Well, as part of job I have created many web projects and
made them live. But it is a different story when you need to do it on your own.
In the company you have different teams to handle various
activities i.e. the Infra team for handling the Deployment and server setup
stuff, Database team to handle the database setup / table creations, the
sitedev team which deals with HTML pages, CSS, and JS and the developers keep
themselves busy with the coding part.
This is a project that I am still working on. I will adding
here the challenges that I have faced so far and their solution so that starter
we developers like me who want to create something all on their own can benefit.
1) Web Server folder structure - Where to place what files
Ok, so this is very important for us to know that which file
need to be place at what location on the webserver. Many of the Linux based
hosting servers give us a very nice interface to manage our application through
"cPanel". I will discuss the same.
Below is an image of what a generic cPanel file structure
looks like,
I will explain the details as colour marked in the image,
a)
Red: These are
custom folders. Some of them were present from before while others I created to
manage my web resources like CSS, Javascript files, images, HTML files and the
JSPs in a much better way. You can create your own folders.
b)
Orange: This
is the Runtime CLASSPATH of our web project. So anything that needs to be
placed in the classpath of the web project like the classes, library JARs, properties
files, web.xml, struts-config.xml etc.
goes here.
c) Green: This
is a configuration file for the web servers based on Tomcat Apache servers. The
only configurational change that I did in it was adding the entry for my custom
error page. Details of which will follow later.
d)
Pink: These are my custom error pages. These are
defined in the .htaccess as discussed above.
error400.jsp is displayed when an error
with error code 404 occurs
error500.jsp is displayed when an error
with error code 500 occurs
e)
Blue: This
file is the first file that is executed when someone types the address of our
application in the browser. It is defined in the web.xml file under
tag.
I hope this gives a fair idea of how the file
system in cPanel is detailed. Let’s get in more details now.
2) Generic error page definition
Importance: This is important because we do not want our
visitors to see a pre-defined ugly error page of our hosting provider when some
error occurs. It is very important for a nice user experience to show our own
error page with information about what to do next. So, let’s get on with it.
As I explained above, we can use the .htaccess file to
define generic error page for our application based on the error codes.
.htaccess is a normal text file and can be opened with any txt editor. Just
note that this file has no extension so when you edit and save it, no extension
is added or else it will stop working.
You can make an entry as follows for you error pages at the
end of the file,
ErrorDocument 404 /error404.jsp
ErrorDocument 500 /error500.jsp
3) Deploying you web application on the Web Server
It is really easy. Though it appeared like a mystery when I
did not know anything before. J
You can use the in built file upload tool of cPanel to
upload your files. But I would suggest you use a FTP application like FileZilla
to do it via FTP. It will make live much simpler as you can upload multiple
file in a go with lot of ease.
So, place you file as detailed below,
a)
The index.jsp and the .htaccess files go in the
root. You also place all your custom folders that may be present under
/WebContent folder in your workspace
here.
b)
Copy all the build .class and properties files
from you workspace location i.e. /build/classes to /WEB-INF /classes
c)
Copy all the required JAR files to following
location i.e. /WEB-INF/lib
d)
Copy all the configuration files and the TAG LIB
files such as, web.xml, struts-config.xml, validation.xml, c.tld, fn.tld etc to
/WEB-INF
That’s all. This completes the deployment of
your web application on the server.
4) Next, challenge
that I faced was while trying to access a file that I had placed in one of the
custom folders through my servlet code. Giving a relation file location will
not at all work here. It may work on our local machine and in eclipse. But when
deployed on the web server, the code would fail.
In order to overcome this issue we need to get the full path
of the file using the Servletcontext. Below is a sample code explaining how to do it,
ServletContext context = getServletContext();
String relFileLoc = "uploadedData/Data.csv";
String fullFileLoc =
context.getRealPath(relFileLoc);
5) Accessing you servlets from the browser
So, you have deployed all you servlet class files and code
on the web server and are ready to access it. But , Hey! why am I not able to
access it.
