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  Solve Hibernate "Too many connections" issue in MySQL

When working with Hibernate and MySQL, sometimes some exceptions will be thrown after sometime. The exception may seem like : java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections" This means there are too many active connections on the MySQL, you can use SHOW STATUS LIKE '%Threads_connected%'; to check the active connections to MySQL. If you want to change the maximum connections allowed to MySQL. You can execute: set global max_co...

   MySQL,Hibernate,Clos     2013-09-04 22:20:49

  About tmpfs

tmpfs is another confusing name in Linux kernel, its implementation is in mm/shmem.c, shmem has no relation to tmpfs at first glance although we know tmpfs is based on memory. We can understand why we use this name by seeing where this is used. In a desktop Linux system, tmpfs is loaded usually: % grep tmpfs /proc/mountsdevtmpfs /dev devtmpfs rw,seclabel,nosuid,relatime,size=1958956k,nr_inodes=489739,mode=755 0 0tmpfs /dev/shm tmpfs rw,seclabel,nosuid,nodev,relatime 0 0tmpfs /run tmpfs rw,seclab...

   tmpfs,Linux,file system     2013-06-14 12:10:56

  Using vi key bindings in bash and zsh

Takeaway: If you prefer to use vi or vim for command-line editing, you can configure shells to use vi key bindings instead of emacs-style key bindings. Here’s how. By default, most shells use emacs-style key bindings for command-line editing and modification. For users of vi or vim, however, you can instead configure shells to use vi key bindings instead. This is done by editing ~/.bashrc in the case of bash, or ~/.zshrc in zsh a...

   vi,Linux,Zsh,bash,key binding     2012-02-07 06:22:36

  bash network interface

Some of us may have seen /dev/tcp/<host>/<port> before, is this a special file system implemented in some BSD kernel? Because there is no /dev/tcp in Linux. Actually, this one is implemented in bash. We no need to rely on wget,nc to do network connection. It's very easy to use this interface: bash-4.2$ cat </dev/tcp/time.nist.gov/13 56188 12-09-18 15:34:26 50 0 0 733.5 UTC(NIST) * bash-4.2$ exec 3<>/dev/tcp/www.w3.org/80 bash-4.2$ echo -e "GET / HTTP/1.0\n\n" >&3 b...

   Bash,Network interface,/dev/tcp     2013-07-20 00:57:52

  Emacs adventures

I have been using Emacs for over a year now. I actually didn’t learn a lot when I started using it (just the basics to get going and then some relatively common keyboard shortcuts), but lately I have been reading and learning much more about it. I’m so grateful by everything I’ve learned from different people on the net that I wanted to share a couple of things I’ve learned, and a simple major mode for editing AsciiDoc documents. As a long-time VIM user, I f...

   Editor,Linux,Emacx,VIM,Shortcuts     2011-11-30 11:56:49

  Flash Player sandboxing is coming to Firefox

Peleus here. In December of 2010, I wrote a blog post describing the first steps towards sandboxing Flash Player within Google Chrome. In the blog, I stated that the Flash Player team would explore bringing sandboxing technology to other browsers. We then spent 2011 buried deep within Adobe laying the groundwork for several new security innovations. Today, Adobe has launched a public beta of our new Flash Player sandbox (aka “Protected Mode”) for the Firefox browser....

   Flash,Sandbox,Google chrome     2012-02-07 06:16:57

  When can Chinese buy fresh food online?

Farmigo is an online agricultural marketing platform. Farmers can post their own products, people can directly purchase their favorite ingredients on it. Farmigo promises that fresh ingredients will be sent to the designated location within 48 hours, but the price is 20-30% cheaper than the supermarket.In other words, Farmigo itself does not sell agricultural products, it just plays a platform intermediary role. Their advantages to attract consumers are fresh ingredients supply, home delivery a...

   Agriculture, Online sales, B2B     2012-12-12 13:37:03

  Java Cipher encryption/decryption example

In Java, Cipher is the API for doing data encryption/decryption. Many cryptographic algorithms such as AES, DES, RC4 etc can be specified when creating Cipher instance. The Cipher instance calls the underlying algorithm specific implementation to do the actual encryption/decryption.  Before doing the encryption/decryption, a key needs to be created and it will be used to do the encryption/decryption. A sample program for performing all these is : import java.security.Key; import javax.cryp...

   Java, Java Security, Cipher, Example, Sample     2015-08-14 07:07:10

  Facebook : App Center is more suitable for developers

Facebook recently announced that they will release their own app store named App Center. It will be released in a few weeks. At the same time, Facebook also released the introduction page of the App Center, it introduces to developers the process of app submission and the standards of app approval.Facebook allows developer to provide charged apps via App Center. Since it has over 900 million active users globally, so many developers are willing to develop apps on this platform. Facebook will dec...

   Facebook,App Center,Introduction     2012-05-13 01:03:56

  Origin of Windows blue screen

Many of you from old ages might see the classical blue Windows blue screen before.Do you still remember the most famous Windows blue screen incident during a presentation of a Windows 98 beta by Bill Gates at COMDEX on April 20 1998. But do you know the history of blue screen? John Vert, an ex-Windoes NT kernel guy, shared the story on Quora.  Back in 1991 John Vert wrote the original code for Windows NT 3.1 that put the video screen back into text mode and the routines to put text on it (a...

   Windows blue screen,History     2013-07-24 09:25:16

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