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
 * Copyright (c) 2021-2021 Contributors to the Eclipse 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;
    }

}