Hi!
I'm a long time user (and big fan) of commons.lang.Validate because it's a very
neat pattern for getting stable software modules.
I'm PMC member on Apache OpenWebBeans and currently also writing the
maven-scm-provider-jgit (JGIT is a native Java implementation of GIT). Since
jgit-core (the part of EGIT we use for the maven-scm-provider-jgit) is BSD and
Shawn likes to have not too much external dependencies, I started writing my
own little Validate helper class and had a hopefully good idea which imho would
also be a good extension to commons.lang.Validate:
A main problem on validation is the message creation which costs a lot of
String operations and therefor also garbage collection. I've now seen that the
latest version in SVN has an additional object parameter for a few functions
which addresses this problem. My proposal now goes even further but requires
java-5 since it uses ellipsis notation.
If msgObject[0] is a String java.text.MessageFormat will be used for creating
the failure message, e.g.
Validate.notNull(nullInt, "testMessageText Integer={0} btw! and Integer2={1}.",
new Integer(42), new Integer(43));
example for isTrue with message construction:
/**
* Validate that b is <code>true</code>
*
* @param b boolean to validate
* @param msgObjects additional Objects added as text message to the
InvalidArgumentException
*/
public static void isTrue(boolean b, Object... msgObjects) {
if (!b) {
throw new IllegalArgumentException(getMessage(msgObjects));
}
}
/**
* private helper function to create an error message from the given Objects
* If the first object in msgObjects is of type {...@code String} then
* {...@code MessageFormat} will be used to format the output message.
*
* @param msgObjects
* @return concatenated String representation of all the objects
*/
private static String getMessage(Object... msgObjects) {
if (msgObjects.length > 0 && msgObjects[0] instanceof String) {
MessageFormat form = new MessageFormat((String) msgObjects[0]);
Object[] params = new Object[msgObjects.length - 1];
System.arraycopy(msgObjects, 1, params, 0, msgObjects.length -
1);
return form.format(params);
}
else {
StringBuffer sb = new StringBuffer("Validation failed: [");
for(int i = 0; i < msgObjects.length; i++) {
if (i > 0) {
sb.append(' ');
}
sb.append(msgObjects[i]);
}
sb.append(']');
return sb.toString();
}
}
I've tested those functions against 'old' Validate handling to ensure that
there are no performance side effects with Java ellipsis handling, and the
performance win is huge [1]. The ellipsis Version only takes < 5% of the time
of the 'old' handling.
WDYT?
a.) Is the implementation ok?
b.) Will there be a java-5 only version of commons.lang in the near future?
c.) Imho we could replace the 1-parameter versions with the proper ellipsis
functions and we are still compile compatible. But I'm not sure if we stay
binary-compatible (needs to be tested).
I wrote a Validate class this way for jgit-core [2] but also have to like this
features in our owns commons.lang.Validate if possible!
txs and LieGrue,
strub
[1] http://pastebin.com/m2cf887a9
[2]
http://github.com/sonatype/JGit/blob/2ab3a576fa67145d6a9f66efd7437c52d567eb68/org.spearce.jgit/src/org/spearce/jgit/util/Validate.java
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