Na baze-podataka.net je izašao moj novi post, ovaj put posvećen priči o rownum-u u Oracle RDBMS-u.
Tema može biti interesantna ljudima koji ranije nisu detaljnije čitali o ovoj pseudo koloni.
Objašnjeno je njeno pravilno korišćenje u upitima , i skrenuta pažnja na neke česte zablude u vezi rownum-a...
Link: http://www.baze-podataka.net/2009/10/19/oracle-rownum/
Monday, 19 October 2009
Wednesday, 7 October 2009
Struts2 config-browser plugin
Great thing that I recently discovered in struts2 is the ability of exploring the entire configuration that Struts2 uses to run your application by just including one .jar file - Struts2 config-browser plugin.jar
Using this plugin is quite easy…
All you need to do is to add struts2-config-browser-plugin-2.x.x.jar to your project.
No other action is required!
Now, after you deploy your project, open config-browser by calling index.action inside config-browser namespace.
for example:
http://localhost:8084/MyApp/config-browser/index.action
After you run it, you’ll get a page containing entire configuration of you application.
You can click on any action you have mapped inside your struts.xml and see all the parameters set for it…
And not only actions!
You can explore the struts constants too, for example…
and other things…
Try it! You could fine some interesting things, and it could actually help you when developing or maintaining application…
Using this plugin is quite easy…
All you need to do is to add struts2-config-browser-plugin-2.x.x.jar to your project.
No other action is required!
Now, after you deploy your project, open config-browser by calling index.action inside config-browser namespace.
for example:
http://localhost:8084/MyApp/config-browser/index.action
After you run it, you’ll get a page containing entire configuration of you application.
You can click on any action you have mapped inside your struts.xml and see all the parameters set for it…
And not only actions!
You can explore the struts constants too, for example…
Try it! You could fine some interesting things, and it could actually help you when developing or maintaining application…
Thursday, 24 September 2009
Creating struts2 login page using Tomcat 6 and JNDI realm
Creating login module when using Struts2 and tomcat can be quite cool and interesting assignement, but can also be a quite annoying job if you are not familiar with all that you need to do…
When creating this module, there are several approaches. For example:
- Creating login module using container managed security
- Creating programmatic login module where you define a “database” of usernames, passwords, and roles. This way you define your login logic by yourself as well.
- Using some 3rd party library
This post describes how to configure Tomcat 6 to support container managed security, using JNDI realm.
I’ll use JNDI realm that enables application server to look for user’s information within Active Directory.
Realms are really cool!
They are, in fact, an instruction for application server on where to look for user names, passwords and roles when a user that tries to login into your application needs to be authenticated or sometimes it’s a “database” of usernames, password and roles itself.
Great thing when using container managed security is that everything is already implemented, and all you have to do is to provide a realm and map several elements in web.xml, regarding security.
Let’s start from the beginning.
At this moment, my web.xml file looks like this:
And as for now, I put all my JSPs in the /jsp/ folder.
This is my application structure:
My task is to create a login system for this application, and to provide that only logged users , with roles “boss” or “manager” are allowed to se my JSP pages ( located in “/jsp/” folder )
To do that, the first thing we’ll do is to define (add ) roles in our web.xml.
This can be done in some other files as well, but I’ll do it here…
Note: These roles must be equal to those in active directory.
So, let’s add these two roles:
Next thing we’ll do is to create a security constraint on accessing web pages:
This way, we deny acces to our resources to anyone except to those of role “boss” or “manager”.
Next thing we need to do is to define the authentication method we will be using.
There are several authentication methods: BASIC, FORM-BASED , DIGEST , SECURE SOCKET LAYER ( SSL) and CLIENT CERTIFICATE AUTHENTICATION.
Which one to use - depends on what exactly you need.
For us, the most interesting method is FORM-BASED authentication.
With this method, you create your custom JSP login form inside your application, with your own look and feel.
There are 3 very important things to know when working with form-based authentication:
- input field containing user name must be named “j_username”
- input field containing password must be named “j_password”
- action for form containing these two inputs must be “j_security_check”
So, let’s create one!
Here is the example of such page,:
Let’s call it “login.jsp”, and place it in the root folder ( /login.jsp )
Now, let’s map it inside web.xml:
For now, this is good, but it’s not enough.
We also need to define a form-error-page inside a <form-login-config> tag…
Application server will open that page when user enters wrong user name or password.
Here is what I’m going to do:
I’ll define login.jsp page to be form-error-page too, but with result=false in URL.
