I'm not new to servlets. But I'm still curious: why javax.servlet package isn't distributed on its own? Why I need some application server installed before I can compile my code?
Short answer, it is distributed separately.
Servlets are a specification and an API. If you want the JAR, download it from the spec site Servlet Spec 3.0.
Obviously if you want to actually deploy your application, you'll still need an implementation (i.e. a server).
The servlet API is available through some jar and you can do with it what you want. On maven it is here. You can compile the code without any application server but it probably won't do what you want. It is only an interface afterall
Servlets are only really relevant in the context of a Web Application and this is why Servlet Containers exist. They are the implementation. Take a look at all the work the container does before a request reaches the servlet: Tomcat Sequence Diagram.
Servlets like other Java EE technology like EJB are Specification from JSR(Java Specification Requests) from Java Community Process Program
The onus is on the Application Server vendor to provide the implementation based on the specifications released.In this case
- for Servlet 2.5
- for Servlet 3.0
Sun / now Oracle does release the javax.servlet package separately and you can download it from Maven Repository also its available within the lib folder of any J2ee complaint application server/web container .
i.e for Tomcat its available in TOMCAT_HOMEDIR/lib/servlet-api
So for developing and compiling , this jar is sufficient , you would only need the Application server only when you want to actually deploy your application.
Related
I have a web app built with Java, Spring MVC, and JDBC. The result is a WAR file.
To run it, the user has to install Java 8 JDK and Tomcat, and deploy the WAR file to the Tomcat server.
It would be great if they could just download the one file run it as a standalone application.
That is, run "the WAR file" and just browse to http://localhost:8080/myapp
Also, on Windows it would be great it was setup as a Server (like Tomcat is when installed with the installer).
Is there any way to do this? Maybe with Spring Boot or something new like that?
Yep, Spring boot is the way to go.
It allows you to build an executable Jar with all dependencies and a Tomcat (by default, can be changed) embedded.
But users will still need to download a JRE to execute the Jar, and a database if it's required, but you can use en embedded database like H2, HSQLDB..., depends what is your needs.
Yes . you can use spring boot to achieve your results. Kindly refer the below link for sample code
https://mkyong.com/spring-boot/spring-boot-hello-world-example-jsp/
You can use embedded jetty server using maven but that would require you to setup few things your app and may have align your existing app, please check this article for more information.
Jetty is similar to tomcat server in terms of running spring application, there are not much difference in terms of development. Tomcat is just more famous.
Other option as others said, is to migrate your app to spring boot which would be easy if you already have app written in spring (But that depends how much code you have and how much time you have)
It has been almost a month since i started working with jsf and jboss. I've worked with jsf before. But i didn't use jboss, just apache with it.
I've done a bit of search and i found that JBOSS is:
WildFly, formerly known as JavaBeans Open Source Software Application Server is an application server that implements the Java Platform, Enterprise Edition. JBoss is written in Java and as such is cross-platform: usable on any operating system that supports Java.
And instead of managed beans, there are Action classes. As far as i know, the concept is the same, but some annotations are different.
Are these the only differences between jsf with and without jboss? What good does it do in a jsf application? Is jboss really required?
No, you don't need specifically JBoss AS (now Wildfly, the name has been recently changed) but you obviously need some web container (de facto web server) which run JSF applications (for instance Tomcat, Jetty, Resin or Wildfly).
Difference between plain web container (Tomcat, Jetty) and application server (Wildfly, Glassfish) is that in AS you can use Java EE technologies like EJB or JMS. For JSF the difference is that JSF libraries are usually bundled with application server so you don't have to put them into your WAR file (or have scope provided in Maven).
I am a little new to J2EE. I have a EJB3 project and I want to run a class on application start-up, how can I do that?
I know in EJB3.1 I can use #startup and #singleton unfortunately that is not a option and I have to use EJb3 and java 5. I have done some research and there were a few solutions but I have been unable to make it work.
WebSphere Application Server version 6.1 does not support EJB3 with a standard installation. You also need to have a feature pack for EJB 3.0 installed.
See this information on the IBM site.
If this is not your issue you should update your question with more detail of what goes wrong.
Your only options prior to WebSphere 8 (with EJB 3.1 support) are:
WebSphere startup beans. These are a programming model extension
Package a WAR with the application, and use a ServletContextListener to initialize state used by the EJBs.
Please I would like to know the major difference between a Jave EE project and a Java Web project in netbeans IDE with respect to the EJB. In fact you can create a web application based on EJB, JPA and JavaServer Faces in Netbeans IDE if you choose the Java Web category.
On the other hand you choose the project category as Jave EE project, NetBeans IDE will create 3 sub-projects, e.g: StoreApp (Enterprise Application project), StoreApp-ejb (EJB project), and StoreApp-war (Web project).
The first one will be packaged as a single .war file, the second one will be packaged as an .ear file, containing the web .war and the EJB .jar.
The difference between these is a bit broad to handle here, but I wouldn't advise on creating EARs unless you know that you want/need to.
I think you should learn firstly about web server and a application server..
well i'll happy to help you.
1) we cannot run enterprise application in web server.. i.e. if u are using EJB etc. to run this EJB project you have to use Application Server like JBoss and many more.
2) while using web server it cannot load any heavy application means if your application having multiple users , in that case connection pooling will come into the picture. for connection pooling Application server much better then web server.
For more you can visit below link:-
What is the difference between application server and web server?
I hope it'll helps you
Thanks!!!
There are 3 kinds of project/application:
Standalone Java application and sometimes call it as swing application. Bundle it in the form of Jar and you can run this application without any web or application server.
Web-application: Basically we have to create a war which is combined with html/jsp,jar etc. This war file has to deployed into webcontainer.
Enterprise Application: We have to create a EAR file which is combined with war, EJB & jar. This has to deployed into application server.
A very helpful tutorial https://www.youtube.com/watch?v=6vMB3rzN_Xw
Hope this helpes... cheers!!!
I have WebLogic (10.3.5) application server installed in a server and in an another
server JBoss AS (7.1.1) installed.
ServletA.java gets compiled using Java EE specific jars in JBoss AS and deployed in WebLogic (during
runtime WebLogic will be using its own Java EE specific jars to execute). Currently, when I access the servlet in WebLogic, I'm not getting any errors, it's working fine.
My question is, is this approach OK or will this create any problems in the future?
As long as you stick to the classes in the Java EE spec and don't use any JBoss specific classes or features this approach is OK.
What can still go wrong is if you rely on server specific behavior (hard to test) or run into bugs on one server.