org.hibernate.engine.jdbc.ColumnNameCache Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* License: GNU Lesser General Public License (LGPL), version 2.1 or later.
* See the lgpl.txt file in the root directory or .
*/
package org.hibernate.engine.jdbc;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.concurrent.ConcurrentHashMap;
/**
* Cache of column-name -> column-index resolutions
*
* @author Steve Ebersole
*/
public final class ColumnNameCache {
private static final float LOAD_FACTOR = .75f;
private final ConcurrentHashMap columnNameToIndexCache;
/**
* Constructs a ColumnNameCache
*
* @param columnCount The number of columns to be cached.
*/
public ColumnNameCache(int columnCount) {
// should *not* need to grow beyond the size of the total number of columns in the rs
this.columnNameToIndexCache = new ConcurrentHashMap(
columnCount + (int)( columnCount * LOAD_FACTOR ) + 1,
LOAD_FACTOR
);
}
/**
* Resolve the column name/alias to its index
*
* @param columnName The name/alias of the column
* @param rs The ResultSet
*
* @return The index
*
* @throws SQLException INdicates a problems accessing the underlying JDBC ResultSet
*/
public Integer getIndexForColumnName(String columnName, ResultSet rs) throws SQLException {
final Integer cached = columnNameToIndexCache.get( columnName );
if ( cached != null ) {
return cached;
}
else {
final Integer index = Integer.valueOf( rs.findColumn( columnName ) );
columnNameToIndexCache.put( columnName, index);
return index;
}
}
}