Recently I got asked to write a java application for my company. I'm a seasoned .Net developer so this is all new ground to me.
My task is to produce an invoicing application that has several high level tasks such as:
Build single invoice
Build all invoices
My company want to be able to call these tasks from a java console application - passing in relevant commands and parameters to invoke the tasks. They also want to be able to invoke the same code from an ASP.NET application.
Therefore my first thought was to use Web Services in Java.
My question is: Can I use Web Services in Java from both a Java Console Application and from an ASP.NET application? Or perhaps are there better alternatives.
Any pointers to get me researching in the right direction would be appreciated.
Thanks.
"My company want to be able to call these tasks from a java console application - passing in relevant commands and parameters to call the tasks. They also want to be able to call the same code from an ASP.NET application."
I'm not sure exactly what you are asking, but I think the simple answer is to ensure that your application has an entry point method so that it can be run as a command line applications. You need a class with a method that looks like this:
package foo.bar;
public class Bazz {
...
public static void main(String[] arguments) {
// parse the arguments and run the application
...
}
}
The signature of the main method is critical:
it must be public static,
it must have the name main,
it must tack a single String[] argument and,
it must have a void return type.
This command can then be run from the command line as follows:
java -cp <YOUR_CLASS_PATH> foo.bar.Baz arg1 arg2 ...
This can also be done by another application written in Java, and (I imagine) from ASP.NET as well.
The simple answer is - yes. Java has libraries for defining Web Services and deploying them, and both Java and .NET have utilities for generating Web Service clients. That's not to say it will be easy though!
If I was you, I would instead investigate creating a REST service using a JAX-RS implementation (my favourite is RestEASY). This will allow you to create a 'web service' without SOAP, i.e. http://server/invoices/1 might return
<invoice>
<items>
<item>apple</item>
<item>banana</item>
<items>
<customer>robert</customer>
<amount>5.00</amount>
</invoice>
Which it then should be easy to interpret in any language. Either way it will be a steep learning curve though. The main difference between Java and .NET is that while a lot of functionality is built in to .NET, in Java it's spread across the ecosystem, which is good because it provides variety, however it can take a bit longer to locate functionality.
Related
I want to develop a service that exposes a rest API to upload plugins and the plugins are locally executable, i.e. other classes from the server use them.
The plugins also:
The plugin should be a jar file that is submitted through the REST API and once is validated, is then made available through another API method to see the metadata and to execute.
Are not too complex (they should all contain at least a a class that extends of an abstract class or an interface implementation of an interface, the service) but could have their own dependencies.
The API allows to validate that the plugin is compliant with the service and that it declares some additional information on an XML or JSON file contained on the JAR.
Have some metadata that has to be exposed through the API (Version, who made it, is it usable, what data can it be handled) in Json form.
All implement an algorithm to perform some data crunch so they all have something like an execute() method. The result of executing this method is handled to another class, so is not totally important to expose it on the API.
Must be able to be uploaded and executed by the other server classes in runtime, so no restart is possible
The thing is that I am not sure where to start, since I had already developed some of the basic API on Spring-boot since it had all the things I needed to easily develop a REST API but the more I read about how to dynamically load modules (plugins) the more I see that Spring does not support this ind of thing and I am not sure a class loader or Service loader would work in that context.
I found out about OSGi framework but I honestly do not know it changing the whole technology stack will help me so I want to make sure it is the right answer, and if yes, then find some resources that point me in the right direction, e.g. some tutorial that implements something similar.
Thank you for any advice.
Checkout OSGi enRoute. It includes a model to developing RESTful services: http://enroute.osgi.org/services/osgi.enroute.rest.api.html.
OSGi sounds like the best match to what you try to do.
You can install everything as a bundle including your main application. Nowadays this is much less work than some years before but still not to be underestimated.
The other option is to start an embedded OSGi framework where you just install your plugins. This is less work but you need to know exactly how it works.
So for both cases I suggest to get help from an external OSGi expert as it speeds up the transition a lot and avoids many wrong paths you will choose as a beginner.
I have a fairly standard Spring Boot app. We are now in a phase of performance testing the application. In order to do this, we need to generate a large set of request objects from a mocking library. The end point uses protobufs, so they need to be dumped into a file and saved for Jmeter. I would like to add some sort of command line functionality to my application to have it generate the performance test assets only.
I have tried things like:
java -cp target/sm-reports-1.0.0-SNAPSHOT.jar com.blah.reportservice.AssetGenerator
or
java -Dloader.main=com.blah.reportservice..AssetGenerator -jar target/sm-reports-1.0.0-SNAPSHOT.jar
While having the functionality in an alternative main class. None of this quite seems to work. Due to the architecture of the parent project here in the company, a module style approach would be a ton of work.
Is there a good way or place to accomplish this? Do I switch on the ApplicaitonBuilder configuration before main on some flag or variable? In an ideal world I would be able to run something like the above with a command line flag to have ti accomplish what I am looking for. Can anyone help or point me int he right direction in the docs?
I have created a web based application using JSP and Servlets and the application uses an SQL Server DB as its backend.
The architecture is like this:
I have all my business logic in a jar file
I have created my views using JSPs and am using servlets to interact with my business logic jar
The jar connects to the database to persist and hydrate information, which is relayed to the JSP by my servlets.
My web application runs on a remote Tomcat server.
Now, I have been given a new requirement. I have to create a command line interface, where I should be able to specify a list of commands and hit enter (or alternatively, create a set of commands and save it in a .bat file or something, and run it), so that my application performs the necessary actions. Basically, I have to create a command line interface, which can be used along with the GUI i already have (JSPs).
