java - プログラムは、トランザクションが閉じられた後、私は操作を行うことができないと述べています

Question

データベースに対して複数の呼び出しを実行しようとしていますが、最初の呼び出し（選択）は正常に機能します。しかし、2番目の呼び出しに入ると、このエラーが発生します。

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after statement closed.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.Util.getInstance(Util.java:381)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
    at com.mysql.jdbc.StatementImpl.checkClosed(StatementImpl.java:380)
    at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1250)
    at MysqlConnect.main(MysqlConnect.java:77)
    at __SHELL13.run(__SHELL13.java:6)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at bluej.runtime.ExecServer$3.run(ExecServer.java:724)

そしてここに私のコードがあります（まだ学習していることを許してください）

import java.sql.*;

public class MysqlConnect{

  public static void main(String[] args) {

  Connection conn = null;

  String url = "jdbc:mysql://localhost:3306/";
  String dbName = "MyBussiness";
  String driver = "com.mysql.jdbc.Driver";
  String userName = "mambo"; 
  String password = "jambo";

  try {
  Class.forName(driver).newInstance();
  conn = DriverManager.getConnection(url+dbName,userName,password);



  System.out.println("Connected to the database");
       /*SELECTING DATA */
       // Get a statement from the connection
       Statement stmt = conn.createStatement() ;
       System.out.println("--------------------------------------------.");
       System.out.println("Retrieving items from the customers table  (USING SELECT)...");
       System.out.println("--------------------------------------------.");
       Thread.sleep(2000);
       // Execute the query
       ResultSet rs = stmt.executeQuery( "SELECT * FROM customers" ) ;

       // Loop through the result set
       while( rs.next() )
       {
          System.out.print( rs.getInt(1) ) ;
          System.out.print(",      ");
          System.out.print( rs.getString(2) );
          System.out.print(",      ");
          System.out.print( rs.getString(3) );
          System.out.print(",      ");
          System.out.print( rs.getString(4) );
          System.out.print(",      ");
          System.out.print( rs.getString(5) );
          System.out.print(",      ");
          System.out.print( rs.getString(6) );
          System.out.print(",      ");
          System.out.print( rs.getString(7) );
          System.out.print(",      ");
          System.out.print( rs.getString(8) );
          System.out.print(",      ");
          System.out.print( rs.getString(9) );
          System.out.print(",      ");
          System.out.println( rs.getString(10) );
        }

       // Close the result set, statement and the connection
       rs.close() ;
       stmt.close() ;



         /*UPDATING DATA */
       // Get a statement from the connection
       conn = DriverManager.getConnection(url+dbName,userName,password);
       Statement stmt2 = conn.createStatement() ;
       System.out.println("---------------------------------------------------------------------------.");
       System.out.println("Updating Customers Table for Customer ID 1 Federico Gutierrez Address1 Field  (USING UPDATE)...");
       System.out.println("---------------------------------------------------------------------------.");
       Thread.sleep(2000);
       // Execute the query
       ResultSet rs2 = stmt.executeQuery("UPDATE Customers SET Address1='999 Mambo Avenue' WHERE CustomerID = 1");

       // Loop through the result set
       while( rs2.next() )
       {
          System.out.print( rs2.getInt(1) ) ;
          System.out.print(",      ");
          System.out.print( rs2.getString(2) );
          System.out.print(",      ");
          System.out.print( rs2.getString(3) );
          System.out.print(",      ");
          System.out.print( rs2.getString(4) );
          System.out.print(",      ");
          System.out.print( rs2.getString(5) );
          System.out.print(",      ");
          System.out.print( rs2.getString(6) );
          System.out.print(",      ");
          System.out.print( rs2.getString(7) );
          System.out.print(",      ");
          System.out.print( rs2.getString(8) );
          System.out.print(",      ");
          System.out.print( rs2.getString(9) );
          System.out.print(",      ");
          System.out.println(rs2.getString(10) );
        }

       // Close the result set, statement and the connection
       rs2.close() ;
       stmt2.close() ;


           /*INSERTING DATA */
       // Get a statement from the connection
       conn = DriverManager.getConnection(url+dbName,userName,password);
       Statement stmt3 = conn.createStatement() ;
       System.out.println("---------------------------------------------------------------------------.");
       System.out.println("Inserting a new customer (Mario Villalobos) into the customers table ... (USING INSERT)");
       System.out.println("---------------------------------------------------------------------------.");
       Thread.sleep(2000);
       // Execute the query
       ResultSet rs3 = stmt.executeQuery("INSERT INTO Customers (SSN, FirstName, LastName, Address1, Address2, State, City, Zip, PhoneNumber)"+ 
                                          " VALUES ('444559999','Mario','Villalobos','777 Boynton Beach','Apt 4R','FL','Boynton Beach','33436','(555)444-5555'");