You can access your servlet correctly though the URL of form
as given below in you workspace, i.e.
http://localhost:8080/servlet-name
But simply replacing localhost:8080 with your domain name
(i.e.
http://domain-name/servlet-name ) does not allow you to access your
servlet.
You need to use URL of following form to access it, i.e.
http://domain-name/servlet/servlet-name
Please note the word servlet in the URL. This is some kind of
restriction from the host servers . I came to know about it through our host
server’s documentation.
6) Want to upload a file to the web Server. Things you need
to know.
Well, the first and last thing that you need to know is that
you need to give write permission to the folder where you want your files to be
saved. If you forget this your files will never get uploaded.
I have also attached here my fileUtil.java file with a
sample code for performing single file upload on the server. For me, the
uploaded data folder was /UploadedData . So, all you have to do is, right click
on the folder name in the cPanel and choose “change permission” option. And
select the write permission. Refer image below,
Download FileUtil.java:
7) Loggers – Key to finding errors and debugging them in you
web application
I do not need to explain why using loggers in your
application is important. But I will definitely help you with how to deploy it
on the web server J
I have used Log4J for my purpose and will explain the same. Hope,
it would be similar for any other loggers that you may use.
Log4J comprises of 2 important things,
a)
Log4J.properties file – this file holds the
various properties needed for Log4J
Like all the other property file it needs to
be placed at following location on the web server i.e. /WEB- INF /classes
b)
The location where the log files would be
created
Now, this is really important and took me
hell lot of time to figure it out. People taking you shared JVM based JSP
hosting for their purpose will know it. J
Well, I read lots tips/hints on the web as
to how to set the path of the log file in the log4j.properties file so that it
can be properly deployed on the web server. Some suggested using a servlet that
was initialized on server startup or to use a ServletListner class. But
somehow, both did not work for me. So this is what I did,
i)
I printed the full path of my log folder in one
of the JSPs by using the code to get the full path of a folder in servlet as explained above i.e. context.getRealPath()
ii)
I wrote this path as the location of my log file
in the log4j.properties file
iii)
Gave write access to my Log folder
I
think this is the quickest and most simplest way to setup log4J for you
application on the web server J
8) Want to use Struts. No problem at all
Setting up struts needs to special treatment. Simply place
the required JARs and the configuration XML files in the locations as already
explained and it will start working.
The only little difficulty that I had was with using the
struts-html and struts-bean Tag libraries in the JSP.
With the setting I have explained, including the tag-libs as below worked for me.
<%@ taglib
uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld"
prefix="bean" %>
9) MySql + Stored Procedure = A hard time till I figured out
the goof up
Setting up the Database is very simple using the PHPMySQL
interface that cPanel provides. I was able to run all kind of select, update
and delete queries but when it came to running stored procedures I got
following error, i.e.
User does
not have access to metadata required to determine stored procedure parameter
types. If rights can not be granted, configure connection with
"noAccessToProcedureBodies=true" to have driver generate parameters
that represent INOUT strings irregardless of actual parameter types
Using “noAccessToProcedureBodies=true” in the connection URL
also did not work for me. It was then I discovered that there was some bug in a
specific version of the MySQL JDBC driver that did not allow “noAccessToProcedureBodies” to work. I had to use “useInformationSchema=true”
attribute in the connection URL to have my stored procedure execute. In case
you face similar issue, please try this out.
10) SVN repository – A must use feature
Most of the Host servers provide a SVN repository as well.
You can check if one exists for you or not by looking for this logo in cPanel,
This is a very nice feature and must use it for sure to keep
a repository of your project so that you can maintain version of it and share across
team members. It was of great help to me lot of times when I accidently deleted
some of my code files and I had to get it back.
So that's all guys that I have got for now. I will keep adding more to this list as I come acroos more challenges.
Hope this makes some one's life easy and my purpose of writing this post will be solved. CHEERS!!
