I have question towards a best practice for configuration of persistence and cache (2nd lvl) within a maven multi module project with spring/jpa/ehcache.
Only a single datasource is needed.
Lets assume
I have 3 domain maven modules containing only the entities:
core_domain
customers_domain (dependency core_domain)
products_domain (dependency core_domain)
I also have 3 integration modules containing repositories:
core_integr
customers_integr (dependency customers_domain, core_integr)
products_integr (dependency products_domain, core_integr)
Now these modules MAY eventually be combined into a single WAR.
One approach might be to define all persistence,transaction and caching configuration in the core_integr module. But this does not cleanly allow configuration per module. It's possible, but not clean.
Is it possible to have a persistence.xml and ehcache.xml per integration module? preferably while keeping spring configuration in the core_integr module.
OR
Do you really need to separate the spring config fully with multiple entitymanagers, persistence_units and cachemanagers all working against the single datasource?
Any advice is welcome.
Related
Experts,
I need some expert advice on how to approach the below use case in spring boot.
I need to have a maven multi-module approach to my project.
I need to have a single jar as output of the final build process.
There are to be common modules for controllers, data access and other functionality
Other modules are to be created based on functionality domain for eg a module for Payroll, a module for Admin etc etc.
Each domain functional module will then have their own controllers extending the common controller, exception handler and so on.
Each module will also have its own set of thyme leaf pages.
The reason for following such an approach is we have development in phases and we will be rolling out based on functional modules.
Here are the issues that I can sense using this approach.
Where do I add the spring web dependency? If I add to the parent pom - it gets replicated across the children and there will be port conflict issues as each module loads. the same issue will also be there the moment I add it to two child modules.
How do I build the fat jar which has all the jars from all modules and works as the final deployment?
All the text that I read i can't see anything even close to what I am trying to achieve.
AD1. They will not unless you are trying to setup independent application context in each module. Of course you can do that(it might be complicated but I believe it's achievable), but for me it's an overkill. Personally I think it's better to have one application context and rely on scanning components that are present in classpath.
AD2. The structure in maven might be a little bit complicated and overwhelming at first glance but it makes sense. Here's how I see it:
Create a parent module that will aggregate each module in project and will declare library/plugin dependencies for submodules.
Create 1-N shared submodules that will be used in other modules. With come common logic, utils, etc.
Create 1-N submodules that will be handling your business logic
Create an application submodule that creates application context and loads configuration and components from classpath
Create a submodule that will be responsible for packaging process, either to war, jar, uber-jar or whatever else you desire. Maven jar plugin should do that for you. For executable uber-jar, you have dedicated tool from spring.
Now you can choose three ways(these ways I know) of loading your modules.
1. Include some modules in maven build based on the build configuration via maven profiles and let spring IoC container load all the components he finds in the classpath
2. Include all of the modules in maven build and load them depending on spring active profiles - you can think about it as of feature flag. You annotate your components or configuration class with #Profile("XYZ") telling spring IoC container whether to instantiate component or not. You will need (most flexible solution) to provide a property file which tells spring which profiles are active and thus which modules should be loaded
3. Mix of these two above.
Solution 1 pros:
build is faster (modules that are not included will be skipped during build)
final build file is light (modules that are not included are... not included ;))
nobody can run module that is not present
Solution 1 contras:
project descriptor in maven may explode as you might have many different profiles
Solution 2 pros:
it's fairly easy and fun to maintain modules from code
less mess in project descriptor
Solution 2 contras:
somebody can run module that is not intended to be run as it's present in classpath, but just excluded during runtime via spring active profiles
final build file might be overweight - unused code is still present in code
build might take longer - unused code will be compiled
Summary:
It's not easy to build well structured project from scratch. It's much more easier to create a monolith and then split it into modules. It's because if you already created a project, you've probably already identified all the domains and relations between them.
Over past 8 years of using maven, I honestly and strongly recommend using gradle as it's far more flexible than maven. Maven is really great tool, but when it comes to weird customization it often fails as it's build capabilities rely on plugins. You can't write a piece of code on the fly to perform some custom build behaviour while buidling your project, you must have a dedicated plugin for doing that. If such plugin exists it's fine, if it's not you will probably end up writing your own and handling its shipment, so anyone in your company can easily perform project build.
I hope it helps. Have fun ;)
I read a lot of posts regarding the ways to use spring-boot-starter-parent in a spring boot project.
Essentially, I read posts (Spring documentation also talks about this) describing two ways to do this
To use spring-boot-starter-parent as the project parent directly. It gives us the benefits of having the dependency management as well as the plugin management.
The other way is to import the spring-boot-starter parent in the project pom (we may need this in case we already have a parent pom for the project).
It allows us to get the benefits of dependency management but not the plugin management)
I am creating a new Maven multi module project. Ideally I would like to have my own custom parent and also get all the benefits of using the Spring-boot-starter-parent.
I was wondering if it made sense to create a custom parent for my maven projects. This parent would in turn be a child of the spring-boot-starter-parent.
