javax.servlet.jsp.jstl.sql.ResultImpl Maven / Gradle / Ivy
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package javax.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 JSTL
* 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 rs 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 rs, int startRow, int maxRows)
throws SQLException
{
rowMap = new ArrayList>();
rowByIndex = new ArrayList();
ResultSetMetaData rsmd = rs.getMetaData();
int noOfColumns = rsmd.getColumnCount();
// Create the column name array
columnNames = new String[noOfColumns];
for (int i = 1; i <= noOfColumns; i++) {
columnNames[i-1] = rsmd.getColumnName(i);
}
// Throw away all rows upto startRow
for (int i = 0; i < startRow; i++) {
rs.next();
}
// Process the remaining rows upto maxRows
int processedRows = 0;
while (rs.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 = rs.getObject(i);
if (rs.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
*/
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
*/
public Object[][] getRowsByIndex() {
if (rowByIndex == null) {
return null;
}
//should just be able to return Object[][] object
return (Object [][])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[]
*/
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
*/
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
*/
public boolean isLimitedByMaxRows() {
return isLimited;
}
}