antlrObjects

Headline

ANTLR-based object-text mapping for Java

An Technology:ANTLR-based parser for a concrete syntax of companies is provided. The underlying grammar is LL(1). The parser translates text into company objects. To this end, a straightforward object model for companies is used. (In fact, the object model is very similar to the one of Contribution:javaComposition. The mapping is described by the semantic actions within the Technology:ANTLR-based parser description. Pretty printing is also supported in the manner that objects can be exported in the concrete syntax. Pretty printing provides an implementation of Feature:Unparsing. Basic operations are implemented on top of the object model in basic OO programming style.

Illustration

The data model is implemented as POJOs. For example Feature:Company looks like this:

/**
 * A company has a name and
 * consists of (possibly nested) departments.
 */
public class Company {

    private String name;
    private List<Department> depts = new LinkedList<Department>();

    public Company() { }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<Department> getDepts() {
        return depts;
    }

}

A Parser for Feature:Company will be generated by Technology:ANTLR using src/main/antlr/Company.g.

A Company if defined by:

company returns [Company c]:
  { $c = new Company(); }
  'company' STRING
  { $c.setName($STRING.text); }
  '{' 
  ( topdept=department
    { $c.getDepts().add($topdept.d); }
  )* 
  '}'
  ;

Feature:Parsing is implemented using the generated Parser:

public class Parsing {

    public static Company parse(String s)
            throws IOException, RecognitionException {
        /*
         * Parsing is implemented in the generated Parser
         * See src/main/antlr/Company.g
         */
        return parseCompany(s);
    }

}

Feature:Unparsing pretty prints the company:

    public void unparseCompany(Company c, String s)
            throws IOException {
        writer = new OutputStreamWriter(new FileOutputStream(s));
        write("company");
        space();
        write(c.getName());
        space();
        write("{");
        right();
        nl();
        for (Department d : c.getDepts())
            unparseDept(d);
        left();
        indent();
        write("}");
        writer.close();
    }

Feature:Total and Feature:Cut are implemented using POJO methods:

public class Total {

    public double total(Company c) {
        double total = 0;
        for (Department d : c.getDepts())
            total += total(d);
        return total;
    }

    public double total(Department d) {
        double total = 0;
        total += d.getManager().getSalary();
        for (Department sub : d.getSubdepts())
            total += total(sub);
        for (Employee e : d.getEmployees())
            total += total(e);
        return total;
    }

    public double total(Employee e) {
        return e.getSalary();
    }

}

public class Cut {

    public void cut(Company c) {
        for (Department d : c.getDepts())
            cut(d);
    }

    public void cut(Department d) {
        cut(d.getManager());
        for (Department sub : d.getSubdepts())
            cut(sub);
        for (Employee e : d.getEmployees())
            cut(e);
    }

    public void cut(Employee e) {
        e.setSalary(e.getSalary() / 2);
    }

}

Test cases are implemented for all Namespace:Features. There are also a valid and an invalid input:

company "ACME Corporation" { department "Research" { manager "Craig" { address "Redmond" salary 123456 } employee "Erik" { address "Utrecht" salary 12345 } employee "Ralf" { address "Koblenz" salary 1234 } } department "Development" { manager "Ray" { address "Redmond" salary 234567 } department "Dev1" { manager "Klaus" { address "Boston" salary 23456 } department "Dev1.1" { manager "Karl" { address "Riga" salary 2345 } employee "Joe" { address "Wifi City" salary 2344 } } } } }

This is not a company.

Relationships

This contribution shows Object-Text mapping using Technology:ANTLR and Language:Java.

For plain syntax checking with Technology:ANTLR see Contribution:antlrAcceptor.

For a basic example of lexing/tokenization with Technology:ANTLR see Contribution:antlrLexer.

For an implementation of Feature:Parsing using semantic actions with Technology:ANTLR see Contribution:antlrParser

For walking a parsed Feature:Company-tree with Technology:ANTLR see Contribution:antlrTrees.

Architecture

The contribution follows a standardized structure:

inputs contains input files for tests
src/main/antlr contains grammar files for Technology:ANTLR.
src/main/java contains the following packages:
- org.softlang.company.features for implementations of Functional requirements.
- org.softlang.company.model for implementations of Feature:Company.
- org.softlang.company.antlr for Technology:ANTLR-generated Java classes (post build).
src/test/java contains the following packages:
- org.softlang.company.tests for Technology:JUnit test cases.