There is no real configuration above and beyond that of configuring a web application to make use of Jython servlets. Add the necessary XML to the web. What is important to note is that the. It is common for the Jython servlets to reside in the same directory as the JSP web pages themselves. This can make things easier, but it can also be frowned upon this concept does not make use of packages for organizing code. For simplicity sake, we will place the servlet code into the same directory as the JSP, but you can do differently if you prefer.
The controller and the view portion of the application will be coded using markup and javascript code. Obviously this technique utilizes JSP to contain the markup, and the javascript can either be embedded directly into the JSP or reside in separate.
The latter is the preferred method in order to make things clean, but some web appplications embed small amounts of Javascript within the pages themselves. The JSP in this example is rather simple, there is no Javascript in the example and it only contains a couple of input text areas.
This JSP will include two forms because we will have two separate submit buttons on the page. Each of these forms will redirect to a different Jython servlet, which will do something with the data that has been supplied within the input text. In our example, the first form contains a small textbox in which the user can type any text that will be re-displayed on the page once the corresponding sumbit button has ben pressed.
Very cool, eh? Not really, but it is of good value for learning the correlation between JSP and the servlet implementation. The second form contains two text boxes in which the user will place numbers, hitting the submit button in this form will cause the numbers to be passed to another servlet that will calculate and return the sum of the two numbers. Below is the code for this simple JSP.
In this case, the text that is contained within the input textbox named p will be passed into the servlet, and redisplayed in on the page. Quick and simple, the servlet takes the request and obtains value contained within the parameter p.
It then assigns that value to a variable named addtext. The code could just as easily have forwarded to a different JSP, which is how we'd go about creating a more in-depth application. The second form in our JSP takes two values and returns the resulting sum to the page. If someone were to enter text instead of numerical values into the text boxes then an error message would be displayed in place of the sum.
While very simplistic, this servlet demonstrates that any business logic can be coded in the servlet, including database calls, etc. If you add the JSP and the servlets to the web applicaton you created in the previous Jython Servlet section then it this example should work out-of-the-box.
At the time of this writing, applets in Jython 2. The static compiler known as jythonc has been removed in Jython 2. Jythonc was good for performing certain tasks, such as static compilation of Jython applets, but it created a disconnect in the development lifecycle as it was a separate compilation step that should not be necessary in order to perform simple tasks such as Jython and Java integration.
In a future release of Jython, namely 2. In Jython, applets are coded in much the same fashion as a standard Java applet. However, the resulting lines of code are significantly smaller in Jython because of it's sophisticated syntax. GUI development in gerneral with Jython is a big productivity boost compared to developing a Java Swing application for much the same reason.
This is why coding applets in Jython is a viable solution and one that should not be overlooked. The only disadvantage of creating a web start application is that it cannot be embedded directly into any web page. A web start application downloads content to the client's desktop and then runs on the client's local JVM. Development of a Java Web Start application is no different than devleopment of a standalone desktop application. The user interface can be coded using Jython and the Java Swing API, much like the coding for an applet user interface.
Once you're ready to deploy a web start application then you need to create a Java Network Launching Protocol JNLP file that is used for deployment and bundle it with the application.
After that has been done, you need to copy the bundle to a web server and create a web page that can be used to launch the application. In this section we will develop a small web start application to demonstrate how it can be done using the object factory design pattern and also using pure Jython along with the standalone Jython JAR file for distribution.
Note that there are probably other ways to achieve the same result and that these are just a couple of possible implementations for such an application. The web start application that we will develop in this demonstration is very simple, but they can be as advanced as you'd like in the end. The purpose of this section is not to show you how to develop a web-based GUI application, but rather, the process of developing such an application.
You can actually take any of the Swing-based applications that were discussed in the GUI chapter and deploy them using web start technology quite easily.
As stated in the previous section, there are many different ways to deploy a Jython web start application. Personally, I prefer to make use of the object factory design pattern to create simple Jython swing applications. However, it can also be done using all. We will discuss each of those techniques in this section.
Quite often I find that if you are mixing Java and Jython code then the object factory pattern works best. The JAR method may work best for you if developing a strictly Jython application. The applicaiton we'll be developing in this section is a simple GUI that takes a line of text and redisplays it in JTextArea.
I used Netbeans 6. To get started with creating an object factory web start application, we first need to create a project. First, create the Main. The goal for Main. This class will be the starting point for the application and then the Jython code will perform all of the work under the covers. Using this pattern, we also need a Java interface that can be implemented via the Jython code, so this example also uses a very simple interface that defines a start method which will be used to make our GUI visible.
Lastly, the Jython class named Below is the code for our Main. Search Projects. My Project. Project of the Day. Spider Man Game in Python.
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Football Game In Python in Python. Load More. In the future, there will also be support for other Jython web frameworks such as Pylons. If you have read through the information contained in the previous sections, then you have a fairly good idea of what it is like to deploy a Jython web application to a Java application server.
There is no difference between deploying Jython web applications and Java web applications for the most part. You must be sure that you include jython. However, I have run into cases with some application servers such as JBoss where it wasn't so cut-and-dry to run a Jython application.
For instance, I have tried to deploy a Jython servlet application on JBoss application server 5. For one, I had to manually add servlet-api. Similarly, I had issues trying to deploy a Jython web application to JBoss as there were several errors that had incurred when the container was scanning jython. All in all, with a bit of tweaking and perhaps an additional XML configuration file in the application, Jython web applications will deploy to most Java application servers.