       // Loop through the result set
       while( rs3.next() )
       {
          System.out.print( rs3.getInt(1) ) ;
          System.out.print(",      ");
          System.out.print( rs3.getString(2) );
          System.out.print(",      ");
          System.out.print( rs3.getString(3) );
          System.out.print(",      ");
          System.out.print( rs3.getString(4) );
          System.out.print(",      ");
          System.out.print( rs3.getString(5) );
          System.out.print(",      ");
          System.out.print( rs3.getString(6) );
          System.out.print(",      ");
          System.out.print( rs3.getString(7) );
          System.out.print(",      ");
          System.out.print( rs3.getString(8) );
          System.out.print(",      ");
          System.out.print( rs3.getString(9) );
          System.out.print(",      ");
          System.out.println(rs3.getString(10) );
        }

       // Close the result set, statement and the connection
       rs3.close() ;
       stmt3.close() ;


                  /*DELETING DATA */
       // Get a statement from the connection
       conn = DriverManager.getConnection(url+dbName,userName,password);
       Statement stmt4 = conn.createStatement() ;
       System.out.println("---------------------------------------------------------------------------.");
       System.out.println("Deleting customer where the name is George...  (USING Delete)");
       System.out.println("---------------------------------------------------------------------------.");
       Thread.sleep(2000);
       // Execute the query
       ResultSet rs4 = stmt.executeQuery("DELETE FROM Customers WHERE FirstName Like '%George%'");

       // Loop through the result set
       while( rs4.next() )
       {
          System.out.print( rs4.getInt(1) ) ;
          System.out.print(",      ");
          System.out.print( rs4.getString(2) );
          System.out.print(",      ");
          System.out.print( rs4.getString(3) );
          System.out.print(",      ");
          System.out.print( rs4.getString(4) );
          System.out.print(",      ");
          System.out.print( rs4.getString(5) );
          System.out.print(",      ");
          System.out.print( rs4.getString(6) );
          System.out.print(",      ");
          System.out.print( rs4.getString(7) );
          System.out.print(",      ");
          System.out.print( rs4.getString(8) );
          System.out.print(",      ");
          System.out.print( rs4.getString(9) );
          System.out.print(",      ");
          System.out.println(rs4.getString(10) );
        }

       // Close the result set, statement and the connection
       rs4.close() ;
       stmt4.close() ;

       //Reseting data
       conn = DriverManager.getConnection(url+dbName,userName,password);
       Statement stmt5 = conn.createStatement() ;
       ResultSet rs5 = stmt.executeQuery("UPDATE Customers SET Address1='555 YY Ave' WHERE CustomerID = 1");
       rs5.close() ;
       stmt5.close() ;

       conn = DriverManager.getConnection(url+dbName,userName,password);
       Statement stmt6 = conn.createStatement() ;
       ResultSet rs6 = stmt.executeQuery("DELETE FROM Customers WHERE FirstName Like '%Mario%'");
       rs6.close() ;
       stmt6.close() ;
       conn = DriverManager.getConnection(url+dbName,userName,password);     
       Statement stmt7 = conn.createStatement() ;
       ResultSet rs7 = stmt.executeQuery("INSERT INTO Customers (SSN, FirstName, LastName, Address1, Address2, State, City, Zip, PhoneNumber)"+ 
                                          " VALUES ('923431432','George','Scott','2325 S Babcock St',' ','FL','Melbourne','32901','(321)984-4910'");
       rs7.close() ;
       stmt7.close() ;
       conn.close() ;


  System.out.println("Disconnected from database");
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
}

どんな助けでも大歓迎です。

注：最初のパスの後で接続が閉じられたと表示されますが、conn.Close（）;がありません。あなたが見ることができるように最後まで。

score 3 · Accepted Answer

ResultSet rs2 = stmt.executeQuery(...)
             // ^^^^

あなたはそこに意味stmt2がありました。ステートメントを再利用しないように、すべてのコードを再確認してください。

score 1 · Accepted Answer

まだ気付いていない場合は、すでに閉じた SQlStatement を再利用しています。この線：

ResultSet rs2 = stmt.executeQuery("UPDATE Customers SET Address1='999 Mambo Avenue' WHERE CustomerID = 1");

