ListWrap.java

/***************************************************************************
   Copyright 2012 Emily Estes

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
***************************************************************************/
package net.metanotion.sqlc;


import java.sql.Connection;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import net.metanotion.util.types.Parser;

/** Transform the result of evaluating an expression into a list whose contents are transformed by a parser.
	@param <V> The type of the elements of the list of the result of the expression.
*/
public final class ListWrap<V> implements QueryExpr<List<V>> {
	public final DoWrap<ResultSet> e;
	public final Parser<V> g;
	/** Create a new list evaluator to consume the result set of the result of the body.
		@param body The expression whose reuslts will be transformed into a list.
		@param g The parser to transform the elements of the list.
	*/
	public ListWrap(final DoWrap<ResultSet> body, final Parser<V> g) {
		this.e = body;
		this.g = g;
	}

	@Override public List<V> eval(final Connection conn, final Map<String,Object> env) throws Exception {
		try (final ResultSet rs = e.eval(conn, env)) {
			final ArrayList<V> ret = new ArrayList<>();
			while(rs.next()) {
				ret.add(g.parse(rs));
			}
			return ret;
		}
	}
}