com.mysema.query.group.GroupByBuilder Maven / Gradle / Ivy
/*
* Copyright 2011, Mysema Ltd
*
* 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 com.mysema.query.group;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import com.mysema.commons.lang.CloseableIterator;
import com.mysema.query.ResultTransformer;
import com.mysema.query.types.Expression;
import com.mysema.query.types.FactoryExpression;
import com.mysema.query.types.FactoryExpressionUtils;
/**
* GroupByBuilder is a fluent builder for GroupBy transformer instances. This class is not to be used directly,
* but via GroupBy.
*
* @author tiwe
*
* @param
*/
public class GroupByBuilder {
private final Expression key;
/**
* Create a new GroupByBuilder for the given key expression
*
* @param key
*/
public GroupByBuilder(Expression key) {
this.key = key;
}
/**
* Get the results as a map
*
* @param expressions
* @return
*/
public ResultTransformer> as(Expression... expressions) {
return new GroupByMap(key, expressions);
}
/**
* Get the results as a closeable iterator
*
* @param expressions
* @return
*/
public ResultTransformer> iterate(Expression... expressions) {
return new GroupByIterate(key, expressions);
}
/**
* Get the results as a list
*
* @param expressions
* @return
*/
public ResultTransformer> list(Expression... expressions) {
return new GroupByList(key, expressions);
}
/**
* Get the results as a map
*
* @param expression
* @return
*/
@SuppressWarnings("unchecked")
public ResultTransformer> as(Expression expression) {
final Expression lookup = getLookup(expression);
return new GroupByMap(key, expression) {
@Override
protected Map transform(Map groups) {
Map results = new LinkedHashMap((int) Math.ceil(groups.size()/0.75), 0.75f);
for (Map.Entry entry : groups.entrySet()) {
results.put(entry.getKey(), entry.getValue().getOne(lookup));
}
return results;
}
};
}
/**
* Get the results as a closeable iterator
*
* @param expression
* @return
*/
public ResultTransformer> iterate(Expression expression) {
final Expression lookup = getLookup(expression);
return new GroupByIterate(key, expression) {
@Override
protected V transform(Group group) {
return group.getOne(lookup);
}
};
}
/**
* Get the results as a list
*
* @param expression
* @return
*/
public ResultTransformer> list(Expression expression) {
final Expression lookup = getLookup(expression);
return new GroupByList(key, expression) {
@Override
protected V transform(Group group) {
return group.getOne(lookup);
}
};
}
private Expression getLookup(Expression expression) {
if (expression instanceof GroupExpression) {
return ((GroupExpression)expression).getExpression();
} else {
return expression;
}
}
/**
* Get the results as a map
*
* @param expression
* @return
*/
public ResultTransformer> as(FactoryExpression expression) {
final FactoryExpression transformation = FactoryExpressionUtils.wrap(expression);
List> args = transformation.getArgs();
return new GroupByMap(key, args.toArray(new Expression[args.size()])) {
@Override
protected Map transform(Map groups) {
Map results = new LinkedHashMap((int) Math.ceil(groups.size()/0.75), 0.75f);
for (Map.Entry entry : groups.entrySet()) {
results.put(entry.getKey(), transform(entry.getValue()));
}
return results;
}
@SuppressWarnings("unchecked")
protected V transform(Group group) {
// XXX Isn't group.toArray() suitable here?
List