Re: [aspectj-users] Cancel a long-running query with AspectJ

[Andy Clement <andrew.clement@xxxxxxxxx>]

Hi,

I think it can do what you want, let me try to write out the shell of an aspect:

aspect QueryCancellation {

  // I don't know which arguments you want, presumably you don't need them all
  pointcut executingQuery(RequestScope request, Connection conn,String
sql, Object[] parameters,  RowHandlerCallback callback):
    execution(* SqlExecutor.executeQuery(..)) &&
args(request,conn,sql,parameters,*,*,callback);

  before():  executingQuery(RequestScope request, Connection
conn,String sql, Object[] parameters,  RowHandlerCallback callback) {
    <stick the ibatis hashmap into the session>
    <store the sql if you need to>
  }

}

cheers
Andy

On 7 March 2011 05:07, Andrei Neacsu <ensoreus18@xxxxxxxxx> wrote:
> Hi,
>
> I need a solution for cancelling a long-running select statement. I'm using
> Spring 3.0.2, iBatis 2.3.0 and Oracle 10g. I managed to get it to work with
> plain JDBC, but because the select is generated dynamically through an
> advanced search screen, I really need to use iBatis.
>
> The iBatis internal class responsible for the creation/retrieval from cache
> of prepared statements is com.ibatis.sqlmap.engine.execution.SqlExecutor.
> The internal method called for every call of queryForList()/queryForObject()
> is SqlExecutor's
>
> public void executeQuery(RequestScope request, Connection conn, String sql,
> Object[] parameters, int skipResults, int maxResults, RowHandlerCallback
> callback) throws SQLException method.
>
> Due to performance reasons, iBatis creates a new prepared statement only if
> one does not already exist for the given select statement. The prepared
> statements are stored/cached in a HashMap where the sql string is the key
> and the prepared statement is the value.
>
> Unfortunately, iBatis and the newer version myBatis don't seem to offer any
> support for cancelling a long running prepared statement.
>
> After trying different other solutions with no success, I think it might be
> possible to work with AspectJ to try to advice the
> SqlExecutor.executeQuery() method and somehow store on the HTTP session the
> iBatis cache map and sql string, both of them available as method arguments.
>
> When the user will try to cancel the long-running query, a check will be
> made from another thread to see if a prepared statement already exists in
> the iBatis cache map for the given sql string, previously stored on the HTTP
> session through AOP. If one does exist, a Statement.cancel() call will be
> issued. I don't see why a solution like this might interfere with the iBatis
> internal mechanisms since if the prepared statement will be canceled, an
> SqlException will be thrown (ORA-01013 user requested cancel of current
> operation) and Ibatis will properly handle that as any other generated
> SqlException.
>
> Using Spring AOP is not an option because it only allows you to pointcut
> methods declared in objects managed by the Spring container. I cannot
> declare SqlExecutor as a Spring bean, because it is created and managed
> internally by iBatis.
>
> Haven't yet tried the above solution with AspectJ since I'm not quite
> familiar with the framework, but I started reading about it.
>
> Can anyone please tell me if this is the right approach for my problem? Can
> I solve it with AspectJ?
>
> Any answer at all will be highly appreciated.
>
> Thanks,
>
> Andrei
>
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