My first GAE java application

Here is the site http://test-java.appspot.com/

I developed it with using GWT and JPA which are two very popular technology.

Google provides a Eclipse PlugIn for GAE, that allows to debug the web application include both server and client side.

Debug java application

export _JAVA_OPTIONS="-Dlax.debug.level=3 -Dlax.debug.all=true"
export LAX_DEBUG=true

The issue with using 'ALTER DATABASE BACKUP CONTROLFILE TO TRACE'

There are some issues with recover control files in RESETLOGS mode after executing 'ALTER DATABASE BACKUP CONTROLFILE TO TRACE',


According to instruction, we need to register log files with using the following comamnd



ALTER DATABASE REGISTER LOGFILE ''


But sometimes the following error occurred

ORA-00604: error occurred at recursive SQL level" error on "ALTER DATABASE REGISTER LOGFILE '/<path>/1_234_636797930.dbf'"

And the work around is using the following command instead

ALTER DATABASE REGISTER PHYSICAL LOGFILE

Linux renew ip command

The -r flag explicitly
releases the current lease, and once the lease has been released, the
client exits. For example, open terminal and type the command:

$ sudo dhclient -r

Now obtain fresh IP:

$ sudo dhclient

There is no need to restart network service. Above command should
work with any Linux distro such as RHEL, Fedora, CentOS, Ubuntu and
others. On a related note you can also try out the following commands:

# ifdown eth0

# ifup eth0

# /etc/init.d/network restart

OR

# /etc/init.d/networking restart

Some tech books read recently

• Troubleshooting Oracle Performance

Very comprehensive.

• Effective Java Second Edition

Provide some simple and nice programming tips

• Scrum and XP from the Trenches

Introductory book

• Ask Tom 2007

Too many contents

The web security tools

netcat - a featured networking utility which reads and writes data across
network connections, using the TCP/IP protocol.

http://netcat.sourceforge.net/

nmap - a free and open source (license) utility for network exploration or
security auditing

http://nmap.org/

paros - a web proxy
for people who need to evaluate the security of their web
applications

http://www.parosproxy.org/index.shtml

Develop the web application running on google app engine

My Example

http://yyang-hhong.appspot.com/

Required libraries

1. simplejson
setup.py install
2. prototype javascript library

How to view PDF file in windows mobile

Most of PDF files are non-tagged files which text cannot be wrapped automatically, but you can use Adobe Acrobat to convert them to tagged file, and here is the instruction.

Guide to Creating Accessible PDF Files with Adobe Acrobat 5

Setup the automation test in windows with using CYGWIN

Some required libraries:

1. openssh

http://www.netadmintools.com/art516.html
2. apache httpd
3. sendmail - ssmtp, mutt
4. cron
5. cygrunsrv
6. vim

Tips:
1. For launching the ANT windows version, use dos2unix to convert the file $ANT_HOME/bin/ant

2. use ' od -c more ' to check if the file contains invisible characters

3. use tr to remove the invalid character, such as DOS escape character

echo `p4 counter $BRANCH_COUNTER_NAME` > $UNIX_TEMP_HOME/output-$BRANCH_COUNTER_NAME
DAS_COUNTER=`tr -d '\r' < $UNIX_TEMP_HOME/output-$BRANCH_COUNTER_NAME` 4. start and stop Apache httpd /usr/sbin/httpd.exe kill -TEAM 'cat /var/run/httpd.pid' 5. install cron and view logs cron-config /usr/bin/cronevents.exe 6. solve the cron error like 'can't switch user context' change the owner for all of files used by cron 7. ssh client can not access the windows network drive, but Cygwin can. the reason is because sshd service is running as LOCAL SYSTEM ACCOUNT.

8. cron job cannot access the existing windows network drive, but you can mount it at the beginning of the cron scripts, for instance

net use l: //test_machine/folder /user:test_user test_password

9. Cygwin Doesn't Register All Environment Variables When Using SSH, and here is a solution

http://smithii.com/node/44

Some good tools for Windows Mobile

I think the best reader for Windows Mobile is IE since it can display the html content with one column layout so user don’t have to move the content horizontally.

I have tried a couple of other reader such as Adobe reader, Text Reader, but unfortunately both
of them don’t support one column layout very well.


And there are a couple of tools that could convert the documents to html doc.



PDF2HTML - convert PDF to html

CHMUNPACKER - convert CHM to html

posting blog with using scribeFire

cool firefox addon!

Danny jumped to M$

Now M$ got three of best borland's chief architect .

A interest query

we have a table items which miss some price for some weeks

Week	Item	Price
1	1	8
2	1	null
3	1	null
4	1	7
1	2	6
2	2	3
3	2	null
1	3	2
2	3	null
3	3	4
4	3	2
5	3	null

we want to have a query to replace the missed price with last available price

SELECT i_item,
i_week,
i_price,
SUM(i_price) over(PARTITION BY new_price) new_price2
FROM (

SELECT i.item AS i_item,
i.week AS i_week,
i.price AS i_price,
SUM(i.price) over(ORDER BY i.item, i.week) new_price
FROM items i)
ORDER BY 1,
2

adopts dbms_rls to restrict the table access

oracle provides a powerful feature that allows developer to audit the table access with user_customized function, here is the sample

create or replace function GEORGEY_SECURITY_FUNCTION return boolean is
Result boolean;
begin
raise_application_error(-20101, 'illegal access');

return(Result);
end GEORGEY_SECURITY_FUNCTION;

BEGIN

dbms_rls.add_policy(object_schema => 'GEORGEY',
object_name => 'PEOPLE',
policy_name => 'GEORGEY_POLICY',
function_schema => 'GEORGEY',
policy_function => 'GEORGEY_SECURITY_FUNCTION',
statement_types => 'SELECT,UPDATE,INSERT,DELETE',
update_check => TRUE,
enable => TRUE,
static_policy => FALSE);

END;

java.net: Sprinkle Some AJAX Magic in Your Struts Web Application

Visual Studio:Microsoft dev tools roadmap

bobbyvandersluis.com | Ten good practices for writing JavaScript in 2005

WWW SQL Designer

meebo.com

Ajax for Java developers: Java object serialization for Ajax