db.py

Java Communicating Agents是一个用于开发网络反应式信息agent的框架

import java
import jacomma
from jacomma.icm.type import Symbol
from jacomma.platform.core import Agent, AgentManager, \
	 MessagePattern, AgentObserver, AgentObserverAdapter


# The Message Handler class
class QueryHandler( Agent.MessageHandler ):
	def onMessage( self, agent, msg ):
		print agent, ": Incoming query", msg.getContent().get( 1 )
		con = agent.getProperty( "connection" )
		try:
			stmt = con.createStatement()
			res = java.util.ArrayList()
			rs = stmt.executeQuery( msg.getContent().get( 1 ) )
			md = rs.getMetaData()
			cc = md.getColumnCount()
			res.add( Symbol( "query-ref" ) )
			head = java.util.ArrayList()
			res.add( head )	
			# column labels
			for i in range( 1, cc + 1 ) :
				head.add( md.getColumnLabel( i ) )
				# result set
			rsl = java.util.ArrayList()
			res.add( rsl )
			while( rs.next() ) :
				cur = java.util.ArrayList()
				rsl.add( cur )
				for i in range( 1, cc + 1 ):
					cur.add( rs.getObject( i ) )
			print agent, "Query processed"
			agent.send( msg.replyto(), res )
		except java.sql.SQLException, exc:
			print agent, exc.getMessage()
			res = java.util.ArrayList()
			res.add( Symbol( "query-error" ) )
			res.add( exc.getMessage() )
			agent.send( msg.replyto(), res )


# The Message Handler class
class UpdateHandler( Agent.MessageHandler ):
	def onMessage( self, agent, msg ):
		print agent, ": Incoming update", msg.getContent().get( 1 )
		con = agent.getProperty( "connection" )
		try:
			stmt = con.createStatement()
			res = java.util.ArrayList()
			res.add( Symbol( "update-ref" ) )
			res.add( java.lang.Integer( stmt.executeUpdate( msg.getContent().get( 1 ) ) ) )
			print agent, "Update processed"
			agent.send( msg.replyto(), res )
		except java.sql.SQLException, exc:
			print agent, exc.getMessage()
			res = java.util.ArrayList()
			res.add( Symbol( "update-error" ) )
			res.add( exc.getMessage() )
			agent.send( msg.replyto(), res )

						
## The pattern test object
class query_test( java.lang.Object ) :
	def equals( self, msg ) :
		l = msg.getContent()
		return java.util.List.isInstance( l ) \
			   and l.size() == 2 \
			   and l.get( 0 ).equals( Symbol( "query" ) ) \
			   and java.lang.String.isInstance( l.get( 1 ) )
	
## The pattern test object
class update_test( java.lang.Object ) :
	def equals( self, msg ) :
		l = msg.getContent()
		return java.util.List.isInstance( l ) \
			   and l.size() == 2 \
			   and l.get( 0 ).equals( Symbol( "update" ) ) \
			   and java.lang.String.isInstance( l.get( 1 ) )

# The local observer
class DBObserver( AgentObserverAdapter ):
	def __init__( self, con ) :
		self.con_ = con
	def onRegisteredAgent( self, agent, at ):
		agent.setProperty( "connection", self.con_ )
		query_ptrn = MessagePattern.createPattern( java.util.List, query_test() )
		agent.registerHandler( query_ptrn, QueryHandler() )
		update_ptrn = MessagePattern.createPattern( java.util.List, update_test() )
		agent.registerHandler( update_ptrn, UpdateHandler() )
	def onDeregisteredAgent( self, agent, at ) :
		self.con_.close()

## the code that creates the agent
def spawnAgent( name, driver, url, user, passwd ) :
	java.lang.Class.forName( driver )
	con = java.sql.DriverManager.getConnection( url, user, passwd )
	return AgentManager.instance.createAgent( name, DBObserver( con ) )