The unique of Tapestry

  What's the difference between web development and traditional C/S application such Swing? Personally I like Swing because it let me more efficient. All the code is Java code and there is little type-cast. And Tapestry also follows this way. The author admitted that:

An advantage for Tapestry, I think, is the way the two pages (the firsts containing the form, the second displaying the result) communicate ... in proper, type-safe Java code.

  This means if you want to invoke a web page, what you face is a java class. Blow is a example:
public IPage doSubmit()
{
ShowProject showProject = getShowProject();
showProject.setProject(getProject());
return showProject;
}
  Get a page class(by injection), give it some value and then you can forward to that page. The page class has included a page and we can say it is the interface of the page. But the best way, I think, is the function like way. Some likes "showProject(project);". Compared with Object initialization which is not undocumented and not self-explaining, function maybe is more intuitive.

  Tapestry just resolved the problem of the two pages communicate. As to multi-page, or a conversation, there are a lot of work. For example, how to get a page's return value?

  Unlike this way that page and bean are bound together, JSF let page outside the backend bean. And a jsf page can bind multi-bean. A backend bean can be used in many jsf pages. This loose bind let a page include another page easily.

JPDA(Java Platform Debugger Architecture)

How let your changed java code updated to server? It is a big problem in develpping any non-trivial JEE project.

Resently, I run a JBoss 4.04 outside of Eclipse. The application archive(EAR) is so big that we can not run it in IDE environment. Then the debug process is boring. After having modify the java code, I have to package it, copy to deploy directory and restart the server. Ant can help me a lot but a debug round still takes me much of time.

In this situation, JPDA will useful. With the help of eclipse, I can use it to connect to a "Remote Java Application". You can find it in "Debug" dialog. Then you can inspect value of a varible and even modify the java code. Before that, you have to add a breakpoint to your java code. Only java with breakpoint can be modified and replaced to the server. This is a nice feature when you need modify code many times. When eclipse has attached remote server, any modified java code could be updated to the server. This is so-called "Hotswap Bug Fixing". Of course the source code should be added to the debug instance's "Source lookup path". Otherwise the server didn't suspend at your breakpoint. And you should mind that the compiled classes were swapped just in the server's memory and didn't updated to the server's file system. So after finished debug, you should copy the classes to the server's deploy directory.

Some other approaches I often used include Hot deploy and restart application (not server).

Hot deploy is used to deploy a archive such as .war or .jar(EJB) automatically when you put them in deploy directory. Most servers has this feature.

Restart application or Reload Context is used to reload all resource(classes and configuration) in one application eg EJB, or War. This approach is heavier than others. Tomcat will throw exception "Out of memory" after reloaded a web application many times.

To Netbeans, It provides debug mode also. There are some differences on "hot class replace" between it and eclipse.

Above is netbeans 6M10 debug tool bar. It has a "Apply Code Changes" button to submit the changed code to server. It need you do manually. This way is different from eclipse which done automatically.

Cygwin tips

1.if the os is windows, the file type will be dos by default. So if you new a shell script, then run it in cygwin, the error like "who/r command not found" will happen. The solution is changing the file type to unix. A approch is using vi. In vi, use ":set ff?" to inquiry file type. Then use ":set fileformat=unix" or ":set ff=unix".

2.In my machine, cygwin.bat is:bash --login -i. This will let shell be a login shell. But only an interactive shell that is not a login shell will read and execute ~/.bashrc. If we want our personal bash, we should create a .profile file in home directory instead of of .bashrc. One example is:

alias h="history"
alias hg="h|grep"

#alias ls='ls --color=auto'
alias la='ls -A'
alias lf='ls -F'
alias ll='ls -l'

 3.use wget with proxy. create a .wgetrc in home directory.

http_proxy = proxy.com:81
no_proxy = localhost

This will make wget to fetch data with proxy by default and you didn't need to swith to proxy model by " -Y on".

