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List:       jakarta-commons-dev
Subject:    Re: [configuration] Accessing from EL script
From:       Brent Verner <brent () rcfile ! org>
Date:       2004-05-18 13:56:34
Message-ID: 20040518135634.GA39661 () rcfile ! org
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[2004-05-18 09:20] Mark R. Diggory said:
> Brent Verner wrote:
> 
> > [2004-05-18 08:43] Mark R. Diggory said:
> > > To extend the subject of refactoring. I want to be able to access 
> > > Configuration objects from EL references in JSP 2.0.
> > > 
> > > ${sessionScope.config.foo.bar}
> > 
> > I do something similar _with_ properties configuration.  The syntax
> > I use is
> > 
> > ${sessionScope.config['some.config.key']}
> > 
> > after doing
> > 
> > session.setAttribute("config",someMap);
> > 
> > I'm not sure it is worth the effort to work around the "['...']"
> > syntax requirement/limitation, since the key/value configuration
> > would have to be copied into something that EL can address
> > directly (most simply a Map of Map [[of Map ] ...])
> > 
> > cheers.
> > brent
> > 
> 
> Yes, but maintaining a generic Map interface on the objects in the 
> configuration hierarchy would probably be very beneficial anywhere that 
> this similar approach of automation/reflection occurs. Would it not? It 
> probably would make for a simple backwards compatible refactoring.

  Yeah, that makes sense.  Here goes a sample impl. that looks like
it'd do what you want.

cheers
  b


import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import java.util.StringTokenizer;

public class x {
  public void insert(Map m, String key, String value){
    // XXX: will not account for non-separator '.' such as a key that looks like \
"some.key.adn[something.that.ya.don't.want.nested].whatever.else"  Map rv = null;
    int dp = key.indexOf(".");
    String rest = null;
    String first = key;
    if( dp > 0 ){
      first = key.substring(0,dp);
      rest = key.substring(dp + 1);
    }
    rv = (Map)m.get(first);
    if( rv == null ){
      rv = new HashMap();
      m.put(first,rv);
    }
    if( rest != null ){
      insert(rv,rest,value);
    }
    else{
      rv.put(first,value);
    }
  }
  public Map blowItOut(Map m){
    Map rv = new HashMap();
    for( Iterator it = m.keySet().iterator(); it.hasNext(); ){
      String k = (String)it.next();
      String v = (String)m.get(k);
      insert(rv,k,v);
    }
    return rv;
  }


  public void go(){
    Map x = new HashMap();
    Map top = null;
    x.put("a.b.c.d","abcd");
    x.put("e.f.g","efgh");
    x.put("h.i.j.k.l.m.n.o.p","hijklmnop");
    x.put("q.r.s","qrs");
    x.put("t.u.v","tuv");
    x.put("w.x.y.and.z","wxyandz");
    top = blowItOut(x);
    System.out.println(x);
    System.out.println(top);
  }
  public static void main(String[] args) throws Exception {
    x y = new x();
    y.go();
  }
}

-- 
"Develop your talent, man, and leave the world something. Records are 
really gifts from people. To think that an artist would love you enough
to share his music with anyone is a beautiful thing."  -- Duane Allman

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