This way we will know that we need to add some warning message to user that didn’t enter valid username and/or password.
Let’s edit that prevoius <login-config>:
and let’s edit that login.jsp page, to show error messages when needed:
So…
We created login.jsp page, we mapped it in the web.xml and earlier before we made an acces constraint to all of our folders so only logged users can access it.
But now question is: “what if our login page uses some image from /images/ folder in it, or some java script from within /js/ , or css from within /css/ as it probably would?”
If we leave everything like this, your login form will not be able to read your css and images, and it will look very bad…
What we now need to do is to make some resource public, so that our login.jsp page could use it…
To do so, we could make some existing folders public ( for example /css/ and /images/ ) , or we could copy particular resources ( some images and css that login.jsp needs ) to some new folder and make public only what has to be public ( what we copied ), nothing more…
We’ll do that…
Let’s call this folder “login_resources”
Let’s place it in the root:
/login_resources/
Copy all the resources that you login.jsp uses to this folder.
We will now create one more security constraint that will allow everyone ( login.jsp ) to access it:
We intentionaly “forgot” to set <auth-constraint> inside <security-constraint> so that everyone could access this resource.
Now, our login form will be able to read all the resources it needs…
And, at the end, we need to add our JNDI realm to our context.xml file
You could add this realm to some other files as well, but I like to add it to context.xml.
Here is one example of it:
Please, visit http://tomcat.apache.org/tomcat-6.0-doc/realm-howto.html for more information on creating realms.
Place this realm inside <context> </context> tag in context.xml file.
So, let’s sumarize:
Our web.xml now looks like this:
Once the user logs in, application server will create a session for him.
You can access it’s user name with
ServletActionContext.getRequest().getUserPrincipal().getName();
or check if he has a sufficient role with
ServletActionContext.getRequest().isUserInRole(“some_role”);
And if you would like to logout, you can use
getRequest().getSession().invalidate();
That’s it for now…
I hope I helped someone and saved him some time...
When creating this module, there are several approaches. For example:
- Creating login module using container managed security
- Creating programmatic login module where you define a “database” of usernames, passwords, and roles. This way you define your login logic by yourself as well.
- Using some 3rd party library
This post describes how to configure Tomcat 6 to support container managed security, using JNDI realm.
I’ll use JNDI realm that enables application server to look for user’s information within Active Directory.
Realms are really cool!
They are, in fact, an instruction for application server on where to look for user names, passwords and roles when a user that tries to login into your application needs to be authenticated or sometimes it’s a “database” of usernames, password and roles itself.
Great thing when using container managed security is that everything is already implemented, and all you have to do is to provide a realm and map several elements in web.xml, regarding security.
Let’s start from the beginning.
At this moment, my web.xml file looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<session-config>
<session-timeout>
15
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
And as for now, I put all my JSPs in the /jsp/ folder.
This is my application structure:
/ - root of application
/jsp/ - contains JSPs
/css/main.css - contains CSS
/js/jsfile.js - contains all of my java script code
/images/ - contains a lot of images
My task is to create a login system for this application, and to provide that only logged users , with roles “boss” or “manager” are allowed to se my JSP pages ( located in “/jsp/” folder )
To do that, the first thing we’ll do is to define (add ) roles in our web.xml.
This can be done in some other files as well, but I’ll do it here…
Note: These roles must be equal to those in active directory.
So, let’s add these two roles:
<security-role>
<role-name>boss</role-name>
</security-role>
<security-role>
<role-name>manager</role-name>
</security-role>
Next thing we’ll do is to create a security constraint on accessing web pages:
<security-constraint>
<web-resource-collection>
<web-resource-name>Protected area</web-resource-name>
<url-pattern>/*</url-pattern>
</web-resource-collection>
<auth-constraint>
<role-name>boss</role-name>
<role-name>manager</role-name>
</auth-constraint>
</security-constraint>
This way, we deny acces to our resources to anyone except to those of role “boss” or “manager”.
Next thing we need to do is to define the authentication method we will be using.
There are several authentication methods: BASIC, FORM-BASED , DIGEST , SECURE SOCKET LAYER ( SSL) and CLIENT CERTIFICATE AUTHENTICATION.
Which one to use - depends on what exactly you need.
For us, the most interesting method is FORM-BASED authentication.
With this method, you create your custom JSP login form inside your application, with your own look and feel.
There are 3 very important things to know when working with form-based authentication:
- input field containing user name must be named “j_username”
- input field containing password must be named “j_password”
- action for form containing these two inputs must be “j_security_check”
So, let’s create one!
