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ArchUnit - is there a way to check package access with a generic placeholder?

I would like to check whether
FOO.model
is only accessed by
FOO.service
and
BAR.model
is only accessed by
BAR.service
and so on.
Is there a way to achieve this with ArchUnit? Like (pseudocode)
classes()
.that().resideInAPackage("{PLACEHOLDER}.model")
.should().onlyBeAccessed().byAnyPackage("{PLACEHOLDER}.service");
I'm aware I could write a test that iterates over all FOO, BAR etc packages, or write a separate test for every package, but I'm looking for a generic out-of-the-box solution where I do not have to update my test class every time I introduce a new package.

You can use a custom condition to test the origin of each access:
classes()
.that().resideInAPackage("..model")
.should(new ArchCondition<JavaClass>("only be accessed from the corresponding service package") {
#Override
public void check(JavaClass javaClass, ConditionEvents conditionEvents) {
javaClass.getAccessesToSelf().forEach(access -> {
String originPackageName = access.getOrigin().getOwner().getPackageName();
String targetPackageName = access.getTarget().getOwner().getPackageName();
String expectedOriginPackageName = targetPackageName.replace(".model", ".service");
boolean satisfied = originPackageName.equals(expectedOriginPackageName);
conditionEvents.add(new SimpleConditionEvent(access, satisfied, access.getDescription()));
});
}
});
(There are probably more sophisticated ways to construct expectedOriginPackageName...)

aggregate not found in the event store

I am trying to add data using CQRS framework AXON. But while hitting the API(used to add an order). I am getting the below error:-
Command 'com.cqrs.order.commands.CreateOrderCommand' resulted in org.axonframework.modelling.command.AggregateNotFoundException(The aggregate was not found in the event store)
But i already have an Aggregate in my code(OrderAggregate.Java).
The Full code can be found at - https://github.com/iftekharkhan09/OrderManagementSystem
API to add Order - http://localhost:8080/confirmOrder
Request Body:-
{
"studentName":"Sunny Khan"
}
Can anyone please tell me where am i doing wrong?
Any help is appreciated!

For other readers, let me share the Aggregate you've created in your repository:
#Aggregate
public class OrderAggregate {
public OrderAggregate(OrderRepositoryData orderRepositoryData) {
this.orderRepositoryData = orderRepositoryData;
}
#AggregateIdentifier
private Integer orderId;
private OrderRepositoryData orderRepositoryData;
#CommandHandler
public void handle(CreateOrderCommand command) {
apply(new OrderCreatedEvent(command.getOrderId()));
}
#EventSourcingHandler
public void on(OrderCreatedEvent event) {
this.orderId=event.getOrderId();
Order order=new Order("Order New");
orderRepositoryData.save(order);
}
protected OrderAggregate() {
// Required by Axon to build a default Aggregate prior to Event Sourcing
}
}
There are several things you can remove entirely from this Aggregate, which are:
The OrderRepositoryData
The OrderAggregate constructor which sets the OrderRepositoryData
The manually saving of an Order in the #EventSourcingHandler annotated function
What you're doing here is mixing the Command Model's concern of making decisions with creating a queryable Order for the Query Model. It would be better to remove this logic entirely from an Aggregate (the Command Model in your example) and move this to an Event Handling Component.
This is however not the culprit for the AggregateNotFoundException you're receiving.
What you've missed is to make the CreateOrderCommand command handler a constructor.
The CreateOrderCommand will create an Order, as it's name already suggests.
Hence, it should be handled by a constructor rather than a regular method.
So, instead of this:
#CommandHandler
public *void* handle(CreateOrderCommand command) {
apply(new OrderCreatedEvent(command.getOrderId()));
}
You should be doing this:
#CommandHandler
public OrderAggregate(CreateOrderCommand command) {
apply(new OrderCreatedEvent(command.getOrderId()));
}
Hope this helps you out #Sunny!

aggregate not found in the event store
The main reason for this exception is, When the axon is trying to save the aggregate it should create the aggragate first.
#CommandHandler
public OrderAggregate(CreateOrderCommand command) {
apply(new OrderCreatedEvent(command.getOrderId()));
}
Also in this way ur
private OrderRepositoryData orderRepositoryData;
won't be initialized, so autowired the orderRepositoryData also.
#Autowired
private OrderRepositoryData orderRepositoryData;
For the successive events you should use same OrderId ,else also it will throw
handleThrowable(java.lang.Throwable,org.springframework.web.context.request.WebRequest)
org.axonframework.modelling.command.AggregateNotFoundException: The aggregate was not found in the event store
at org.axonframework.eventsourcing.EventSourcingRepository.doLoadWithLock(EventSourcingRepository.java:122)

Pattern for persisting data in Realm?

