这个问题
<P>Unable to connect<BR>java.sql.SQLException: [Oracle][ODBC][Ora]ORA-12541: TNS: 没有监听器<BR> at sun.jdbc.odbc.JdbcOdbc.createSQLException(Unknown Source)<BR> at sun.jdbc.odbc.JdbcOdbc.standardError(Unknown Source)<BR> at sun.jdbc.odbc.JdbcOdbc.SQLDriverConnect(Unknown Source)<BR> at sun.jdbc.odbc.JdbcOdbcConnection.initialize(Unknown Source)<BR> at sun.jdbc.odbc.JdbcOdbcDriver.connect(Unknown Source)<BR> at java.sql.DriverManager.getConnection(Unknown Source)<BR> at java.sql.DriverManager.getConnection(Unknown Source)<BR> at TableDisplay.<init>(TableDisplay.java:17)<BR> at TableDisplay.main(TableDisplay.java:114)<BR>Exception in thread "main" java.lang.NullPointerException<BR> at TableDisplay.getTable(TableDisplay.java:38)<BR> at TableDisplay.<init>(TableDisplay.java:27)<BR> at TableDisplay.main(TableDisplay.java:114)<BR><BR>这个问题怎么解决?<BR>我的java代码如下:<BR>import java.sql.*;<BR>import java.awt.*;<BR>import javax.swing.*;<BR>import java.awt.event.*;<BR>import java.util.*;<BR>public class TableDisplay extends JFrame {<BR> private Connection connection;<BR> private JTable table;<BR> <BR> public TableDisplay(){<BR> String url = "jdbc:odbc:mouse";<BR> String username = "system";<BR> String password = "manager";<BR> <BR> try {<BR> Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");<BR> connection = DriverManager.getConnection(url, username, password);<BR> } catch (ClassNotFoundException e) {<BR> System.out.println("Failed to load JDBC/ODBC driver");<BR> e.printStackTrace();<BR> System.exit(1);<BR> } catch (SQLException e) {<BR> System.err.println("Unable to connect");<BR> e.printStackTrace();<BR> }<BR> <BR> getTable();<BR> setSize(450,150);<BR> setVisible(true);<BR> }<BR> <BR> private void getTable(){<BR> Statement statement;<BR> ResultSet resultSet;<BR> <BR> String query = "select * from students";<BR> try {<BR> statement = connection.createStatement();<BR> resultSet = statement.executeQuery(query);<BR> displayResultSet(resultSet);<BR> statement.close();<BR> } catch (SQLException e) {<BR> e.printStackTrace();<BR> }<BR> }<BR> <BR> private void displayResultSet(ResultSet rs){<BR> boolean moreRecords = false;<BR> try {<BR> moreRecords = rs.next();<BR> } catch (SQLException e) {<BR> e.printStackTrace();<BR> }<BR> if(!moreRecords){<BR> JOptionPane.showMessageDialog(this,"ResultSet contained no records");<BR> setTitle("No records to display");<BR> return;<BR> }<BR> <BR> setTitle("Students table from mouse");<BR> <BR> Vector columnHeads = new Vector();<BR> Vector rows = new Vector();<BR> <BR> try {<BR> ResultSetMetaData rsmd = rs.getMetaData();<BR> <BR> for(int i = 1;i<=rsmd.getColumnCount();++i)<BR> columnHeads.addElement(rsmd.getCatalogName(i));<BR> do{<BR> rows.addElement(getNextRow(rs,rsmd));<BR> }while(rs.next());<BR> <BR> table = new JTable(rows,columnHeads);<BR> JScrollPane scroller = new JScrollPane(table);<BR> getContentPane().add(scroller,BorderLayout.CENTER);<BR> this.validate();<BR> } catch (SQLException e) {<BR> e.printStackTrace();<BR> }<BR> }<BR> <BR> private Vector getNextRow(ResultSet rs,ResultSetMetaData rsmd){<BR> Vector currentRow = new Vector();<BR> <BR> try {<BR> for(int i=1;i<=rsmd.getColumnCount();++i)<BR> switch(rsmd.getColumnType(i)){<BR> case Types.VARCHAR:<BR> currentRow.addElement(rs.getString(i));<BR> break;<BR> case Types.INTEGER:<BR> currentRow.addElement(new Long(rs.getLong(i)));<BR> break;<BR> default:<BR> System.out.println("Type was :"+rsmd.getColumnTypeName(i));<BR> }<BR> } catch (SQLException e) {<BR> e.printStackTrace();<BR> }<BR> return currentRow;<BR> }<BR> <BR> public void shutDown(){<BR> try {<BR> connection.close();<BR> } catch (SQLException e) {<BR> System.out.println("Unable to disconnect");<BR> e.printStackTrace();<BR> }<BR> }<BR> <BR> public static void main(String[] args) {<BR> TableDisplay td = new TableDisplay();<BR> td.addWindowListener(new WindowAdapter(){<BR> public void windowClosing(WindowEvent e){<BR> //td.shutDown();<BR> System.exit(0);<BR> }<BR> });<BR> <BR> }</P><P>}<BR></P> 你的监听服务没有启动把?没有服务是不行的,而且我看你现在还在使用vector,这个东西已经过时了,你可以选择别的用一下.
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