I'm having a problem I simply can't get my head around.
I'm creating a jsf application where I (as administrator) can upload a jar file, and that way around update the application.
Through this tutorial: http://docs.oracle.com/javase/tutorial/deployment/jar/jarclassloader.html I have managed to classload the jar file. The first issue is that I can only class load as "Object" and not cast to an other class type. I get a ClassCastException.
JarClassLoader jcl=new JarClassLoader(url);
Class cl= jcl.retreiveClass(jcl.getMainClassName());
Object ob=cl.newInstance(); //I would like to make this a RouteBuilder object instead of Object
Concretely I'm using Apache Camel, where I can add routes to an existing "core" (CamelContext). What's happening is that I have the core of apache camel running in my web app, and I can then add routes runtime. It's a route I want to package as a jar and load into the app runtime (I want to develop and test the route in my local environment, and then afterwords upload it to the production application). A concrete route is just a simple java class that extends RouteBuilder. I want to upload the jar, classLoad (URLClassLoader) the main class (maybe the whole jar? - does that make sense?), and convert it to a RouteBuilder. This seems to be impossible. I have chosen to upload the jar file to a folder outside my war, so that the routes do not get erased when I restart the webapp (is this smart or should this be done in an other way?). Is that a problem regarding name spaces? Furthermore, I haven't been able to find out whether I need to traverse my entire jar file and classload ever single class inside. Any comments on that?
To me it seems like I have some fundamental misconceptions on how extending / updating a java application is done. I simply can't find any good examples/explanations on how to solve my problem and therefore I conclude that I don't get this on a conceptual level.
Could someone elaborate on how to extend a running jsf application (I guess the same issues are relevant in native java apps), explain how to upload and class load a jar at runtime, and how to cast loaded classes to other class types than Object?
Thanks
Lasse
If you are interested in loading Routes without stopping your application you could consider using an OSGi container like Karaf. Karaf provides support for Apache Camel routes out-of-the-box: http://camel.apache.org/karaf.html
All class loading is managed by the OSGi container and you just need to run some commands to update things. I am not sure if this could work with your JSF application but it worths to take a look.
Related
I have an ear file with a web module and a ejb module(just used for message driven beans). The ejb module has dependency on web module and it's classes. I would need to load the web module first and then ejb module. But the liberty always loading the ejb module first causing com.ibm.ws.container.service.state.StateChangeException: java.lang.NoClassDefFoundError:
How to control the order of modules loading within the same ear file? On traditional webshpere there is an option called 'Starting weight'. Whichever module has lowest value takes precedence and loads it first. so the application works good on tradition Websphere. However, this property seems missing on Liberty. I already looked at this. It only talks about deploying the multiple war files and their order.
If your EJB module depends on Web, that is bad design. It should be the other way around.
If you have such situation , proper way would be to extract shared classes in to a common jar file, let say mycommon.jar and then put that into ear\lib folder. In this way they will be visible by both modules ejb and web.
If your EJB module depends on the javax web api (e.g. servletRequest) that is even worse, and you should redesign such classes to POJO DTOs.
As a last resort you could try what is described here and add <initialize-in-order>true</initialize-in-order> in your application.xml.
FRowe's solution will not work, as classes are not shared between the applications, so changing load order of apps will not help. Each Java™ EE application has its own class loader in a running Liberty server.
Consider using the ability to control app start order as described here: https://www.openliberty.io/blog/2020/06/05/graphql-open-liberty-20006.html?_ga=2.4728563.17466047.1620833568-1423690488.1614284842&cm_mc_uid=99965752544816136653536&cm_mc_sid_50200000=61078141620909829332#ORDER
You'll have to deploy the war module as an app instead of packaging it within the ear, but you should be able to achieve the proper ordering.
I am creating a library using spring-boot (v2.1.6.RELEASE) as a starter project that will facilitate as base extension jar responsible for configuring and starting up some of the components based on client project properties file.