Here is the example of such page,:
<html>
<head>
<title>Login Page for Examples</title>
<body bgcolor="white">
<form method="POST" action="j_security_check" >
<table border="0" cellspacing="5">
<tr>
<th align="right">Username:</th>
<td align="left"><input type="text" name="j_username"></td>
</tr>
<tr>
<th align="right">Password:</th>
<td align="left"><input type="password" name="j_password"></td>
</tr>
<tr>
<td align="right"><input type="submit" value="Log in"></td>
<td align="left"><input type="reset"></td>
</tr>
</table>
</form>
</body>
</html>
Let’s call it “login.jsp”, and place it in the root folder ( /login.jsp )
Now, let’s map it inside web.xml:
<login-config>
<auth-method>FORM</auth-method>
<form-login-config>
<form-login-page>/login.jsp</form-login-page>
</form-login-config>
</login-config>
For now, this is good, but it’s not enough.
We also need to define a form-error-page inside a <form-login-config> tag…
Application server will open that page when user enters wrong user name or password.
Here is what I’m going to do:
I’ll define login.jsp page to be form-error-page too, but with result=false in URL.
This way we will know that we need to add some warning message to user that didn’t enter valid username and/or password.
Let’s edit that prevoius <login-config>:
<login-config>
<auth-method>FORM</auth-method>
<form-login-config>
<form-login-page>/login.jsp</form-login-page>
<form-error-page>/login.jsp?result=false</form-error-page>
</form-login-config>
</login-config>
and let’s edit that login.jsp page, to show error messages when needed:
<html>
<head>
<title>Login Page for Examples</title>
<body bgcolor="white">
<%
String result = request.getParameter("result");
if(result == null)
result = "";
if (result.equalsIgnoreCase("false"))
{
%>
<span style="color: red">
Wrong user name or password
<br>
</span>
<%
}
%>
<form method="POST" action="j_security_check" >
<table border="0" cellspacing="5">
<tr>
<th align="right">Username:</th>
<td align="left"><input type="text" name="j_username"></td>
</tr>
<tr>
<th align="right">Password:</th>
<td align="left"><input type="password" name="j_password"></td>
</tr>
<tr>
<td align="right"><input type="submit" value="Log in"></td>
<td align="left"><input type="reset"></td>
</tr>
</table>
</form>
</body>
</html>
So…
We created login.jsp page, we mapped it in the web.xml and earlier before we made an acces constraint to all of our folders so only logged users can access it.
But now question is: “what if our login page uses some image from /images/ folder in it, or some java script from within /js/ , or css from within /css/ as it probably would?”
If we leave everything like this, your login form will not be able to read your css and images, and it will look very bad…
What we now need to do is to make some resource public, so that our login.jsp page could use it…
To do so, we could make some existing folders public ( for example /css/ and /images/ ) , or we could copy particular resources ( some images and css that login.jsp needs ) to some new folder and make public only what has to be public ( what we copied ), nothing more…
We’ll do that…
Let’s call this folder “login_resources”
Let’s place it in the root:
/login_resources/
Copy all the resources that you login.jsp uses to this folder.
We will now create one more security constraint that will allow everyone ( login.jsp ) to access it:
<security-constraint>
<web-resource-collection>
<web-resource-name>Unprotected area</web-resource-name>
<url-pattern>/login_resources/*</url-pattern>
</web-resource-collection>
</security-constraint>
We intentionaly “forgot” to set <auth-constraint> inside <security-constraint> so that everyone could access this resource.
Now, our login form will be able to read all the resources it needs…
And, at the end, we need to add our JNDI realm to our context.xml file
You could add this realm to some other files as well, but I like to add it to context.xml.
Here is one example of it:
<Realm
className="org.apache.catalina.realm.JNDIRealm"
debug="99"
connectionURL="ldap://localhost:389"
userPattern="uid={0},ou=people,dc=mycompany,dc=com"
roleBase="ou=groups,dc=mycompany,dc=com"
roleName="cn"
roleSearch="(uniqueMember={0})"
/>
Please, visit http://tomcat.apache.org/tomcat-6.0-doc/realm-howto.html for more information on creating realms.
Place this realm inside <context> </context> tag in context.xml file.
