Christian Migowski schrieb:
Hi,
is this considered a bug:
If I load a list with commons-configuration, then add new entries to
that list and try to save it back to file, I get a
"java.lang.IllegalArgumentException: prepareAdd: Passed in key must
contain a whitespace!" exception.
If I do not modify the list, saving works.
If I remove entries from the list, saving works as well.
Very simple demo-program:
XML File:
<config>
<liste>eintrag 1</liste>
<liste>eintrag 2</liste>
<liste>eintrag 3</liste>
</config>
program:
public static void main(String[] args) {
XMLConfiguration masterconfig;
try {
masterconfig = new XMLConfiguration("democonfig.xml");
masterconfig.setExpressionEngine(new XPathExpressionEngine());
List<String> test = masterconfig.getList("liste");
masterconfig.setProperty("liste", test); //ok, no changes
masterconfig.save();
test.remove("eintrag 2");
masterconfig.setProperty("liste", test); //ok, one <liste>
element is removed from file
masterconfig.save();
test.add("neuer eintrag");
masterconfig.setProperty("liste", test); //exception
masterconfig.save();
} catch (Exception e) {
e.printStackTrace();
}
}
I think commons-configuration should work consistent on all this cases.
best regards,
christian!
At least I can explain what is happening here.
When setProperty() is invoked with a list (or array) for the new
property value, it does the following:
- First it obtains the current values of the affected property (as a list).
- It then iterates over both the list with the new values and the list
with the current values.
- As long as both lists have elements, the current elements are
overridden by the new ones.
- If at the end of the iteration the list with the current values has
still more values (i.e. the list with the new values had fewer elements
than the current values), the remaining elements are removed.
- Otherwise, if the list with the new values has more elements, the
additional values are added by calling addProperty().
It is the last step that causes the problems you see. If an
XPathExpressionEngine is used, addProperty() uses a special format for
the properties keys: a path to an existing node (to which new data is to
be added), followed by whitespace, followed by the name(s) of the new
node(s) to be added. This is because we only can interpret XPath
expressions on an existing nodes structure.
Now, in your test program when you try to add a new element,
addProperty() is called behind the scenes, but cannot interpret the
passed in key.
I agree that this is inconsistent, but unfortunately I don't know how to
fix this. We might be able to work around the problem in some cases
(e.g. if the property to be set has already some values, adding new
elements can be performed directly on the nodes structure). But when
setProperty() is used for adding a new property, I cannot see an easy
solution.
Oliver
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