代码如下:
public static void main( String[] args ) throws ClassNotFoundException,
SQLException, InstantiationException, IllegalAccessException{
Class.forName( "com.mysql.jdbc.Driver" );
Connection c =
DriverManager.getConnection( "jdbc:mysql://localhost/test", "cgh", "cgh" );
System.out.println( c );
PreparedStatement ps =
c.prepareStatement("select next from hibernate_unique_key");
//这里出现空指针错误!}如果使用Statement s = c.createStatement();则没有问题?很是郁闷,不知道哪里的原因,敬请指教。。
public static void main( String[] args ) throws ClassNotFoundException,
SQLException, InstantiationException, IllegalAccessException{
Class.forName( "com.mysql.jdbc.Driver" );
Connection c =
DriverManager.getConnection( "jdbc:mysql://localhost/test", "cgh", "cgh" );
System.out.println( c );
PreparedStatement ps =
c.prepareStatement("select next from hibernate_unique_key");
//这里出现空指针错误!}如果使用Statement s = c.createStatement();则没有问题?很是郁闷,不知道哪里的原因,敬请指教。。
Exception in thread "main" java.lang.NullPointerException
at com.mysql.jdbc.PreparedStatement.asSql(PreparedStatement.java:562)
at com.mysql.jdbc.PreparedStatement.asSql(PreparedStatement.java:504)
at com.mysql.jdbc.PreparedStatement.toString(PreparedStatement.java:3228)
at java.lang.String.valueOf(Unknown Source)
at java.lang.StringBuffer.append(Unknown Source)
at com.mysql.jdbc.trace.Tracer.printParameters(Tracer.aj:240)
at com.mysql.jdbc.trace.Tracer.printEntering(Tracer.aj:167)
at com.mysql.jdbc.trace.Tracer.entry(Tracer.aj:126)
at com.mysql.jdbc.trace.Tracer.ajc$before$com_mysql_jdbc_trace_Tracer$1$f51c62b8(Tracer.aj:45)
at com.mysql.jdbc.Connection.registerStatement(Connection.java)
at com.mysql.jdbc.Statement.<init>(Statement.java:190)
at com.mysql.jdbc.PreparedStatement.<init>(PreparedStatement.java:429)
at com.mysql.jdbc.ServerPreparedStatement.asSql(ServerPreparedStatement.java:338)
at com.mysql.jdbc.PreparedStatement.asSql(PreparedStatement.java:504)
at com.mysql.jdbc.ServerPreparedStatement.toString(ServerPreparedStatement.java:2226)
at java.lang.String.valueOf(Unknown Source)
at java.lang.StringBuffer.append(Unknown Source)
at com.mysql.jdbc.trace.Tracer.printParameters(Tracer.aj:240)
at com.mysql.jdbc.trace.Tracer.printEntering(Tracer.aj:167)
at com.mysql.jdbc.trace.Tracer.entry(Tracer.aj:126)
at com.mysql.jdbc.trace.Tracer.ajc$before$com_mysql_jdbc_trace_Tracer$1$f51c62b8(Tracer.aj:45)
at com.mysql.jdbc.Connection.registerStatement(Connection.java)
at com.mysql.jdbc.Statement.<init>(Statement.java:190)
at com.mysql.jdbc.PreparedStatement.<init>(PreparedStatement.java:411)
at com.mysql.jdbc.ServerPreparedStatement.<init>(ServerPreparedStatement.java:275)
at com.mysql.jdbc.Connection.prepareStatement(Connection.java:4245)
at com.mysql.jdbc.Connection.prepareStatement(Connection.java:4185)
at StatementTest.main(StatementTest.java:25)