JarCastingETP: An Erlang Term Parser for Java.
Given a String of Erlang terms, ETP will parse the string into a tree of ETP Java objects. Calling toString() on an ETP object will render a tree as an Erlang term.
Building
You'll need Maven to build etp.
mvn package
Also, ETP is available via the Sonatype OSS repository:
<dependency>
<groupId>com.github.metadave</groupId>
<artifactId>etp</artifactId>
<version>0.6-SNAPSHOT</version>
</dependency>
Usage
EPTTerm com.metadave.etp.ETP.parse(String s)
EPTTerm com.metadave.etp.ETP.parse(InputStream is)
An ETP term is made up of any of these classes:
- ETPTerm (abstract base class for all other ETP objects)
- ETPAtom
- ETPQuotedAtom
- ETPBinary
- ETPBoolean
- ETPDouble
- ETPFun
- ETPLong
- ETPList
- ETPPid
- ETPRef
- ETPString
- ETPTerm
- ETPTuple
Rendering
Call toString() on a ETPTerm object will render a valid Erlang term to a String. Note - at the moment, ETP doesn't prevent you setting invalid values on an ETPTerm object. Validation coming soon.
Grammar
Antlr 4 grammar here
Example
// at the moment, whitespace and comments between terms aren't retained
ETPTuple tuple = (ETPTuple)ETP.parse("{mylist, [1,2,3,4], \n" +
"my_string, \"Hello world\"}");
// All ETP objects subclass ETPTerm
// you can use "instanceof" to see what the result of the parse is
ETPAtom atom = (ETPAtom)tuple.getValue(0);
System.out.println("Atom = " + atom);
ETPList list = (ETPList)tuple.getValue(1);
// use getValue() to access the list of terms
for(ETPTerm v : list.getValue()) {
System.out.println(" List item " + v);
}
ETPAtom my_string_atom = (ETPAtom)tuple.getValue(2);
System.out.println(my_string_atom);
ETPString s = (ETPString)tuple.getValue(3);
System.out.println(s.getValue()); // getValue() gets the "raw" value
System.out.println(s.toString()); // toString() gets the string representation
// you can set values on the ETP structure and call toString() to render
// a new Erlang term
atom.setValue("new_atom_value");
list.getValue().add(new ETPLong(100));
System.out.println(tuple.toString());
yields the following output:
Atom = mylist
List item 1
List item 2
List item 3
List item 4
my_string
Hello world
"Hello world"
{new_atom_value,[1,2,3,4,100],my_string,"Hello world"}
Status & TODO
- Javadocs, better documentation
- Term validation during setValue() to prevent bad terms from being rendered to a String.
- Comments and whitespace are lost during parse. Not sure if I'm going to bother.
- binding parse results to an object model
- $\n
- 2#101
Contributing
Fork this repo, create a branch with
git checkout -b your_branch_name
Submit a pull request when your code is ready for review.
License
http://www.apache.org/licenses/LICENSE-2.0.html
© 2014 Dave Parfitt