EJB Vs JSP/POJO/Servlets, etc

I'm familiar with several J2EE technologies and decided to start learning some design patterns. EJB comes up a lot in the business tier, so I've been looking at more info about them.
What I can't find a clear answer on at the moment is why exactly you would choose to use them over existing features. The ads/disads seem to be about half and half, and the ads are mainly from a development perspective (although they make apps more complicated).
So, does EJB do anything to improve scalability and performance in a considerable way as compared to JSP, POJO, etc, or is it mainly for increased decoupling of tiers and subsequent better maintenance and reusibility?

Technically, the answer is that EJB does not add anything that cannot be done with regular business objects...
The difference is how easy it is to do the things you need.
With EJB before EJB3 there is a lot more effort that goes into using the technology, this is why people often will use regular business objects... they may only need one or two of the things EJBs bring to the table, so the pain of EJBs is not worth the gain.
EJB3 is a lot easier to implement (than previous EJB specifications) so we should start to see people using this technology more.
When you are asking about EJB vs POJO the question you need to ask yourself first is: have we decided how the application will be deployed?
If that decision has been made, then you will be able to know what flavour of EJB is available (if at all) on your application server.
e.g. if it will be deployed on Tomcat => no EJBs at all
if it will be deployed on Websphere => (at the moment) EJBs but not EJB3 are available
if it will be deployed on Glassfish or JBoss5 (or possibly some versions of JBoss4) => EJB3 is available.
Where I see EJBs fitting into the MVC application is in the Model layer, i.e. they provide a means of abstracting your model so that it can be expressed in terms of business methods, etc. This can simplify the controller. But again, it is nothing that cannot be done with regular POJOs.

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Regards,
Usman Ali

hello
JSP and servlet is web programming, may be little bit different to development local application.
1st, you should have two computers: one is server and the other is local workstation. This server should have a static IP address, that other people can go into your server. Workstation is any computer normal you use it.
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Reality, you have many technical thing to solve, eg setup web server etc. However, you can write your source code and test it, then open to outside people.
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How to create thumbnail images on the fly from JSP or servlet?

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When they upload pictures i need to create thumbnail for them on the fly.
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thnx.

Here is how you can create dynamic images:
http://developer.java.sun.com/developer/JDCTechTips/2001/tt0821.html#tip2
However, if you want to create gifs/jpegs and save them to the disk it depends from where you want to create the images. It is different if you are creating from another image or just drawing one from scratch etc.. But in the end you will probably need to use one of the imageencoder classes and write the result to the disk with the file io classes.

Load balancing for JSPs and servlets

Hi:
          I am using IIS as the proxy server, with the WLS plug-in, to a WLS
          cluster. This provides round robin load balancing just fine. Will it
          provide weight based load balancing if I set 'weblogic.system.weight'
          differently on each server, or is that not relevant for clustering JSPs
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          Sincerely,
          Ashish


Currently the plugins ( for NES, IIS and Apache) just use the round robin
          algorithm. the property
          weblogic.system.weight is used only be weblogic's replica aware clusterable
          RMI/EJB stubs.
          To use this property for your JSP/Servlet load balancing you have to use
          weblogic server as proxy fron-ending your weblogic cluster.
          --Viresh Garg
          Ashish Vimal wrote:
          > Hi:
          > I am using IIS as the proxy server, with the WLS plug-in, to a WLS
          > cluster. This provides round robin load balancing just fine. Will it
          > provide weight based load balancing if I set 'weblogic.system.weight'
          > differently on each server, or is that not relevant for clustering JSPs
          > and servlets?
          > Sincerely,
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Beans, jsp and servlets

i want to use jsp to servlet communication. i use a bean with session scope for each user. in the jsp pages i simply use the jsp command -<jsp:useBean id="cart" scope="session" class="DummyCart" /> and set properties etc. how can i use a servlet and set proprties for the same session bean as i cannot useBean there...

