CODEWITHSUNDEEP
javaparsingantlrgrammardsl
dsafa
dsafa

Reputation: 793

Java DSL implementation using ANTLRv4

So, due to the assignment I was given, I've ended up wondering around what actually the next step might be.

To clarify things, I am supposed to implement a DSL language by using Java. The language should enable the "user" the specify and create questionnaire forms based of course on the input.

The following input should provide the output as given bellow:

form taxOfficeExample { 
 "Did you sell a house in 2010?"
   hasSoldHouse: boolean
 "Did you buy a house in 2010?"
   hasBoughtHouse: boolean
 "Did you enter a loan?"
   hasMaintLoan: boolean

if (hasSoldHouse) {
 "What was the selling price?"
   sellingPrice: money
 "Private debts for the sold house:"
   privateDebt: money
 "Value residue:"
   valueResidue: money = (sellingPrice - privateDebt)
}
}

Step 1 Step 2

The parser technology which I've chosen is the ANTLRv4 which seams to be the best option for this platform. Anyway, I am familiar with all the models, terminology etc - such as parsing, lexems, grammars etc - but one thing is still lacking - the bridge between Java and ANTLRv4.

So basically what I would like to know based on your experience, what is the bridge between ANTLRv4 and Java? For example, once I define a grammar for the DSL, how can that grammar (language) be applied? What is the bridge between those two entities?

I'm asking this questions only because I'm quite new within this area, therefore, any tips, pointers to research papers etc will be appreciated!

Thanks

Upvotes: 3

Views: 1240

Answers (1)

Ira Baxter
Ira Baxter

Reputation: 95420

You write an ANTLR4 grammar; you'll get an "AST" for free.

Walk the tree --> visit all the nodes.

At each node, you want to try to generate a text string in your targeted language that realizes the effect of that node, assuming that the effects of other nodes already visited have been realized.

As a practical matter, sometimes you have to generate code out-of-order ("a+b" parsed will have "+" as the root and that will get visited first, but it is clear that "a" must be fetched [so need code to generate that], and "b" must be fetched first), or that you will have to collect data from "far away in the tree" to do code generation. This means that sometimes during the tree walk, you must navigate to some other node in the tree that is not the next or previous node in the tree walk.

Often your code generation consists of printing fixed boilerplate code, alternating with text from other places (e.g., "push(A)", "push(B)", "add", where 'push(' ')' and 'add' are boilerplate, and 'A' and 'B' are text generated from other tree nodes.

The code you generate: it could be in any language; you seem to have chosen to do it in Java, so you get to generate Java source code.

The GUI elements are implied by your DSL: most of your operations are "paint a label, paint a yes/no box", so your generated java code is likely to call on some GUI library of your choice that can achieve those actions.

All of this is a standard realization of so-called "syntax-directed translation". If it isn't clear to you at this point, you need to read an article or book on the topic (Aho/Sethi/Ullman Compilers is good), and you to have to actually build a bad one (means, "start coding") in order to understand what goes right and what goes wrong. Having done one, you'll have a lot of insight into what went wrong, and then you can try to do it better.

Upvotes: 5

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