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JDBC Type 4 driver for MySQL
/*
* Copyright (c) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify it under
* the terms of the GNU General Public License, version 2.0, as published by the
* Free Software Foundation.
*
* This program is also distributed with certain software (including but not
* limited to OpenSSL) that is licensed under separate terms, as designated in a
* particular file or component or in included license documentation. The
* authors of MySQL hereby grant you an additional permission to link the
* program and your derivative works with the separately licensed software that
* they have included with MySQL.
*
* Without limiting anything contained in the foregoing, this file, which is
* part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
* version 1.0, a copy of which can be found at
* http://oss.oracle.com/licenses/universal-foss-exception.
*
* 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 General Public License, version 2.0,
* for more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package com.mysql.cj.protocol.a.result;
import java.util.ArrayList;
import java.util.List;
import com.mysql.cj.Messages;
import com.mysql.cj.exceptions.ExceptionFactory;
import com.mysql.cj.protocol.ColumnDefinition;
import com.mysql.cj.protocol.Resultset.Concurrency;
import com.mysql.cj.protocol.ResultsetRow;
import com.mysql.cj.protocol.ResultsetRows;
import com.mysql.cj.protocol.a.BinaryRowFactory;
import com.mysql.cj.protocol.a.NativeMessageBuilder;
import com.mysql.cj.protocol.a.NativeProtocol;
import com.mysql.cj.result.Row;
/**
* Model for result set data backed by a cursor (see http://dev.mysql.com/doc/refman/5.7/en/cursors.html and
* SERVER_STATUS_CURSOR_EXISTS flag description on http://dev.mysql.com/doc/internals/en/status-flags.html).
* Only works for forward-only result sets (but still works with updatable concurrency).
*/
public class ResultsetRowsCursor extends AbstractResultsetRows implements ResultsetRows {
/**
* The cache of rows we have retrieved from the server.
*/
private List fetchedRows;
/**
* Where we are positionaly in the entire result set, used mostly to
* facilitate easy 'isBeforeFirst()' and 'isFirst()' methods.
*/
private int currentPositionInEntireResult = BEFORE_START_OF_ROWS;
/**
* Have we been told from the server that we have seen the last row?
*/
private boolean lastRowFetched = false;
/**
* Communications channel to the server
*/
private NativeProtocol protocol;
/**
* Have we attempted to fetch any rows yet?
*/
private boolean firstFetchCompleted = false;
protected NativeMessageBuilder commandBuilder = new NativeMessageBuilder(); // TODO use shared builder
/**
* Creates a new cursor-backed row provider.
*
* @param ioChannel
* connection to the server.
* @param columnDefinition
* field-level metadata for the results that this cursor covers.
*/
public ResultsetRowsCursor(NativeProtocol ioChannel, ColumnDefinition columnDefinition) {
this.currentPositionInEntireResult = BEFORE_START_OF_ROWS;
this.metadata = columnDefinition;
this.protocol = ioChannel;
this.rowFactory = new BinaryRowFactory(this.protocol, this.metadata, Concurrency.READ_ONLY, false);
}
@Override
public boolean isAfterLast() {
return this.lastRowFetched && this.currentPositionInFetchedRows > this.fetchedRows.size();
}
@Override
public boolean isBeforeFirst() {
return this.currentPositionInEntireResult < 0;
}
@Override
public int getPosition() {
return this.currentPositionInEntireResult + 1;
}
@Override
public boolean isEmpty() {
return this.isBeforeFirst() && this.isAfterLast();
}
@Override
public boolean isFirst() {
return this.currentPositionInEntireResult == 0;
}
@Override
public boolean isLast() {
return this.lastRowFetched && this.currentPositionInFetchedRows == (this.fetchedRows.size() - 1);
