I downloaded the sample provided for spring micro services orchestration from GITHUB
it works as the details given in the description, but now I am trying t build my own workflow and not able to map how the call flow(code gets exectued) from one activity to other activity.
In the bpnm guide it shows the first activity name as Retrieve Shopping Cart and second one as Validate Address but when I start the workflow with rest call from the below code
public class ShoppingCartRestController {
#Autowired
private ProcessEngine camunda;
#RequestMapping(value = "/{scId}/submit", method = RequestMethod.POST)
public ResponseEntity<?> placeOrderPOST(#PathVariable("scId") String scId) {
ProcessContext context = new ProcessContext();
submitShoppingCart(scId, context);
if (context.getError() != null) {
return new ResponseEntity<>(context.getError(), HttpStatus.FORBIDDEN);
}
return new ResponseEntity<>(context.getResponse(), HttpStatus.OK);
}
private ProcessInstance submitShoppingCart(String scId, ProcessContext context) {
return camunda.getRuntimeService().startProcessInstanceByKey(//
"submitShoppingCart", //
Variables //
.putValue(ProcessConstants.VAR_SC_ID, scId).putValue(ProcessConstants.VAR_CTX, context));
}
}
from the above I am not able to get how it delegates to retrieve address and in turn that delegates to validate address and so on to end the flow ?
And how the process is linked from submitShoppingCart.bpmn (Name in this and Actual classes are not matching ?
Question 2 first: java api and process match via the processes technical id.
you see it in the "startProcessInstanceByKey" call: submitShoppingCart is the technical id of the process. In The modeller, you find it at the very top of the properties panel.
Question 1: The camunda Java API links service Tasks to execution via JavaDelegate interfaces. So for each service task, there is a class that implements what should happen in its execute(DelegateExecution execution) method.
In spring projects, these delegates are in general referred to by their bean names ... in your example, the "Retrieve Shopping Card" service is backed by the ${retrieveShoppingCartActivity} delegate. By convention, the bean name equals the class name, so look for RetrieveShoppingCartActivity to see what's inside.
Related
I would like to use the Action<S,E> to call an external api. How can i add more data into this Action in order to invoke an external API? Another question is what if i want to send back the response (pass data to another State)
What is the best way to add more data? I'm trying to find an alternative of using context (which i know is possible but very ugly using Key-value).
Calling an external API is the same as any executing code, you can wire in your action any executable code. This includes autowiring a Service or Gateway and retrieve the data you need.
Regarding the second question, in my company we are using the extended state (context) to expose data. Before we release the state machine we get the data inside of it and serialise to a response object using object mapper.
Here is a snippet for illustration
#Configuration
#RequiredArgsConstructor
public class YourAction implements Action<States, Events> {
private final YourService service;
#Override
public void execute(final StateContext<States, Events> context) {
//getting input data examples
final Long yourIdFromHeaders = context.getMessageHeaders().get(key, Long.class);
final Long yourIdFromContext = context.getExtendedState().get(key, Long.class);
//calling service
final var responseData = service.getData(yourIdFromContext);
//storing results
context.getExtendedState().getVariables().put("response", responseData);
}
In our Angular + Spring boot application application, we have 2 Controllers (2 Services are internally referenced). In first controller, We are sending a File from UI and reading the content of the file , query an external application and retrieve a set of data and return only a sub-set of Data, for entering as recommendation for UI fields. why we are returning only sub-set of data received from the external application? Because, we need only those sub-set data for showing recommendations in UI.
Once the rest of the fields are filled, then, we call another controller to generate a report. But, for generation of files, the second service requires the rest of the data from external application, which is received by the first service. I understand that Autowiring the first service in the second service, will create new instance of the first service and I will not get the first service instance, which is used to query the external application. I also like to avoid calling the external application again to retrieve the same data again in the second service. My question is how to fetch the data received by the first service in the second service?
For example:
First controller (ExternalApplicationController), which delegates loading of loading/importing of data from files
public class Department{
private Metadata metadata; // contains data such as name, id, location, etc.,
private Collection<Employee> employees; // the list of employees working in the department.
}
#RestController
#RequestMapping("/externalApp")
public class ExternalApplicationController{
#Autowired
private ExternalApplicationImportService importService;
#PostMapping("/importDepartmentDataFromFiles")
public Metadata importDepartmentDataFromFiles(#RequestParam("files") final MultipartFile[] files) {
return this.importService.loadDepartmentDetails(FileUtils.getInstance().convertToFiles(files)).getMetadata();
}
}
The first service (ExternalApplicationImportService), which delegates the request to the external application for loading of department data.
