I am looking to learn the Spring Boot Microservices Saga based project. I went through web and found many theoretical links like https://www.baeldung.com/cs/saga-pattern-microservices and https://microservices.io/patterns/data/saga.html, but I don't find the simple source code witch depicts the working code.
Can anyone please share the link to source code which is working POC?
You can try the following if it helps:
https://github.com/berndruecker/trip-booking-saga-java
Although I would suggest you using the Axon framework. It is designed for an event-driven system. You can easily find many examples related to the saga in axon as well. May be something like this: https://github.com/dashsaurabh/saga-pattern-axon-spring-boot-sample
Related
The following example https://github.com/graphql-java/graphql-java-subscription-example which use's graphql-java for subscriptions over a websocket.
How can the same idea be done within the spring version? GraphQLSubscriptionResolver needs to return a publisher but I am unable to work out how this can then be used with a web socket.
The example above seems fine within a none spring version.
A good friend of mine has made an example in his github repository.
The code is not the nicest (because it was for our own personal needs) but it is a nice example
Have fun
Here's a port of the graphql-java example using GraphQL-SPQR with Spring Boot. I'll soon merge it into the GraphQL-SPQR samples project.
Same as with the other answer, while it uses GraphQL-SPQR to generate the schema, the Spring and websockets bit is the same as you'd have with graphql-java directly.
There's now a new and somewhat more realistic example using GraphQL SPQR Spring Boot Starter. It publishes updates when a relevant mutation runs.
I just published a workshop in which you can learn how to implement the subscription operations.
http://graphql-java.wesovilabs.com
Let me know If you have any doubt
I hope you find it useful!
Thanks
I have a number of micro-services built with Spring Boot, so for a bit of fun, I thought I'd have a go at adding HATEOAS to them to help set up cross-resource linking. It seems to work quite nicely within a particular project, but I was wondering whether there's a good way to link across APIs. As an example, imagine I have 3 services:
A user details service:
Code:
/users/{userid}
A user calendar service:
Code:
/users/{userid}/appointments
/users/{userid}/appointments/{appointmentid}
A user messaging service:
Code:
/users/{userid}/messages
/users/{userid}/messages/{messageid}
To make this browsable via the API, it would be good to have links from a user resource to its appointments and messages. Similarly, it would be nice to have links back from those resources. This is all very achievable when I have a single API with everything on the classpath, where I can write code such as:
Code:
user.add(linkTo(methodOn(CalendarController.class).appointments(user.getKey())).withRel("appointments"))
However I'm not able to do this if CalendarController is not on the classpath of the service I'm currently hitting.
Is there a good/recommended method for creating links to controllers which are not in the current project?
Referenced from spring forums
Maybe this is a bit more involved than you were hoping, but as mentioned here, this is exactly what Eureka is for. It also has really nice integration with the new Spring Cloud project.
I was thrown into a CXF-based project in which the basic HowTo tutorials are easy to follow and implement but the moment there is a problem or a bug in the system, all kinds of exceptions are thrown without me understanding any of the relationship between the various components.
I know that CXF builds on top of Spring.
But I have no experience with Spring and I don't know how it works.
I have also seen references to JAXWS in the cxf.xml but I don't know how it is related to either Spring or CXF.
I can build a perfectly working (simple) CXF-based web service. Contract first, using wsdl2java in a pom.xml (copycatting a sample).
But the moment I face a problem, I am stumped, relying on some tips and clues gleaned from the web.
Ideally, I would like to have a tutorial that walks me through the history of how web services evolved from Java only, to J2EE, to JAXWS, to Spring, to CXF.
But I couldn't find any.
I did find the official Apache CXF documentation but it assumes a lot of prior knowledge that is more than just knowing the Java language.
Any recommendations on how to get to a point of truly understanding what I am doing when I build a web service?
A recommended book? Online tutorial?
Thanks.
Yip it is a bit of a learning curve but well worth it. As far as books are concerned you can try the following.
