/*
* 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;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.apache.empire.commons.StringUtils;
import org.apache.empire.data.DataType;
import org.apache.empire.db.DBColumn;
import org.apache.empire.db.DBColumnExpr;
import org.apache.empire.db.DBDatabaseDriver;
import org.apache.empire.db.DBExpr;
/**
* This class is used to decode a set of keys to the corresponding target values.
* For most drivers this will be performed by the "case ? when A then X else Y end" statement.
* <P>
* There is no need to explicitly create instances of this class.<BR>
* Instead use {@link DBColumnExpr#when(DBCompareExpr, Object) }
* <P>
* @author doebele
*/
public class DBDecodeExpr extends DBAbstractFuncExpr
{
private final Map<?,?> valueMap;
private final Object elseExpr;
/**
* Constructs a DBDecodeExpr
* @param expr the expression to be decoded
* @param valueMap a map of keys and values used for decoding
* @param elseExpr the expression returned if the condition is false (may be null)
* @param dataType the target data type
*/
public DBDecodeExpr(DBColumnExpr expr, Map<?,?> valueMap, Object elseExpr, DataType dataType)
{
super(expr, expr.getUpdateColumn(), false, dataType);
// Save Info
this.valueMap = valueMap;
this.elseExpr = elseExpr;
}
@Override
protected String getFunctionName()
{
return "decode";
}
@Override
public void addReferencedColumns(Set<DBColumn> list)
{
expr.addReferencedColumns(list);
for (Map.Entry<?,?> e : valueMap.entrySet())
{ // Check Key of Value for Expressions
if (e.getKey() instanceof DBExpr)
((DBExpr)e.getKey()).addReferencedColumns(list);
if (e.getValue() instanceof DBExpr)
((DBExpr)e.getValue()).addReferencedColumns(list);
}
if (elseExpr instanceof DBExpr)
((DBExpr)elseExpr).addReferencedColumns(list);
}
@Override
public void addSQL(StringBuilder sql, long context)
{
DBDatabaseDriver driver = getDatabase().getDriver();
StringBuilder inner = new StringBuilder();
// Generate parts
for (Iterator<?> i = valueMap.keySet().iterator(); i.hasNext();)
{
Object key = i.next();
Object val = valueMap.get(key);
String part = driver.getSQLPhrase(DBDatabaseDriver.SQL_FUNC_DECODE_PART);
part = StringUtils.replaceAll(part, "{0}", getObjectValue(expr.getDataType(), key, DBExpr.CTX_DEFAULT, ""));
part = StringUtils.replaceAll(part, "{1}", getObjectValue(this.getDataType(), val, DBExpr.CTX_DEFAULT, ""));
inner.append(driver.getSQLPhrase(DBDatabaseDriver.SQL_FUNC_DECODE_SEP));
inner.append(part);
}
// Generate other
if (elseExpr != null)
{ // Else
String other = driver.getSQLPhrase(DBDatabaseDriver.SQL_FUNC_DECODE_ELSE);
other = StringUtils.replaceAll(other, "{0}", getObjectValue(getDataType(), elseExpr, DBExpr.CTX_DEFAULT, ""));
inner.append(driver.getSQLPhrase(DBDatabaseDriver.SQL_FUNC_DECODE_SEP));
inner.append(other);
}
DBValueExpr param = new DBValueExpr(getDatabase(), inner, DataType.UNKNOWN);
// Set Params
String template = driver.getSQLPhrase(DBDatabaseDriver.SQL_FUNC_DECODE);
super.addSQL(sql, template, new Object[] { param }, context);
}
}