A bean is just a class, and can be instantiated without means of a tag:DummyCart dc = new DummyCart();
session.setAttribute("cart", dc);To pull the class out of the session (when set by tag or not):DummyCart dc = (DummyCart)session.getAttribute("cart");

Pls. help me out..Accessing ejb through jsp

hi all,
I am running my ejb on the j2sdkee.1.2.1 and jdk1.3 on Windows 2000. I am facing a problem while accessing the ejb from the jsp page. Its running fine when accessing through a client application. The following is the error when I try to access it using:
http://localhost:8000/first/FirstEJB.jsp
Error: 500
Internal Servlet Error:
org.apache.jasper.JasperException: Unable to compile class for JSP
     at org.apache.jasper.runtime.JspLoader.loadJSP(JspLoader.java:287)
     at org.apache.jasper.runtime.JspServlet$JspServletWrapper.loadIfNecessary(JspServlet.java:137)
     at org.apache.jasper.runtime.JspServlet$JspServletWrapper.service(JspServlet.java:148)
     at org.apache.jasper.runtime.JspServlet.serviceJspFile(JspServlet.java:247)
     at org.apache.jasper.runtime.JspServlet.service(JspServlet.java:352)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:865)
     at org.apache.tomcat.core.ServiceInvocationHandler.method(ServletWrapper.java:626)
     at org.apache.tomcat.core.ServletWrapper.handleInvocation(ServletWrapper.java:534)
     at org.apache.tomcat.core.ServletWrapper.handleRequest(ServletWrapper.java:378)
     at org.apache.tomcat.core.Context.handleRequest(Context.java:644)
     at org.apache.tomcat.core.ContextManager.service(ContextManager.java:440)
     at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:144)
     at org.apache.tomcat.service.TcpConnectionThread.run(TcpEndpoint.java:310)
     at java.lang.Thread.run(Thread.java:484)
Root cause:
java.lang.NullPointerException
     at java.io.File.(File.java:181)
     at org.apache.jasper.compiler.JspCompiler.computeClassFileData(JspCompiler.java:285)
     at org.apache.jasper.compiler.JspCompiler.getClassName(JspCompiler.java:103)
     at org.apache.jasper.compiler.Compiler.compile(Compiler.java:105)
     at org.apache.jasper.runtime.JspLoader$2.run(JspLoader.java:273)
     at java.security.AccessController.doPrivileged(Native Method)
     at org.apache.jasper.runtime.JspLoader.loadJSP(JspLoader.java:270)
     at org.apache.jasper.runtime.JspServlet$JspServletWrapper.loadIfNecessary(JspServlet.java:137)
     at org.apache.jasper.runtime.JspServlet$JspServletWrapper.service(JspServlet.java:148)
     at org.apache.jasper.runtime.JspServlet.serviceJspFile(JspServlet.java:247)
     at org.apache.jasper.runtime.JspServlet.service(JspServlet.java:352)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:865)
     at org.apache.tomcat.core.ServiceInvocationHandler.method(ServletWrapper.java:626)
     at org.apache.tomcat.core.ServletWrapper.handleInvocation(ServletWrapper.java:534)
     at org.apache.tomcat.core.ServletWrapper.handleRequest(ServletWrapper.java:378)
     at org.apache.tomcat.core.Context.handleRequest(Context.java:644)
     at org.apache.tomcat.core.ContextManager.service(ContextManager.java:440)
     at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:144)
     at org.apache.tomcat.service.TcpConnectionThread.run(TcpEndpoint.java:310)
     at java.lang.Thread.run(Thread.java:484)
The name of the jsp file is FirstEJB.jsp
The name of the ear file is FirstEJB - Stateless Session Bean
The name of the WAR File is FirstWAR
I have created a Web Component named first
Can anyone tell me how to access the ejb using jsp?
Thanks,
ajit

Hello all,
Sorry for the trouble. I got the mistake..I had not given the context in the deploytool..
Thanks,
ajit

Calling an EJB from jsp - ServletException

I am unable to call an EJB from jsp, unless I put the actuall classes of
          the EJB into the classpath. Is this the right way to do it?
          The exception is:
          Servlet failed with ServletException
          javax.servlet.ServletException: Servlet class: 'jsp_servlet._result'
          could not be loaded - the requested class wasn't found in the
          classpath:
          '/local/apps/bea/wlserver6.0/config/gmodomain/applications/.wl_temp_do_not_delete/wl_local_comp34107.war:/local/apps/bea/wlserver6.0/./config/gmodomain/applications/.wl_temp_do_not_delete/WEB-INF/_tmp_war_gmo_gmo_webwar:/local/apps/bea/wlserver6.0/config/gmodomain/applications/.wl_temp_do_not_delete/WEB-INF/_tmp_war_gmo_gmo_webwar'
          at
          weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:532)
          at weblogic.servlet.jsp.JspStub.prepareServlet(JspStub.java:191)
          at weblogic.servlet.jsp.JspStub.prepareServlet(JspStub.java:148)
          at
          weblogic.servlet.internal.ServletStubImpl.getServlet(ServletStubImpl.java:306)
          at
          weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:208)
          at
          weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:246)
          at
          weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:1265)
          at
          weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:1622)
          at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:137)
          at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
          where result.jsp is the jsp page calling the EJB. I did an import of the
          EJB classes in the jsp.
          like i said, it works if I put the bean classes in the classpath. But is
          it right?
          if I have these in the exploded format, do I need to put anything in the
          application web.xml under:
          wlserver6.0/config/gmodomain/applications/DefaultWebApp_gmo/WEB-INF ?
          redhat 6.2, wl6.0sp1
          here are the xml files:
          web.xml:
          <?xml version="1.0"?>
          <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application
          2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
          
          <web-app>
          <display-name>My Web Application</display-name>
          <description>none</description>
          <ejb-ref>
          <ejb-ref-name>MyWeb</ejb-ref-name>
          <ejb-ref-type>Session</ejb-ref-type>
          <home>com.blah.ejb.myweb.WyWebHome</home>
          <remote>com.blah.ejb.myweb.MyWeb</remote>
          </ejb-ref>
          </web-app>
          weblogic.xml:
          <!DOCTYPE weblogic-web-app PUBLIC "-//BEA Systems, Inc.//DTD Web
          Application 6.0//EN"
          "http://www.bea.com/servers/wls600/dtd/weblogic-web-jar.dtd">
          <weblogic-web-app>
          <jsp-descriptor>
          <jsp-param>
          <param-name>
          pageCheckSeconds
          </param-name>
          <param-value>
          1
          </param-value>
          </jsp-param>
          <jsp-param>
          <param-name>
          verbose
          </param-name>
          <param-value>
          true
          </param-value>
          </jsp-param>
          <jsp-param>
          <param-name>compileCommand</param-name>
          <param-value>/local/apps/jdk1.3.0_02/bin/javac</param-value>
          </jsp-param>
          </jsp-descriptor>
          <reference-descriptor>
          <ejb-reference-description>
          <ejb-ref-name>MyWeb</ejb-ref-name>
          <jndi-name>MyWeb</jndi-name>
          </ejb-reference-description>
          </reference-descriptor>
          </weblogic-web-app>
          thanks,
          Gary


Did you package your JSPs in a WAR and your EJBs in a JAR and package the
          WAR and JAR in an EAR? That is how to do it in 6.0. Works well.
          Peace,
          Cameron Purdy
          Tangosol, Inc.
          http://www.tangosol.com
          +1.617.623.5782
          WebLogic Consulting Available
          "gmo" <[email protected]> wrote in message
          news:[email protected]...
          > I am unable to call an EJB from jsp, unless I put the actuall classes of
          > the EJB into the classpath. Is this the right way to do it?
          > The exception is:
          > Servlet failed with ServletException
          > javax.servlet.ServletException: Servlet class: 'jsp_servlet._result'
          > could not be loaded - the requested class wasn't found in the
          > classpath:
          >
          '/local/apps/bea/wlserver6.0/config/gmodomain/applications/.wl_temp_do_not_d
          elete/wl_local_comp34107.war:/local/apps/bea/wlserver6.0/./config/gmodomain/
          applications/.wl_temp_do_not_delete/WEB-INF/_tmp_war_gmo_gmo_webwar:/local/a
          pps/bea/wlserver6.0/config/gmodomain/applications/.wl_temp_do_not_delete/WEB
          -INF/_tmp_war_gmo_gmo_webwar'
          >
          > at
          >
          weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.jav
          a:532)
          >
          > at weblogic.servlet.jsp.JspStub.prepareServlet(JspStub.java:191)
          >
          > at weblogic.servlet.jsp.JspStub.prepareServlet(JspStub.java:148)
          >
          > at
          >
          weblogic.servlet.internal.ServletStubImpl.getServlet(ServletStubImpl.java:30
          6)
          >
          > at
          >
          weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java
          :208)
          >
          > at
          >
          weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java
          :246)
          >
          > at
          >
          weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletCo
          ntext.java:1265)
          >
          > at
          >
          weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java
          :1622)
          >
          > at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:137)
          >
          > at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
          >
          > where result.jsp is the jsp page calling the EJB. I did an import of the
          > EJB classes in the jsp.
          > like i said, it works if I put the bean classes in the classpath. But is
          > it right?
          > if I have these in the exploded format, do I need to put anything in the
          > application web.xml under:
          > wlserver6.0/config/gmodomain/applications/DefaultWebApp_gmo/WEB-INF ?
          >
          > redhat 6.2, wl6.0sp1
          >
          > here are the xml files:
          > web.xml:
          >
          > <?xml version="1.0"?>
          > <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application
          > 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
          >
          > 
          >
          > <web-app>
          > <display-name>My Web Application</display-name>
          > <description>none</description>
          > <ejb-ref>
          > <ejb-ref-name>MyWeb</ejb-ref-name>
          > <ejb-ref-type>Session</ejb-ref-type>
          > <home>com.blah.ejb.myweb.WyWebHome</home>
          > <remote>com.blah.ejb.myweb.MyWeb</remote>
          > </ejb-ref>
          > </web-app>
          >
          > weblogic.xml:
          >
          > <!DOCTYPE weblogic-web-app PUBLIC "-//BEA Systems, Inc.//DTD Web
          > Application 6.0//EN"
          > "http://www.bea.com/servers/wls600/dtd/weblogic-web-jar.dtd">
          > <weblogic-web-app>
          > <jsp-descriptor>
          > <jsp-param>
          > <param-name>
          > pageCheckSeconds
          > </param-name>
          > <param-value>
          > 1
          > </param-value>
          > </jsp-param>
          > <jsp-param>
          > <param-name>
          > verbose
          > </param-name>
          > <param-value>
          > true
          > </param-value>
          > </jsp-param>
          > <jsp-param>
          > <param-name>compileCommand</param-name>
          > <param-value>/local/apps/jdk1.3.0_02/bin/javac</param-value>
          > </jsp-param>
          > </jsp-descriptor>
          > <reference-descriptor>
          > <ejb-reference-description>
          > <ejb-ref-name>MyWeb</ejb-ref-name>
          > <jndi-name>MyWeb</jndi-name>
          > </ejb-reference-description>
          > </reference-descriptor>
          > </weblogic-web-app>
          >
          > thanks,
          >
          > Gary
          >
          >

Which Web Client Framework? BC4J-JSP, UIX-JSP, UIX-XML, etc

Trying to determine which, if any of the JDeveloper frameworks, to use for do web browser (HTML) clients.
What are the pros/cons of BC4J-JSP, UIX-JSP, UIX-XML, etc?
What are some common things you might rule out using one or more of the frameworks?
I plan to be using BC4J, updating, inserting data (currently MS-SQL) and the apps will run on WebLogic 7 or Caucho Resin (webapps no EJB) in a cluster. I would like to be as RAD as possible and still be able to do what I need to do. One main concern is being able to add custom HTML/JavaScript for things like client side validation. I didn't see a way to do this when doing BC4J-JSP. Is that right?
If I define any validation in the BC4J, will UIX utilized any of this to define a JavaScript validator or must it be redudantly defined?
One other concern is what the framework requires in terms of architecture, like do I have to have sticky sessions in my web cluster or can it work fine stateless or stateful?
For UIX-XML, how is this architected for performance? Specifically, is the XML effectively compiled and converted into something more efficient and performant or does it do XML parsing all the time? Is there any significant performance differences between the frameworks?
Is there any significant difference in dealing with security? Anything in the framework to make it easier to handle certain users being able to see/edit different set of data?
I have things like some groups can edit only certain entities (product info but not pricing), others only certain types of products (possibly subclass entities) and others situations where what fields than can edit varies. Obviously I can handle this programmatically, but I was wondering what the frameworks had to offer, especially in terms of having different views of the same data.
Steve