#Service
public class ExternalApplicationImportService{
private final ExternalApp app;
public Department loadDepartmentDetails(File file){
return app.loadDepartmentDetails(file);
}
}
The Metadata from the ExternalApplicationController is used to populated UI fields and after doing some operations (filling up some data), user requests to generate a report(which contains details from the employees of that department)
#RestController
#RequestMapping("/reportGenerator")
public class ReportController{
#Autowired
private ReportGenerationService generationService;
#PostMapping("/generateAnnualReports")
public void generateAnnualReports(){
generationService.generateAnnualReports();
}
}
#Service
public class ReportGenerationService{
public void generateAnnualReports(){
//here I need access to the data loaded in the ExternalApplicationImportService.
}
}
So, I would like to access the data loaded in the ExternalApplicationImportService in the ReportGenerationService.
I also see that there would be more services created in the future and might need to access the data loaded in the ExternalApplicationImportService.
How can this be designed and achieved?
I feel that I'm missing something how to have a linking between these services, for a given user session.
Thanks,
Paul
You speak about user session. Maybe you could inject the session of your user directly in your controllers and "play" with it?
Just adding HttpSession as parameter of your controllers' methods and spring will inject it for you. Then you just have to put your data in the session during the first WS call. And recover it from the session at the second WS call.
#RestController
#RequestMapping("/reportGenerator")
public class ReportController{
#PostMapping("/generateAnnualReports")
public void generateAnnualReports(HttpSession session){
generationService.generateAnnualReports();
}
}
Alternatively for the second call you could use:
#RestController
#RequestMapping("/reportGenerator")
public class ReportController{
#PostMapping("/generateAnnualReports")
public void generateAnnualReports(#SessionAttribute("<name of your session attribute>") Object yourdata){
generationService.generateAnnualReports();
}
}
You are starting from a wrong assumption:
I understand that Autowiring the first service in the second service, will create new instance of the first service and I will not get the first service instance, which is used to query the external application.
That is not correct: by default, Spring will create your bean as singleton, a single bean definition to a single object instance for each Spring IoC container.
As a consequence, every bean in which you inject ExternalApplicationImportService will receive the same instance.
To solve your problem, you only need a place in where temporarily store the results of your external app calls.
You have several options for that:
As you are receiving the same bean, you can preserve same state in instance fields of ExternalApplicationImportService.
#Service
public class ExternalApplicationImportService{
private final ExternalApp app;
// Maintain state in instance fields
private Department deparment;
public Department loadDepartmentDetails(File file){
if (department == null) {
department = app.loadDepartmentDetails(file);
}
return department;
}
}
Better, you can use some cache mechanism, the Spring builtin is excellent, and return the cached result. You can choose the information that will be used as the key of the cached data, probably some attribute related to your user in this case.
#Service
public class ExternalApplicationImportService{
private final ExternalApp app;
#Cacheable("department")
public Department loadDepartmentDetails(File file){
// will only be invoked if the file argument changes
return app.loadDepartmentDetails(file);
}
}
You can store the information returned from the external app in an intermediate information system like Redis, if available, or even in the application underlying database.
As suggested by Mohicane, in the Web tier, you can use the http sessions to store the attributes you need to, directly as a result of the operations performed by your controllers, or even try using Spring session scoped beans. For example:
#RestController
#RequestMapping("/externalApp")
public class ExternalApplicationController{
#Autowired
private ExternalApplicationImportService importService;
#PostMapping("/importDepartmentDataFromFiles")
public Metadata importDepartmentDataFromFiles(#RequestParam("files") final MultipartFile[] files, HttpSession session) {
Deparment department = this.importService.loadDepartmentDetails(FileUtils.getInstance().convertToFiles(files));
session.setAttribute("department", department);
return deparment.getMetadata();
}
}
And:
#RestController
#RequestMapping("/reportGenerator")
public class ReportController{
#Autowired
private ReportGenerationService generationService;
#PostMapping("/generateAnnualReports")
public void generateAnnualReports(HttpSession session){
Department department = (Department)session.setAttribute("department");
// Probably you need pass that information to you service
// TODO Handle the case in which the information is not present in the session
generationService.generateAnnualReports(department);
}
}
In my opinion, the second of the proposed approaches is the best one but all are valid mechanisms to share your data between the two operations.
my recommendation for you will be to revisit your design of classes and build a proper relationship between them. I feel you need to introduce the extra logic to manage your temporal data for report generation.
#Mohicane suggested to use HTTP Session in above answer. It might be a possible solution, but it has an issue if your service needs to be distributed in the future (e.g. more than one runnable instance will serve your WEB app).
I strongly advise:
creating a separate service to manage Metadata loading process, where you will have load(key) method
you need to determine by yourself what is going to be a key
both of your other services will utilize it
this service with method load(key) can be marked by #Cacheable annotation
configure your cache implementation. As a simple one you can use In-Memory, if a question becomes to scale your back-end app, you can easily switch it to Redis/DynamoDB or other data storages.
