Java，ResultSet.close（），PreparedStatement.close（） - 为什么？ [英] Java, ResultSet.close(), PreparedStatement.close() -- what for?
问题描述
在我的网络应用程序中，我广泛使用数据库。
In my web-application, i make extensive use of a database.
我有一个抽象的servlet，所有需要数据库连接的servlet都继承。该抽象servlet创建一个数据库连接，调用抽象方法，它必须由继承的servlet来覆盖以执行其逻辑，然后关闭连接。我不使用连接池，因为我的应用程序将有非常有限数量的用户和操作。
I have an abstract servlet, from which all the servlets that need a database connection, inherit. That abstract servlet creates a database connection, calls the abstract method which must be overriden by the inheriting servlets to do their logic, and then closes the connection. I do not use connection pooling, because my application will have a very limited number of users and operations.
我的问题是，如果我没有关闭 ResultSet code> PreparedStatement s和语句是我的继承servlet创建的，如果 Connection
My question is, what's the worst that can happen if i don't ever close the ResultSets, PreparedStatements and Statements that my inheriting servlets create, if the Connections that create them are always closed?
推荐答案
注意：当一个Statement对象被关闭时，它的当前ResultSet对象（如果存在）也被关闭。
Note:When a Statement object is closed, its current ResultSet object, if one exists, is also closed.
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所以你不必担心关闭ResultSet，只要你总是及时关闭语句。
So you don't need to worry about closing ResultSets, as long as you always close Statements in a timely manner.
Connection＃close（）不作出相应的保证，但它确实说：
The javadoc for Connection#close() does not make a corresponding guarantee, but it does say:
立即释放此Connection对象的数据库和JDBC资源，而不是等待它们被自动释放。
Releases this Connection object's database and JDBC resources immediately instead of waiting for them to be automatically released.
您可能合理地认为这意味着任何语句将被关闭。查看开源的jTDS驱动程序，并查看一个知名和昂贵的商业数据库的驱动程序，我可以看到他们做到了这一点。
Which you might reasonably construe as implying that any statements will be closed. Looking at the open-source jTDS driver, and peeking into the driver for a well-known and expensive commercial database, i can see that they do exactly that.
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