Question

如果发生异常，try-with-resources会关闭所有打开的资源吗？

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

即使它会抛出异常，它也会被关闭。

无论try语句是否完成，它都将被关闭通常或突然

参考： http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

Answer 2

是的，但不是在try块之外或在其正文内部（在资源声明之后）初始化的那些。

// 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(/*...*/);
}

^*当try-with-resources关闭Statement时，JDBC说该语句应该关闭它创建的ResultSet。所以它可能会被关闭，但这只是因为JDBC契约而不是因为尝试使用资源。

如果发生异常，try-with-resources会关闭资源吗？

2 个答案: