Group items tagged

Stateless beans must have a dependent scope while a stateful session bean can have any scope. By default they are transactional, but you can use the transaction attribute annotation.

CDI beans can be injected into EJBs and EJBs can be injected into CDI beans

When to use which bean How do you know when to use which bean? Simple.

In general, you should use CDI beans unless you need the advanced functionality available in the EJBs such as transactional functions. You can write your own interceptor to make CDI beans transactional, but for now, its simpler to use an EJB until CDI gets transactional CDI beans which is just around the corner

Comparing JSF Beans, CDI Beans and EJBs

JSF Managed Beans

In short, don’t use them if you are developing for Java EE 6 and using CDI. They provide a simple mechanism for dependency injection and defining backing beans for web pages, but they are far less powerful than CDI beans.

JSF beans cannot be mixed with other kinds of beans without some kind of manual coding.

CDI Beans

includes a complete, comprehensive managed bean facility

interceptors, conversation scope, Events, type safe injection, decorators, stereotypes and producer methods

JSF-like features, you can define the scope of the CDI bean using one of the scopes defined in the javax.enterprise.context package (namely, request, conversation, session and application scopes). If you want to use the CDI bean from a JSF page, you can give it a name using the javax.inject.Named annotation

Comparing JSF Beans, CDI Beans and EJBs

Comparing JSF Beans, CDI Beans and EJBs

JSF Managed Beans

for each workspace, in files stored in <workspace>/.metadata/.plugin/org.eclipse.core.runtime/.settings

for each project --for project-level settings -- in files stored in a .settings sub-directory of your project folder

Is there an UML editor for Eclipse? An Eclipse Modelling project-based UML editor can be installed from the Eclipse update site "Modelling > UML2 Tools SDK". See Creating UML 2 diagrams with Eclipse UML2 Tools - Tutorial for an introduction.

How do I debug Eclipse? How can I see what plug-ins are being started? Why aren't the plug-ins I installed showing up in the UI? How do I start the OSGi console?

Debugging OSGi Bundle Loading Issues There are a few flags you can pass to Eclipse on the commandline or in your eclipse.ini file that might help: -consolelog - log everything in workspace/.metadata/.log to the console where you launched Eclipse as well -debug - more verbose console output -console - start the Equinox OSGi console to interact with OSGi directly -noexit - when Eclipse closes, keep the OSGi console running until you type 'exit' or hit CTRL-C so you can keep debugging See Where Is My Bundle? for an overview of how to use the OSGi console for diagnosing problems.

Debugging Eclipse Using Eclipse You can also debug an Eclipse instance from another instance through remote debugging: Start the instance to be debugged with "-vmargs -Xdebug -agentlib:jdwp=transport=dt_socket,server=y,address=8000". You should see a message like "Listening for transport dt_socket at address: 8000" Open Run → Debug Configurations... and create a Remote Java Application configuration with connection type "Socket Attach" and connecting to the client at port 8000. Set the project to a bundle project with the right dependencies for the bundles that you are trying to debug. Launch the configuration. The JDWP agent supports other useful arguments, like "suspend=n" so that the process does not suspend. For more details, see Oracle's Java Debug Wire Protocol (JDWP) connection docs.

I just installed Eclipse on my 64-bit system, but it does not start. What is the problem? Make sure that you have downloaded the 64-bit version of Eclipse (it should have x86_64 somewhere in its name) and have installed a 64-bit JVM. Likewise, if you run a 32-bit JVM, then you should use the 32-bit version of Eclipse.

When I start Eclipse it says "Workspace in use or cannot be created, choose a different one.", what should I do? There are a couple of things you can try. Delete the workspace/.metadata/.lock file. Check your running processes to make sure there aren't any remaining Java or Eclipse processes running. When in doubt, restart your computer. :) Try starting Eclipse on a different workspace (from the workspace selection dialog, or by using a command line argument like -data /home/user/tmp-workspace), then switch back to your original workspace.

How do I uninstall a plug-in? You can view your list of installed software by checking your installation details from about dialog. Help > About > Installation Details

I'm having memory, heap, or permgen problems, what can I do? FAQ How do I increase the heap size available to Eclipse? FAQ How do I increase the permgen size available to Eclipse?

