jakarta.servlet.jsp.jstl.sql.ResultImpl Maven / Gradle / Ivy
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/*
* Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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 jakarta.servlet.jsp.jstl.sql;
import java.io.Serializable;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.SortedMap;
import java.util.TreeMap;
/**
*
* This class creates a cached version of a ResultSet. It's represented as a Result implementation,
* capable of returing an array of Row objects containing a Column instance for each column in the
* row. It is not part of the Jakarta Standard Tab Library API; it serves merely as a back-end to ResultSupport's static
* methods. Thus, we scope its access to the package.
*
* @author Hans Bergsten
* @author Justyna Horwat
*/
class ResultImpl implements Result, Serializable {
private List> rowMap;
private List rowByIndex;
private String[] columnNames;
private boolean isLimited;
/**
* This constructor reads the ResultSet and saves a cached copy. It's important to note that this object will be
* serializable only if the objects returned by the ResultSet are serializable too.
*
* @param resultSet an open ResultSet, positioned before the first row
* @param startRow beginning row to be cached
* @param maxRows query maximum rows limit
* @exception java.sql.SQLException if a database error occurs
*/
public ResultImpl(ResultSet resultSet, int startRow, int maxRows) throws SQLException {
rowMap = new ArrayList<>();
rowByIndex = new ArrayList<>();
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
int noOfColumns = resultSetMetaData.getColumnCount();
// Create the column name array
columnNames = new String[noOfColumns];
for (int i = 1; i <= noOfColumns; i++) {
columnNames[i - 1] = resultSetMetaData.getColumnName(i);
}
// Throw away all rows upto startRow
for (int i = 0; i < startRow; i++) {
resultSet.next();
}
// Process the remaining rows upto maxRows
int processedRows = 0;
while (resultSet.next()) {
if (maxRows != -1 && processedRows == maxRows) {
isLimited = true;
break;
}
Object[] columns = new Object[noOfColumns];
SortedMap columnMap = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
// JDBC uses 1 as the lowest index!
for (int i = 1; i <= noOfColumns; i++) {
Object value = resultSet.getObject(i);
if (resultSet.wasNull()) {
value = null;
}
columns[i - 1] = value;
columnMap.put(columnNames[i - 1], value);
}
rowMap.add(columnMap);
rowByIndex.add(columns);
processedRows++;
}
}
/**
* Returns an array of SortedMap objects. The SortedMap object key is the ColumnName and the value is the ColumnValue.
* SortedMap was created using the CASE_INSENSITIVE_ORDER Comparator so the key is the case insensitive representation
* of the ColumnName.
*
* @return an array of Map, or null if there are no rows
*/
@Override
public SortedMap[] getRows() {
if (rowMap == null) {
return null;
}
// should just be able to return SortedMap[] object
return rowMap.toArray(new SortedMap[0]);
}
/**
* Returns an array of Object[] objects. The first index designates the Row, the second the Column. The array stores the
* value at the specified row and column.
*
* @return an array of Object[], or null if there are no rows
*/
@Override
public Object[][] getRowsByIndex() {
if (rowByIndex == null) {
return null;
}
// should just be able to return Object[][] object
return rowByIndex.toArray(new Object[0][0]);
}
/**
* Returns an array of String objects. The array represents the names of the columns arranged in the same order as in
* the getRowsByIndex() method.
*
* @return an array of String[]
*/
@Override
public String[] getColumnNames() {
return columnNames;
}
/**
* Returns the number of rows in the cached ResultSet
*
* @return the number of cached rows, or -1 if the Result could not be initialized due to SQLExceptions
*/
@Override
public int getRowCount() {
if (rowMap == null) {
return -1;
}
return rowMap.size();
}
/**
* Returns true if the query was limited by a maximum row setting
*
* @return true if the query was limited by a MaxRows attribute
*/
@Override
public boolean isLimitedByMaxRows() {
return isLimited;
}
}