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JPA EntityManager: Why use persist() over merge()?
...e example will help.
MyEntity e = new MyEntity();
// scenario 1
// tran starts
em.persist(e);
e.setSomeField(someValue);
// tran ends, and the row for someField is updated in the database
// scenario 2
// tran starts
e = new MyEntity();
em.merge(e);
e.setSomeField(anotherValue);
// tran ends ...
Use of Application.DoEvents()
... could click the same menu item or button that causes the same loop to get started. Now you have two nested loops executing DoEvents(), the previous loop is suspended and the new loop is starting from scratch. That could work, but boy the odds are slim. Especially when the nested loop ends and th...
VC DDE（Dynamic Data Exchange）与EXCEL连接 - C/C++ - 清泛网 - 专注C/C++及内核技术
...: 0xx\n", iReturn);
Sleep(1500);
return 0;
}
//Start DDE Server and wait for it to become idle.
HINSTANCE hRet = ShellExecute(0, "open", szTopic, 0, 0, SW_SHOWNORMAL);
if ((int)hRet < 33)
{
printf("Unable to Start DDE Server: 0xx\n", hRet);
...
Should I use single or double colon notation for pseudo-elements?
...f single colons will not be allowed for new pseudo-elements, shouldn't you start using double colons to get in the habit?
– andrewtweber
Jan 4 '16 at 19:02
...
How to kill an Android activity when leaving it so that it cannot be accessed from the back button?
In an given Android activity, I would like to start a new activity for the user at some point. Once they leave the first activity and arrive at the second, the first activity is stale and I want to remove it completely so it can not be accessed again from the back button.
...
Find full path of the Python interpreter?
...r "already in the python shell" examples, all assume that the python shell started is what you get if you type python from the shell. If you start with an explicit different path (e.g. /opt/python/2.5/bin/python), or use python3 and then run those python commands, all of them produced incorrect answ...
Configuring user and password with Git Bash
...ng access token and a Windows environment, there is a simple way to do it:
Start menu → Credential Manager → Windows Credentials → find the line (Git: https://whatever/your-repository/url) → edit,
user name is "PersonalAccessToken" and password is your access token.
...
Flags to enable thorough and verbose g++ warnings
Often in C under gcc , I will start with the following set of warning flags (painfully assembled from multiple sources):
5...
How to reset postgres' primary key sequence when it falls out of sync?
...sort to the ALTER SEQUENCE syntax i.e.
ALTER SEQUENCE table_name_id_seq RESTART WITH 1;
ALTER SEQUENCE table_name_id_seq RESTART; -- 8.4 or higher
But ALTER SEQUENCE is of limited use because the sequence name and restart value cannot be expressions.
It seems the best all-purpose solution is to ...
Web-scraping JavaScript page with Python
...simple example:
class MySpider(scrapy.Spider):
name = "jsscraper"
start_urls = ["http://quotes.toscrape.com/js/"]
def start_requests(self):
for url in self.start_urls:
yield SplashRequest(
url=url, callback=self.parse, endpoint='render.html'
)
d...