The issue I am facing is that if the client project's SpringBoot Application class contains the same package path as library everything works like charm! but when client project contains different package path and includes ComponentScan, it is not able to load or start components from the library.
Did anyone encounter this issue? how to make client application to auto-configure some of the components from library jar?
Note: I am following the library creation example from here: https://www.baeldung.com/spring-boot-custom-starter
There are many things that can go wrong here, without seeing relevant parts of actual code its hard to tell something concrete. Out of my head, here are a couple of points for consideration that can hopefully lead to the solution:
Since we use starters in our applications (and sometimes people use explicit component scanning in there spring applications) and this obviously works, probably the issue is with the starter module itself. Don't think that the fact that the component scan is used alone prevents the starter from being loaded ;)
Make sure the starter is a: regular library and not packaged as a spring boot application (read you don't use spring boot plugin) and have <packaging>jar</packaging> in your pom.xml or whatever you use to build.
Make sure you have: src/main/resources/META-INF/spring.factories file
(case sensitive and everything)
Make sure that this spring.factories file indeed contains a valid reference on your configuration (java class annotated with #Configuration). If you use component scanning in the same package, it will find and load this configuration even without spring factories, in this case, its just kind of another portion of your code just packaged as a separate jar. So this looks especially "suspicious" to me.
Make sure that #Configuration doesn't have #Conditional-something - maybe this condition is not obeyed and the configuration doesn't start. For debugging purposes maybe you even should remove these #Conditional annotations just to ensure that the Configuration starts. You can also provide some logging inside the #Configuration class, like: "loading my cool library".
Grails has amazing validation; is it possible to use it independent of the Grails framework?
We have a Java/Groovy Camel-based web application we can't convert to a Grails application. I'd love to use the Grails-style validation with the declarative constraints but have been unable to successfully configure the application to work with Grails libraries without converting the whole thing.
The validation provided by Grails is just a wrapper around Spring's bean validation framework. Since Grails is open source you can take a look at how it's done and adapt it to your own needs. The best place to start looking is the GrailsDomainClassValidator and DomainClassGrailsPlugin to get an idea of how it's done. Another point of interest would be the #Validateable AST annotation.
As far as I know, and from what I can see in the source, there isn't a stand alone way to do this outside of a Grails project without writing your own adaptation/implementation.
You can use a external validation without problem. It is possible, for example, using a external "jar" (that do a validation) file on the "lib" folder of your Grails project. Through this way, you can use the API of this jar file. It's a simple way that you can use.
Can i use a service in the class file which is generated using javaassist. how can i achieve that?? and as this class is created dynamically how can i register that this class is using the provided service of another class?
I've asked a similar question here.
The smallest unit of 'installation' would be a bundle. You could generate a sort of 'virtual bundle' around your class file, including a OSGI-INF/componentX.xml descriptor, and install that into OSGi.
If it changes, regenerate the bundle and update OSGi.
I didn't go down this path as I have a lot of generated code (about 4500 different scripts that all have dependencies) and I fear that I'd get into problems if I'd generate that many bundles.
I also got a tip about the Felix Dependency manager, but I haven't thoroughly checked that out yet, it might do the things we need.
I would like to use an ajax toolkit/framework like ZK (www.zkoss.org) or GWT. But I don't know whether it's possible to bundle resources in a JAR? Do you know which one support such resource loading?
Not sure what your goal is, but if its to bundle a web application into one file, then you can do that with a WAR file - assuming your deploying onto a java webcontainer like tomcat or jboss.
My goal is to summarize the Java-classes and also their Templates-files for the view of various application modules, each in one Java-Jar-File. These modules I use in another application, which of course I summarize in a WAR-File for Deployment. I would like to know which ajax-Framework/Toolkit does support this.
Take a look at http://www.ztemplates.org which is simple and easy to learn. This one allows you to put all related templates, javascript and css into one jar and use it transparently. Means you even have not to care about declaring the needed javascript in your page when using a provided component, as the framework does it for you.