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[EMAIL PROTECTED] wrote: | i'm using tomcat 5.5.9 for a web server application where many | clients connect and do stuffs. each time they login to the server, | for example, a database query is performed. Application works, but | reading | http://tomcat.apache.org/tomcat-5.5-doc/jndi-datasource-examples-howto.html#Common%20Problems | some doubt come to my mind. It's interesting that non-native English speakers often use the word "doubt" rather than the more usual "question". Just FYI (and any other non-native English speakers who happen to be reading), the word "doubt" typically has a connotation closer to "suspicion", rather than an interrogative. The better term in English is "question". In Italiano, la parola "doubt" e piu similare a "uno dubbio", "una domanda" non. Me dispiace per mio Italiano malo... seguo solo due semestri d'Italiano. ;) | [W]hat's the best way to "get connection from connection pool"? | | Here is what i've done: Your context.xml looks just fine, as does web.xml. | Then i have Database.java class where i have the method: | | private Connection getConnection() throws Exception { This one also looks good. I would recommend that you use an application-specific exception that any thrown exceptions, or that you throw if any objects are null, but that's just my own personal feeling. | that get connection for all of the 20-30 methods in Database.java | that do a query each. An example of method in Database.java that use it is: | | // get user info | public UserData getUserData(UserData res, String un, String pw) { | Connection con = null; | Statement stmt = null; | ResultSet rst = null; | try { [snip] | } | catch (Exception e1) { | return null; | } You should not do this: exceptions should be (wrapped and) re-thrown or logged (or both!). Never swallow an exception. Note that you will swallow your own Exception that you throw in the body of the try/catch block, thereby wasting the entire "throw" in the first place. | // close resources | finally { | try { | rst.close(); | rst = null; Don't forget to check for null. This is an NPE just waiting to happen. I would recommend a method in Database.java like this: protected void close(Connection conn, Statement s, ResultSet r) { ~ if(null != r) ~ try { ~ r.close(); ~ } catch (SQLException sqle) { ~ logger.warn("Cannot close result", sqle); ~ } ~ if(null != s) ~ try { ~ s.close(); ~ } catch (SQLException sqle) { ~ logger.warn("Cannot close statement", sqle); ~ } ~ if(null != conn) ~ try { ~ conn.close(); ~ } catch (SQLException sqle) { ~ logger.warn("Cannot close connection", sqle); ~ } } ...and use that, rather than repeating the code all over the place. | At the moment, methods are not static, so each time a client thread | need to login, for example, i do (new Database()).getUserData(res, un, pw). | | First question is if that solution is correct or create each time a | new Database class is useless/stupid. This is a matter of taste, in my opinion. I would prefer to write an interface called Database and then write an implementation of that interface. Then, have a dependency-injection framework such as Spring call setDatabase(Database) on the object that needs to access the database (such as a servlet or whatever) and then use it that way. It also makes it much easier to unit-test your code because you can "mock" the Database class if you want to. | If it's stupid, should i make the | methods static? or should i create a static database object each time | server is started? Object allocation is cheap, so i wouldn't worry too much about it. Your Database class does not contain any members, so it doesn't take up much memory, etc. | Second, is that getConnection() method a correct way for what the | article | (http://tomcat.apache.org/tomcat-5.5-doc/jndi-datasource-examples-howto.html#Common%20Problems) | meant about "get connection from connection pool"? Yes. - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkfZcfcACgkQ9CaO5/Lv0PD85gCggizSgcs3NrvN1yCXIhjlvP8z kFUAn1nTN+T96Z3G3p6RkQzJUYswcjl7 =zRYV -----END PGP SIGNATURE----- --------------------------------------------------------------------- To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
