Request for refactoring: Config.getXXX()
Weijun Wang
weijun.wang at oracle.com
Tue Jun 19 02:07:54 UTC 2012
This is about the internal class sun.security.krb5.Config.
If you want to get a value from inside krb5.conf, you can call
getDefault(String). This might be good to get a value from the
[libdefaults] section. However, the method was designed to be so smart
that it can recursively search for key/value pairs no matter how deep it is.
For example, given a krb5.conf
[s1]
a=b
[s2]
c=d
[s3]
e = {
f = g
}
getDefault("a") = "b", getDefault("c") = "d", and astonishingly,
getDefault("f") = "g".
I don't think this is a good design, for several reasons:
1. It depends on the order of sections if there are key/value pairs with
the same key.
2. It ignores wrong settings. For example, when doing a cross-realm
auth, the Realm.getRealmsList(from,to) is used to get a path which
should be defined in [capaths]. However, the method simply crawls
recursively into any subsection it found and won't notice the [capaths]
being mistakenly typed as [capath]
3. It lacks certain features. Because the function always return a
String (same with the getDefault(String,String) method), getDefault("e")
can only return a null. Therefore there is no way to find out the
existence of the subsection e unless we also know it contains a key f.
4. The current Config class needs to know what subsections contains more
subsections, and it hardcodes names like [capaths] and [realms].
In short, it's just too smart and becomes unsafe to use. I suggest
removing all this smartness and a user must use the full paths to get a
value, say,
kdc = config.get("realms", "SUN.COM", "kdc")
My full spec is:
1. The Config class should understand a krb5.conf without knowing any
specific section names. All it maintains is a Value, which can be either of
String
List<Value>
TreeMap<String,Value>
Here I use TreeMap to preserve the order (might not be necessary).
2. The basic retrieval method will be
Value get(String... key)
3. There are simply methods if you already know what the type in your
case is
String getAsString(String... key)
List<String> getAsStringList(String... key)
The compatibility risk will be low, and if there really comes a
compatibility issue, most likely it will be because the caller had
written his krb5.conf wrong.
One of the advantages of the original design is that when a key is
provided in both [libdefaults] and a given realm, the method can find it
anyway. This will be useful for keys like kdc_timeout, max_retries.
However, I think this automatic retrieval is confusing and error-prone,
I'd rather manually call the get() method twice.
Thanks
Max
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