Re: Path Expression => Attribute

[Andrus Adamchik]

You need to prefix DB_PATH expressions with "db:". This is how  
expression parser distinguishes between the two types of paths. E.g.:

  public DbAttribute pathToDbAttribute(Class baseClass, String path) {
     if(!path.startsWith("db:")) {
        path = "db:" + path;
     }
     ...
  }

Andrus

On Apr 7, 2006, at 4:40 PM, Tobias SCHOESSLER wrote:

Andrus, this worked fine, thank you. I use this method to lookup the
ObjAttribute for a given path now.

      public ObjAttribute pathToObjAttribute(Class baseClass,  
String path)
{
            ObjEntity rootEntity =
ctxt.getEntityResolver().lookupObjEntity(baseClass);
            ObjAttribute attribute =
(ObjAttribute)Expression.fromString(path).evaluate(rootEntity);
            return attribute;
      }

In the simplest case I feed this the name of an attribute in the  
baseClass
and it returns me the ObjAttribute. e.G. 'countryCode'

However it turned out that I rather need to use Db Paths to also be  
able to
specify PK  values. I changed the method to

      public DbAttribute pathToDbAttribute(Class baseClass, String  
path) {
            DbEntity rootEntity =
ctxt.getEntityResolver().lookupDbEntity(baseClass);
            DbAttribute attribute =
(DbAttribute)Expression.fromString(path).evaluate(rootEntity);
            return attribute;
      }

I expect to be able to feed it the corresponding database attribute  
name
now e.G. COUNTRY_CODE but this fails with the exception

Caused by: org.objectstyle.cayenne.exp.ExpressionException: [v.1.1.3
September 28 2005] Invalid expression type: 'ObjPath',  DB_PATH is
expected.
        at
org.objectstyle.cayenne.map.DbEntity.resolvePathComponents 
(DbEntity.java:249)
        at
org.objectstyle.cayenne.exp.parser.ASTPath.evaluateEntityNode 
(ASTPath.java:108)
        at
org.objectstyle.cayenne.exp.parser.ASTObjPath.evaluateNode 
(ASTObjPath.java:85)
        at
org.objectstyle.cayenne.exp.parser.SimpleNode.evaluate 
(SimpleNode.java:243)
        ... 43 more






             Andrus Adamchik
             <[EMAIL PROTECTED]
              
le.org>                                                    To
                                       cayenne- 
[EMAIL PROTECTED]
             Monday, 3  
April                                            cc
             2006 16:44
                                                                    
Subject
                                       Re: Path Expression =>  
Attribute
             Please respond to
             [EMAIL PROTECTED]
             bator.apache.org







You can evaluate an expression with root ObjEntity:

String path = "toArtist.exhibitArray.closingDate";
ObjEntity rootEntity = context.getEntityResolver().lookupObjEntity
(Painting.class);
ObjAttribute attribute = Expression.fromString(path).evaluate
(rootEntity);

Andrus

On Apr 3, 2006, at 6:36 PM, Tobias SCHOESSLER wrote:

hi,

How do I get from a path expression  to the resulting attribute
object.

E.g. Is there anything that I can use to parse a path like

toArtist.exhibitArray.closingDate

and get the corresponding ObjAttribute for closingDate.

As a precondition i would assume that the path evaluates to an
attribute.

thanks

regards

Tobias