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/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2009 by Red Hat Inc and/or its affiliates or by
* third-party contributors as indicated by either @author tags or express
* copyright attribution statements applied by the authors. All
* third-party contributions are distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.engine.jdbc;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.hibernate.engine.jdbc.spi.SqlExceptionHelper;
import org.hibernate.internal.CoreMessageLogger;
import org.hibernate.internal.util.ClassLoaderHelper;
import org.jboss.logging.Logger;
/**
* A proxy for a ResultSet delegate, responsible for locally caching the columnName-to-columnIndex resolution that
* has been found to be inefficient in a few vendor's drivers (i.e., Oracle and Postgres).
*
* @author Steve Ebersole
* @author Gail Badner
*/
public class ResultSetWrapperProxy implements InvocationHandler {
private static final CoreMessageLogger LOG = Logger.getMessageLogger(
CoreMessageLogger.class,
ResultSetWrapperProxy.class.getName()
);
private static final Class[] PROXY_INTERFACES = new Class[] { ResultSet.class };
private static final SqlExceptionHelper SQL_EXCEPTION_HELPER = new SqlExceptionHelper();
private final ResultSet rs;
private final ColumnNameCache columnNameCache;
private ResultSetWrapperProxy(ResultSet rs, ColumnNameCache columnNameCache) {
this.rs = rs;
this.columnNameCache = columnNameCache;
}
/**
* Generates a proxy wrapping the ResultSet.
*
* @param resultSet The resultSet to wrap.
* @param columnNameCache The cache storing data for converting column names to column indexes.
* @return The generated proxy.
*/
public static ResultSet generateProxy(ResultSet resultSet, ColumnNameCache columnNameCache) {
return (ResultSet) Proxy.newProxyInstance(
getProxyClassLoader(),
PROXY_INTERFACES,
new ResultSetWrapperProxy( resultSet, columnNameCache )
);
}
/**
* Determines the appropriate class loader to which the generated proxy
* should be scoped.
*
* @return The class loader appropriate for proxy construction.
*/
public static ClassLoader getProxyClassLoader() {
ClassLoader cl = ClassLoaderHelper.getContextClassLoader();
if ( cl == null ) {
cl = ResultSet.class.getClassLoader();
}
return cl;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if ( "findColumn".equals( method.getName() ) ) {
return findColumn( (String) args[0] );
}
if ( isFirstArgColumnLabel( method, args ) ) {
try {
final Integer columnIndex = findColumn( (String) args[0] );
return invokeMethod(
locateCorrespondingColumnIndexMethod( method ),
buildColumnIndexMethodArgs( args, columnIndex )
);
}
catch ( SQLException ex ) {
final String msg = "Exception getting column index for column: [" + args[0] +
"].\nReverting to using: [" + args[0] +
"] as first argument for method: [" + method + "]";
SQL_EXCEPTION_HELPER.logExceptions( ex, msg );
}
catch ( NoSuchMethodException ex ) {
LOG.unableToSwitchToMethodUsingColumnIndex( method );
}
}
return invokeMethod( method, args );
}
/**
* Locate the column index corresponding to the given column name via the cache.
*
* @param columnName The column name to resolve into an index.
* @return The column index corresponding to the given column name.
* @throws SQLException if the ResultSet object does not contain columnName or a database access error occurs
*/
private Integer findColumn(String columnName) throws SQLException {
return columnNameCache.getIndexForColumnName( columnName, rs );
}
private boolean isFirstArgColumnLabel(Method method, Object[] args) {
// method name should start with either get or update
if ( ! ( method.getName().startsWith( "get" ) || method.getName().startsWith( "update" ) ) ) {
return false;
}
// method should have arguments, and have same number as incoming arguments
if ( ! ( method.getParameterTypes().length > 0 && args.length == method.getParameterTypes().length ) ) {
return false;
}
// The first argument should be a String (the column name)
//noinspection RedundantIfStatement
if ( ! ( String.class.isInstance( args[0] ) && method.getParameterTypes()[0].equals( String.class ) ) ) {
return false;
}
return true;
}
/**
* For a given {@link ResultSet} method passed a column name, locate the corresponding method passed the same
* parameters but the column index.
*
* @param columnNameMethod The method passed the column name
* @return The corresponding method passed the column index.
* @throws NoSuchMethodException Should never happen, but...
*/
private Method locateCorrespondingColumnIndexMethod(Method columnNameMethod) throws NoSuchMethodException {
final Class[] actualParameterTypes = new Class[columnNameMethod.getParameterTypes().length];
actualParameterTypes[0] = int.class;
System.arraycopy(
columnNameMethod.getParameterTypes(),
1,
actualParameterTypes,
1,
columnNameMethod.getParameterTypes().length - 1
);
return columnNameMethod.getDeclaringClass().getMethod( columnNameMethod.getName(), actualParameterTypes );
}
private Object[] buildColumnIndexMethodArgs(Object[] incomingArgs, Integer columnIndex) {
final Object[] actualArgs = new Object[incomingArgs.length];
actualArgs[0] = columnIndex;
System.arraycopy( incomingArgs, 1, actualArgs, 1, incomingArgs.length - 1 );
return actualArgs;
}
private Object invokeMethod(Method method, Object[] args) throws Throwable {
try {
return method.invoke( rs, args );
}
catch ( InvocationTargetException e ) {
throw e.getTargetException();
}
}
}
