When I execute following code all is good:
ResultSet rs = con.prepareStatement("SELECT r.UID AS R FROM r").executeQuery();
System.out.println(rs.getMetaData().getColumnLabel(1));
rs.next();
System.out.println(rs.getString("R"));
the result is:
R
23
But when I execute following code:
ResultSet rs = con.prepareStatement("SELECT r.UID AS R FROM r").executeQuery();
CachedRowSetImpl rslt = new CachedRowSetImpl();
rslt.populate(rs);
System.out.println(rslt.getMetaData().getColumnLabel(1));
rslt.next();
System.out.println(rslt.getString("R"));
the result is:
R
java.sql.SQLException: Invalid column name
Why does it throw an exception here?
The problem is that the reference implementation of CachedRowSet (com.sun.rowset.CachedRowSetImpl) contains a bug: When you retrieve a column by name, it uses the columnName, and not the columnLabel, therefor going against the rest of the JDBC specification which uses the columnLabel to retrieve values. This bug makes it impossible to retrieve values from the rowset by the columnLabel.
The bug at Oracle is https://bugs.java.com/bugdatabase/view_bug?bug_id=7046875, but (surprise, surprise) they have made it unavailable for public viewing.
There are two potential workaround. One is to check if your driver provides a property to also have the ResultSetMetaData.getColumnName(..) method return the columnLabel value, the second workaround would be to create a subclass of CachedRowSetImpl (which unfortunately requires a lot of overriding methods).
The version below is copied from this message: Re: Regression from 2.1.6
import java.math.BigDecimal;
import java.sql.Array;
import java.sql.Blob;
import java.sql.Clob;
import java.sql.Ref;
import java.sql.SQLException;
import java.util.Calendar;
import java.util.Collection;
import java.util.Hashtable;
import javax.sql.rowset.RowSetMetaDataImpl;
import com.sun.rowset.CachedRowSetImpl;
public class FixedCachedRowSetImpl extends CachedRowSetImpl {
private static final long serialVersionUID = -9067504047398250113L;
private RowSetMetaDataImpl RowSetMD;
public FixedCachedRowSetImpl() throws SQLException {
super();
}
public FixedCachedRowSetImpl(Hashtable env) throws SQLException {
super(env);
}
private int getColIdxByName(String name) throws SQLException {
RowSetMD = (RowSetMetaDataImpl) this.getMetaData();
int cols = RowSetMD.getColumnCount();
for (int i = 1; i <= cols; ++i) {
String colName = RowSetMD.getColumnLabel(i);
if (colName != null) if (name.equalsIgnoreCase(colName))
return (i);
else
continue;
}
throw new SQLException(resBundle.handleGetObject("cachedrowsetimpl.invalcolnm").toString());
}
@Override
public Collection<?> toCollection(String column) throws SQLException {
return toCollection(getColIdxByName(column));
}
@Override
public String getString(String columnName) throws SQLException {
return getString(getColIdxByName(columnName));
}
@Override
public boolean getBoolean(String columnName) throws SQLException {
return getBoolean(getColIdxByName(columnName));
}
@Override
public byte getByte(String columnName) throws SQLException {
return getByte(getColIdxByName(columnName));
}
@Override
public short getShort(String columnName) throws SQLException {
return getShort(getColIdxByName(columnName));
}
@Override
public int getInt(String columnName) throws SQLException {
return getInt(getColIdxByName(columnName));
}
@Override
public long getLong(String columnName) throws SQLException {
return getLong(getColIdxByName(columnName));
}
@Override
public float getFloat(String columnName) throws SQLException {
return getFloat(getColIdxByName(columnName));
}
@Override
public double getDouble(String columnName) throws SQLException {
return getDouble(getColIdxByName(columnName));
}
@Override
public BigDecimal getBigDecimal(String columnName, int scale) throws SQLException {
return getBigDecimal(getColIdxByName(columnName), scale);
}
@Override
public byte[] getBytes(String columnName) throws SQLException {
return getBytes(getColIdxByName(columnName));
}
@Override
public java.sql.Date getDate(String columnName) throws SQLException {
return getDate(getColIdxByName(columnName));
}
@Override
public java.sql.Time getTime(String columnName) throws SQLException {
return getTime(getColIdxByName(columnName));
}
@Override
public java.sql.Timestamp getTimestamp(String columnName) throws SQLException {
return getTimestamp(getColIdxByName(columnName));
}
@Override
public java.io.InputStream getAsciiStream(String columnName) throws SQLException {
return getAsciiStream(getColIdxByName(columnName));
}
@Override
public java.io.InputStream getUnicodeStream(String columnName) throws SQLException {
return getUnicodeStream(getColIdxByName(columnName));
}
@Override
public java.io.InputStream getBinaryStream(String columnName) throws SQLException {
return getBinaryStream(getColIdxByName(columnName));
}
@Override
public Object getObject(String columnName) throws SQLException {
return getObject(getColIdxByName(columnName));
}
@Override
public int findColumn(String columnName) throws SQLException {
return getColIdxByName(columnName);
}
@Override
public java.io.Reader getCharacterStream(String columnName) throws SQLException {
return getCharacterStream(getColIdxByName(columnName));
}
@Override
public BigDecimal getBigDecimal(String columnName) throws SQLException {
return getBigDecimal(getColIdxByName(columnName));
}
@Override
