Java SQLite - 接続を閉じるには？

Question

DAOメソッドで人々がfinally{}を使用するデータベース接続を閉じる例がたくさんありましたが、私の場合、DAOメソッド（例：insertUsers（））では、呼び出されたメソッドに例外がスローされます。この場合、どうやって接続を閉じることができますか？

SELECT + INSERTにしようとすると、「SQLiteException - データベースはロックされています」というエラーが表示されます。

ここに私のコードです：

DAO

public static Connection con = null; 
private static boolean hasData = false; 

private void getConnection() throws ClassNotFoundException, SQLException { 
    Class.forName("org.sqlite.JDBC"); 
    con = DriverManager.getConnection("jdbc:sqlite:ProjFarmacia.db"); 
    initialise(); 
} 

private void initialise() throws SQLException { 
    if(!hasData){ 
     hasData = true; 
     Statement state = con.createStatement(); 
     ResultSet res = state.executeQuery("SELECT name FROM sqlite_master WHERE type='table' AND name='caixa'"); 
     if(!res.next()){ 
      Statement state2 = con.createStatement(); 
      state2.execute("CREATE TABLE caixa(id integer, timestamp integer, valorTotal double, notas1 integer, notas2 integer," 
        + " notas5 integer, notas10 integer, notas20 integer" 
        + "notas50 integer, notas100 integer, moedas1 integer, moedas5 integer, moedas10 integer, moedas25 integer" 
        + "moedas50 integer, moedas1R integer, primary key(id));"); 
     } 
    } 
} 




public ResultSet getCaixaByDate(long timestamp) throws ClassNotFoundException, SQLException{ 
    if(con == null){ 
     getConnection(); 
    } 

    Statement state = con.createStatement(); 
    ResultSet res = state.executeQuery("SELECT * FROM caixa WHERE timestamp=" + "'" + timestamp + "'" + ";"); 
    return res; 
} 


public void createCaixa(Caixa caixa) throws ClassNotFoundException, SQLException{ 
    if(con == null){ 
     getConnection(); 
    } 
    PreparedStatement prep = con.prepareStatement("INSERT INTO caixa VALUES(?,?);"); 
    prep.setLong(1, caixa.getTimestamp()); 
    prep.setDouble(2, caixa.getValorTotal()); 
    con.close(); 
} 

メインアプリケーション

try { 
     ResultSet rs = caixaDAO.getCaixaByDate(timestamp); 

     //If not exists in database 
     if(!rs.next()){ 
      Caixa caixa = new Caixa(); 
      caixa.setTimestamp(timestamp); 
      caixa.setValorTotal(venda.getValorDaVenda()); 

      //Inserting new Caixa 
      caixaDAO.createCaixa(caixa); 
     }else{ 
      System.out.println("Caixa already created!!!"); 
     } 

    } catch (ClassNotFoundException | SQLException ex) { 
     Logger.getLogger(VendaMedicamento.class.getName()).log(Level.SEVERE, null, ex); 
} 

Answer 1

Connection conn = null; 
PreparedStatement ps = null; 
ResultSet rs = null; 

try { 
    // Do stuff 
    ... 

} catch (SQLException ex) { 
    // Exception handling stuff 
    ... 
} finally { 
    if (rs != null) { 
     try { 
      rs.close(); 
     } catch (SQLException e) { /* ignored */} 
    } 
    if (ps != null) { 
     try { 
      ps.close(); 
     } catch (SQLException e) { /* ignored */} 
    } 
    if (conn != null) { 
     try { 
      conn.close(); 
     } catch (SQLException e) { /* ignored */} 
    } 
} 

出典：私はDAOのメソッドを実装する方法をのJava7-try-with-resources

try (Connection conn = DriverManager.getConnection("DB_URL","DB_USER","DB_PASSWORD"); 
      PreparedStatement ps = conn.prepareStatement("SQL"); 
      ResultSet rs = ps.executeQuery()) { 

     // Do stuff with your ResultSet 

    } catch (SQLException ex) { 
     // Exception handling stuff 
    } 

例と@ JaLe29の

Answer 2

例：

Caixa getCaixaByDate(long timestamp) { 
    Caixa result = null; 
    try(Connection con = getConnection(); 
      PreparedStatement statement = con.prepareStatement("SELECT * FROM caixa WHERE timestamp=?")) { 
     statement.setLong(1, timestamp); 

     try (ResultSet res = statement.executeQuery()) { 
      result = new Caixa(); 
      result.setTimestamp(res.getLong("timestamp")); // this is just an example 
      //TODO: mapping the other input from the ResultSet into the caixa object 
     } catch (SQLException e) { 
      result = null; 
      Logger.getLogger("MyLogger").log(Level.SEVERE, "error while mapping ResultSet to Caixa: {0}", e.getMessage()); 
     } 
    } catch (SQLException e) { 
     Logger.getLogger("MyLogger").log(Level.SEVERE, "error while reading Caixa by date: {0}", e.getMessage()); 
    } 
    return result; 
} 

ビジネスロジックはこのようになりますこの方法：

public void createCaixaIfNotExist(long timestamp, double valorDaVenda) { 
    if (caixaDao.getCaixaByDate(timestamp) == null) { 
     Caixa newCaixa = new Caixa(); 
     newCaixa.setTimestamp(timestamp); 
     newCaixa.setValorTotal(valorDaVenda); 
     caixaDao.createCaixa(newCaixa); 
    } 
}