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我正在使用一個簡單的應用程序來幫助Apache.Derby學習數據庫並在Eclipse中工作。 下面的代碼運行正常，但conn.getMetaData（）不返回任何有意義的關於表 - colnameslist.size例如是0.但是，我添加meta.getDatabaseProductName（）以查看發生了什麼，並返回'Apache.Derby'如此我想這是有某種聯繫的。connection.getMetaData似乎沒有返回表信息
The connection url is "jdbc:derby:C:/Users/RonLaptop/MyDB".
The string passed into getTableContents() is "MYENERGYAPP.ENERGYTABLE7".
因爲它沒有錯誤，我有點損失。
package com.energy;
import javax.swing.*;
import javax.swing.table.*;
import java.sql.*;
import java.util.*;
/** an immutable table model built from getting
metadata about a table in a jdbc database
*/
public class JDBCTableModel extends AbstractTableModel {
Object[][] contents;
String[] columnNames;
Class[] columnClasses;
public JDBCTableModel (Connection conn,
String string)
throws SQLException {
super();
getTableContents (conn, string);
}
protected void getTableContents (Connection conn,
String string)
throws SQLException {
// get metadata: what columns exist and what
// types (classes) are they?
DatabaseMetaData meta = conn.getMetaData();
String productName = meta.getDatabaseProductName();
String[] types = null;
System.out.println ("got meta = " + meta);
ResultSet results =
meta.getColumns (null, null, string, null) ;
System.out.println ("got column results");
ArrayList colNamesList = new ArrayList();
ArrayList colClassesList = new ArrayList();
while (results.next()) {
colNamesList.add (results.getString ("COLUMN_NAME"));
System.out.println ("name: " +
results.getString ("COLUMN_NAME"));
int dbType = results.getInt ("DATA_TYPE");
switch (dbType) {
case Types.INTEGER:
colClassesList.add (Integer.class); break;
case Types.FLOAT:
colClassesList.add (Float.class); break;
case Types.DOUBLE:
case Types.REAL:
colClassesList.add (Double.class); break;
case Types.DATE:
case Types.TIME:
case Types.TIMESTAMP:
colClassesList.add (java.sql.Date.class); break;
default:
colClassesList.add (String.class); break;
};
System.out.println ("type: " +
results.getInt ("DATA_TYPE"));
}
columnNames = new String [colNamesList.size()];
colNamesList.toArray (columnNames);
columnClasses = new Class [colClassesList.size()];
colClassesList.toArray (columnClasses);
// get all data from table and put into
// contents array
Statement statement =
conn.createStatement();
results = statement.executeQuery ("SELECT * FROM " +
string);
ArrayList rowList = new ArrayList();
while (results.next()) {
ArrayList cellList = new ArrayList();
for (int i = 0; i<columnClasses.length; i++) {
Object cellValue = null;
if (columnClasses[i] == String.class)
cellValue = results.getString (columnNames[i]);
else if (columnClasses[i] == Integer.class)
cellValue = new Integer (
results.getInt (columnNames[i]));
else if (columnClasses[i] == Float.class)
cellValue = new Float (
results.getInt (columnNames[i]));
else if (columnClasses[i] == Double.class)
cellValue = new Double (
results.getDouble (columnNames[i]));
else if (columnClasses[i] == java.sql.Date.class)
cellValue = results.getDate (columnNames[i]);
else
System.out.println ("Can't assign " +
columnNames[i]);
cellList.add (cellValue);
}// for
Object[] cells = cellList.toArray();
rowList.add (cells);
} // while
// finally create contents two-dim array
contents = new Object[rowList.size()] [];
for (int i=0; i<contents.length; i++)
contents[i] = (Object []) rowList.get (i);
System.out.println ("Created model with " +
contents.length + " rows");
// close stuff
results.close();
statement.close();
}
// AbstractTableModel methods
public int getRowCount() {
return contents.length;
}
public int getColumnCount() {
if (contents.length == 0)
return 0;
else
return contents[0].length;
}
public Object getValueAt (int row, int column) {
return contents [row][column];
}
// overrides methods for which AbstractTableModel
// has trivial implementations
public Class getColumnClass (int col) {
return columnClasses [col];
}
public String getColumnName (int col) {
return columnNames [col];
}
}
請重新表述您的問題。這段代碼有什麼問題？ – adatapost 2012-01-07 15:09:59
對不起，我沒有明確問題。我無法收集數據庫信息 - col名稱，類型和值，但沒有提供線索的錯誤。然而下面的rcook答案解決了它 - 情況敏感性。 – ron 2012-01-07 16:38:25