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JPA: How to have one-to-many relation of the same Entity type
...em.persist(daughter);
em.getTransaction().commit();
}
In this case, all three entity instances must be persisted before transaction commit. If I fail to persist one of the entities in the graph of parent-child relationships, then an exception is thrown on commit(). On Eclipselink, this is a...
How to duplicate virtualenv
...is to use pip to generate a requirements file. A requirements file is basically a file that contains a list of all the python packages you want to install (or have already installed in case of file generated by pip), and what versions they're at.
To generate a requirements file, go into your origin...
In Python, how do you convert a `datetime` object to seconds?
...datetime(1970,1,1)).total_seconds()
1256083200.0
The starting date is usually specified in UTC, so for proper results the datetime you feed into this formula should be in UTC as well. If your datetime isn't in UTC already, you'll need to convert it before you use it, or attach a tzinfo class that ...
Canary release strategy vs. Blue/Green
...old until someone flips a feature toggle. Breaking your application into small, independently releaseable services is another, since there is less to test and less that can break.
You need to do a canary release if you're not completely certain that the new version will function correctly in produc...
Check if a div exists with jquery [duplicate]
...re using jQuery I don't see any reason to use getElementById, unless you really need the performance improvement (e.g. it's in a long loop or something, though I can't think of how this would come up, that you need to run thousands of select queries over and over). It's just much more verbose, over ...
Find size of object instance in bytes in c#
...
First of all, a warning: what follows is strictly in the realm of ugly, undocumented hacks. Do not rely on this working - even if it works for you now, it may stop working tomorrow, with any minor or major .NET update.
You can use th...
What is the use case of noop [:] in bash?
... to do.
while keep_waiting; do
: # busy-wait
done
The : builtin dates all the way back to the Thompson shell, it was present in Unix v6. : was a label indicator for the Thompson shell's goto statement. The label could be any text, so : doubled up as a comment indicator (if there is no goto comm...
How can I disable ARC for a single file in a project?
... objects) where the rules of ARC are a little more fragile right now. I recall hearing that there was a way to disable ARC on a per-file basis, though I have been unable to find this option.
...
finding the type of an element using jQuery
... When using $("#elementId").get(0).tagName the tagName will be in all caps - TR, DIV etc etc
– Jarede
Oct 18 '12 at 14:41
7
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How to ISO 8601 format a Date with Timezone Offset in JavaScript?
...
The below should work properly, and for all browsers (thanks to @MattJohnson for the tip)
Date.prototype.toIsoString = function() {
var tzo = -this.getTimezoneOffset(),
dif = tzo >= 0 ? '+' : '-',
pad = function(num) {
va...