[[Category:APIDesignPatterns]]

[[Category:APIDesignPatterns]]

Last, but not least, this API pattern supports easy interruption of long computations. The ''Response'' or even the ''Request'' can contain ''boolean isCancelled()'' method which may allow the provider of the ''compute'' method implementation to check this value and exist earlier, before everything is computed. In addition to this, the ''addResult'' methods can check this flag themselves, and potentially abort the computation by their own, usually by emitting some checked exception.

Last, but not least, this API pattern supports easy interruption of long computations. The ''Response'' or even the ''Request'' can contain ''boolean isCancelled()'' method which may allow the provider of the ''compute'' method implementation to check this value and exist earlier, before everything is computed. In addition to this, the ''addResult'' methods can check this flag themselves, and potentially abort the computation by their own, usually by emitting some checked exception.

 

[[APIDesignPatterns|API Design pattern]] that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.

[[APIDesignPatterns|API Design pattern] that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.

<source lang="java" snippet="grow.request.response"/>

<source lang="java" snippet="grow.request.response"/>

Design pattern that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.

[[APIDesignPatterns|API Design pattern] that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.

<source lang="java" snippet="grow.request.response"/>

<source lang="java" snippet="grow.request.response"/>

Design pattern that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.

Design pattern that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.

<source lang="java">

<source lang="java" snippet="grow.request.response"/>

public void compute(Request request, Response response);

 

 

 

 

</source>

==== Evolution Story ====

==== Evolution Story ====

The evolution of the whole pattern is based on the assumption that the fixed point of communication with users of the API is the ''ComputeSomething'' interface with its one method that has to be implemented. From this interface we have two evolution paths:

The evolution of the whole pattern is based on the assumption that the fixed point of communication with users of the API is the ''Compute'' interface with its one method that has to be implemented. From this interface we have two evolution paths:

# clients of the API can require more methods to call. those can be added to Request class

# clients of the API can require more methods to call. those can be added to Request class

# the infrastructure may want to give the clients more richer way to specify return values. This means to add new methods into the Response class.

# the infrastructure may want to give the clients more richer way to specify return values. This means to add new methods into the Response class.

Related to this, the API pattern allows the infrastructure, which provides the ''Response'' class, to process the results sooner before they are fully computed. The ''compute'' method can still be running, incrementally computing its results, and yet, the infrastructure may process the already generated values.

Related to this, the API pattern allows the infrastructure, which provides the ''Response'' class, to process the results sooner before they are fully computed. The ''compute'' method can still be running, incrementally computing its results, and yet, the infrastructure may process the already generated values.

Last, but not least, this API pattern supports easy interruption of long computations. The ''Response'' or even the ''Request'' can contain ''boolean isCancelled()'' method which may allow the provider of the ''compute'' method implementation to check this value and exist earlier, before everything is computed. In addition to this, the ''addResult'' methods can check this flag themselves, and potentially abort the computation by their own, usually by emitting some checked exception.

Last, but not least, this API pattern supports easy interruption of long computations. The ''Response'' or even the ''Request'' can contain ''boolean isCancelled()'' method which may allow the provider of the ''compute'' method implementation to check this value and exist earlier, before everything is computed. In addition to this, the ''addResult'' methods can check this flag themselves, and potentially abort the computation by their own, usually by emitting some checked exception.

# clients of the API can require more methods to call. those can be added to Request class

# clients of the API can require more methods to call. those can be added to Request class

# the infrastructure may want to give the clients more richer way to specify return values. This means to add new methods into the Response class.

# the infrastructure may want to give the clients more richer way to specify return values. This means to add new methods into the Response class.

public static final class Request {

public static final class Request {

private Request() {}

Request() {}

public int getArg1();

public int getArg1();

public static final class Response {

public static final class Response {

private Response() {}

Response() {}

public void addResult(int r);

public void addResult(int r);

}

}

</source>

</source>

Design pattern that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.

Design pattern that solves the problem of growing parameters and return values from API methods. Beyond its basic purpose, it can help with delivering multiple results and providing the results in an incremental way, one by one. It also helps a lot with ability to cancel a computation in the middle.