So, let’s sumarize:
Our web.xml now looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<session-config>
<session-timeout>
15
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<security-role>
<role-name>boss</role-name>
</security-role>
<security-role>
<role-name>manager</role-name>
</security-role>
<security-constraint>
<web-resource-collection>
<web-resource-name>Protected area</web-resource-name>
<url-pattern>/*</url-pattern>
</web-resource-collection>
<auth-constraint>
<role-name>boss</role-name>
<role-name>manager</role-name>
</auth-constraint>
</security-constraint>
<security-constraint>
<web-resource-collection>
<web-resource-name>Unprotected area</web-resource-name>
<url-pattern>/login_resources/*</url-pattern>
</web-resource-collection>
</security-constraint>
<login-config>
<auth-method>FORM</auth-method>
<form-login-config>
<form-login-page>/login.jsp</form-login-page>
<form-error-page>/login.jsp?result=false</form-error-page>
</form-login-config>
</login-config>
Once the user logs in, application server will create a session for him.
You can access it’s user name with
ServletActionContext.getRequest().getUserPrincipal().getName();
or check if he has a sufficient role with
ServletActionContext.getRequest().isUserInRole(“some_role”);
And if you would like to logout, you can use
getRequest().getSession().invalidate();
That’s it for now…
I hope I helped someone and saved him some time...
Tuesday, 22 September 2009
Using simple theme and custom CSS in Struts2
Simple theme in Struts2 is great when you want to use your own CSS , and control everything by yourself when it comes to GUI.
Probably many of you (us :-) ) tried using Struts2 with your own CSS without setting default theme to SIMPLE and came up with bunch of unfamiliar tags , like
<table class="wwFormTable">
In your HTML…
Well , if you want to use your own CSS and get your application to look like you wanted to, you need to either create your own new theme ( harder ), or just use Simple theme and use your own CSS ( easier ).
In order to switch to simple theme, just copy/paste this line to your struts.properties file:
Visit
http://devtalks.blogspot.com/2009/07/create-struts2-project-in-netbeans.html
if you are using NetBeans , or
http://devtalks.blogspot.com/2009/07/eclipse-galileo-and-struts2.html
if you are using eclipse
on how to create Struts2 project , and struts.properties file
And that’s it! This way your pages will not contain those annoying
<table class="wwFormTable"> tags…
ISSUES
One thing I noticed when using simple theme is that struts tag <s:fielderror> doesn’t seems to “work” as it should…
You cannot just say, for example,
and expect from struts2 to show errors if your validator doesn’t succeed in validating filed “firstName” .
As a matter of fact, struts2 will indeed dispatch to your INPUT result, but it will not show any errors!
Fortunately , There is a solution to this problem: just use
<s:fielderror> <s:param>filed_name</s:param> </s:fielderror>
instead of
<s:fielderror />
in your .jsp pages and your validation will again act as it should…
ALTERING FieldErrors , ActionMessages and ActionErrors
Speaking of fielderrors, I often see people asking how to change the way Struts is showing field errors action messages and action errors…
You do this by extending the theme you are using. When using simple theme, all you need to do is:
- Create subfolders “template” and “simple” inside folder “classes”
If you open one of these files, you’ll see how these messages are generated.
You can change all that just by editing that file.
Lets say you don’t want your application to show fielderrors as <ul> <li> </li> <ul> elements.
You just need to open the fielderror.ftl and change the part that does this:
So, instead of having
Something like this:
with something like this:
And for now on, every Action message in your application will look like a green box containing messages.
Here is the css I used:
div.mymessage
{
right: 0;
bottom: 0;
left: 0;
width:300px;
margin: auto;
color: #33CC33;
border-color:#009900;
border-style:solid ;
border-width:1px;
border-collapse: collapse;
font-weight: bold;
text-align: center;
background-color:#DDFFDD;
}
This is just a simple example what you can do with extending a theme...
Probably many of you (us :-) ) tried using Struts2 with your own CSS without setting default theme to SIMPLE and came up with bunch of unfamiliar tags , like
<table class="wwFormTable">
In your HTML…
Well , if you want to use your own CSS and get your application to look like you wanted to, you need to either create your own new theme ( harder ), or just use Simple theme and use your own CSS ( easier ).
In order to switch to simple theme, just copy/paste this line to your struts.properties file:
struts.ui.theme=simple
Visit
http://devtalks.blogspot.com/2009/07/create-struts2-project-in-netbeans.html
if you are using NetBeans , or
http://devtalks.blogspot.com/2009/07/eclipse-galileo-and-struts2.html
if you are using eclipse
on how to create Struts2 project , and struts.properties file
And that’s it! This way your pages will not contain those annoying
<table class="wwFormTable"> tags…
ISSUES
One thing I noticed when using simple theme is that struts tag <s:fielderror> doesn’t seems to “work” as it should…
You cannot just say, for example,
<s:fielderror />
<s:textfield name=”firstName” />
and expect from struts2 to show errors if your validator doesn’t succeed in validating filed “firstName” .