...I am little confused then about how BC4J works and what is meant by "session" here.
When you talk about appmodules in the plural, does this mean that there are potentially multiple instances of the same data on a single server or there is a common datastore with pending data and client specific stuff varying?
The common datastore is the database. Each client (momentarily, during the span of their request) uses an instance of an application module from the pool. The pool can grow and shrink with load on your system and all of the various tuning parameters. Our doc on the AM Pool covers all the parameter settings and their users.
What kind of "session" is this?
It is an abstract notion of a session for a user. The implementation used for Web clients uses the HTTP Session Key as the session key. However, we have other session implementations (and you can provide your own to do custom stuff for more sophisticated needs). We don't store anything else in the HTTP Session to the best of my knowledge. This way in a cluster, the web container doesn't have to waste time propagating all of your serialized HTTP Session state among cluster members. This session key also include an id for the application module and together those provide the key to store your pending state in the database for the "Stateful == Managed State" feature.
I assume that if I have a cluster which doesn't use session-to-same-server-affinity but uses JDBC for http-session persistance or distributed in-memory http-sessions then I cannot use stateful BC4J even though I can use http-sessions.
You can use BC4J in this way because the browser will send a cookie that contains the key to your database-stored pending state. In this way, we work great in a server farm for failover and/or scalability reasons.
Even if I use stateless BC4J, are there issues with round-robin'ng all requests to different servers in a cluster?
As I said, both our Stateless and Stateful features are designed to be used in Server farms, no problem.
BTW I wouldn't necessarily say you picked the wrongs terms for the modes, but I know what you mean. There's problems with these terms. I am trying to explain to my mgrs/engineers that there is some state in stateless transactions - that simply making everything "stateless" doesn't mean don't lose anything in a disastrous failure. I am arguing to get support for sessions in our cluster, that the performance gain and simplified development is worth it as long as you put intelligent limits on what you store in the session. Right now, they are insisting on randomly sending requests into two entirely different data centers, with two different clusters.
Amen. I have seen too many developers make the mistake of trying to be totally stateless, only to completely complicate their development environment with having to peristent partially-completed transaction data to the database. I've seen this done with sets of "Shadow" tables (yuck!) or using hand-written techniques similar to what BC4J provides a robust implementation of in the box.
We've tuned our "Stateless With Affinity for Server Farms" model over several releases of carefully studying the performance of the Web apps built by our internal Oracle Applications teams using BC4J (over 20 of them now, and growing!) so compared with a hand-written strategy for your web-tier state management, using BC4J's implementation will be much more productive for you.
We're tuning and tweaking and enhancing it even more for the 9.0.3 release as new needs are highlighted with continued use by our customers (both Oracle internal and external).

What is the diff between jsp and servlet

is thr any other difference betwwen jsp and servlet, tht: jsp is automatic generated servlet and jsp has different types of tag, due this we have write less amount of code.any other technically difference between these two?

As you mentioned JSP automatically gets converted into a Servlet and then compiled. From the server's perspective other than the transformation process, there is no real difference.
However, in coding there are some minor differences such as additional access to pre-defined variables and different syntax for some minor things such as imports and etc.
Perhaps somebody else more knowledgeable can fill you in further.
Hope that was helpful.

EJBs vs. POJOs

Architecture question: If I have four classes that work together to perform a service, what would make me deploy these as an EJB instead of simply packaging them in a jar file and deploying them to the app server as a lightweight component? I know EJBs offer security, transaction capability, etc. But if my four classes are fairly simple and don't need to use a transaction, isn't it easier and less bulky to simply jar them up and make them available to any client more efficiently? I have utilized EJBs and like them, however, for cases like I described above, I need to be better versed in the reasons to use one technique over the other so I can design appropriately. There must be some valid reasons to use the "simple" component (jar'd classes) in some situations instead of producing an EJB.
Thanks for any input or any help in pointing me to a good whitepaper or book that explains this. Most books and articles I read on EJBs explains the benefits, but I have yet to see a head to head comparison or recommendations of alternatives for "packages" of functionality.

What you are saying makes sense to me, if you don't need these services, security, transactions, clustering, etc. then you really don't need EJB's.
Here is an article on this subject:
http://www.theserverside.com/resources/article.jsp?l=Is-EJB-Appropriate

I have to ping a machine from my JSP or Servlet

I have to ping a machine from my JSP or Servlet what is the best method to do this...

1) There is a method in java.net.InetAddress called isReachable in JDK 1.5. Because the majority of the Web containers do not support JDK 1.5 nowadays, you can't use it directly in your servlet or JSP. (JBoss 3.2.4 promises to support JDK 1.5 but I couldn't use it with the Beta2.) If you have lots and lots of memory you can try to keep a program running in 1.5 that simply does the "ping" thing, and communicates via sockets with your servlet or JSP.
2) JNI in Web containers can be used but imposes several problems in class loaders. If you can find a JNI library that can do ICMP ECHO try to use it, but the deployment of the JNI library depends heavily on the Web container.
3) You can have a program (written in C for instance) that is continuously running and does only the "ping" function, and communicates via sockets with your servlet and JSP. You can have it running now and wait some years until the "isReachable" method is available to your programs.
4) You could try to Runtime.exec the "ping" command-line executable, but if you are using a Web container you could have some problems (for instance, if you run the Web container as a Windows service the command will not be adequately run, or it runs but never terminates, etc.)

