/*
* 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.empire.db.expr.column;
// Java
import java.util.Set;
import org.apache.empire.data.DataType;
import org.apache.empire.db.DBColumn;
import org.apache.empire.db.DBColumnExpr;
import org.apache.empire.db.DBDatabase;
import org.apache.empire.db.DBDatabaseDriver;
import org.apache.empire.xml.XMLUtil;
import org.w3c.dom.Element;
/**
* This class is used for declaring constant values in SQL.
* <P>
* There is no need to explicitly create instances of this class.<BR>
* Instead use {@link DBDatabase#getValueExpr(String)} or one of it's overloads
* <P>
*
*/
public class DBValueExpr extends DBColumnExpr
{
public final DBDatabase db;
public final Object value;
public final DataType type;
public final DBColumnExpr column;
/**
* Constructs a new DBValueExpr object set the specified parameters to this object.
*/
public DBValueExpr(DBDatabase db, Object value, DataType type)
{
this.db = db;
this.value = value;
this.type = type;
this.column = null;
}
/**
* Construct a new DBValueExpr object set the specified parameters to this object.
*/
public DBValueExpr(DBColumnExpr col, Object value)
{
this.column = col;
this.type = col.getDataType();
this.db = col.getDatabase();
this.value = value;
}
/**
* Returns the current DBDatabase object.
*
* @return the current DBDatabase object
*/
@Override
public DBDatabase getDatabase()
{
return db;
}
/**
* Returns the data type of the DBColumnExpr object.
*
* @return the data type
*/
@Override
public DataType getDataType()
{
return type;
}
/**
* Returns the column name.
*
* @return the column name
*/
@Override
public String getName()
{
return (column != null) ? column.getName() : null;
}
/** this helper function calls the DBColumnExpr.addXML(Element, long) method */
@Override
public Element addXml(Element parent, long flags)
{
Element elem;
if (column!=null)
{ // Update Column
elem = column.addXml(parent, flags);
}
else
{ // Add a column expression for this function
elem = XMLUtil.addElement(parent, "column");
String name = getName();
if (name!=null)
elem.setAttribute("name", getName());
// Add Other Attributes
if (attributes!=null)
attributes.addXml(elem, flags);
// add All Options
if (options!=null)
options.addXml(elem, flags);
}
// Done
elem.setAttribute("function", "value");
return elem;
}
/**
* Returns null.
*
* @return null
*/
@Override
public DBColumn getUpdateColumn()
{
return (column != null) ? column.getUpdateColumn() : null;
}
/**
* Always returns false since value expressions cannot be an aggregate.
*
* @return false
*/
@Override
public boolean isAggregate()
{
return false;
}
/**
* Creates the SQL-Command.
*
* @param buf the SQL-Command
* @param context the current SQL-Command context
*/
@Override
public void addSQL(StringBuilder buf, long context)
{
DBDatabaseDriver driver = db.getDriver();
String text = (driver!=null) ? driver.getValueString(value, getDataType()) : String.valueOf(value);
buf.append(text);
}
/**
* @see org.apache.empire.db.DBExpr#addReferencedColumns(Set)
*/
@Override
public void addReferencedColumns(Set<DBColumn> list)
{
// nothing to do!
return;
}
}