As a matter of fact, struts2 will indeed dispatch to your INPUT result, but it will not show any errors!
Fortunately , There is a solution to this problem: just use
<s:fielderror> <s:param>filed_name</s:param> </s:fielderror>
instead of
<s:fielderror />
in your .jsp pages and your validation will again act as it should…
ALTERING FieldErrors , ActionMessages and ActionErrors
Speaking of fielderrors, I often see people asking how to change the way Struts is showing field errors action messages and action errors…
You do this by extending the theme you are using. When using simple theme, all you need to do is:
- Create subfolders “template” and “simple” inside folder “classes”
- Find actionerror.ftl , actionmessage.ftl and fielerror.ftl ( or just those which you would like to extend ) in struts2-core-2.x.x.jar , inside “template.simple” package. You can find this .JAR inside your “libraries” folder.
- Copy these files to your new template -> simple folder created in earlier step.
You can change all that just by editing that file.
Lets say you don’t want your application to show fielderrors as <ul> <li> </li> <ul> elements.
You just need to open the fielderror.ftl and change the part that does this:
So, instead of having
like it is in original file, we can just remove <ul> <li> </li> <ul> elements, and change it with, for example, simple <span> </span> element. That will do the trick. ;-)
Or let’s, for example,change the way your Action message is shown in an application.
Let’s say we need a green box with all the action messages shown in it…Something like this:
To do this, you could just open the actionmessage.ftl file, and change the original
<#if (actionMessages?? && actionMessages?size > 0)>
<ul<#rt/>
<#if parameters.cssClass??>
class="${parameters.cssClass?html}"<#rt/>
<#else>
class="actionMessage"<#rt/>
</#if>
<#if parameters.cssStyle??>
style="${parameters.cssStyle?html}"<#rt/>
</#if>
>
<#list actionMessages as message>
<li><span>${message!}</span></li>
</#list>
</ul>
</#if>
with something like this:
<#if (actionMessages?? && actionMessages?size > 0)>
<div class="mymessage"><br><span<#rt/>
<#if parameters.cssClass??>
class="${parameters.cssClass?html}"<#rt/>
<#else>
class="actionMessage"<#rt/>
</#if>
<#if parameters.cssStyle??>
style="${parameters.cssStyle?html}"<#rt/>
</#if>
>
<#list actionMessages as message>
<span>- ${message!}</span>
</#list>
</span><br><br></div>
</#if>
Here is the css I used:
div.mymessage
{
right: 0;
bottom: 0;
left: 0;
width:300px;
margin: auto;
color: #33CC33;
border-color:#009900;
border-style:solid ;
border-width:1px;
border-collapse: collapse;
font-weight: bold;
text-align: center;
background-color:#DDFFDD;
}
This is just a simple example what you can do with extending a theme...
Sunday, 16 August 2009
Stigla majica sa Eclipse Galileo Blogathon-a
Sunday, 9 August 2009
Create and use an oracle connection pool in Tomcat 6.xx
NOTE: this post is in fact a translation and a shorter version of post that I wrote on my other blog ( www.baze-podataka.net ). It is translated using Google translate tool and than slightly modified by me. So, if you have any complaints, please complain to Google ;-)
Creating a connection pool is a very good practice when developing applications that often connect to the database because it is much "cheaper" to use one of the already created connections, then to repeat the entire process of Connecting to the database every time we need a connection.
It’s such a good practice that many application servers already have their own implementation of connection pooling.
Such server is Tomcat.
All that is left for us to do, of course, is to set all the properties of server that we need to use, and to provide the appropriate drivers that work with a specific database.
Then, if necessary, just take the connection from the pool, and use it, but take care of their proper use.
In this post, I will set Tomcat 6.0.18.
A database for which I’ll create a connection pool is Oracle 10g.
There’s a lot of tutorials, texts and examples about this on the Internet, but very often related to older versions of Tomcat (ver. 4, 5, 5.5).
Unfortunately, for all of these earlier versions of Tomcat many specifications and settings are different, so it probably won’t work with version 6.xx. At least that was the case with me.
So, let’s create an oracle connection pool!
Prerequisites:
First thing you need to have is , of course, Tomcat.
You can download it following this link.
If you use NetBeans to write a code, as I do, you can use Tomcat that comes bundled with the installation of the IDE itself.
