如果發生異常，請嘗試使用資源關閉資源？

Question

如果發生異常，請嘗試使用資源關閉所有打開的資源？

private void insertUserInAccessTable(int user_id) throws SQLException { 
    final String sql = "bla bla"; 
    try(Connection con = ...; PreparedStatement ps = ...) { 
     ... 
     if(i==0) throw new SQLException(); 
    } 
} 

Answer 1

是的，但不是那些它的身體（在資源申報之後）。

// This connection is initialized beforehand and will not be 
// closed automatically by try-with-resources 
Connection conn = // ... 

// The statement WILL always be closed, exception or not, before exiting the try block 
try (Statement stmt = conn.createStatement()) 
{ 
    // This result set will NOT be closed (directly) by try-with-resources 
    ResultSet rs = stmt.executeQuery(/*...*/); 
} 

^*當試穿與資源關閉Statement，JDBC說，聲明應該關閉它創建的ResultSet。所以它可能會被封閉，但只是因爲JDBC合同而不是因爲試用資源。

Answer 2

即使它會拋出異常，它也會被關閉。

將不管封閉的try語句是否完成 正常或突然

參考：這是try塊或內外部的初始化 http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html