Eclipse seems to be hanging on startup. How can I find out why? If none of the solutions outlined in this section reveal the problem, then you can try debugging an Eclipse instance as a debug target from another Eclipse instance. This is surprisingly easy: Start Eclipse in a "new" blank workspace (e.g., C:\TEMP\WS, or /tmp) Create a new Debug configuration: Run -> Debug Configurations; then click on "Eclipse Applications" and select the New Launch Configuration. If you believe it's something about a particular workspace, then set the workspace to your normal workspace. If you believe the hang is caused by a particular plugin, disable the plugin and verify. Launch and then see. Using this approach, you can break with the debugger to see where hangs are occurring. You can also change the selection of plugins that the instance is launched with.

I was working on a project and doing something or other does not work. Where should I start? Try refreshing your projects. Try cleaning your your projects using the menu item Project/Clean to trigger a rebuild. Try closing/reopening your projects. Try restarting Eclipse.

4.2 Where are Eclipse's log files located?

Where are Eclipse's log files located? <workspace>/.metadata/.log You can view this workspace log as a view if you have PDE installed on your computer (which you would if you have downloaded the Eclipse SDK). You can open that view via Window -> Show View -> Other -> PDE Runtime -> Error Log. <eclipse install>/configuration/<sometimestamp>.log <eclipse install>/configuration/org.eclipse.update/install.log

Where are Eclipse preferences stored?

Where are Eclipse preferences stored?

Where are Eclipse preferences stored?

Where are update site bookmarks stored? It is within an XML file called <user_home>/.eclipse/org.eclipse.platform_3.1.2/configuration/org.eclipse.update/bookmarks.xml. Your Eclipse version may vary.

In general, JDBC Templates are a poor solution. They don’t have enough abstraction to work on different databases because you use plain SQL in queries. There is also no real ORM mapping which results in quite a lot of boilerplate code

SimpleJdbcTemplate(ds)

@InterceptorBinding

The discussion whether or not to use Spring vs. Java EE for new enterprise Java applications is a no-brainer

Why migrate?

since then fallen a prey to the hungry minds of Venture Capitalists and finally into the hands of a virtualization company called VMware

While the different companies and individuals behind the Spring framework have been doing some work in the JCP their voting behavior on important JSRs is peculiar to say the least

outdated ORM solution like JDBC templates

some developers completely stopped looking at new developments in the Java EE space and might have lost track of the current state of technology

size of the deployment archive

fairly standard Java EE 6 application will take up about 100 kilobytes

comparable Spring application weighs in at a whopping 30 Megabytes!

Lightweight

Firing up the latest JBoss AS 7 Application Server from scratch and deploying a full blown Java EE 6 application into the server takes somewhere between two and five seconds on a standard machine. This is in the same league as a Tomcat / Spring combo

Dependency injection

Java EE 6, the Context and Dependency Injection (CDI) specification was introduced to the Java platform, which has a very powerful contextual DI model adding extensibility of injectable enterprise services

Aspect Oriented Programming

“AOP Light” and this is exactly what Java EE Interceptors do

common pitfall when taking AOP too far is that your code might end up all asymmetric and unreadable. This is due to the fact that the aspect and its implementation are not in the same place. Determining what a piece of code will do at runtime at a glance will be really hard

Testing

With Arquillian we can get rid of mocking frameworks and test Java EE components in their natural environment

Tooling

capabilities comparison matrix below to map Spring’s technology to that of Java EE

Capability Spring JavaEE Dependency Injection Spring Container CDI Transactions AOP / annotations EJB Web framework Spring Web MVC JSF AOP AspectJ (limited to Spring beans) Interceptors Messaging JMS JMS / CDI Data Access JDBC templates / other ORM / JPA JPA RESTful Web Services Spring Web MVC (3.0) JAX-RS Integration testing Spring Test framework Arquillian *

consideration of the system as a whole

A developer who lacks the ability to give good names to concepts and data in their code is like a mute translator

creates a bad sort of dependency where we need to update the base class every time we make a new derived class. Not good!