My issue is how to organize the code. Let say I have a User class
public class User extends RealmObject {
#PrimaryKey
private String id;
#Required
private String name;
public User() { // per requirement of no args constructor
id = UUID.randomUUID().toString();
}
// Assume getter & setter below...
}
and a Util class is needed to handles the save in an asynchronous manner since RealmObjects cannot have methods other than getter/setter.
public class Util {
public static void save(User user, Realm realm) {
RealmAsyncTask transaction = realm.executeTransaction(new Realm.Transaction() {
#Override
public void execute(Realm realm) {
realm.copyToRealm(user); // <====== Argument needs to be declared final in parent method's argument!
}
}, null);
}
}
The intention is to put save() in a Util class to prevent spreading similar save code all over the code-base so that every time I wanted to save I would just call it as such:
User u = new User();
u.setName("Uncle Sam");
Util.save(u, Realm.getDefaultInstance());
Not sure if this affects performance at all, but I was just going to save all fields overwriting what was there except for the unique id field every single time.
The problem is that I now need to set the "user" argument as final in the Util.save() method, which means I cannot pass in the object I need to save other than once.
Is there a different way of handling this? Maybe a different pattern? Or am I looking at this all wrong and should go back to SQLite?

Why is it a problem to set public static void save(final User user, Realm realm) ? It just means you cannot reassign the user variable to something else.
That said, the existence of a save() method can be a potential code smell as you then spread the update behaviour across the code base. I would suggest looking into something like the Repository pattern (http://martinfowler.com/eaaCatalog/repository.html) instead.
Realm is actually working on an example showing how you can combine the Model-View-Presenter architecture with a Repository to encapsulate updates which is a good pattern for what you are trying to do here. You can see the code for it here: https://github.com/realm/realm-java/pull/1960

Design patterns that can replace if statements

Our application is getting complex, it has mainly 3 flow and have to process based on one of the 3 type. Many of these functionalities overlap each other.
So currently code is fully of if-else statements, it is all messed up and not organised. How to make a pattern so that 3 flows are clearly separated from each other but making use of power of re-usability.
Please provide some thoughts, this is a MVC application, where we need to produce and consume web servicees using jaxb technology.
May be you can view the application as a single object as input on which different strategies needs to be implemented based on runtime value.

You did not specify what your if-else statements are doing. Say they filtering depending on some value.
If I understand your question correctly, you want to look at Factory Pattern.
This is a clean approach, easy to maintain and produces readable code. Adding or removing a Filter is also easy, Just remove the class and remove it from FilterFactory hashmap.
Create an Interface : Filter
public interface Filter {
void Filter();
}
Create a Factory which returns correct Filter according to your value. Instead of your if-else now you can just use the following :
Filter filter = FilterFactory.getFilter(value);
filter.filter();
One common way to write FilterFactory is using a HashMap inside it.
public class FilterFactory{
static HashMap<Integer, Filter> filterMap;
static{
filterMap = new HashMap<>();
filterMap.put(0,new Filter0());
...
}
// this function will change depending on your needs
public Filter getFilter(int value){
return filterMap.get(value);
}
}
Create your three(in your case) Filters like this: (With meaningful names though)
public class Filter0 implements Filter {
public void filter(){
//do something
}
}
NOTE: As you want to reuse some methods, create a FilterUtility class and make all your filters extend this class so that you can use all the functions without rewriting them.

Your question is very broad and almost impossible to answer without some description or overview of the structure of your application. However, I've been in a similar situation and this is the approach I took:
Replace conditions with Polymorphism where possible
it has mainly 3 flow and have to process based on this one of the 3
type. Many of these functionalities overlap each other.
You say your project has 3 main flows and that much of the code overlaps each other. This sounds to me like a strategy pattern:
You declare an interface that defines the tasks performed by a Flow.
public interface Flow{
public Data getData();
public Error validateData();
public void saveData();
public Error gotoNextStep();
}
You create an abstract class that provides implementation that is common to all 3 flows. (methods in this abstract class don't have to be final, but you definitely want to consider it carefully.)
public abstract class AbstractFlow{
private FlowManager flowManager
public AbstractFlow(FlowManager fm){
flowManager = fm;
}
public final void saveData(){
Data data = getData();
saveDataAsXMl(data);
}
public final Error gotoNextStep(){
Error error = validateData();
if(error != null){
return error;
}
saveData();
fm.gotoNextStep();
return null;
}
}
Finally, you create 3 concrete classes that extend from the abstract class and define concrete implementation for the given flow.
public class BankDetailsFlow extends AbstractFlow{
public BankDetailsData getData(){
BankDetailsData data = new BankDetailsData();
data.setSwiftCode(/*get swift code somehow*/);
return data;
}
public Error validateData(){
BankDetailsData data = getData();
return validate(data);
}
public void onFormSubmitted(){
Error error = gotoNextStep();
if(error != null){
handleError(error);
}
}
}

