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What is the difference between persist() and merge() in JPA and Hibernate?
...these
other entities are annotated with the
cascade=PERSIST or cascade=ALL
annotation element value or specified
with the equivalent XML descriptor
element.
If X is a removed entity,
it becomes managed.
If X is a
detached object, the
EntityExistsException may be thrown
when the...
Why is String immutable in Java?
...le for several reasons, here is a summary:
Security: parameters are typically represented as String in network connections, database connection urls, usernames/passwords etc. If it were mutable, these parameters could be easily changed.
Synchronization and concurrency: making String immutable aut...
Proper Linq where clauses
...collection where as in the first one, it's applying the first predicate to all items first and the result (which is narrowed down at this point) is used for the second predicate and so on. The results get narrowed down every pass but still it involves multiple passes.
Also the chaining (first metho...
SQL Server NOLOCK and joins
...e are equivalent though for 2005 it is not the case:
[SQL Server 2008 R2]
All lock hints are propagated to all the tables and views that are accessed by the query plan, including tables and views referenced in a view. Also, SQL Server performs the corresponding lock consistency checks.
[SQL Server ...
MySQL indexes - what are the best practices?
...SQL databases for a while now but never properly learnt about them. Generally I put an index on any fields that I will be searching or selecting using a WHERE clause but sometimes it doesn't seem so black and white.
...
Comparing Haskell's Snap and Yesod web frameworks
...
Full disclosure: I'm one of the lead developers of Snap.
First of all, let's talk about what Snap is. Right now the Snap team maintains five different projects on hackage: snap-core, snap-server, heist, snap, and xmlhtml. snap-server is a web server that exposes the API defined by snap-co...
Determine if a function exists in bash
..., built-in function, external command, or just not defined. Example:
$ LC_ALL=C type foo
bash: type: foo: not found
$ LC_ALL=C type ls
ls is aliased to `ls --color=auto'
$ which type
$ LC_ALL=C type type
type is a shell builtin
$ LC_ALL=C type -t rvm
function
$ if [ -n "$(LC_ALL=C type -t rvm)...
Bootstrap 3 and 4 .container-fluid with grid adding unwanted padding
...anks a bunch. I'd like to remove it when I'm using a column, though. I really don't want to mess with the core bootstrap css. I suspect there must be a sanctioned way to do this. Any thoughts?
– Tim
Aug 22 '14 at 13:22
...
javac option to compile all java files under a given directory recursively
...oject and don't have any proper build tools nearby, you can always use a small trick that javac offers: the classnames to compile can be specified in a file. You simply have to pass the name of the file to javac with the @ prefix.
If you can create a list of all the *.java files in your project, it'...
Get protocol, domain, and port from URL
...
This doesn't work at all if you have a URL string, right? (i.e. you need to be at location for this to work)
– Nick T
Oct 5 '15 at 22:57
...