java.sql.SQLException：连接已关闭 [POOL-HikariCP]

Question

您好，我的连接有问题，它在执行查询时正在关闭连接。我不知道会发生什么 D: 这是配置：

private static HikariDataSource Hikari;
public static String ID_Usuario;

public void connectToDatabase() {       

    Hikari = new HikariDataSource();       
    Hikari.setDriverClassName("com.mysql.jdbc.Driver");
    Hikari.setJdbcUrl("jdbc:mysql://localhost:3306/bank");
    Hikari.setUsername("root");
    Hikari.setPassword(""); 
    Hikari.setMaximumPoolSize(5);
    Hikari.setConnectionTimeout(300000);
    Hikari.addDataSourceProperty("cachePrepStmts", "true");
    Hikari.addDataSourceProperty("prepStmtCacheSize", "250");
    Hikari.addDataSourceProperty("prepStmtCacheSqlLimit", "2048");
    Hikari.setConnectionTestQuery("SELECT 1");
}

public HikariDataSource getHikari(){
    return Hikari;
}

现在，这是我使用池的类，首先我收到了来自 Hikari.getConnection() 的连接。然后我把它保存在“连接”中

Pool HikariPool;
HikariDataSource Hikari;
Connection connection;

  public SQL() {
    initComponents();
  }

    public void initComponents(){
        HikariPool= new Pool();
        HikariPool.connectToDatabase();

    Hikari=HikariPool.getHikari();

    try{
       connection= Hikari.getConnection();
    }catch(SQLException e){
        e.printStackTrace();
    }
}

我在 validateLogin() 中使用“连接”

public int validateLogin(String nip){
   int validation=0;
   String SQL="SELECT * FROM bank.account WHERE No_Account='"+account+"'   
    AND NIP='"+nip+"'";
    try{
        Statement stm=Conexion.createStatement();
        ResultSet rs= stm.executeQuery(SQL);
...

在“语句 stm=connection.createStatement();”行发生错误

上面写着：

[AWT-EventQueue-0] INFO com.zaxxer.hikari.HikariDataSource - HikariPool-0  
- is starting.
java.sql.SQLException: Connection is closed at   
com.zaxxer.hikari.pool.ProxyConnection$ClosedConnection$1.invoke
(ProxyConnection.java:468)
at com.sun.proxy.$Proxy0.createStatement(Unknown Source)...

为什么要关闭连接？

Answer 1

您的代码结构对我来说还不是很清楚。但我认为您不想在initComponents() 中分配连接。当您需要运行查询时，您应该获取一个 Connection，然后将其关闭以将其返回到池中。

类似...

public int validateLogin(String nip) {
   int validation=0;
   String SQL="SELECT * FROM bank.account WHERE No_Account='"+account+"'   
    AND NIP='"+nip+"'";
    try (Connection conn = SQL.getConnection();
         Statement stm = conn.createStatement()) {
       ResultSet rs = stm.executeQuery(SQL);
       ...
    }
    catch (SQLException e) {
       ...
    }

“try with resources”会自动关闭连接和语句。

SQL.getConnection() 在哪里做了类似的事情：

public Connection getConnection() throws SQLException {
   return Hikari.getConnection();
}