Package com.google.appengine.api.search.query

Class QueryTreeWalker<T extends QueryTreeContext<T>>

java.lang.Object

com.google.appengine.api.search.query.QueryTreeWalker<T>

Type Parameters:

T - the context used by the visitor

public class QueryTreeWalker<T extends QueryTreeContext<T>>
extends Object

The walking of the query tree. This class takes care of visiting a tree resulting from parsing a query. As it traverses the tree it calls appropriate methods of the visitor, set at the construction time. The class uses a depth-first search, visiting all children of a node, before visiting the node. The visit is done by calling an appropriate method of the visitor. Typical code should match the following pattern:

 class MyVisitor implements QueryTreeVisitor {
   ...
 }
 class MyContext extends QueryTreeContext<MyContext> {
   ...
   @Override
   protected MyContext newChildContext() {
     return new MyContext();
   }
 }

 MyContext context = new MyContext();
 QueryTreeWalker<MyContext> walker = new QueryTreeWalker<MyContext>(new MyVisitor());
 Tree root = parser.query(queryStr);
 walker.walk(root, context);
 // retrieve whatever information you need from context
 

Constructor Summary

Constructors

Constructor	Description
QueryTreeWalker(QueryTreeVisitor<T> visitor)	Creates a new query walker that calls the given visitor.

Method Summary

Modifier and Type	Method	Description
static org.antlr.runtime.tree.Tree	simplify(org.antlr.runtime.tree.Tree tree)
void	walk(org.antlr.runtime.tree.Tree tree, T context)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

QueryTreeWalker

public QueryTreeWalker(QueryTreeVisitor<T> visitor)

Creates a new query walker that calls the given visitor.

Parameters:

visitor - the visitor to be called by this walker

Method Detail

walk

public void walk(org.antlr.runtime.tree.Tree tree,
                 T context)
          throws QueryTreeException

Parameters:

tree - the tree to be walked

context - the context in which the tree is walked

Throws:

QueryTreeException

simplify

public static org.antlr.runtime.tree.Tree simplify(org.antlr.runtime.tree.Tree tree)