}
@Override
public void close() {
this.metadata = null;
this.owner = null;
}
@Override
public boolean hasNext() {
if (this.fetchedRows != null && this.fetchedRows.size() == 0) {
return false;
}
if (this.owner != null) {
int maxRows = this.owner.getOwningStatementMaxRows();
if (maxRows != -1 && this.currentPositionInEntireResult + 1 > maxRows) {
return false;
}
}
if (this.currentPositionInEntireResult != BEFORE_START_OF_ROWS) {
// Case, we've fetched some rows, but are not at end of fetched block
if (this.currentPositionInFetchedRows < (this.fetchedRows.size() - 1)) {
return true;
} else if (this.currentPositionInFetchedRows == this.fetchedRows.size() && this.lastRowFetched) {
return false;
} else {
// need to fetch to determine
fetchMoreRows();
return (this.fetchedRows.size() > 0);
}
}
// Okay, no rows _yet_, so fetch 'em
fetchMoreRows();
return this.fetchedRows.size() > 0;
}
@Override
public Row next() {
if (this.fetchedRows == null && this.currentPositionInEntireResult != BEFORE_START_OF_ROWS) {
throw ExceptionFactory.createException(Messages.getString("ResultSet.Operation_not_allowed_after_ResultSet_closed_144"),
this.protocol.getExceptionInterceptor());
}
if (!hasNext()) {
return null;
}
this.currentPositionInEntireResult++;
this.currentPositionInFetchedRows++;
// Catch the forced scroll-passed-end
if (this.fetchedRows != null && this.fetchedRows.size() == 0) {
return null;
}
if ((this.fetchedRows == null) || (this.currentPositionInFetchedRows > (this.fetchedRows.size() - 1))) {
fetchMoreRows();
this.currentPositionInFetchedRows = 0;
}
Row row = this.fetchedRows.get(this.currentPositionInFetchedRows);
row.setMetadata(this.metadata);
return row;
}
private void fetchMoreRows() {
if (this.lastRowFetched) {
this.fetchedRows = new ArrayList<>(0);
return;
}
synchronized (this.owner.getSyncMutex()) {
try {
boolean oldFirstFetchCompleted = this.firstFetchCompleted;
if (!this.firstFetchCompleted) {
this.firstFetchCompleted = true;
}
int numRowsToFetch = this.owner.getOwnerFetchSize();
if (numRowsToFetch == 0) {
numRowsToFetch = this.owner.getOwningStatementFetchSize();
}
if (numRowsToFetch == Integer.MIN_VALUE) {
// Handle the case where the user used 'old' streaming result sets
numRowsToFetch = 1;
}
if (this.fetchedRows == null) {
this.fetchedRows = new ArrayList<>(numRowsToFetch);
} else {
this.fetchedRows.clear();
}
// TODO this is not the right place for this code, should be in protocol
this.protocol.sendCommand(
this.commandBuilder.buildComStmtFetch(this.protocol.getSharedSendPacket(), this.owner.getOwningStatementServerId(), numRowsToFetch),
true, 0);
Row row = null;
while ((row = this.protocol.read(ResultsetRow.class, this.rowFactory)) != null) {
this.fetchedRows.add(row);
}
this.currentPositionInFetchedRows = BEFORE_START_OF_ROWS;
if (this.protocol.getServerSession().isLastRowSent()) {
this.lastRowFetched = true;
if (!oldFirstFetchCompleted && this.fetchedRows.size() == 0) {
this.wasEmpty = true;
}
}
} catch (Exception ex) {
throw ExceptionFactory.createException(ex.getMessage(), ex);
}
}
}
@Override
public void addRow(Row row) {
// TODO consider to handle additional List addedRows along with fetchedRows
// they could be read by next() after all fetches are done
}
public void afterLast() {
throw ExceptionFactory.createException(Messages.getString("ResultSet.ForwardOnly"));
}
public void beforeFirst() {
throw ExceptionFactory.createException(Messages.getString("ResultSet.ForwardOnly"));
}
public void beforeLast() {
throw ExceptionFactory.createException(Messages.getString("ResultSet.ForwardOnly"));
}
public void moveRowRelative(int rows) {
throw ExceptionFactory.createException(Messages.getString("ResultSet.ForwardOnly"));
}
public void setCurrentRow(int rowNumber) {
throw ExceptionFactory.createException(Messages.getString("ResultSet.ForwardOnly"));
}
}