I have Spring boot multi module micro service application like below
parent module
-childmodule1
-childmodule2
-childmodule3
Currently each child modules are depolyed as single jar.
I need to implement java 9 modularity feature for each child module.
As per my understanding we need to create separate modules for each childmodule and each seperate module can be deployed as separate jars.
say if childmodule1 had two modules moduleA and moduleB , Then it can be deployed as two jars?
How does the childmodule1 having two jars communicates with other childmodules?
Do I really need java 9 modularity feature to the springboot mutli module projects. If yes ,how can i make use of the modularity benefits to my application.
Im new to micro service architecture and java 9 modularity. Can someone please help on this
Related
As Springboot multimodule produces single fat jar will that be good idea to use spring boot multimodule project for microservices
Yes, Actually it is a very good idea to use the multimodule project.
Below are some advantages of that:
Gives clarity about the code and project module
Decouples the layer.
Easy to modify/add the module. Suppose your persistence module is already implemented with Couchbase and now you wanted to switch to Mongo DB then you just need to change the persistence module(dependency, code, configuration) not other parts of a project.
Easy to maintain.
No, I believe. Actually, it is bad design to generate single fat jar for multimodule project in Spring Boot. Suppose, we have multimodule project having 3 sub-modules for different microservices. Then each module will have its individual pom right? that we need to refer in main project's pom as module. Now, assume anyhow we are able to define packaging in main module pom as single fat jar for all the sub-modules. Then, you are not following the microservices architecture guidlines. It will be a kind of monolithic architecture, because all your services are there in a single unit (a jar). Although it would be easy to maintain, but difficuilt to configure through Jenkins pipelines. I mean you have to customize your Jenkins pipelines.
You may refer following url for more details : https://thebasictechinfo.com/spring-boot/spring-boot-microservices-architecture-spring-cloud-netflix-oss
Spring boot starter project provides extensive set of functionalities auto configured. But for our application we want to have only a subset of functionality. May be only one feature out of the spring boot starter project. So is it advised to have custom starter project on top of spring boot provided starter project to mask some of the features or write new starter project directly from lower level libraries?
Spring boot starter project provides extensive set of functionalities
auto configured
There are two separate concerns you are talking about.
I think the auto configured part is something which is Spring boot's opinionated way of configuring. As an example if in classpath it finds a in-memory database library ( like H2) it automatically creates a datasource (pointing to embedded in-memory database) which is available for autowiring without you writing the configuration in a Java config class. Of course you can create you own datasource of choice by including appropriate driver jar for that database. Similarly lots of other configurations are done by default by classpath scanning and availability of certain jars and classes.
The second part - is more of a dependency issue in general. Say you want to use web mvc part in Spring boot. This will require a consistent set of dependencies and transitive dependencies as well. Rather than finding and declaring the dependency in your build tool of choice ( maven, gradle etc) it has created the concept of starter projects where you simply mention the parent and all the right dependencies would be pulled on. This gives a great way to correctly lock your dependencies. However if you want to include any different version than what is provided by boot starter ( provided there is no compatibility issues with those different versions) you can still add explicitly in your build tool. For e.g., maven will by default include the highest version of a particular dependency among all available via transitive dependencies when it resolves dependency for an artifact.
I am trying to convert my existing multi-module maven Spring project to Spring Boot project. The reason is make it self contain and follow Martain Fowler's microservices concept.
However, the problem I have encounter is when try to clean build, seems the spring boot is trying to find the Main method from every module, which of course will failed.
Is this feature currently supported by Spring Boot 1.1.6.RELEASE or I did something wrong?
Thanks
It sounds like you've added Spring Boot's Maven plugin to every module in your build – it's what's looking for a main method. You should only add the Spring Boot plugin to a module if its a service that you want to run. If the module's just code that's shared between your services, the Spring Boot plugin isn't needed in that module.
Are there any differences in capabilities of the EJB when defining / running it from a WAR vs. an EJB container? What are the benefits vs. drawbacks of deciding on one approach vs. other.
What capabilities do we lose when accessing it from a WAR?
In our case, the developers want to use the EJB for creating / accessing REST webservice.
One of our architects has mentioned below. And for this reason he wants to have a separate EJB that would be added ( the jar ) to EAR but also to WAR for using it as REST endpoint. i would prefer not to have it in multiple places
I’d prefer our approach to put transaction/service based code in EJBs to
leverage Container Managed Transactions, JPA, MDB and all the good stuff EJBs
have to offer.
From the documentation I have read on using EJB as a REST service implementation, it says
Add the EJB class to the WEB-INF/classes directory of your WAR file or to a
JAR that is located in your WEB-INF/lib directory. When a client makes a request
to a JAX-RS annotated enterprise bean, the JAX-RS runtime environment looks up
and uses an EJB instance of the class to invoke the resource method.
So, I want to know, if we put the EJB in the WAR - as in creating the source in the WAR's source so that the class will be added to WEB-INF/classes when the WAR is built, instead of having to put the same ejb jar in two different places based on what it is used for - as a REST webservice endpoint vs. other capabilities, will it satisfy all the requirements or I will have to put the jar in two places?
I am using Websphere 8.5 with EJB 3.1, if that makes a difference in the answer.
There are two primary differences highlighted in section 15.4 of the EJB 3.1 specification:
All EJBs in a WAR share the component namespace (java:comp) with the WAR and all other EJBs in the WAR. Normally, each EJB has its own component namespace. This makes it easier to share reference names and bindings (though this can be done explicitly in EE 6 with java:module or java:app), but it increases the chance of conflict in a large WAR.
EJB classes are loaded by the WAR class loader. In practice, this doesn't matter much, it's just something to be aware of if you encounter class loading problems.
If you want to use an EJB as a REST service, you must package the EJB in the WAR. If you're concerned about "duplicating" EJB logic inside the WAR and for an EJB module, you could declare a base class in the EJB module, and then declare subclasses in the WAR and EJB modules that extend the base class and are annotated #Stateless or #Singleton.
Regarding EJB capabilities there is no difference between packaging an EJB in a WAR or in an EJB module.
There are situations where you have to package EJBs in WARs e.g. if you have a REST endpoint which is at the same time an EJB.
Most often WARs encapsulate frontend functionality. In these situations it is just from a design perspective not advisable to put the EJBs into WARs.
I'm new to Spring and try to setup a project which is split into 3 submodules. As build tool I'm using maven. My problem is, that I don't know where to add Springs "magic".
My 3 submodules are "ORM" (holds all the hibernate staff to access the database) "BusinessLogic" (which should hold the complete logic) and "WebApp" (adds as the only "client" to the app / logic).
I want to use SpringMVC for the WebApp which seems to be no problem. As "BusinessLogic" should hold the complete logic I thought of adding the Spring related stuff (Bean definition / DI) in that module. But then I don't know how to setup Spring when accessing the module form the webapp.
The hole project is being ported from a JavaEE / JBoss app where "ORM" and "BusinessLogic" (implemented as EJBs) where put into one .ear archive and the webapp into a seperate one (.war). JNDI was used to access the beans from the webapp, but I completely want to decouple the application from JBoss and deploy it on a Tomcat webserver.
At the moment I've created all three modules as separate Maven projects ("ORM" and "BusinessLogic" as .jar, "WebApp" as .war packaging), linked by a "parent" project.
Thanks for any hints on project setup :).
Greetings
Ben
you could configure spring context in your web.xml and you can perform import of Spring sub-modules context. You can add import's configuration of sub-modules in your webApp application context.