I've got 2 different web applications running.
'Web application A' has all the business logic layer services.
I need to invoke methods defined in 'Web application A' from 'Web application B'.
How can I use services(or methods) from 'Web application B' without sending
a http request ?
So far I've found that you can invoke a java programme as described in this question.
Execute a Java program from our Java program
I wonder which one is the right way. Call method by sending a http request or call some method directly. Could you also tell me which one is better, and why ?
Edit
Could I use Springframework's remote invoking ?
http://static.springsource.org/spring/docs/2.0.x/reference/remoting.html
Which one is more desirable. Spring remoting or EJB ?
We are using Tomcat.
Remote EJB invocation is the standard way to make a call between two applications in the Java EE world.
I thing RESTful Web Services is the right way of doing this. You will just expose some of your classes and method as a service and some other application may call them whenever it wants. See this very basic tutorial from Oracle.
Related
I have one webserver with 2 instances of tomcat running. On each tomcat instance I have multiple web apps or web services.
What is the best way to call a function (or trigger some event with parameters) from a webapp of the first tomcat server on a webapp running on the second tomcat server. If it's for example a call using a url with parameters then this call should be secure and not accessible from outside the server.
I've read something about getting the servlet context but is this possible on different tomcat instances? Im thinking that this is only possible with webapps running in the same instance.
I dont want to use CORBA, RMI or SOAP because this is a bit oversized for my problem ... that is what Im thinking :)
Code examples are welcome. Thank you!
The ServletContext is only valid within the same container and can't be shared between two JVMs. The simplest method to do what you're asking is to just use some variety of RPC between the two containers, and RMI doesn't seem like particular overkill. The other usual approach would be a simple HTTP Web service (note the lowercase "s") that invokes your logic in the receiving container.
Spring's HTTPInvoker is great for this. You can use a Java interface, and your code on each instance doesn't need to know the call is remote - it just calls Java methods.
For security, you can use the Sun HTTP server on a different port (instead of using a servlet within Tomcat) and listen only on localhost.
Have a look here
http://static.springsource.org/spring/docs/3.2.x/spring-framework-reference/html/remoting.html#remoting-httpinvoker
Use Simple REST services , not that much secured .
I'm absolutely new to GWT, java and eclipse, but I'm an experienced MS programmer.
I installed eclipse and GWT and created a default project (called it test2) with pre-built sample gwt code. It comes with one java web service on the backend called 'GreetingService' which has a single web method called 'greetServer' that takes a single parameter called 'input'. I tried to invoke it in the web browser with many different combinations, but with no success (my project name is called 'test2):
http://127.0.0.1:8888/test2/greetServer?input=hello
http://127.0.0.1:8888/greetServer?input=hello
http://127.0.0.1:8888/test2/greetingService/greetServer?input=hello
http://127.0.0.1:8888/test2/greetingService?input=hello
etc
but I get http error 404 not found.
My question is, how can I invoke the web service from a browser and see the return data? I know this can be done easily with WCF or asmx web services but I'm not familiar with java web services.
Thanks a bunch!
The GWT Remote Service Servlet only uses HTTP Post. If you want to see the data (which will be encoded by gwt anyway) use could use firebug and take a look at the traffic.
The greeting service isn't intended to be a web service. It's a demo of GWT's remote procedure call (RPC) facility over AJAX. As with most RPC frameworks, the server side is only intended to be called from the generated client stub.
I am trying to consume a java web service from .NET.
When I add service reference to generate proxy and run the programme i get the error below
The formatter threw an exception while
trying to deserialize the message:
There was an error while trying to
deserialize parameter
http://order.x.service.y.com:requestPayment.
Apparently I have to tweak the proxy classes generated bacause of differences in namespaces between JAVA and .NET but am not sure how.
It sounds like the java web service has at least some non-interoperable features.
Do you have access to the java web service code? If so, maybe you can create your own proxy class that can talk with it. I would not try to change the auto-generated proxy code. I'd suggest hooking up to the java web service manually instead of by adding a Service Reference.
Although this article is geared mainly to consuming WCF services, it goes into some depth in consuming services manually. You'll be able to follow most of the steps for manual proxy connection even though you're pointing to a java service.
I am migrating a Java RMI application to Java Web Service (school assignment) and I've encountered an issue...
Currently my Java Server creates an instance of the Remote Object, this object has a constructor and takes a parameter (int ID) which tells it which database to load in memory - works like a charm ...