Next, we need the appropriate JDBC drivers for Oracle 10g. This means you need an ojdbc14.jar file that comes within the Oracle itself.
Copy this file to <Tomcat home dir>/lib/ folder.
And, of course, we need a database installed too.
Check whether the database you wish to use is available and whether you can connect to it.
create a connection pool
Creating the pool is a quite fast and easy job.
For example, if your application context path is /myapp , it is necessary for you to:
1. Edit the context.xml file, which is located within the META-INF folder of your project like this:
By setting these parameters you determine how this pool will “look” like.
Visit Tomcat’s website for a list of all available parameters.
2. In the web.xml file of your application, you need to insert:
And that's it!
Of course, this is not the only way to create connection pool in Tomcat-6, but it is quite simple, don't you think?
Hot to use connections within our web applications
Using connection pool’s connections within our web applications is as easy as creating the pool itself.
In Java EE, DataSource objects are obtained using the JNDI lookup mechanism.
All you need to do to get a connection is something like this:
and that’s it.
If you are interested in learning more about connection pool, and the best ways of using it, I suggest you to visit my earlier post , and read the 11th chapter of the book I wrote about...
Creating a connection pool is a very good practice when developing applications that often connect to the database because it is much "cheaper" to use one of the already created connections, then to repeat the entire process of Connecting to the database every time we need a connection.
It’s such a good practice that many application servers already have their own implementation of connection pooling.
Such server is Tomcat.
All that is left for us to do, of course, is to set all the properties of server that we need to use, and to provide the appropriate drivers that work with a specific database.
Then, if necessary, just take the connection from the pool, and use it, but take care of their proper use.
In this post, I will set Tomcat 6.0.18.
A database for which I’ll create a connection pool is Oracle 10g.
There’s a lot of tutorials, texts and examples about this on the Internet, but very often related to older versions of Tomcat (ver. 4, 5, 5.5).
Unfortunately, for all of these earlier versions of Tomcat many specifications and settings are different, so it probably won’t work with version 6.xx. At least that was the case with me.
So, let’s create an oracle connection pool!
Prerequisites:
First thing you need to have is , of course, Tomcat.
You can download it following this link.
If you use NetBeans to write a code, as I do, you can use Tomcat that comes bundled with the installation of the IDE itself.
Next, we need the appropriate JDBC drivers for Oracle 10g. This means you need an ojdbc14.jar file that comes within the Oracle itself.
Copy this file to <Tomcat home dir>/lib/ folder.
And, of course, we need a database installed too.
Check whether the database you wish to use is available and whether you can connect to it.
create a connection pool
Creating the pool is a quite fast and easy job.
For example, if your application context path is /myapp , it is necessary for you to:
1. Edit the context.xml file, which is located within the META-INF folder of your project like this:
<?xml version=”1.0? encoding=”UTF-8??>
<Context path=”/myapp” docBase=”myapp” reloadable=”false”>
<Resource name=”jdbc/oracleconnection” auth=”Container”
type=”javax.sql.DataSource” username=”existing_username” password=”user_password”
driverClassName=”oracle.jdbc.driver.OracleDriver” url=”jdbc:oracle:thin:@xxx.xxx.xxx.xxx:1521:sid”
maxActive=”10? maxIdle=”5?/>
</Context>
By setting these parameters you determine how this pool will “look” like.
Visit Tomcat’s website for a list of all available parameters.
2. In the web.xml file of your application, you need to insert:
<resource-ref>inside tags <web-app> and </web-app>
<res-ref-name>jdbc/oracleconnection</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
And that's it!
Of course, this is not the only way to create connection pool in Tomcat-6, but it is quite simple, don't you think?
Hot to use connections within our web applications
Using connection pool’s connections within our web applications is as easy as creating the pool itself.
In Java EE, DataSource objects are obtained using the JNDI lookup mechanism.
All you need to do to get a connection is something like this:
Connection connection = null;
InitCtx context = new InitialContext ();
EnvCtx context = (Context) initCtx.lookup ( "java:comp/ENV");
DataSource ds = (DataSource) envCtx.lookup ("JDBC/oracleconnection");
connection = ds.getConnection ();
and that’s it.
If you are interested in learning more about connection pool, and the best ways of using it, I suggest you to visit my earlier post , and read the 11th chapter of the book I wrote about...
Wednesday, 29 July 2009
Eclipse Galileo and Struts2
I was quite surprised with how many people came to my blog and read my earlier post on how to create a blank Struts2 project and start using this framework in NetBeans 6.5
With a release of new Eclipse, I thought it would be interesting to do the same thing, but now in this IDE.
