mysql - Managing database connections in java -

-



a full day of googling problem has left me more confused ever i'm appealing help. i'm trying use pooled connections mysql db i'm misunderstanding something. below snippets of code application scans folder new directories represent "jobs"; when found, database objects created each folder found. based _insert() method on pattern found on so. understanding connections closed , returned connection pool. however, noticed that, after adding 8 objects, code hang on getconnection(). found somewhere default number of active connections 8, added debug line limit number of active connections 2. sure enough, 2 objects added before code hangs.

what's going on? need change make these connections freed , added pool? found one post mentioned poolableconnection class i'm confused documentation fact other examples i've found don't seem use it.

the scanner class creates job objects in database based on folders found in particular directory on disk:

public class scanner extends thread {     public void run() {              syncjobs();     }      void syncjobs(list<string> foldernames) {         (string foldername : foldernames) {             job job = addjobtodb(foldername);         }     }      job addjobtodb(string foldername ) {         job job = new job();         job.name = foldername;         job.save();         return job;     }    }

there's abstract base class objects (each objects overrides _insert):

public abstract class dbobject {     private final int insert() {         return _insert();     }      public final void save() {         if (id == 0)             id = insert();         else             update();     }    }

and there's actual job object (with insert method shown):

public class job extends dbobject {     public int _insert()  {         string query = "insert jobs (name) values (?)";         connection conn = null;         preparedstatement ps = null;         resultset rs = null;             int id = 0;         try {             conn = database.getconnection();             ps = conn.preparestatement(query, statement.return_generated_keys);             ps.setint(1, id);             ps.executeupdate();             rs = ps.getgeneratedkeys();             rs.next();             id = rs.getint(1);         } catch (exception e) {             system.out.println(e.getmessage());                      } {             dbutils.closequietly(rs);             dbutils.closequietly(ps);             dbutils.closequietly(conn);         }         return id;     }        }

and, lastly, database object provides connections:

import org.apache.commons.dbcp.basicdatasource; public final class database {     private static final basicdatasource datasource = new basicdatasource();      static {         datasource.seturl("jdbc:mysql://localhost:3306/dbname?useunicode=true&usejdbccomplianttimezoneshift=true&uselegacydatetimecode=false&servertimezone=utc");         datasource.setusername("user");         datasource.setpassword("****");               // line added debugging: sure enough, 2 objects created.          datasource.setmaxactive(2);     }      public static connection getconnection() throws sqlexception {         return datasource.getconnection();     }       }





wiki

Comments

Post a Comment

Popular posts from this blog

python - Read npy file directly from S3 StreamingBody -

-
i have many .npy (numpy) , .json files saved in s3, need download , load these files. for json files downloading files , loading dictionary using following code: obj = s3.object(bucket, key) response = obj.get() body = response['body'].read().decode('utf-8') data = json.loads(body) that way avoid writing .json file disk , reading it. now want same .npy files, equivalent? currently downloading file, saving temp file on disk , loading np.load avoid if possible. following https://stackoverflow.com/a/28196540/3509999 : obj = s3.object(bucket, key) io.bytesio(obj.get()["body"].read()) f: # rewind file f.seek(0) arr = np.load(f) wiki
Read more

python - Minimize function with Scipy minimize -

-
trying obtain d value (integer) std_diff objective function minimal, using scipy minimize. my code: def std_diff(d): return std(diff(df['bn'].values,d)); scipy.optimize import minimize b=(3,) res = minimize(std_diff,(1,), method='slsqp', bounds = b) **df['bn'].values** out[72]: array([ 2, 2, 2, 2, 3, 2, 7, 5, 7, 11, 8, 2, 11, 7, 15, 8, 7, 12, 21, 19, 32, 35, 40, 35, 21, 19, 25, 20, 40, 80, 99], dtype=int64) error is"indexerror: many indices array " in case not use bounds : res = minimize(std_diff,(1,), method='slsqp'), error: > in _minimize_slsqp(func, x0, args, jac, bounds, constraints, maxiter, > ftol, iprint, disp, eps, callback, **unknown_options) > 368 fx = float(np.asarray(func(x))) > 369 except: > --> 370 raise valueerror("objective function must return scalar") > 371 # compute constraints > 3
Read more

kotlin - Out-projected type in generic interface prohibits the use of metod with generic parameter -

-
i start using kotlin , defined interface this: interface aadapter<vh : recyclerview.viewholder> { fun oncreateaviewholder(parent: viewgroup): vh fun onbindaviewholder(v: vh, position: int) } and when try use on code: class klasa ( private val adapter: aadapter<*> ) { fun dosth(){ //... val vh = this.adapter.oncreateaviewholder(parent) //on below line error adapter.onbindaviewholder(v, position) //... } } i error out-projected type 'aadapter<*>' prohibits use of 'public abstract fun onbindaviewholder(v: t, position: int): unit i tied add "in" or "out" definition i'm confused. how allow it. replace aadapter<*> aadapter<recyclerview.viewholder> . class klasa ( private val adapter: aadapter<recyclerview.viewholder> ) { // ... because have declared aadapter has type parameter vh type subclass of recyclerview.
Read more