I am totally new to this. Can anyone throw light on where and how I can start?
Any little help is greatly appreciated.
EDIT
This is what my web application does. User can see a list of test scripts (written in Selenium WebDriver). He can choose script(s), choose a host on where to run them from, and click "Run", and the test executes on the said machines.
Now, I want a command line interface, which will eliminate the need for the GUI. Let's say, I simply want the user to be able to type a command like "execute My_Script_1", and the script should be executed.
The test scripts, the selenium drivers, everything reside on the App server.
My command line interface should be able to work on Windows command prompt.
Thank you.
Are you using Spring?
Can you specify, what exactly your CLI should do?
You may do, what Thomas said.
You also may use template engines like Velocity.. To form your output.
Use some kind of JavaCurses-like library to make your output... Look well.
Specifying commands...
Hm.. think about your business logic what exactly you are showing to user.
Remember webapp ui is webapp ui. Console ui is different. And user expects different behaviour
So commands like
show goods category="for kids"
Will be great.
Also don't forget about different help commands
yourJarName.jar --help / -h and etc
If your are want to write application with interactive mode... think about help command there.
You say you have your business logic in a JAR.
Why not starting another project with this JAR as a dependency and build it as an executable jar ?
Then simply use System.in and System.out to interact with the user.
EDIT :
So your application is hosted. Do you have an API like REST or SOAP or any other ?
Then you can build a client reading a string that the user has written, parsing it and calling the right service in your API.
I see two options:
Create a client-side CLI that generates the same data your server
receives. In other words, you don't modify your server code, and you create a
client-side CLI module (with jQuery for example) that parses the command lines and sends
exactly the same thing your actual GUI sends.
Set up a text area in your web app (decorated as a CLI) that reacts
on each Enter key pressed, and sends the line(s) to your server. On
your server, you can create a utility class (say CLIParser.java for
instance), and use Args4j to parse the received command,
validate it and run it.
Have you looked at Primefaces terminal? http://www.primefaces.org/showcase/ui/misc/terminal.xhtml
You data structure looks simple enough. Also you mentioned you designed your application the way the business logic is separated from the front end.
In this case you may consider exposing your business logic as a REST based WebService. It should not be that hard since you have layered structure in your application.
Looks like a few methods:
list scripts - returns a list of available scripts list hosts
returns a list of available hosts run script(scriptName, hostAddress)
runs script scriptName on a host with on address hostAddress possibly returns the results if your application supports this
All three look like a good candidates for GET methods.
You may consider Jersey or Resteasy or another framework.
You can find plenty tutorials for both of them. Take a look for example here.
From your command line application you can make calls to your web service in different ways. Just because I used to work with Jersey JAX-RS implementation most of the time, I found use of Jersey client(the latest stable version) the most convenient. Here you can find a short tutorial how you can do it from your command line application with Jersey client. JBoss also has a client API as a part of their framework(also fully certified JAX-RS implementation). You may even decide not to use any client API and do all the work manually utilizing HttpURLConnection, but I would not recommend. There is no big difference in using client API or do all the work manually with HttpURLConnection for the simple service, but you never know when your application becomes not that simple because of new requirements your client could not think of at the beginning.
Hope that helps
*Hello Guys..! *
Normally a java program needs main() function to execute the code otherwise it'll returns an error[java.lang.NoSuchMethodError: main Exception in thread "main"]..! In struts2 we are using action classes & bean classes(java codes) but they don't needs main() function in it. What is the concept behind this..? By the way I'm a newbie to the Struts framework.
This is because the Struts framework provides the infrastructure to get the application up and running. As a user of the framework, you implement specific classes that are called by the framework code.
Struts itself runs inside an application server such as Tomcat, and usually it is the server that contains the main() method which is ultimately responsible for starting up your application.
This is an example of inversion of control -- many application frameworks work this way.
You need a main() method in applications started from the command line as that's the API that the JVM expects to execute in that case. Code called from within other frameworks must implement whatever API that framework expects. In many cases that framework implements main() and calls your code via some other API. This is usually more robust than public void main(String[] args) allows. In other instances the framework is itself called from another abstraction (e.g. a Web Application within a Web Framework within a App Container).
Suppose I have a java program, myProgram.jar, which I have running on a server. To start the program I would type this into the terminal:
>java -jar myProgram.jar
and the program would continue to run indefinitely. Now what about if the program had a function such as
void processInput(String text){
//process the text
}
and I wanted to SSH into the server and call this function with a particular string? so I could log into my server at any time and alter the state of my program. Is this possible?
This can be done, but not easily.
There are standard ways to achieve what you probably want: MBeans. Take a look at http://docs.oracle.com/javase/tutorial/jmx/mbeans/standard.html
You'll have a number of options here. The simplest would be if you only needed to provide your custom text as an argument at startup to the Java program - in which case you any arguments at the end of your java command would be passed as a String array into your programs main method.
Otherwise, you'll be looking to to implement some sort of remote procedure call (RPC). You could use something like Java RMI (remote method invocation) - where your main execution of your program starts, and you could use child executions of your program (or another client library all together) that calls methods within your main execution while it is still running. If you wanted to extend this further, you could have it host web services over standard HTTP, and use SOAP or REST calls.
There are many additional options and variations here, depending upon your exact requirements.
+1 for DagR's suggestion - again, depending upon exactly what you're looking to do, JMX may be a good fit for this as well.
You could implement a Java client application that calls methods on the Java application running on the server using RMI. Then when you ssh into the server you can run your client application with the parameters you need and have it call the methods in the other program.