Обсуждение: PSQLException instead of java.net.SocketException
Each time I initiate my servlet, I get an exception. It is thrown when I call the executeQuery method of a statement instance. He throws a PSQLException. However, when I take a look at the stack trace, it appears to be a java.net.SocketException was thrown. My best guess is the exception was catched and a PSQLException was thrown in the catch block. I already have a catch block for PSQLException which is designed to warn me for SQL syntax errors, not socket exceptions. So I want to make an additional catch block for a java.net.SocketException. However I don't know how. Can someone please help me here? Reason I want to do this: I can't solve sql syntax errors automatically, but I can solve socketexceptions automatically by just refreshing the window on the client side. However if someone can solve the cause in stead of the catching exception, that's even better. here is the exception: An I/O error has occured while flushing the output - Exception: java.net.SocketException: Socket closed here is part of the stack trace: java.net.SocketException: Socket closed at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:99) at java.net.SocketOutputStream.write(SocketOutputStream.java:136) at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:66) at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:124) at org.postgresql.PG_Stream.flush(PG_Stream.java:352) at org.postgresql.core.QueryExecutor.sendQuery(QueryExecutor.java:159) at org.postgresql.core.QueryExecutor.execute(QueryExecutor.java:70) at org.postgresql.jdbc1.AbstractJdbc1Connection.ExecSQL(AbstractJdbc1Connection.java:505) at org.postgresql.jdbc1.AbstractJdbc1Statement.execute(AbstractJdbc1Statement.java:320) at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:48) at org.postgresql.jdbc1.AbstractJdbc1Statement.executeQuery(AbstractJdbc1Statement.java:153) at org.postgresql.jdbc1.AbstractJdbc1Statement.executeQuery(AbstractJdbc1Statement.java:141) at menus.DBMenu.getQuery(DBMenu.java:705) at menus.DBMenu.Menupage(DBMenu.java:165) at menus.DBMenuShow.doGet(DBMenuShow.java:132) Nico.
Nico, PSQLException will/should store the cause internally, you should be able to get the cause out of it and act appropriately. Dave Nico wrote: >Each time I initiate my servlet, I get an exception. It is thrown when I >call the executeQuery method of a statement instance. He throws a >PSQLException. However, when I take a look at the stack trace, it appears to >be a java.net.SocketException was thrown. My best guess is the exception was >catched and a PSQLException was thrown in the catch block. I already have a >catch block for PSQLException which is designed to warn me for SQL syntax >errors, not socket exceptions. So I want to make an additional catch block >for a java.net.SocketException. However I don't know how. Can someone please >help me here? >Reason I want to do this: I can't solve sql syntax errors automatically, but >I can solve socketexceptions automatically by just refreshing the window on >the client side. However if someone can solve the cause in stead of the >catching exception, that's even better. >here is the exception: >An I/O error has occured while flushing the output - Exception: >java.net.SocketException: Socket closed >here is part of the stack trace: >java.net.SocketException: Socket closed > at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:99) > at java.net.SocketOutputStream.write(SocketOutputStream.java:136) > at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:66) > at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:124) > at org.postgresql.PG_Stream.flush(PG_Stream.java:352) > at org.postgresql.core.QueryExecutor.sendQuery(QueryExecutor.java:159) > at org.postgresql.core.QueryExecutor.execute(QueryExecutor.java:70) > at >org.postgresql.jdbc1.AbstractJdbc1Connection.ExecSQL(AbstractJdbc1Connection.java:505) > at >org.postgresql.jdbc1.AbstractJdbc1Statement.execute(AbstractJdbc1Statement.java:320) > at >org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:48) > at >org.postgresql.jdbc1.AbstractJdbc1Statement.executeQuery(AbstractJdbc1Statement.java:153) > at >org.postgresql.jdbc1.AbstractJdbc1Statement.executeQuery(AbstractJdbc1Statement.java:141) > at menus.DBMenu.getQuery(DBMenu.java:705) > at menus.DBMenu.Menupage(DBMenu.java:165) > at menus.DBMenuShow.doGet(DBMenuShow.java:132) > >Nico. > > > >---------------------------(end of broadcast)--------------------------- >TIP 4: Don't 'kill -9' the postmaster > > > > -- Dave Cramer http://www.postgresintl.com 519 939 0336 ICQ#14675561
Nico wrote:
> My best guess is the exception was
> catched and a PSQLException was thrown in the catch block.
Yes, this is exactly what's happening. In general the driver will throw
a SQLException for all errors, including connection-level problems.
> I already have a
> catch block for PSQLException which is designed to warn me for SQL syntax
> errors, not socket exceptions. So I want to make an additional catch block
> for a java.net.SocketException. However I don't know how. Can someone please
> help me here?
You probably want to look at SQLException.getSQLState(). That gives a
somewhat standardized string that describes the error in more detail.
The driver passes through error codes received from the server directly,
and synthesizes appropriate error codes in some other cases (e.g.
connection failure).
In your case you want to look for all error codes starting with "08"
("Connection Exception"). See
http://www.postgresql.org/docs/current/static/errcodes-appendix.html for
a list of codes.
You could also do it by looking at the nested exception of the
SQLException, but that's not standard and isn't guaranteed to work; it's
really there to give extra information to a human, not for programmatic
logic.
-O