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);
}
Related
I have a doubt regarding the usage of webclient in cirumstances when you need to invoke another service which is slow in responding and then use its data to process something and return in the call to your own api.
e.g. my doSometing method is called by service to retrive top order from a list.My service fetches the list from another service "order-service"
#RestController
public class TestController {
#Autowired
private TestService testService;
#GetMapping("/test")
public String doSomething() {
return WebClient.create()
.get()
.uri("http://localhost:9090/order-service")
.retrieve()
.bodyToMono(List.class)
.block().get(0).toString();
//may be do more processing on the list later.
}
As you can see , it currently blocks the calling thread which beats the purpose of async.Also , in future i might need to do more processing on this List before returning.
Am i using webclient correctly(is it serving any purpose here)?
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
I have to create a batch job where I need to fetch data from 1 DB and after processing dump that data to another DB where auto generated ID would be assigned to persisted data. I need to send that data along with generated ID to solace queue.
Reader(DB1) --data1--> Processor --data2--> Writer (DB2) --data3--> Writer (Solace Publisher)
I am using spring boot-2.2.5.RELEASE and spring-boot-starter-batch.
I have created a job having 1 step that read data from DB1 and write data to DB2 via RepositoryItemReader and RepositoryItemWriter respectively. This is working fine.
Now next task is to send persisted data having generated ID to solace stream (using spring-cloud-starter-stream-solace).
I have below questions. Please assist as I am totally new to spring batch
How can I get the complete record after it's saved to DB2 based on some parameter? Do I have to write my own RepositoryItemWriter having StepExecution Context or can I somehow use the existing RepositoryItemWriter.
Once I got the record I need to use solace stream and there I have publish method which expects argument(record) to be published. I think again I need to write my own Item Writer and either I could use the record passed from above repositoryItemWriter by StepExecutionContext or should I query into DB2 directly from here based on some parameter ?
Either of the above case I need to use stepexecution context but can I use available RepositoryItemWriter or do I have to write my own?
Is there any other concept which is handy in this handy instead of using above approaches?
Passing data to future steps is a common pattern in Spring Batch. According to the documentation https://docs.spring.io/spring-batch/docs/current/reference/html/common-patterns.html#passingDataToFutureSteps you can use stepExecution to store and retrieve your generated IDs. In your case the writers are also listeners which has before step methods annotated with #BeforeStep. For example:
public class DB2ItemWriter implements ItemWriter<Object> {
private StepExecution stepExecution;
public void write(List<? extends Object> items) throws Exception {
// ...
ExecutionContext stepContext = this.stepExecution.getExecutionContext();
stepContext.put("generatedIds", ids);
}
#BeforeStep
public void saveStepExecution(StepExecution stepExecution) {
this.stepExecution = stepExecution;
}
}
and then you retrieve the ids in the next writer
public class SolacePublisherItemWriter implements ItemWriter<Object> {
public void write(List<? extends Object> items) throws Exception {
// ...
}
#BeforeStep
public void retrieveGeneratedIds(StepExecution stepExecution) {
ExecutionContext stepExecutionContext = stepExecution.getExecutionContext();
this.generatedIds = stepExecutionContext.get("generatedIds");
}
}
I have created a job having 1 step that read data from DB1 and write data to DB2 via RepositoryItemReader and RepositoryItemWriter respectively. This is working fine.
I would add a second step that reads data from the table (in which records have been persisted by step 1 and have their IDs generated) and push it to solace using a custom writer.
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.
My question is about what is best way to inhibit an endpoint that is automatically provided by Olingo?
I am playing with a simple app based on Spring boot and using Apache Olingo.On short, this is my servlet registration:
#Configuration
public class CxfServletUtil{
#Bean
public ServletRegistrationBean getODataServletRegistrationBean() {
ServletRegistrationBean odataServletRegistrationBean = new ServletRegistrationBean(new CXFNonSpringJaxrsServlet(), "/user.svc/*");
Map<String, String> initParameters = new HashMap<String, String>();
initParameters.put("javax.ws.rs.Application", "org.apache.olingo.odata2.core.rest.app.ODataApplication");
initParameters.put("org.apache.olingo.odata2.service.factory", "com.olingotest.core.CustomODataJPAServiceFactory");
odataServletRegistrationBean.setInitParameters(initParameters);
return odataServletRegistrationBean;
} ...
where my ODataJPAServiceFactory is
#Component
public class CustomODataJPAServiceFactory extends ODataJPAServiceFactory implements ApplicationContextAware {
private static ApplicationContext context;
private static final String PERSISTENCE_UNIT_NAME = "myPersistenceUnit";
private static final String ENTITY_MANAGER_FACTORY_ID = "entityManagerFactory";
#Override
public ODataJPAContext initializeODataJPAContext()
throws ODataJPARuntimeException {
ODataJPAContext oDataJPAContext = this.getODataJPAContext();
try {
EntityManagerFactory emf = (EntityManagerFactory) context.getBean(ENTITY_MANAGER_FACTORY_ID);
oDataJPAContext.setEntityManagerFactory(emf);
oDataJPAContext.setPersistenceUnitName(PERSISTENCE_UNIT_NAME);
return oDataJPAContext;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
...
My entity is quite simple ...
#Entity
public class User {
#Id
private String id;
#Basic
private String firstName;
#Basic
private String lastName;
....
Olingo is doing its job perfectly and it helps me with the generation of all the endpoints around CRUD operations for my entity.
My question is : how can I "inhibit" some of them? Let's say for example that I don't want to enable the delete my entity.
I could try to use a Filter - but this seems a bit harsh. Are there any other, better ways to solve my problem?
Thanks for the help.
As you have said, you could use a filter, but then you are really coupled with the URI schema used by Olingo. Also, things will become complicated when you have multiple, related entity sets (because you could navigate from one to the other, making the URIs more complex).
There are two things that you can do, depending on what you want to achieve:
If you want to have a fined grained control on what operations are allowed or not, you can create a wrapper for the ODataSingleProcesor and throw ODataExceptions where you want to disallow an operation. You can either always throw exceptions (i.e. completely disabling an operation type) or you can use the URI info parameters to obtain the target entity set and decide if you should throw an exception or call the standard single processor. I have used this approach to create a read-only OData service here (basically, I just created a ODAtaSingleProcessor which delegates some calls to the standard one + overridden a method in the service factory to wrap the standard single processor in my wrapper).
If you want to completely un-expose / ignore a given entity or some properties, then you can use a JPA-EDM mapping model end exclude the desired components. You can find an example of such a mapping here: github. The mapping model is just an XML file which maps the JPA entities / properties to EDM entity type / properties. In order for olingo to pick it up, you can pass the name of the file to the setJPAEdmMappingModel method of the ODataJPAContext in your initialize method.