structured-fields

A parser for the HTTP Structured Fields syntax defined in IETF RFC 9651.

Features

• Parsing and Serialization
• (Still) supports Java 8
• Zero dependencies (except for tests)
• Comprehensive parsing diagnostics

Links

• https://greenbytes.de/tech/specs/rfc9651.html
• https://www.rfc-editor.org/rfc/rfc9651.html
• https://github.com/httpwg/structured-header-tests
• API docs: https://reschke.github.io/structured-fields/apidocs/

Minimal Example

 {
     Parser p = new Parser("a=?0, b, c; foo=bar");
     Dictionary d = p.parseDictionary();
     for (Map.Entry<String, Item<? extends Object>> e : d.get()) {
         String key = e.getKey();
         Item<? extends Object> item = e.getValue();
         Object value = item.get();
         Parameters params = item.getParams();
         System.out.println(key + " -> " + value + (params.isEmpty() ? "" : (" (" + params.serialize() + ")")));
     }
 }

gives:

 a -> false
 b -> true
 c -> true (;foo=bar)

Testing Client

Here's a command line tool which will feed all arguments into the parser (as if obtained from multiple field lines), parsed as Item, List, or Dictionary, and return diagnostic information.

$ $ java -jar target/structured-fields-0.6-SNAPSHOT.jar 'date;v=@1' 'number;v=123' '( token );bool'

Item: >>date;v=@1,number;v=123,( token );bool<<
        ---------^ (0x2c) Extra characters in string parsed as Item

List: date;v=@1, number;v=123, (token);bool (OuterList)
  date;v=@1, number;v=123, (token);bool (OuterList)
    date (TokenItem)
      ;v=@1 (Parameters)
        v -> @1 (DateItem)
    number (TokenItem)
      ;v=123 (Parameters)
        v -> 123 (IntegerItem)
    (token) (InnerList)
      token (TokenItem)
      ;bool (Parameters)
        bool -> ?1 (BooleanItem)


Dict: >>date;v=@1,number;v=123,( token );bool<<
        -----------------------^ (0x28) Key must start with LCALPHA or '*': '(' (\u0028)

Status

This implementation is experimental and makes no promises yet on API stability (feedback on what might be missing is appreciated).

In the mid-term, this code might transition to the Apache HTTP Components project.

Maven Coordinates

<dependency>
  <groupId>org.greenbytes.http</groupId>
  <artifactId>structured-fields</artifactId>
  <version>0.5</version>
</dependency>