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/*
* SSSync, a Simple and Stupid Synchronizer for data with multi-valued attributes
* Copyright (C) 2014 Ludovic Pouzenc <ludovic@pouzenc.fr>
*
* This file is part of SSSync.
*
* SSSync is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* SSSync 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with SSSync. If not, see <http://www.gnu.org/licenses/>
*/
package data.io.sql;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Iterator;
import data.MVDataEntry;
import data.io.AbstractMVDataReader;
/**
* Stream-oriented reader from a particular RDBMS source.
*
* @author lpouzenc
*/
public class SQLRelDataReader extends AbstractMVDataReader {
private final Connection conn;
private final String request;
private transient String columnNames[];
private transient ResultSet rs;
private transient boolean didNext;
private transient boolean hasNext;
/**
* Build a new reader from an existing connection and a File containing a SELECT statement.
* @param dataSourceName A short string representing this reader (for logging)
* @param conn A pre-established SQL data connection
* @param queryFile An SQL file containing an SQL SELECT statement
* @throws IOException
*/
public SQLRelDataReader(String dataSourceName, Connection conn, File queryFile) throws IOException {
this.dataSourceName = dataSourceName;
this.conn = conn;
this.request = readEntireFile(queryFile);
}
/**
* Build a new reader from an existing connection and a String containing a SELECT statement.
* @param dataSourceName A short string representing this reader (for logging)
* @param conn A pre-established SQL data connection
* @param query A String containing an SQL SELECT statement
* @throws IOException
*/
public SQLRelDataReader(String dataSourceName, Connection conn, String query) {
this.dataSourceName = dataSourceName;
this.conn = conn;
this.request = query;
}
/**
* {@inheritDoc}
* Note : multiple iterators on the same instance are not supported
*/
@Override
public Iterator<MVDataEntry> iterator() {
try {
// Reset iterator-related attributes
hasNext = false;
didNext = false;
// Close and free any previous request result
if ( rs != null ) {
rs.close();
}
// (Re-)Execute the SQL request
Statement stmt = conn.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
rs = stmt.executeQuery(request);
// Get the column names
ResultSetMetaData rsmd = rs.getMetaData();
columnNames = new String[rsmd.getColumnCount()];
for (int i = 0; i < columnNames.length ; i++) {
// Java SQL : all indices starts at 1 (it sucks !)
columnNames[i] = rsmd.getColumnName(i+1);
}
} catch (SQLException e) {
throw new RuntimeException("Could not execute query : " + e.getMessage() + "\n" + request );
}
return this;
}
/**
* {@inheritDoc}
*/
@Override
public boolean hasNext() {
// java.sql.ResultSet don't implement Iterable interface at all
// It's next() don't return anything except hasNext() result but it moves the cursor !
if (!didNext) {
try {
hasNext = rs.next();
} catch (SQLException e) {
throw new RuntimeException(e);
}
didNext = true;
}
return hasNext;
}
/**
* {@inheritDoc}
*/
@Override
public MVDataEntry next() {
MVDataEntry result = null;
try {
if (!didNext) {
rs.next();
}
didNext = false;
//TODO Instead of always use the first col, user could choose a specific columnName like in LDAP
String key = rs.getString(1);
result = new MVDataEntry(key);
for (int i = 0; i < columnNames.length ; i++) {
// Java SQL : all indices starts at 1 (it sucks !)
result.splitAndPut(columnNames[i], rs.getString(i+1), ";"); // TODO regex should be an option
}
} catch (SQLException e) {
throw new RuntimeException("Exception while reading next line in SQL resultset", e);
}
return result;
}
/**
* Helper function to load and entire file as a String.
* @param file
* @return
* @throws IOException
*/
private static String readEntireFile(File file) throws IOException {
FileReader input = new FileReader(file);
StringBuilder contents = new StringBuilder();
char[] buffer = new char[4096];
int read = 0;
do {
contents.append(buffer, 0, read);
read = input.read(buffer);
} while (read >= 0);
input.close();
return contents.toString();
}
}
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