According to sequence diagram I should create firstly method "regisreItem(Item item)" with argument "item" as an object. I see my problem that the constructor for "items" is called after the method "regisreItem(Item item)" so that I have nothing to insert into "regisreItem(Item item)" method according sequence diagramm. Or not ?
Sequence diagram
Class diagram
Here is a part of sequence diagram i am interested in
https://drive.google.com/open?id=1eJolWNoN32IubP3iaaXPc_cLM5Es08hK
Here is all my sort of code.
Please provide me some sort of code ho is it possible to implement.
And clarify the beginning of sequence diagram.
Since the operation registerItem expects an item as parameter, the Auctioneer object needs to create it, before calling the operation. That means the Auctioneer has to send a create message, not the Auction (using new Item() as a parameter is not possible in a sequence diagram - and it doesn’t change the creator anyway). i1 and i2 are attributes of the interaction. They can be used as parameters of registerItem.
addBid also expects a bidder. Again the attributes Max and Moritzof the interaction should be used here.
In a real program these interaction attributes would be temporary variables of the Auction::addBid operation or of the Auctioneer. The Auctioneer is probably not supposed to have variables, therefore the registerItem Operation should probably only have generic data types such as stringas parameters.
The Auction is supposed to send messages to i1 and i2, however, since these are attributes of the interaction, the Auction object does not know them. It’s Ok to omit this detail, but it would be better to show how the Auction finds the relevant Item, for example with a findItemByName Operation called on itself.
A better alternative is, to let the Auction send the messages to its own attribute allItems. Then two lifelines would represent the same attribute, but with different objects. A selector could be used to distinguish between the two objects in the slot defined by this attribute (allItems[0], allItems[1], this is optional). The same is applicable to allBids instead of b300EUR and the like.
You can get around the issue of the Item constructor being called after registerItem by using:
registerItem(new Item(...));
and passing in the attributes of Item i1 and i2. That will create the new Item and then it can be added to the auction Item list.
I'm assuming the start of the sequence diagram is the auctioneer creating or opening an already created auction and then adding a list of items that will be used in the auction by repeatedly calling registerItem(new Item(...)); which can then have bids added to them by Max and Moritz via the Auction object
Related
This question is more about the convention or approach to follow.
So, I have an scenario in which there are four input text fields on the view in two pairs, lets say they are:
first pair : FirstName and LastName
second pair : Department and designation
and there is only one search button. Here, if user starts enter into the first pair, the second pair got disabled/non-editable and vice-versa.
When user clicks on the search button, request goes to some controller/servlet/action,
Now, in my business logic, what should be the approach to write method(s) for this search.
write a single method for all four fields then check the value of the arguments, and decide what would be the query to perform.
write two methods with specified paired parameters only.
The less arguments the better (if your following the "Clean Code" school, as taught by Robert Martin for example).
In your case: isn't the best option to pass down some sort of Map? Keys could be the various search "categories"; and values would be the corresponding values. That way, there is always only one parameter; and your business logic is written right from the beginning to simply deal with all map entries?
That way, you can always add/remove categories, without changing the interface.
EDIT: as you are still asking about the "conceptional" 2 vs 4 parameter thing; for that I would suggest: do some research; you can start studying here!
Number one is the worst solution imho. I'd write a simple container for the four values and pass that container to one specific function. That way you can put validation logic in that container and have the function simply do its work.
I've got loads of the following to implement.
validateParameter(field_name, field_type, field_validationMessage, visibleBoolean);
Instead of having 50-60 of these in a row, is there some form of nested hashmap/4d array I can use to build it up and loop through them?
Whats the best approach for doing something like that?
Thanks!
EDIT: Was 4 items.
What you could do is create a new Class that holds three values. (The type, the boolean, and name, or the fourth value (you didn't list it)). Then, when creating the HashMap, all you have to do is call the method to get your three values. It may seem like more work, but all you would have to do is create a simple loop to go through all of the values you need. Since I don't know exactly what it is that you're trying to do, all I can do is provide an example of what I'm trying to do. Hope it applies to your problem.
Anyways, creating the Class to hold the three(or four) values you need.