次のようにする必要があります。

ResultSet rs2 = stmt2.executeQuery("UPDATE Customers SET Address1='999 Mambo Avenue' WHERE CustomerID = 1");

score 0 · Accepted Answer

いくつかの修正が行われましたが、コードはまだ良くありません。動作するはずです。

    import java.sql.*;

public class MysqlConnect{

  public static void main(String[] args) {

  Connection conn = null;

  String url = "jdbc:mysql://localhost:3306/";
  String dbName = "MyBussiness";
  String driver = "com.mysql.jdbc.Driver";
  String userName = "mambo"; 
  String password = "jambo";

  try {
  Class.forName(driver).newInstance();
  conn = DriverManager.getConnection(url+dbName,userName,password);



  System.out.println("Connected to the database");
       /*SELECTING DATA */
       // Get a statement from the connection
       Statement stmt = conn.createStatement() ;
       System.out.println("--------------------------------------------.");
       System.out.println("Retrieving items from the customers table  (USING SELECT)...");
       System.out.println("--------------------------------------------.");
       Thread.sleep(2000);
       // Execute the query
       ResultSet rs = stmt.executeQuery( "SELECT * FROM customers" ) ;

       // Loop through the result set
       while( rs.next() )
       {
          System.out.print( rs.getInt(1) ) ;
          System.out.print(",      ");
          System.out.print( rs.getString(2) );
          System.out.print(",      ");
          System.out.print( rs.getString(3) );
          System.out.print(",      ");
          System.out.print( rs.getString(4) );
          System.out.print(",      ");
          System.out.print( rs.getString(5) );
          System.out.print(",      ");
          System.out.print( rs.getString(6) );
          System.out.print(",      ");
          System.out.print( rs.getString(7) );
          System.out.print(",      ");
          System.out.print( rs.getString(8) );
          System.out.print(",      ");
          System.out.print( rs.getString(9) );
          System.out.print(",      ");
          System.out.println( rs.getString(10) );
        }

       // DO NOT Close the result set, statement and the connection



         /*UPDATING DATA */
       // Get a statement from the connection
       System.out.println("---------------------------------------------------------------------------.");
       System.out.println("Updating Customers Table for Customer ID 1 Federico Gutierrez Address1 Field  (USING UPDATE)...");
       System.out.println("---------------------------------------------------------------------------.");
       Thread.sleep(2000);
       // Execute the UPDATE
      stmt.executeUpdate("UPDATE Customers SET Address1='999 Mambo Avenue' WHERE CustomerID = 1");

       // Loop through the result set
      //NO ResultSet for UPDATE

       // DON'T Close the result set, statement and the connection



           /*INSERTING DATA */
       // Get a statement from the connection

       System.out.println("---------------------------------------------------------------------------.");
       System.out.println("Inserting a new customer (Mario Villalobos) into the customers table ... (USING INSERT)");
       System.out.println("---------------------------------------------------------------------------.");
       Thread.sleep(2000);
       // Execute the UPDATE
    stmt.executeUpdate("INSERT INTO Customers (SSN, FirstName, LastName, Address1, Address2, State, City, Zip, PhoneNumber)"+ 
                                          " VALUES ('444559999','Mario','Villalobos','777 Boynton Beach','Apt 4R','FL','Boynton Beach','33436','(555)444-5555'");

       // Loop through the result set INSERT HAS NO RESULTSET

       // Close the result set, statement and the connection


                  /*DELETING DATA */
       // Get a statement from the connection
       System.out.println("---------------------------------------------------------------------------.");
       System.out.println("Deleting customer where the name is George...  (USING Delete)");
       System.out.println("---------------------------------------------------------------------------.");
       Thread.sleep(2000);
       // Execute the query, NO UPDATE
       stmt.executeUpdate("DELETE FROM Customers WHERE FirstName Like '%George%'");

       // Loop through the result set


       // Close the result set, statement and the connection

       //Reseting data
       stmt.executeUpdate("UPDATE Customers SET Address1='555 YY Ave' WHERE CustomerID = 1");

       stmt.executeUpdate("DELETE FROM Customers WHERE FirstName Like '%Mario%'");

       stmt.executeUpdate("INSERT INTO Customers (SSN, FirstName, LastName, Address1, Address2, State, City, Zip, PhoneNumber)"+ 
                                          " VALUES ('923431432','George','Scott','2325 S Babcock St',' ','FL','Melbourne','32901','(321)984-4910'");

   // NOW CLOSE DB RS, STATEMENT, CONN
       rs.close() ;


       stmt.close() ;
       conn.close() ;


  System.out.println("Disconnected from database");
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
}

java - プログラムは、トランザクションが閉じられた後、私は操作を行うことができないと述べています

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