As you probably already know, Eclipse is one of the famous and certainly one of the best Java IDEs.
Well, about a month ago people from Eclipse foundation released a 3.5 version of Eclipse, called Galileo.
I develop almost all my project using NetBeans, and have never done any Struts2 programming using Eclipse.
That is why I decided to write a post on how to create a Struts2 example in new Eclipse release: Galileo. That's quite fun because that way I (we) get to learn on how to use Struts2 in Eclipse, and get to see Galileo in action a little bit closer…
Note: In this post, I’ll use much of the text , entire source code and application logic from my previous post and concetrate only on the differences between these two IDEs.
So, let’s get started:
First of all we need Eclipse Galileo. Go to the http://www.eclipse.org/downloads/ and download Eclipse IDE for Java EE Developers.
Next thing we need is Struts2 itself. Go to http://struts.apache.org/2.x/index.html and download the latest version of Struts2.
I downloaded struts-2.1.6-all.zip
You won't be needing all the libraries in it. Just 6 of them. Because of this, you can download essential dependencies only.
When you download one of these archives, extract it to some location, for example: c:\Struts2
It is now time to start a new project. Start Eclipse Galileo.
Click file --> new --> Dynamic web project
Let’s call this project GalileoStruts2Example
I’ll use Tomcat 6 . You can use some other server that you have available , it is completely up to you.
Hello-validation.xml:
<!DOCTYPE validators PUBLIC
"-//OpenSymphony Group//XWork Validator 1.0.2//EN"
"http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">
<validators>
<field name="name">
<field-validator type="requiredstring">
<param name="trim">true</param>
<message>Please enter name</message>
</field-validator>
</field>
</validators>
Let’s see how our project tree looks at this stage:
Edit struts.xml, and web.xml:
struts.xml must be located in “classes” folder located in the root of WEB-INF folder:
web.xml:
At the end, our project looked like this:
A small conclusion of mine: great thing about Eclipse is that you can do just about everything with it , with just a little few extra settings and installations...
Unfortunately, for me - many things and options remained a little bit more complicated and unintuitive regarding to some other IDEs. That is such a shame!
Nevertheless , for me , Eclipse continues to be one of the best choices!.
Enjoy Struts2 and Galileo!
With a release of new Eclipse, I thought it would be interesting to do the same thing, but now in this IDE.
As you probably already know, Eclipse is one of the famous and certainly one of the best Java IDEs.
Well, about a month ago people from Eclipse foundation released a 3.5 version of Eclipse, called Galileo.
I develop almost all my project using NetBeans, and have never done any Struts2 programming using Eclipse.
That is why I decided to write a post on how to create a Struts2 example in new Eclipse release: Galileo. That's quite fun because that way I (we) get to learn on how to use Struts2 in Eclipse, and get to see Galileo in action a little bit closer…
Note: In this post, I’ll use much of the text , entire source code and application logic from my previous post and concetrate only on the differences between these two IDEs.
So, let’s get started:
First of all we need Eclipse Galileo. Go to the http://www.eclipse.org/downloads/ and download Eclipse IDE for Java EE Developers.
Next thing we need is Struts2 itself. Go to http://struts.apache.org/2.x/index.html and download the latest version of Struts2.
I downloaded struts-2.1.6-all.zip
You won't be needing all the libraries in it. Just 6 of them. Because of this, you can download essential dependencies only.
When you download one of these archives, extract it to some location, for example: c:\Struts2
It is now time to start a new project. Start Eclipse Galileo.
Click file --> new --> Dynamic web project
Let’s call this project GalileoStruts2Example
I’ll use Tomcat 6 . You can use some other server that you have available , it is completely up to you.
Click Finish.
Your project tree will look like this:
Your project tree will look like this:
Now, in order to use Struts2 libraries, let's add those essential dependencies to project:
Right-click on the project --> properties --> Java Build Path , select Libraries tab and click on the “Add External JARs” button.
Go to folder where you extracted Struts2 libraries and select ( add to project ) following files:
- struts2-core-2.1.6.jar
- freemarker-2.3.13.jar
- ognl-2.6.11.jar
- commons-fileupload-1.2.1.jar
- commons-logging-1.0.4.jar
- xwork-2.1.2.jar
Most of the tutorials on the web are written for older version of struts2, at the time when commons-fileupload-1.2.1.jar was not mandatory, so even when following all the steps in tutorial , you just couldn't get your project to work ( with newer version of Struts2 ) !
