Tutorial :How to handle a java class with hundreds of fields? [closed]



Question:

I'm trying to design a program that uses a third party API. The third party API describes an input with 296 fields, and an output with 179 fields. Obviously I want classes to represent the input and output. Are there any tricks to designing a class with so many fields? Should I have a normal getter and setter for every field?

Note: Because you ask, the API takes a string with all the fields in fixed width format as input, and returns a string with the output also in the fixed width format. It's very hard to interpret a non-flat structure out of that.


Solution:1

Yikes.

One options is to simply use a Map or similar property holder.

Another option: use a series of nested classes, to add organization (e.g. Order.Person.ContactInfo.Address.ZipCode, rather then just Order.ZipCode). I'm not at all sure I like this one, as it means additional complexity, but without it, finding the particular getter/setter you want (say via autocompletion in an IDE) becomes a nightmare.

Yet another option: if you do create a single class with many properties, consider using the "expression builder" pattern, in which each "setter" returns the object itself, enabling you to chain setters together:

myObject.setPropertyA("Foo").setPropertyB("Bar").setPropertyC("Baz")...  

which can create a quicker and more fluent interface then

myObject.setPropertyA("Foo");  myObject.setPropertyB("Bar");  myObject.setPropertyC("Baz");  ...  


Solution:2

Perhaps wrap API methods having unwieldy number of parameters and apply Introduce Parameter Object refactoring repeatedly, grouping logically related parameters into parameter objects, especially if results map into existing model objects wherein adaptor pattern could be applied.


Solution:3

I'd seriously consider simply using two hashtables if ultimate performance isn't the killer criterion.


Solution:4

Can you use a java.util.Map instead of a class with setters/getters ?


Solution:5

How about code generation? Create a file with the input parameters and another with the output parameters. Then create whatever code templates you want: getters, setters, constants. Then multiply the two together.

If you need to re-architect it, just modify the templates and regenerate.


Solution:6

Wow, that's a lot of fields. Regardless...

How does the API interact with this class? If it provides an implementation of the class structure required, you should definitely go with that.


Solution:7

The third party API must be declaring some type/class for handling the output data, right? Assuming this API is a Java class, then obviously they need to return a single Output object from their method.

If this is the case, to interact with this API I would create a wrapper object which

  1. Wrapped the input fields/object and output object
  2. Only had public accessor methods for the fields my program cared about interacting with (I have a feeling that you don't need to access all 296 fields)

This way, the rest of your program only needs to know about the existence of the fields that it needs to know about, and the rest of the fields (and the 3rd party objects themselves) are completely hidden/abstracted away.


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