org.apache.openjpa.jdbc.kernel.exps.GetColumn Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.openjpa.jdbc.kernel.exps;
import org.apache.openjpa.jdbc.kernel.JDBCStore;
import org.apache.openjpa.jdbc.meta.ClassMapping;
import org.apache.openjpa.jdbc.sql.SQLBuffer;
import org.apache.openjpa.kernel.StoreContext;
import org.apache.openjpa.lib.util.Localizer;
import org.apache.openjpa.util.UnsupportedException;
import org.apache.openjpa.util.UserException;
/**
* Returns the SQL alias of the named column for use in a query. Note that
* to retrieve columns in the table of the candidate object, you must
* explicitly qualify the extension with this, as demonstrated
* in the second example below.
* Examples:
* "company.address.ext:getColumn (\"ID\") == 5"
* "this.ext:getColumn (\"CLS\") == \"org.apache.openjpa.example.Person\""
*
*
* @nojavadoc
*/
public class GetColumn
implements JDBCFilterListener {
public static final String TAG = "getColumn";
private static final Localizer _loc = Localizer.forPackage
(GetColumn.class);
public String getTag() {
return TAG;
}
public boolean expectsArguments() {
return true;
}
public boolean expectsTarget() {
return true;
}
public Object evaluate(Object target, Class targetClass, Object[] args,
Class[] argClasses, Object candidate, StoreContext ctx) {
throw new UnsupportedException(_loc.get("no-in-mem", TAG));
}
public void appendTo(SQLBuffer buf, FilterValue target,
FilterValue[] args, ClassMapping type, JDBCStore store) {
if (!args[0].isConstant())
throw new UserException(_loc.get("const-only", TAG));
if (!target.isPath())
throw new UserException(_loc.get("path-only", TAG));
// alias the column using the target's context, so that the
// correct relation path to the target is used
ClassMapping mapping = target.getClassMapping();
String colName = args[0].getValue().toString();
buf.append(target.getColumnAlias(colName, mapping.getTable()));
}
public Class getType(Class targetClass, Class[] argClasses) {
return Object.class;
}
}