Now, migrating this to Web Services is causing my a problem - first I needed to add a default constructor because it wouldn't deploy without it, and then while doing some reading all these discussions about "stateless web services" kept coming up ...
For example, if I "start" my webservice with parameter(0) it would load from Databse 0 and all requests from Clients would be done using that data... I want this to only happen when I start the WebService and NOT everytime the client connects... Loading from the DB is expensive and takes time, so I want to do it once so that clients when they connect just deal with the data in memory ...
This is how it works with my Java RMI .... but can this also work with Web Services?
Any advice would be much appreciated.
Thanks,
Perhaps you should consider splitting your presentation from the backing service. Consider the WebService simply a presentation layer and the database processing the service being presented. The web service should really just be referencing the database via a handle to a single instance rather than actually being that instance. This means that the "state" is then held in the database instance not the web service.
One way to consider this (although I would not suggest that you implement it this way) is to consider the Web Service as the RMI client of the database rather than the RMI server service.
Hope this helps.
Kind regards,
Malcolm
I have a problem with web services. They are programed in Java and are running on a WASCE server ( both are on the same server).
My problem that i want to solve:
We have two Web services: App1 and App2
In App1 i want to call a function that is in App2. How can i do this? Is this even possible?
I tried creating a soapClient inside the App1 so i can connect to the App2 but that doesn't work.
exp:
I have a client that calls app1 gets data from app1 and send it to app2 then get back the response data from app2 and send it to an other function into the app1.
What i want to do is to skip the client part and do it directly so that app1 can send directly the data to the app2 and then receive an answer do whatever it needs to do.
For the note: Both of the web services use the connection to the database.
Thank you in advance.
(it has been edited with additional data)
What does "doesn't work" mean? Exactly what happens?
Start by generating some client code for App2. Can you use that from some simple Java environment, or say a Servlet. If that works, what happens when you try to call it from inside your App 1 Service implementation code?
However: if these are related services running in the same JVM can you not set up some simpler relationship using java libraries. My preferred way of developing a service is first to develop some useful Java code, and make sure that works, then "wrap" it as a Web Service. In which case I have a callable routine that can just be invoked as Java.
It's definitely possible, with differing levels of complexity and feasibility depending on exactly what it is you want, and the restrictions you place on it.
Probably one of the simplest ways to go about this, if you don't have a problem with the method in App2 being public, is to simply create a web service exposing that method and call if from App1.
If you want App2's method to be essentially "protected", so that it can be called by App1 but not by public clients, then there are several alternative options. Firstly, you could use firewalls or equivalent to prevent external requests to the service URL. Alternatively, you could expose the method through some form of interprocess communication; RMI would be the obvious native one for Java (set up an RMI method in App2 and export this through a manager, then obtain the reference in App1 and invoke the method remotely). Depending on exactly what it is you want to do, you may be better off with a framework that does all this under the covers; e.g. distributed objects through something like Terracotta.
You should give more detail in your question, though - currently the only thing you've really specified is that you want to call "a function" in App2 from App1. There are dozens (if not hundreds) of ways to go about this and the best one(s) will depend on the details of what you're trying to do.
EDIT (in light of comments): It's not the details of what you want to do that are lacking - I understand fine that you want to call some method in App2 from within App1. It's more the architectural details - what languages are both clients coded in, what libraries are you using to do the web services, are both clients on the same machine or separate ones (and if same machine, same JVM or not), are there any firewall issues that could inhibit certain kinds of connectivity, are there any office-political restrictions that could inhibit your options, are there any security restrictions that could do the same (such as whether you can expose the functionality of App2's method publically or not). All of these will shape what is possible and what is optimal - because at the end of the day, all networking is basically I want to use resources on that remote computer from here. Without more architectural specifics, there are literally dozens of ways that you could achieve this.
Regarding exposition: You would create a web service to expose App2's function in the same way you would create any other web service (with the details being dependent on the tool/framework you're using). As an example if you're using a tool that supports the JSR-181 annotations, you'd write a method in App2 that performs this function, and annotate it with #WebMethod. Then you'd ensure that if this method is not part of an existing webservice class you'd annotate its class with #WebService. I was presuming that since you already have a couple of web services, you'd know how to write/define them.
As for accessing the web service from App1, this can be done quite simply by a Java SOAP client. A tool such as WSDL2Java can create a stub class modelling the remote service that you can call; alternatively you can get a richer interface with something like CXF.
What WS library are you using currently, and what errors have you encountered when trying to use it to perform this interaction?