Lets take example, suppose you have model say "Data" [which has some attributes and getters,setters, optional methods].In context of Mobile application ,in particular Android application there can be two modes Off-line or On-line. If device is connected to network , data is sent to network else stored to local database of device.
In procedural way someone can , define two models as OnlineData,OfflineData and write code as[The code is not exact ,its just like pseudo code ]:
if(Connection.isConnected()){
OnlineData ond=new OnlineData();
ond.save();//save is called which stores data on server using HTTP.
}
else{
OfflineData ofd=new Onlinedata();
ofd.save();//save is called which stores data in local database
}
A good approach to implement this is using OOPS principles :
Program to interface not Implementation
Lets see How to DO THIS.
I am just writing code snippets that will be more effectively represent what I mean.The snippets are as follows:
public interface Model {
long save();//save method
//other methods .....
}
public class OnlineData extends Model {
//attributes
public long save(){
//on-line implementation of save method for Data model
}
//implementation of other methods.
}
public class OfflineData extends Model {
//attributes
public long save(){
//off-line implementation of save method for Data model
}
//implementation of other methods.
}
public class ObjectFactory{
public static Model getDataObject(){
if(Connection.isConnected())
return new OnlineData();
else
return new OfflineData();
}
}
and Here is code that your client class should use:
public class ClientClass{
public void someMethod(){
Model model=ObjectFactory.getDataObject();
model.save();// here polymorphism plays role...
}
}
Also this follows:
Single Responsibility Principle [SRP]
because On-line and Off-line are two different responsibilities which we can be able to integrate in Single save() using if-else statement.

After loong time I find opensource rule engine frameworks like "drools" is a great alternative to fit my requirement.

Best design pattern/approach for a long list of if/else/execute branches of code

I have a "legacy" code that I want to refactor.
The code basically does a remote call to a server and gets back a reply. Then according to the reply executes accordingly.
Example of skeleton of the code:
public Object processResponse(String responseType, Object response) {
if(responseType.equals(CLIENT_REGISTERED)) {
//code
//code ...
}
else if (responseType.equals(CLIENT_ABORTED)) {
//code
//code....
}
else if (responseType.equals(DATA_SPLIT)) {
//code
//code...
}
etc
The problem is that there are many-many if/else branches and the code inside each if is not trivial.
So it becomes hard to maintain.
I was wondering what is that best pattern for this?
One thought I had was to create a single object with method names the same as the responseType and then inside processResponse just using reflection call the method with the same name as the responseType.
This would clean up processResponse but it moves the code to a single object with many/many methods and I think reflection would cause performance issues.
Is there a nice design approach/pattern to clean this up?

Two approaches:
Strategy pattern http://www.dofactory.com/javascript/strategy-design-pattern
Create dictionary, where key is metadata (in your case metadata is responseType) and value is a function.
For example:
Put this in constructor
responses = new HashMap<string, SomeAbstraction>();
responses.Put(CLIENT_REGISTERED, new ImplementationForRegisteredClient());
responses.Put(CLIENT_ABORTED, new ImplementationForAbortedClient());
where ImplementationForRegisteredClient and ImplementationForAbortedClient implement SomeAbstraction
and call this dictionary via
responses.get(responseType).MethodOfYourAbstraction(SomeParams);
If you want to follow the principle of DI, you can inject this Dictionary in your client class.

My first cut would be to replace the if/else if structures with switch/case:
public Object processResponse(String responseType, Object response) {
switch(responseType) {
case CLIENT_REGISTERED: {
//code ...
}
case CLIENT_ABORTED: {
//code....
}
case DATA_SPLIT: {
//code...
}
From there I'd probably extract each block as a method, and from there apply the Strategy pattern. Stop at whatever point feels right.

The case you've describe seems to fit perfectly to the application of Strategy pattern. In particular, you've many variants of an algorithm, i.e. the code executed accordingly to the response of the remote server call.
Implementing the Stategy pattern means that you have to define a class hierachy, such the following:
public interface ResponseProcessor {
public void execute(Context ctx);
}
class ClientRegistered implements ResponseProcessor {
public void execute(Context ctx) {
// Actions corresponding to a client that is registered
// ...
}
}
class ClientAborted implements ResponseProcessor {
public void execute(Context ctx) {
// Actions corresponding to a client aborted
// ...
}
}
// and so on...
The Context type should contain all the information that are needed to execute each 'strategy'. Note that if different strategies share some algorithm pieces, you could also use Templeate Method pattern among them.
You need a factory to create a particular Strategy at runtime. The factory will build a strategy starting from the response received. A possibile implementation should be the one suggested by #Sattar Imamov. The factory will contain the if .. else code.
If strategy classes are not to heavy to build and they don't need any external information at build time, you can also map each strategy to an Enumeration's value.
public enum ResponseType {
CLIENT_REGISTERED(new ClientRegistered()),
CLIENT_ABORTED(new ClientAborted()),
DATA_SPLIT(new DataSplit());
// Processor associated to a response
private ResponseProcessor processor;
private ResponseType(ResponseProcessor processor) {
this.processor = processor;
}
public ResponseProcessor getProcessor() {
return this.processor;
}
}