the cache
implemented in ProxyDirContext class. We do not access the file system
directly, nor need to open a JAR file.
- It can be created from a String if necessary.
Such use relies on DirContextURLStreamHandler.bindThread(..) being
called earlier in the same thread.
- Some components would like to get "real" resource URL from this one.
Maybe it can be exposed through some special header name,
How such real URL can be prepared?
- A resource lookup is performed twice. The first time in
ServletContext.getResource() (implemented in ApplicationContext.getResource())
to return null for non-existing paths.
The second time in DirContextURLConnection.connect().
It is good that there is a cache in ProxyDirContext that saves time
for repeated lookups.
- Using URLs involves encoding/decoding.
If there were some other API to access resources in a web application,
I would prefer some opaque object that allows access to resource
properties, but is converted to string/url form only on demand.
f) Connection, created from jndi: URL
DirContextURLStreamHandler, DirContextURLConnection
- DirContextURLConnection provides information about resource via
methods such as getContentLength(), getHeaderField(str).
- It exposes DirContext through some APIs, such as
Is this feature going to be preserved for compatibility, or to be
- DirContextURLConnection.list(): a public method, that is not part of
the usual URL API. So URL API is lacking. Maybe some other methods
could be added.
A possible candidate could be "isCollection()", instead of asking for
getContentType() and checking its value against ResourceAttributes.COLLECTION_TYPE.
8. Review the connector shutdown code for timing and threading issues
particularly any that may result in a client socket being left open after a
- Complete.
9. Remove the svn keywords from all the files. (Just Java files?)
- Complete.
10. Code to the interfaces in the o.a.catalina package and avoid coding directly
to implementations in other packages. This is likely to require a lot of
work. Maybe use Structure 101 (or similar) to help.
- Partially complete - probably as far as is practical.
11. Merge Service and Engine
- Decided not to do this.
12. Java 7 updates
- Use of <> operator where possible
- Complete
- Use of try with resources
- Complete
- Catching multiple exceptions
- Started
- javax.[annotation to el] complete
- remainder TODO
13. Fix all FindBugs warnings
- Complete
14. Review date formatting with a view to reducing duplication.