com.mysema.query.sql.RelationalPathUtils 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.sql;
import java.util.HashMap;
import java.util.Map;
import com.mysema.query.types.Expression;
import com.mysema.query.types.FactoryExpression;
import com.mysema.query.types.Path;
import com.mysema.query.types.Projections;
import com.mysema.query.types.QBean;
/**
* RelationalPathUtils provides static utility methods for {@link RelationalPath} instances
*
* @author tiwe
*
*/
@SuppressWarnings("unchecked")
public final class RelationalPathUtils {
public static FactoryExpression createProjection(RelationalPath path) {
if (path.getType().equals(path.getClass())) {
throw new IllegalArgumentException("RelationalPath based projection can only be used with generated Bean types");
}
try {
// ensure that empty constructor is available
path.getType().getConstructor();
return createBeanProjection(path);
} catch (NoSuchMethodException e) {
// fallback to constructor projection
return createConstructorProjection(path);
}
}
private static FactoryExpression createConstructorProjection(RelationalPath path) {
Expression[] exprs = path.getColumns().toArray(new Expression[path.getColumns().size()]);
return Projections.constructor((Class)path.getType(), exprs);
}
private static FactoryExpression createBeanProjection(RelationalPath path) {
Map> bindings = new HashMap>();
for (Path column : path.getColumns()) {
bindings.put(column.getMetadata().getName(), column);
}
if (bindings.isEmpty()) {
throw new IllegalArgumentException("No bindings could be derived from " + path);
}
return new QBean((Class)path.getType(), true, bindings);
}
private RelationalPathUtils() {}
}