The bonus to deploying your application on a Java application server is that you are in complete control of the environment. For instance, you could embed the jython. Likewise, you are in control of other necessary components such as database connection pools and soforth. If you deploy to another service that lives in "the cloud", you have very little control over the environment.
In the next section, we'll study one such environment by Google which is known as the Google App Engine. While this "cloud" service is an entirely different environment than your basic Java web application server, it contains some nice features that allow one to test applications prior to deployment in the cloud. The new kid on the block, at least for the time of this writing, is the Google App Engine.
Fresh to the likes of the Java platform, the Google App Engine can be used for deploying applications written in just about any language that runs on the JVM, Jython included. The App Engine went live in April of , allowing Python developers to begin using it's services to host Python applications and libraries. In the spring of , the App Engine added support for the Java platform. It has been mentioned that more programming languages will be supported at some point in the future, but at the time of this writing Python and Java were the only supported languages.
The App Engine actually runs a slightly slimmed-down version of the standard Java library. You must download and develop using the Google App Engine SDK for Java in order to ensure that your application will run in the environment. The SDK comes complete with a development web server that can be used for testing your code before deploying, and several demo applications ranging from easy JSP programs to sophisticated demos that use Google authentication.
No doubt about it, Google has done a good job at creating an easy learning environment for the App Engine so that developers can get up and running quickly. You will learn how to deploy a Jython servlet application as well as a WSGI application utilizing modjy. Once you've learned how to develop and use a Jython Google App Engine program using the development environment, you will learn a few specifics about deploying to the cloud.
If you have not done so already, be sure to visit the link mentioned in the previous paragraph and download the SDK so that you can follow along in the sections to come. Please note that the Google App Engine is a very large topic. Entire books could be written on the subject of developing Jython applications to run on the App Engine.
With that said, I will cover the basics to get up and running with developing Jython applications for the App Engine. Once you've read through this section I suggest to go to the Google App Engine documentation for further details. This is a very simple Java application that allows one to sign in using an email address and post messages to the screen.
In order to start the SDK web server and run the "guestbook" application, open up a terminal and traverse into the directory where you expanded the Google App Engine. Of course, if you are running on windows there is a corresponding. Once you've issued the preceeding command it will only take a second or two before the web server starts. This is a basic JSP-based Java web application, but we can deloy a Jython application and use it in the same manner as we will see in a few moments.
Prior to deploying your application to the cloud, you must of course set up an account with the Google App Engine. If you have another account with Google such as GMail, then you can easily activate your App Engine account using that same username. Enter your existing account information or create a new account to get started.
After your account has been activated you will need to create an application by clicking on the "Create Application" button. You have a total of 10 available application slots to use if you are making use of the free App Engine account. Once you've created an application then you are ready to begin deploying to the cloud. In this section of the book, we create an application known as jythongae.
This is the name of the application that you must create on the App Engine. You must also ensure that this name is supplied within the appengine-web. The Google App Engine provides project templates to get you started deveoping using the correct directory structure. Eclipse has a plugin that makes it easy to generate Google App Engine projects and deploy them to the App Engine.
In this text we will cover the use of Netbeans 6. For the purposes of this tutorial, we will make use of the nbappengine plugin. If you are using Eclipse you will find a section following this tutorial that provides some Eclipse plugin specifics. Once you've added the new update center you can select the Available Plugins tab and add all of the plugins in the "Google App Engine" category then choose Install.
After doing so, you can add the "App Engine" as a server in your Netbeans environment using the "Services" tab. Once you have added the App Engine server to Netbeans then it will become an available deployment option for your web applications. For the deployment server, choose "Google App Engine", and you will notice that when your web application is created an additional file will be created within the WEB-INF directory named appengine-web.
Any of the. Our application is going to make use of three Jython servlets, namely NewJythonServlet. In our appengine-web. We should create a lib directory and place jython. We should now have a directory structure that resembles the following:. Now that we have the applicaton structure set up, it is time to begin building the actual logic.
In a traditional Jython servlet application we need to ensure that the PyServlet class is initialized at startup and that all files ending in. As we've seen in chapter 13, this is done in the web. However, I have found that this alone does not work when deploying to the cloud. I found some inconsistencies while deploying against the Google App Engine development server and deploying to the cloud.
For this reason, I will show you the way that I was able to get the application to function as expected in both the production and development Google App Engine environments. In chapter 12, the object factory pattern for coercing Jython classes into Java was discussed. If this same pattern is applied to Jython servlet applications then we can use the factories to coerce our Jython servlet into Java bytecode at runtime.
We then map the resulting coerced class to a servlet mapping in the application's web. We can also deploy our Jython applets and make use of PyServlet mapping to the.
I will comment in the source where the code for the two implementations differs. In order to use object factories to coerce our code, we must use an object factory along with a Java interface, and once again we will use the PlyJy project to make this happen. Please note that if you choose to not use the object factory pattern and instead use PyServlet you can safely skip forward to the next subsection.
The first step is to add PlyJy. There is a Java servlet contained within the PlyJy project named JythonServletFacade , and what this Java servlet does is essentially use the JythonObjectFactory class to coerce a named Jython servlet and then invoke it's resulting doGet and doPost methods.
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