Now, your project will look like this:
Right-click on the project --> properties --> Java Build Path , select Libraries tab and click on the “Add External JARs” button.
Go to folder where you extracted Struts2 libraries and select ( add to project ) following files:
- struts2-core-2.1.6.jar
- freemarker-2.3.13.jar
- ognl-2.6.11.jar
- commons-fileupload-1.2.1.jar
- commons-logging-1.0.4.jar
- xwork-2.1.2.jar
Most of the tutorials on the web are written for older version of struts2, at the time when commons-fileupload-1.2.1.jar was not mandatory, so even when following all the steps in tutorial , you just couldn't get your project to work ( with newer version of Struts2 ) !
Now, your project will look like this:
Now, copy these six JARs into the “lib” folder located in the root of WEB-INF folder.
These files will be uploaded to App Server , and a deployed application will use it.
We could put this files into main lib folder of application server, but it is most probably better this way...
We need to create one more folder in the root of the WEB-INF , and name it "classes".
This is where you will create struts.xml, and if needed - a struts.properties file.
I'll put all my JSP's into new folder, "jsp" , which I will create in the root of "WebContent" folder.
All Java code that we write, we will place into some package in the "Java Resources: src" folder.
I'll create one now, called "struts2Example" and a "Hello" Class in it.
If you use validaton, put all Validation XMLs inside class's package too...
We could put this files into main lib folder of application server, but it is most probably better this way...
We need to create one more folder in the root of the WEB-INF , and name it "classes".
This is where you will create struts.xml, and if needed - a struts.properties file.
I'll put all my JSP's into new folder, "jsp" , which I will create in the root of "WebContent" folder.
All Java code that we write, we will place into some package in the "Java Resources: src" folder.
I'll create one now, called "struts2Example" and a "Hello" Class in it.
If you use validaton, put all Validation XMLs inside class's package too...
This is how, at minimum, your Struts2 project structure should look like.
I'll create one small Struts2 application now. Nothing complicated.
User will enter his name, and press "submit" and other page will open , saying Hello to this user.
So, let's first create a Java class extending ActionSupport class , named Hello, inside Struts2Example package.
Let's make it to look something like this:
I'll create one small Struts2 application now. Nothing complicated.
User will enter his name, and press "submit" and other page will open , saying Hello to this user.
So, let's first create a Java class extending ActionSupport class , named Hello, inside Struts2Example package.
Let's make it to look something like this:
package struts2Example;
import com.opensymphony.xwork2.ActionSupport;
public class Hello extends ActionSupport
{
private String name, message;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getMessage() {
return "Hello " + getName();
}
public void setMessage(String message) {
this.message = message;
}
}
We now need two JSPs, for example "nameinput.jsp" and a "response.jsp"
Each JSP needs to contain this line, in order to use struts2 custom tags in it:
<%@ taglib prefix="s" uri="/struts-tags" %>
nameinput.jsp:
Each JSP needs to contain this line, in order to use struts2 custom tags in it:
<%@ taglib prefix="s" uri="/struts-tags" %>
nameinput.jsp:
response.jsp:
Let's create an XML validation file for Hello class, and make a name property mandatory.
Hello-validation.xml:
<!DOCTYPE validators PUBLIC
"-//OpenSymphony Group//XWork Validator 1.0.2//EN"
"http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">
<validators>
<field name="name">
<field-validator type="requiredstring">
<param name="trim">true</param>
<message>Please enter name</message>
</field-validator>
</field>
</validators>
Let’s see how our project tree looks at this stage:
There's only 2 things left for us to do:
Edit struts.xml, and web.xml:
struts.xml must be located in “classes” folder located in the root of WEB-INF folder:
This is where place a file struts.properties if we need to use it, as well…
web.xml:
And if we press “Run” button, and choose a server on which it is supposed to run
we’ll get something looking like this:
But don't worry. Everything is OK, we just didin't handle default page...
If we append entername.action on the URL , our new application will open:
If we append entername.action on the URL , our new application will open:
If we do not enter name and press “submit”:
but if we do enter name and press “Submit”:
So, I hope I helped you to understand how to create an empty struts2 project in Eclipse Galileo.
At the end, our project looked like this:
Unfortunately, for me - many things and options remained a little bit more complicated and unintuitive regarding to some other IDEs. That is such a shame!
Nevertheless , for me , Eclipse continues to be one of the best choices!.
Enjoy Struts2 and Galileo!
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