UserDBDBMpublic class UserDBDBM extends UserDB | A trivial "database" for User objects, stored in a flat file.
Since this is exected to be used heavily, and to avoid the overhead
of re-reading the file, the "Singleton" Design Pattern is used
to ensure that there is only ever one instance of this class. |
| Fields Summary |
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| protected static final String | DEF_NAME | | protected DBM | db |
| Constructors Summary |
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protected UserDBDBM()Default Constructor
this(DEF_NAME);
| protected UserDBDBM(String fn)Constructor
super();
db = new DBM(fn);
String k;
Object o;
// Iterate through contents of DBM, adding into list.
for (o=db.firstkeyObject(); o!=null; o=db.nextkey(o)) {
// firstkey/nextkey give Key as Object, cast to String.
k = (String)o;
o = db.fetch(k); // Get corresponding Value (a User)
users.add((User)o); // Add to list.
}
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| Methods Summary |
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| public synchronized void | addUser(User nu)Add one user to the list, both in-memory and on disk.
// Add it to the in-memory list
super.addUser(nu);
// Add it to the on-disk version: store in DB with
// key = nickname, value = object.
db.store(nu.getName(), nu);
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