public boolean columnUpdated(String columnName) throws SQLException {
return columnUpdated(getColIdxByName(columnName));
}
@Override
public void updateNull(String columnName) throws SQLException {
updateNull(getColIdxByName(columnName));
}
@Override
public void updateBoolean(String columnName, boolean x) throws SQLException {
updateBoolean(getColIdxByName(columnName), x);
}
@Override
public void updateByte(String columnName, byte x) throws SQLException {
updateByte(getColIdxByName(columnName), x);
}
@Override
public void updateShort(String columnName, short x) throws SQLException {
updateShort(getColIdxByName(columnName), x);
}
@Override
public void updateInt(String columnName, int x) throws SQLException {
updateInt(getColIdxByName(columnName), x);
}
@Override
public void updateLong(String columnName, long x) throws SQLException {
updateLong(getColIdxByName(columnName), x);
}
@Override
public void updateFloat(String columnName, float x) throws SQLException {
updateFloat(getColIdxByName(columnName), x);
}
@Override
public void updateDouble(String columnName, double x) throws SQLException {
updateDouble(getColIdxByName(columnName), x);
}
@Override
public void updateBigDecimal(String columnName, BigDecimal x) throws SQLException {
updateBigDecimal(getColIdxByName(columnName), x);
}
@Override
public void updateString(String columnName, String x) throws SQLException {
updateString(getColIdxByName(columnName), x);
}
@Override
public void updateBytes(String columnName, byte x[]) throws SQLException {
updateBytes(getColIdxByName(columnName), x);
}
@Override
public void updateDate(String columnName, java.sql.Date x) throws SQLException {
updateDate(getColIdxByName(columnName), x);
}
@Override
public void updateTime(String columnName, java.sql.Time x) throws SQLException {
updateTime(getColIdxByName(columnName), x);
}
@Override
public void updateTimestamp(String columnName, java.sql.Timestamp x) throws SQLException {
updateTimestamp(getColIdxByName(columnName), x);
}
@Override
public void updateAsciiStream(String columnName, java.io.InputStream x, int length) throws SQLException {
updateAsciiStream(getColIdxByName(columnName), x, length);
}
@Override
public void updateBinaryStream(String columnName, java.io.InputStream x, int length) throws SQLException {
updateBinaryStream(getColIdxByName(columnName), x, length);
}
@Override
public void updateCharacterStream(String columnName, java.io.Reader reader, int length) throws SQLException {
updateCharacterStream(getColIdxByName(columnName), reader, length);
}
@Override
public void updateObject(String columnName, Object x, int scale) throws SQLException {
updateObject(getColIdxByName(columnName), x, scale);
}
@Override
public void updateObject(String columnName, Object x) throws SQLException {
updateObject(getColIdxByName(columnName), x);
}
@Override
public Object getObject(String columnName, java.util.Map<String, Class<?>> map) throws SQLException {
return getObject(getColIdxByName(columnName), map);
}
@Override
public Ref getRef(String colName) throws SQLException {
return getRef(getColIdxByName(colName));
}
@Override
public Blob getBlob(String colName) throws SQLException {
return getBlob(getColIdxByName(colName));
}
@Override
public Clob getClob(String colName) throws SQLException {
return getClob(getColIdxByName(colName));
}
@Override
public Array getArray(String colName) throws SQLException {
return getArray(getColIdxByName(colName));
}
@Override
public java.sql.Date getDate(String columnName, Calendar cal) throws SQLException {
return getDate(getColIdxByName(columnName), cal);
}
@Override
public java.sql.Time getTime(String columnName, Calendar cal) throws SQLException {
return getTime(getColIdxByName(columnName), cal);
}
@Override
public java.sql.Timestamp getTimestamp(String columnName, Calendar cal) throws SQLException {
return getTimestamp(getColIdxByName(columnName), cal);
}
@Override
public void updateRef(String columnName, java.sql.Ref ref) throws SQLException {
updateRef(getColIdxByName(columnName), ref);
}
@Override
public void updateClob(String columnName, Clob c) throws SQLException {
updateClob(getColIdxByName(columnName), c);
}
@Override
public void updateBlob(String columnName, Blob b) throws SQLException {
updateBlob(getColIdxByName(columnName), b);
}
@Override
public void updateArray(String columnName, Array a) throws SQLException {
updateArray(getColIdxByName(columnName), a);
}
@Override
public java.net.URL getURL(String columnName) throws SQLException {
return getURL(getColIdxByName(columnName));
}
}
You could also look at org.springframework.jdbc.support.rowset.ResultSetWrappingSqlRowSet, which also says:
Note: Since JDBC 4.0, it has been clarified that any methods using a String to identify the column should be using the column label. The column label is assigned using the ALIAS keyword in the SQL query string. When the query doesn't use an ALIAS, the default label is the column name. Most JDBC ResultSet implementations follow this new pattern but there are exceptions such as the com.sun.rowset.CachedRowSetImpl class which only uses the column name, ignoring any column labels. As of Spring 3.0.5,
ResultSetWrappingSqlRowSetwill translate column labels to the correct column index to provide better support for thecom.sun.rowset.CachedRowSetImplwhich is the default implementation used byJdbcTemplatewhen working with RowSets.