struts2 session login

Reference:
Sessions in struts2 application

Simple Struts login in example

Eclipse update

For WPT

For Juno :

http://download.eclipse.org/webtools/repository/juno/

For Indigo :

http://download.eclipse.org/webtools/repository/indigo/

Reference: 

WTP-update 

Virtual Box 上 安裝 CentOS Guest Additions

Problem:

1. "building the virtualbox guest additions kernel modules [失敗]"
2. "Building the OpenGL support module FAILED "


1. Solution: (內容為參考 竹林小屋 Virtual Box 上 安裝 CentOS Guest Additions )

所需套件：
1.gcc
2.kernel-devel
3.kernel-headers

安裝流程：
yum install gcc    #安裝gcc，會同時安裝很多相依套件
yum install kernel-devel    #安裝kernel-devel
yum install kerner-headers    #安裝kernel-headers

安裝完成之後，還必須注意一點........
kernel、kernel-devel、kernel-headers三個套件版本要一樣！
否則人生失敗句可能還會再重現XD
rpm -qa | grep kernel    #檢查三個套件的版本是否一樣

筆者遇到kernel版本比其他兩個還要低，所以還要升級一下。
yum update kernel    #升級kernel版本

升級好之後，重新開機使用新的kernel。(不曉得有沒有不用重開的方法)

2. solution (http://it.oyksoft.com/post/6568/):

cd /media/VBOXADDITIONS_4.1.8_75467/
export MAKE='/usr/bin/gmake -i'
./VBoxLinuxAdditions.run


"make -i" , -i, --ignore-errors   Ignore errors from commands.忽略错误

3. 如果 kernel update 後, 程式
要從新 recompile 程式, 但會出現 /etc/init.d/vbox setup
yum install -y  kernel-devel

location hash explaination

Reference:
網頁設計筆記(二十一) 一頁式網頁 location.hash
mozilla Window.location
jQuery hashchange event

css float and clear property

1. Explaintion:
The float proper can set the div or other as the layout that out of the regular, which is such a hidden man in the content, and others is not see this float block,
and the other content will layout there self deployment which ignore the float block and behaviour, ex wrap the div, which such there is no float block exist.

The clear proper is set to the other content block, that will know there has a float block, and it will new a layout to deploy itself



Reference:
w3c 
修正 CSS 對於 float 區塊, 使用 clear:both 無效的解法
 Overflow清除Float效果的妙用

struts2 OGNL value Get Method

1. Problem:
there are some difference method to get struts2 value such as $, #,
but what is the difference between them??


2. Solution:

• objectName: object in the ValueStack (default/root object in the OGNL context), such as an Action property
• #objectName: object in the ActionContext but outside of the ValueStack, specifically...
• %{ OGNL expression } is used to force OGNL evaluation of an attribute that would normally be interpreted as a String literal.

Reference:
whats-the-difference-between-and-signs-in-struts-tags

R plot png x11 error in centos

Problem:

Using the R to plot the figure and want to store with png file,
such as png(file="a.png")
but it will appear
Error in  png(file="a.png"): X11 is not available

Solution:

I used the R.2.15.2.
1. First you should install the important package for plotting
{
yum install -y cairo-devel.x86_64
yum install -y libpng-devel.x86_64 
}

2. configure and compile the R
{

 ./configure --with-x=no


  R is now configured for x86_64-unknown-linux-gnu

  Source directory:          .
  Installation directory:  
  C compiler:                gcc -std=gnu99  -g -O2
  Fortran 77 compiler:       gfortran  -g -O2

  C++ compiler:              g++  -g -O2
  Fortran 90/95 compiler:    gfortran -g -O2
  Obj-C compiler:            

  Interfaces supported:     
  External libraries:        readline
  Additional capabilities:   PNG, TIFF, NLS, cairo
  Options enabled:           shared BLAS, R profiling, Java

then 
make
}

3. Execute the R and check the png is TURE
{
> capabilities()
    jpeg      png     tiff    tcltk      X11     aqua http/ftp  sockets
   FALSE     TRUE     TRUE    FALSE    FALSE    FALSE     TRUE     TRUE
  libxml     fifo   cledit    iconv      NLS  profmem    cairo
    TRUE     TRUE     TRUE     TRUE     TRUE    FALSE     TRUE
}

4. Check and setting the bitmapType as cairo in R environment
{
>options(bitmapType="cairo")
}

Reference:

unable to start PNG / X11 in rstudio
How to get R to compile with PNG support
R install
R dowload

Centos x11