Apache CXF Web Service Development
Spring In Action
Please be aware that J2EE and Spring are not evolutionary linked to each other Spring was more a reaction to the heavy weight J2EE specification of old. CXF is a web services toolkit/API that can be used outside of J2EE as well.
I would suggest you also join the user lists of the CXF projects and ask questions there. Also why not post some of the code causing exceptions here so we can help you with more detail?
I m a newbie & i m good at Struts framework. Today i tried a tutorial for Spring MVC Framework.
The example url that i tried following is as below:
http://static.springsource.org/docs/Spring-MVC-step-by-step/part6.html
I think they have made this tutorial much more complex especially near its end. I saw some errors mainly typos in part 5, part 6 of tutorial. I found Spring framework as not properly organized and how would we know what classes to extend especially when their names are so weird (pardon my language) e.g. AbstractTransactionalDataSourceSpringContextTests.
Overall i found that Spring is making things much more complex than it should be. I'm surprised why there is such a hype about Springs being very easy to learn.
any suggestion how to learn spring easily ? how to judge what to extend ? is there a quick reference or something?
The tutorial you have referred to covers all the layers of the application - data access, business logic and web. For someone who is looking to only get a feel of Spring MVC, which addresses concerns specific to the web layer of the application, this could be more information than required. Probably that is why you got the feeling that the tutorial is complex.
To answer your questions, Spring is easy to learn because the whole framework is designed to work with POJOs, instead of relying on special interfaces, abstract classes or such. Developers can write software as normal Java applications - interfaces, classes and enums and use Spring to wire the components up, without having to go out of the way to achieve the wiring. The tutorial you have referred to tries to explain things in a little bit more detail than experienced programmers would typically do in a real application, probably because the authors wanted the readers to get enough insight into how Spring works so that concepts are understood well.
In most applications (regardless of their size or nature), there is typically no need to extend Spring classes or to implement specialised classes. The Spring community is quite large and an even larger ecosystem of readily available components exists that integrate with Spring. It is therefore very rare that one has to implement a Spring component to achieve something. For example, let us take the example of the data access layer. Different teams like using different approaches to accessing databases. Some like raw JDBC, others like third-party ORMs like iBatis or Hibernate while some others like JPA. Spring distributions contain classes to support all these approaches. Similarly, lets say someone was looking to incorporate declarative transaction management in their application. Again, transaction management can be done in many different ways and a large number of transaction management products are available for people to use. Spring integration is available for most of these products, allowing teams to simply choose which product they want to use and configure it in their Spring application.
Recent Spring releases have mostly done away with extensive XML based configuration files, which being external to the Java code did make Spring application a bit cumbersome to understand. Many things can be done nowadays with annotations. For example,
#Controller
public class AuthenticationController
{
...
}
Indicates that AuthenticationController is a web MVC controller class. There are even ways to avoid using the Controller annotation and follow a convention-over-configuration approach to simplify coding even further.
A good and simple tutorial to Spring MVC is available at http://www.vaannila.com/spring/spring-mvc-tutorial-1.html. This tutorial uses XML based configuration for Spring beans instead of annotations but the concepts remain the same.
I have seen tutorial you follow , Its seems you have follow wrong one first , you first tried to simple one, Instead of tutorials you should go for book first
I recommend you two books to understand the power of Spring
spring in action and spring recipes.
For practical you can use STS a special ide for spring project development.Its have some predefined template you dont't need to write whole configuration yourself.
In starting just see simple tutorials like Spring mvc hello world , form controller than go for big ones
Spring is very cool , All the best.
I'd like to learn Spring MVC framework basis.
My personal experience tells clearly that more than reading manuals, docs, howtos only is only one important part of self-training, but to capitalize real experience you need to solve real problems.
May someone suggest a fake-project that I can implement in my free-time, avoiding only-theoretical approaches and at the same time watch at the main issues of Spring programming?
Does a NerdDinner.com-like free-chapter somewhere exists for Spring?
You could go through each of the Spring samples, and attempt to recreate them on your own.
I have found that a very effective method for learning Spring is to go on the Spring JIRA and solve a bug. It forces you to get down and dirty in the code, and you get to see what's really going on behind the scenes.