HELP with EJB to JSP Integration tool WLS 7.0

          Hi,
          Has anyone used the EJB2JSP Integration tool in WLS 7.0? I can't find any documenation
          except for the page at http://edocs.bea.com/wls/docs70/jsp/ejb2jsp.html. It is
          not much help. I can get the graphical tool to run, but not import a .jar file.
          This is the error I get when trying to open an ejb.jar.
          C:\bea\user_projects\myTestDomain\applications\DefaultWebApp\WEB-INF\classes\EJB\Spike>java
          weblogic.servlet.ejb2jsp.gui.Main
          error occurred: java.lang.NullPointerException
          java.lang.NullPointerException
          at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:287)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:250)
          at weblogic.servlet.ejb2jsp.Utils.createBeanDescriptor(Utils.java:343)
          at weblogic.servlet.ejb2jsp.Utils.createDefaultDescriptor(Utils.java:314)
          at weblogic.servlet.ejb2jsp.Utils.createDefaultDescriptor(Utils.java:266)
          at weblogic.servlet.ejb2jsp.gui.Main.loadFromPaths(Main.java:391)
          at weblogic.servlet.ejb2jsp.gui.Main.doNew(Main.java:378)
          at weblogic.servlet.ejb2jsp.gui.Main$5.run(Main.java:575)
          at weblogic.servlet.ejb2jsp.gui.MainWorker.run(Main.java:757)
          at java.lang.Thread.run(Thread.java:479)
          error occurred: java.lang.NullPointerException
          java.lang.NullPointerException
          at weblogic.servlet.ejb2jsp.gui.Main.doNew(Main.java:379)
          at weblogic.servlet.ejb2jsp.gui.Main$5.run(Main.java:575)
          at weblogic.servlet.ejb2jsp.gui.MainWorker.run(Main.java:757)
          at java.lang.Thread.run(Thread.java:479)
          Is this error and the fix to it obvious to someone else? If so, I would appreciate
          some help!
          THank you!!
          Wendy


Try weblogic.servlet.ejb2jsp.gui.Main
Kris

Choice between JSP and Servlet

I am new to JSP and Servlet. I know JSP container will convert JSP to servlet
eventually. But in application development's standpoint, anything can be
done in servlet can also be done in JSP? Some people told me we can
use the combination of both in one application.
My question is in what situation we use JSP alone, servlet alone, or
combination of both??
Please advise. Thanks!!

Use a combination of both.
Your Web application should have a single servlet that all HTTP requests are POSTed to. All the servlet does is act like a traffic cop: it figures out what the request is, delegates to other objects that do the work, and forward the result to the next JSP, whatever that is. It's called a front controller servlet.
The JSPs should just be pure dynamic presentation. Everything displayed in the pages should have been generated by the servlet and its helper classes. No database queries, etc. Your JSPs will be a lot better off if you learn JSTL and eliminate all scriptlet code.
Check out frameworks like Struts.

PL/SQL vs JSP vs Servlets

We are in the stage of deciding which language to develop portlets. I lean towards JSP or servlets for the wide array of Java libraries we can use. I think the only advantage of PL/SQL is speed. Thanks.

It depends. If your developers are mainly Java developers, you'll probably prefer building web portlets. But if you have a strong PL/SQL skill set you could choose the latter. Additionally, if you're developing content that is database intensive you may want to build PL/SQL portlets since they transact with the database faster. If you're going to aggregate content from various web sites, using web providers is preferable. It's a matter of choice based on your requirements and preferences.

Deploying a WAR file containing .jsp and servlets (also uses JNI)