Referances:
Spring Caching
Spring Caching Guide
Currently we have exposed our methods like this
#RestController
#RequestMapping("/app/person")
public class PersonResource {
#Timed
public void delete(#PathVariable Long id) {
log.debug("REST request to delete Person: {}", id);
personRepository.delete(id);
}
}
The operations of this method, in terms of input and output, are very clear to the user developer.
This article http://spring.io/guides/gs/accessing-data-rest/ shows how to expose JPARepositories directly obviating the need of a service layer.
#RepositoryRestResource(collectionResourceRel="people", path="people")
public interface PersonRepository extends JpaRepository<PersonEntity, Long> {
}
It is not obvious to me how I can make a "delete operation" available with PathVariable Long id.
There is an excellent article on this topic. https://github.com/spring-projects/spring-data-rest/wiki/Configuring-the-REST-URL-path
But it actually shows how to supress export of a delete operation.
As documented here, Spring Data REST will expose item resources for the repository you declare. Thus, all you need to do is discover the URI of the resource to delete and issue a DELETE request to it.
Is it possible to run multiple instance of the same service in the osgi framework?
More specific, I need to start multiple instances of a service, but each instance should recieve different parameters. This is because the services have similar functionality. But instead of writing a service for every variation, I want to reuse one implementing class.
I've already found the registerService method in the framework api.
ServiceRegistration<?> registration = bundlecontext.registerService(
className, class, null);
however, i seem to create only one instance of each class. Is there a workaround for this?
preferably something like
ServiceRegistration<?> registration = bundlecontext.registerService(
className + "#" + (++counter), new classInstance(), null);
Note that using Declarative Services with the corresponding annotations makes this quite easy, here's an excerpt from the Apache Sling codebase (ConfiguredFeature.java):
#Component(
name = "org.apache.sling.featureflags.Feature",
metatype = true,
configurationFactory = true,
policy = ConfigurationPolicy.REQUIRE)
#Service
public class ConfiguredFeature implements Feature {
#Property(label = "Name", description = "Short name of this feature")
private static final String NAME = "name";
private String name;
#Activate
private void activate(final Map<String, Object> configuration) {
this.name = PropertiesUtil.toString(configuration.get(NAME), "");
}
...
}
Using configurationFactory = true and policy = ConfigurationPolicy.REQUIRE causes one instance of this service to be created for each corresponding OSGi configuration, which is a natural way of creating multiple instances.
You could create a ManagedServiceFactory. The factory can register a new service for each configuration set in Configuration Admin.
I have a simple example here which uses Felix DependencyManager to register the component: https://github.com/paulbakker/osgicourse/tree/master/greeterfactory/src/greeterfactory
You have the parameters slightly wrong, or at least misleading:
ServiceRegistration<?> registration = bundlecontext.registerService(
className, class, null);
The second parameter to registerService is an object, not a class. This is an object you instantiate yourself. You can create as many as you like, in whatever way you like, before passing them to OSGi.
However if you are doing this with externally-supplied configuration data, should look into Declarative Services and their ability to receive config from the OSGi Configuration Admin service.
UPDATE
Taking another look at your question, I see the counter that you tried to add to the class name. This is not required and in fact not permitted either. Just call registerService multiple times.
I have previously written Spring MVC web applications where there is a front controller and we have a request mapping in each of the methods and this method in turn invokes a service implementation finally returning a view to the UI. Now when I design JSF applications am not able to understand the flow as such -
This is what I currently have in my application:
The initial index.html redirects to the login page.
A backing bean for the login page which populates label values. Since it is an input form there is no other logic involved.
Once the user clicks on submit -> in the action method I have logic which will invoke the service(No.1) for authentication process and redirect the user to the home page by returning the name of the page
The home page displays various fields which are bound to a backing bean whose fields have to be populated by another web service call(No.2).
It is between the steps (3) and (4), I have a confusion. Previously in Spring I had an explicit mapping and I can "actually" control the logic in the front controller method. In JSF, I dont know whether the logic for No.2 web service call should be combined along with authentication call since I dont have a method to populate the beans.
It is as if I dont have the explicit control over the flow. I have read many articles trying to understand this but not am able to understand. Please provide me pointers and also some references which will actually explain this better.
Why can't you control the logic in JSF bean?Example usage with EJB
#ManagedBean
#RequestScoped
public class LoginBean {
#EJB
private AuthBean authBean;
#EJB
private UserSettings settingsBean;
private String name, password;
#PostConstruct
private void init() {
//do your initialization here
}
public String loginAction() {
User user = authBean.authenticate(user, password);
if(user != null) {
UserSetting settings = settingsBean.getSettings(user.getId());
return "home";
}
}
//setters and getters
}