For example,
Class Fields{
String field_name;
Integer field_type;
Boolean validationMessageVisible;
Fields(String name, Integer type, Boolean mv) {
// this.field_name = name;
this.field_type = type;
this.validationMessageVisible = mv;
}
Then put them in a HashMap somewhat like this:
HashMap map = new HashMap<String, Triple>();
map.put(LOCAL STRING FOR NAME OF FIELD, new Field(new Integer(YOUR INTEGER),new Boolean(YOUR BOOLEAN)));
NOTE: This is only going to work as long as these three or four values can all be stored together. For example if you need all of the values to be stored separately for whatever reason it may be, then this won't work. Only if they can be grouped together without it affecting the function of the program, that this will work.
This was a quick brainstorm. Not sure if it will work, but think along these lines and I believe it should work out for you.
You may have to make a few edits, but this should get you in the right direction
P.S. Sorry for it being so wordy, just tried to get as many details out as possible.
The other answer is close but you don't need a key in this case.
Just define a class to contain your three fields. Create a List or array of that class. Loop over the list or array calling the method for each combination.
The approach I'd use is to create a POJO (or some POJOs) to store the values as attributes and validate attribute by attribute.
Since many times you're going to have the same validation per attribute type (e.g. dates and numbers can be validated by range, strings can be validated to ensure they´re not null or empty, etc), you could just iterate on these attributes using reflection (or even better, using annotations).
If you need to validate on the POJO level, you can still reuse these attribute-level validators via composition, while you add more specific validations are you´re going up in the abstraction level (going up means basic attributes -> pojos -> pojos that contain other pojos -> etc).
Passing several basic types as parameters of the same method is not good because the parameters themselves don't tell much and you can easily exchange two parameters of the same type by accident in the method call.
There are often times when I have need for a RowCallbackHandler, because in processing the result set I don't map each row to a single type, nor each result set to a single data structure. Instead, I may map the majority rows to a specific Java bean, and add the remainder to a list for post-processing.
In these cases, I need a callback with return type void, and the only callback which satisfies this is RowCallbackHandler.
But I don't come across many examples of this, and I have to admit, it's aesthetically nicer to use JDBC and loop through a ResultSet, than to use the clunky Spring callbacks. Is RowCallbackHandler more common than I think? I'm curious what people have to say...
Edit: Some people have asked for my data model. Okay, there's a nodes table and an edges table. If there's an edge between nodes A and B, that edge can signify two things:
A and B are disjoint nodes that interact
A is a member of B, or vice versa
In the second case, I need to add these group nodes to a list. They can't be mapped to a Java bean yet, because they don't signify interactions between disjoint nodes.
Perhaps what I should be doing, instead, is to have 2 queries, one that retrieves case (1), another that retrieves case (2). Case (1) could be mapped to a Java bean, case (2) to a List.
If this is indeed better, then maybe RowCallbackHandler is a bad code smell?
If what you want is to process the whole result set, without returning anything, simply use a ResultSetExtractor<Void> (and one of the JdbcTemplate methods taking it as argument).
You can create a new class that's composed of your bean objects(s), plus the list. Then fill it in a ResultSetExtractor or RowCallbackHandler. Then your return type can change from void to the new class' type.
How a particular fact inserted in the knowledge through a java code and its corresponding fact in a DRL file are mapped or bound to each other, Because as in my application I can insert multiple facts of the same type, wanted to know how a particular rule(condition) will pick a particular fact for its execution.
need some info or sample examples.
thanks.
A rule that matches an Object type for example Person(), will be activated for all the Person instances that you insert inside your session. Adding constrains inside the Object type like for example: Person(name == "John") only the instance with name John will activate that rule.
Cheers
I was wondering how you use your ddd model within a web application. Within Eric Evan Cargo application there's the Cargo class which contains the value object Itinerary. Within Itinerary is a collection of Legs, again a value object. All value objects hide the surrogate id to the outside world.
So when using this domain model, how would I create a web app, where you can click on a cargo itinerary, list all legs and then show the details of a leg by redirecting to a new "leg detail" page. Usually I would pass the LegId within the query fields and read it out again on the detail page. But since it has no id, how would you do that?
Using the index of a leg which might change when the collection gets sorted?
Passing all values within the query fields since this is the value object identity?
Sounds like a step backwards to me :)
If the leg has no id, the only way you have to refer to it is through the Cargo, which has an identity, and therefore can be associated with a URI/URL. To refer to a specific leg, you have only the index, which can be a number, or a dictionary key. If you have sorting issues, you can define two lists: one with the canonical ordering for reference purposes, and another with the ordering, mapping order position and canonical index.
As for the reason why the value objects in Evans' example have ids, I think it's for serialization purposes.
Of course, you can also opt for a Itinerary/Leg with identity.