Deploying a WAR file containing .jsp and servlets (also uses JNI) on Windows 2000
We had problems making it initially work on Sun ONE Web Server 6.0 Service Pack 1 because of lack of good iPlanet Web
Server documentation on deploying such files.
This is how we went about it:
1) Make one of the servlet and JSP (must call another Java Class) web application (.war) examples work with iPlanet Web
Server.
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\HelloWorld\HelloWorld.war
and
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
a) Go to your Web Server Administration to deploy the application using GUI Web Application Deploy.
(We usually use command line, we experienced some issues with the GUI version, but maybe it is fixed in the new Web Server
service packs)
From browser, open http://yourserver:8888/
Click on Select a Server:Manage
Click on Virtual Server Class
Click on https-yourserver
Click on the Web Applications Tab
Then, click on Deploy Web Application
Enter the following -
WAR File On: Local
WAR File Path: C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Application URI: /jakarta
Installation Directory: c:\iPlanet\examples\jakarta-examples
By clicking on OK it deployed the application.
I can verify that it is deployed by selecting "Edit Web Applications" and I see the following entry:
Edit     /jakarta     c:/iPlanet/examples/jakarta-examples
Also, c:/iPlanet/examples/jakarta-examples should have the similar following directory structure ..
- [images]
- [jsp]
- index.html
- [servlets]
- [META-INF]
- [WEB-INF]
- [classes]
- [tlds]
- web.xml
- index.html
I restarted the server and accessed it using the following URL from my IE browser:
http://yourserver/jakarta/index.html
Then I clicked on the JSP Examples and tried some JSP examples.
b) Alternatively, you can also deploy the same example from the command-line.
Make sure C:\iPlanet\Servers\bin\https\httpadmin\bin\ is in your path
wdeploy deploy      -u /jakarta
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\jakarta-examples
          C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Restart the web server (I don't think you have to restart, but .. might as well).
2)Deploy your web-application
My Foo.war has the following structure.
You can use jar tf Foo.war to look at the file contents from command line (assuming you have JDK installed and the bin is
in your PATH)
Foo.war
- [META-INF]
- [WEB-INF]
- web.xml
- [classes]
- Bar.class
- MoServlet.class
- [lib]
- ThirdParty.jar
- [natlib]
- extlib.dll
- foo.jsp
Here is our application scenario:
foo.jsp uses a class call Bar (it is not in any package). The Bar java class uses classes from ThirdParty.jar. The
ThirdParty.jar in turn uses JNI to load library extlib.dll. foo.jsp also calls /servlet/Mo as well.
Now to deploy it, do the following:
(a) Make sure that within foo.jsp, you import the Bar class ( I don't know why you have to do it, but if you don't you get
JSP compile error).
<%@page language="java" import="Bar" contentType="text/html"%>
(b) Check web.xml (for Servlets)
Within web.xml, make sure you have the following mappings:
<servlet>
<servlet-name> MoLink </servlet-name>
<servlet-class> MoServlet </servlet-class>
</servlet>
<servlet-mapping>
<servlet-name> MoLink </servlet-name>
<url-pattern> /servlet/Mo </url-pattern>
</servlet-mapping>
(c) Deploy the application
Using command line:
wdeploy deploy      -u /foo
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\foo-dir
          Foo.war
(d) Change web-apps.xml file (for picking up ThirdParty.jar)
It is located in
C:\iPlanet\Servers\https-yourserver\config
You should see something similar to following after successful deployment.
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true"/>
Change it to look like following to pick up the ThirdParty.jar
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true">
<class-loader reload-interval="300"
          classpath="C:/iPlanet/examples/foo-dir/WEB-INF/lib/ThirdParty.jar"
          delegate="false"/>
</web-app>
(e) Change jvm12.conf file (for JNI)
It is located in
C:\iPlanet\Servers\https-yourserver\config
Add or uncomment the following lines:
#optional - just helps with instrumenting the jsp and servlet code
jvm.include.CLASSPATH=1
jvm.enableDebug=1
nes.jsp.enabledebug=1
jvm.trace=7
jvm.verboseMode=1
#required for JNI
java.compiler=NONE
jvm.classpath=.;C:\JDK1.3.1\lib\tools.jar;C:/iPlanet/Servers/plugins/servlets/examples/legacy/beans.10/SDKBeans10.jar;
jvm.option=-Xrs
jvm.option=-Xnoagent
# not sure if this is needed for iPlanet web server
jvm.option=-Djava.library.path=C:/iPlanet/examples/foo-dir/natlib/ -Djava.compiler=NONE
(f) Change magnus.conf file (for JNI)
We HAD to change this file in order for ThirdParty.jar file to pick up the native C++ code using JNI. Apparently, the
iPlanet Web Server doesn't pick the Environment Variable Path. Because when we had the directory containing the DLL just
in Path, it didn't work.
Change Extrapath directive:
ExtraPath C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
to
ExtraPath c:/iPlanet/examples/foo-dir/natlib;C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
(g) Apply changes from the Web Server Administration Console and Restart the web server.
You should be able to see the behaviour that you want from your application.
http://yourserver/foo/foo.jsp
Hope this was helpful!!!
Sonu

