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/*
 * 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; } }




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