RESTful Web development

  What RESTful means? I found this document : RESTful Rails development is very clear to express this point. And It is also quickly to test it in Rails. Soon you will find the amazing of RESTful. It just used HTTP GET, POST, DELETE, PUT to manage the resource and some likes JDBC CRUD implement. And more it is a new RPC implement. It has been used widely in web service. So a web service can be invoked by RESTful URL. And I think it make web service more powerful. In some traditional web application, for example a struts or JSF application, RESTful just provides nice URL format.

  But obviously RESTful will be more important when application need to invoke 3rd party functions

Visual library of NetBeans

Today I evaluated Visual library of NetBeans org. There are not too much information about it on Sun's site. And it is a part of NetBeans 6 M9. I guest it was just separated from Netbeans as a standalone project. It's many feature is same as JGraph which has been used by many users. But I think this library provides more about UI design but not only concerning on graph as done by JGrah. For example, it has a feature "ComponentWidget - AWT/Swing components on scene". So you can do this:

JButton button = new JButton();
button.setText("xixi");
ComponentWidget widget = new ComponentWidget(this,button);

Then I have a question: Is Visual Web (netbeans) developed on this library? If so, Visual Library is very cool! (From this post, just page flow navigator is based on Visual Library.)
There is a video which created a demo on Visual library. You can find that a JasperReports tool called jarvis is also base on this library. It looks powerful.

Question on JSF state saving

JSF state is restored or used in "Restore View" of JSF life cycle. These state can be stored in 2 places:client and server. There are some links about the difference of them:

http://www.jroller.com/page/mert?entry=state_saving_method_client_side
http://www.jroller.com/page/cagataycivici?entry=jsf_state_saving_best_of
http://www.jroller.com/page/cenkcivici?entry=changing_default_state_management_method

These states are used to store data about the JSF component tree(the elements in f:view), including components and component id. They can be seen between 2 request. That is the difference from backend bean. At first thought most of components have no state, or just have a value which presents its state. A text field has state? But YES. Disable/Enable is a common state. In the component implement java code, saveState and restoreState methods deal all these work: choose some attributes and save them to an object which can be found as a hidden field named javax.faces.ViewState in client's browser source code. It was Base64 encoding. And of course, the view state has been configurated to be stored in the client. In Sun's webui implement, many attributes are stored in view state, such as javascript event method and style.

Some component such as Table can be very complex and has its own states such as the current page number and ordered column. If these states doesn't be stored in component tree, we have to save them in hidden input field.

Myfaces even has a component t:saveState just for storing data. See here.

This technology is powerful when user's action is within one page. When page is refreshed, all he has done are saved. If he just jumps between page, navigate from one page to another page, then the state of a page is discarded, and more it is useless. In one page scenario, AJAX is also a good choice. They all improve user's experience.

Somebody provides stateless approach.

There is a cool tool called FacesTrace to monitor JSF application. It displays not only session data, but also the whole JSF life cycle dynamically.

test code and use Microsoft Writer

test code
if (component instanceof ValueHolder && (null != (converter = ((ValueHolder)

the css please refers here. make sure that css code block should be placed in <head> and started with .post.

  In your blog, you should enbrace your code with <code> tag in HTML view.  And in your code block, you cann't use <> these simble. You change it into HTML code by some tools like phpfi. It also provides highlighting feature.

  But this approach is some boring. Later I found M$ Live Writer. It is cool. You can edit blog on offline mode and post it when online. You also can download blog item, modify it, and update it to Blogger. You also can delete blog by Writer although Writer didn't remind you. The editor is css-enable. And more interesting it is extensible.

  It's disadvantage I found until now is that it cann't upload image file(Blogger does not support it). It can just add a image link.

  (6.4 add)Today Writer beta2 is released. It has many nice feature. The biggest imprement is that my article can use tag. Well Done! It looks really cool! I think Microsoft will let it more powerful.

  The reason of Writer's existen is:1)It provide offline edit mode; 2)It is WYEIWYS editor; 3) web editor is not so much convenient until now. You will find these problem specially when the article is some long.