Deploying a WAR file containing .jsp and servlets (also uses JNI) on Windows 2000
We had problems making it initially work on Sun ONE Web Server 6.0 Service Pack 1 because of lack of good iPlanet Web
Server documentation on deploying such files.
This is how we went about it:
1) Make one of the servlet and JSP (must call another Java Class) web application (.war) examples work with iPlanet Web
Server.
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\HelloWorld\HelloWorld.war
and
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
a) Go to your Web Server Administration to deploy the application using GUI Web Application Deploy.
(We usually use command line, we experienced some issues with the GUI version, but maybe it is fixed in the new Web Server
service packs)
From browser, open http://yourserver:8888/
Click on Select a Server:Manage
Click on Virtual Server Class
Click on https-yourserver
Click on the Web Applications Tab
Then, click on Deploy Web Application
Enter the following -
WAR File On: Local
WAR File Path: C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Application URI: /jakarta
Installation Directory: c:\iPlanet\examples\jakarta-examples
By clicking on OK it deployed the application.
I can verify that it is deployed by selecting "Edit Web Applications" and I see the following entry:
Edit     /jakarta     c:/iPlanet/examples/jakarta-examples
Also, c:/iPlanet/examples/jakarta-examples should have the similar following directory structure ..
- [images]
- [jsp]
- index.html
- [servlets]
- [META-INF]
- [WEB-INF]
- [classes]
- [tlds]
- web.xml
- index.html
I restarted the server and accessed it using the following URL from my IE browser:
http://yourserver/jakarta/index.html
Then I clicked on the JSP Examples and tried some JSP examples.
b) Alternatively, you can also deploy the same example from the command-line.
Make sure C:\iPlanet\Servers\bin\https\httpadmin\bin\ is in your path
wdeploy deploy      -u /jakarta
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\jakarta-examples
          C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Restart the web server (I don't think you have to restart, but .. might as well).
2)Deploy your web-application
My Foo.war has the following structure.
You can use jar tf Foo.war to look at the file contents from command line (assuming you have JDK installed and the bin is
in your PATH)
Foo.war
- [META-INF]
- [WEB-INF]
- web.xml
- [classes]
- Bar.class
- MoServlet.class
- [lib]
- ThirdParty.jar
- [natlib]
- extlib.dll
- foo.jsp
Here is our application scenario:
foo.jsp uses a class call Bar (it is not in any package). The Bar java class uses classes from ThirdParty.jar. The
ThirdParty.jar in turn uses JNI to load library extlib.dll. foo.jsp also calls /servlet/Mo as well.
Now to deploy it, do the following:
(a) Make sure that within foo.jsp, you import the Bar class ( I don't know why you have to do it, but if you don't you get
JSP compile error).
<%@page language="java" import="Bar" contentType="text/html"%>
(b) Check web.xml (for Servlets)
Within web.xml, make sure you have the following mappings:
<servlet>
<servlet-name> MoLink </servlet-name>
<servlet-class> MoServlet </servlet-class>
</servlet>
<servlet-mapping>
<servlet-name> MoLink </servlet-name>
<url-pattern> /servlet/Mo </url-pattern>
</servlet-mapping>
(c) Deploy the application
Using command line:
wdeploy deploy      -u /foo
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\foo-dir
          Foo.war
(d) Change web-apps.xml file (for picking up ThirdParty.jar)
It is located in
C:\iPlanet\Servers\https-yourserver\config
You should see something similar to following after successful deployment.
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true"/>
Change it to look like following to pick up the ThirdParty.jar
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true">
<class-loader reload-interval="300"
          classpath="C:/iPlanet/examples/foo-dir/WEB-INF/lib/ThirdParty.jar"
          delegate="false"/>
</web-app>
(e) Change jvm12.conf file (for JNI)
It is located in
C:\iPlanet\Servers\https-yourserver\config
Add or uncomment the following lines:
#optional - just helps with instrumenting the jsp and servlet code
jvm.include.CLASSPATH=1
jvm.enableDebug=1
nes.jsp.enabledebug=1
jvm.trace=7
jvm.verboseMode=1
#required for JNI
java.compiler=NONE
jvm.classpath=.;C:\JDK1.3.1\lib\tools.jar;C:/iPlanet/Servers/plugins/servlets/examples/legacy/beans.10/SDKBeans10.jar;
jvm.option=-Xrs
jvm.option=-Xnoagent
# not sure if this is needed for iPlanet web server
jvm.option=-Djava.library.path=C:/iPlanet/examples/foo-dir/natlib/ -Djava.compiler=NONE
(f) Change magnus.conf file (for JNI)
We HAD to change this file in order for ThirdParty.jar file to pick up the native C++ code using JNI. Apparently, the
iPlanet Web Server doesn't pick the Environment Variable Path. Because when we had the directory containing the DLL just
in Path, it didn't work.
Change Extrapath directive:
ExtraPath C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
to
ExtraPath c:/iPlanet/examples/foo-dir/natlib;C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
(g) Apply changes from the Web Server Administration Console and Restart the web server.
You should be able to see the behaviour that you want from your application.
http://yourserver/foo/foo.jsp
Hope this was helpful!!!
Sonu

EJB Vs JSP/POJO/Servlets, etc

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