Store UUID in MySql

There are two ways to store UUID in MySQL. The one is save it as varchar(36), the other is save is as varbinary(16). The first way is easy for developer, just set UUID string in field of entity and insert it into database. But the second way can save disk space and quick.

Java get element in set

There are a lot of ways to get one element from set. I do not recommend you to do this. If you need get one of them use List instead.

JQuery append() prepend() after() and before()

There are some methods in JQuery change the content of page. Different methods add the element to different position. In this blog I will show you the different of them. You can also save the following code as html file and run it. Click the different button can add the different element to the page.

Search string in linux directory

grep command can help you search specific string in file. Learn basic use of it click here. grep is very powerful. It can help us to search specific string in a Linux directory. For example, we have two files in tmp directory.

Ajax post serialized form to SpringMVC

You can submit a form directly or use Ajax to submit data.In this page I will show you how to use Ajax post serialized form data to SpringMVC. In this way your application will be more friendly.

Front End tutorial

There are lots of technologies in Front End. In this tutorial I will show you how to use common page front-end technology. Hope these blogs help you.

Ajax post json xml to SpringMVC

We can use json and xml to store complex data in our application. In this post I will show you how to use Ajax post xml and json to springMVC. For quickly starting I use Spring Boot in my example. The code also works in SpringMVC.

Java convert object xml example

There are many ways to convert object to xml. In this post I will show you how to use XStream to convert object to xml. In order to use XStream add maven dependency like following.

Linux find command examples

find is a very useful command when you want "find" something in Linux. In the page I will learn the basic use of this command with you. For the detail of find you can learn from manual(type man find in command line).

google 403 error your client does not have permission to get url

Today I meet this error when I use Chrome google something. I change the search word the error is still there. After restarting Chrome I try to google again it is still doesn't work. To solve this problem just clear the cache of Chrome like following.

JQuery add remove tr in table

In this page I will show you how to use JQuery remove and add tr element in table. Copy the code following and click remove or add button. If you do not want remove the first tr element or add after last tr element just change the JQuery selector.

Spring Boot http status code

It is easy to custom your own 404 or 500 page in SpringMVC(I use Spring Boot to make an example). It is not friendly for browser and search engine to return an error page without http status code. There are several ways to return page with http status code. I will show you the easiest way in this blog.

GitHub markdown code highlight identifier

You can use code block in markdown to make code read easily. GitHub support different language identifier to highlight the keywords. The list of identifiers are here. Click highlight.js demo page for detail.

Solve OutOfMemoryError UncaughtExceptionHandler

In this page I will show you how to solve Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread. This error means there is not enough memory to run your application. What you need to do is increasing memory. The key question is there are a lot of arguments for java which is right?

Generate OutOfMemoryError java heap space

OutOfMemoryError means the memory is not enough for your program. After this error Java virtual machine will tell you the detail. When you want solve this problem, you should first of all get to understand it. In this page I will show you how to generate OutOfMemoryError: Java heap space programatically.