If I am not missing anything, this way I could get the benefits of having the dependency management and plugin management from spring-boot-starter-parent and at the
same time have a custom parent for all my projects where I could define some other common dependencies or if needed override the dependencies defined in the
spring-boot-starter-parent which would then be inherited by all my projects.
Does this design make sense or am I missing something.
What are the drawbacks of this approach?
There are no drawbacks -- this is exactly what you're meant to do if you want a multimodule spring-boot project. However, consider this: typically multi-module projects have all modules versioned together, released together, and dependant on each other. This rarely makes sense in a group of spring-boot modules, which are typically of the micro-service style and which require independent evolution. So, you should question your need for a multi-module project at all.
I Implemented two maven project each using spring MVC, Hibernate, Jax-RS service. they have separate configuration, database, controllers, models, services.
I need to combine both the project in such a way that one is work as parent and other should be its child and can access parent services.
If you want to share configuration among projects, you can use a parent pom.
If you want to combine two projects as subprojects of one larger one, you can use modules. Both concepts are described in
https://maven.apache.org/guides/introduction/introduction-to-the-pom.html#Project_Inheritance_vs_Project_Aggregation
If you want to access classes from project in another project, add a dependency in the dependencies section of your pom.
We are using spring boot in a multi-module project.
We have a Domain access module which has the common domain object classes, repositories, together with configuration for the datasource, JPA, Hibernate, etc. These are configured using a application.properties. We put all this configuration into the common module to save duplicating these common configurations in the higher level modules.
This all works fine when building the domain module, so the configurations are loaded correctly in the test units.
However the problems start when we try to use the domain module in the higher layer modules; they have their own application.properties which means Spring loads them and not the the Domain module application.properties, which this means the data source is not configured because only the higher module application.properties are loaded.
What we would like is both the domain module and higher level application properties to be loaded by Spring. But we can't see any easy way to do this.
I'm thinking this must be a common problem, and wonder if there any recommended solutions for this problem?
As we are using spring-boot the solution should ideally use annotations instead of applictionContext.xml.
Maybe you should only use application.properties in the top-level aggregator project?
You can always use #PropertySource in the child projects to configure them with a name that is specific to their use case.
Or you can use different names for each project and glue them together in the top-level project using spring.config.location (comma-separated).
I agree with #Dave Syer. The idea of splitting an application into multiple modules is that each of those is an independent unit, in this case a jar file. Theoretically you could split each of those jar files into their own source repositories, and then use them across multiple projects. Let's say you want to reuse these domain classes in both a web and batch application, if all the APPLICATION level configuration is stored within each of the individual modules, it severely reduces their reusability.
IMO only the aggregating module should contain all of the configuration necessary to run as an application, everything else is simply a dependency that can be remixed and reused as necessary.
Maybe another approach could be to define specific profiles for each module and use the application.properties file just to specify which profiles are active
using the spring.profiles.include property.
domain-module
- application.properties
- application-domain.properties
app-module
- application.properties
- application-app.properties
and into the application.properties file of app-module
spring.profiles.include=domain,app
Another thing you can do (besides only using application.properties at the top-level as Dave Syer mentions) is to name the properties file of the domain module something like domainConfig.properties.
That way you avoid the name clash with application.properties.
domainConfig.properties would contain all the data needed for the domain module to be able to tested on it's own. The integration with the rest of the code can easily be done either using multiple #PropertySource (one for domainConfig.properties and one for application.properties) or configuring a PropertySourcesPlaceholderConfigurer bean in your Java Config (check out this tutorial) that refers to all the needed property files
in spring-boot since 2.4 support spring.config.import
e.g
application.name=myapp
spring.config.import=developer.properties
# import from other module
spring.config.import=classpath:application-common.properties
or with spring.config.activate.on-profile
spring.config.activate.on-profile=prod
spring.config.import=prod.properties
ref: https://spring.io/blog/2020/08/14/config-file-processing-in-spring-boot-2-4
We have a very comfortable setup using JPA through Spring/Hibernate, where we attach a PersistenceUnitPostProcessor to our entity manager factory, and this post processor takes a list of project names, scans the classpath for jars that contain that name, and adds those jar files for scanning for entities to the persistence unit, this is much more convenient than specifying in persistence.xml since it can take partial names and we added facilities for detecting the different classpath configurations when we are running in a war, a unit test, an ear, etc.
Now, we are trying to replace Spring with Seam, and I cant find a facility to accomplish the same hooking mechanism. One Solution is to try and hook Seam through Spring, but this solution has other short-comings on our environment. So my question is: Can someone point me to such a facility in Seam if exists, or at least where in the code I should be looking if I am planning to patch Seam?
Thanks.
If you're running in a Java EE container like JBoss 6 (and I really recommend so), all you need is to package your beans into a jar, place a META-INF/persistence.xml inside it and place the jar into your WAR or EAR package. All #Entity annotated beans inside the jar will be processed.
For unit-testing, you could point the <jar-file> element to the generated .class output directory and Hibernate will also pick the Entities. Or even configure during runtime using Ejb3Configuration.addAnnotatedClass;
#see http://docs.jboss.org/hibernate/entitymanager/3.6/reference/en/html/configuration.html