DriverManagerDataSource in Spring Framework

javax.sql Interface DataSource

今天看了一天的spring,想使用里面提供的JdbcTemplate，看上去非常酷的样子，不过其中涉及到了一个DataSource接口，不知道干嘛的，好不容易才找到了一个讲的比较清楚的解释。

Implementation of SmartDataSource that configures a plain old JDBC Driver via bean properties, and returns a new Connection every time.

Useful for test or standalone environments outside of a J2EE container, either as a DataSource bean in a respective ApplicationContext, or in conjunction with a simple JNDI environment. Pool-assuming Connection.close() calls will simply close the connection, so any DataSource-aware persistence code should work.

In a J2EE container, it is recommended to use a JNDI DataSource provided by the container. Such a DataSource can be exported as a DataSource bean in an ApplicationContext via JndiObjectFactoryBean, for seamless switching to and from a local DataSource bean like this class.

If you need a “real” connection pool outside of a J2EE container, consider Apache’s Jakarta Commons DBCP. Its BasicDataSource is a full connection pool bean, supporting the same basic properties as this class plus specific settings. It can be used as a replacement for an instance of this class just by changing the class name of the bean definition to “org.apache.commons.dbcp.BasicDataSource”.

HTTP State Management Mechanism

STATE AND SESSIONS

This document describes a way to create stateful sessions with HTTP requests and responses. Currently, HTTP servers respond to each client request without relating that request to previous or subsequent requests; the technique allows clients and servers that wish to exchange state information to place HTTP requests and responses within a larger context, which we term a “session”. This context might be used to create, for example, a “shopping cart”, in which user selections can be aggregated before purchase, or a magazine browsing system, in which a user’s previous reading affects which offerings are presented.

There are, of course, many different potential contexts and thus many different potential types of session. The designers’ paradigm for sessions created by the exchange of cookies has these key attributes:

1. Each session has a beginning and an end.

2. Each session is relatively short-lived.

3. Either the user agent or the origin server may terminate a session.

4. The session is implicit in the exchange of state information.

Struts中谈到的session

2.2 JavaBeans and Scope

Within a web-based application, JavaBeans can be stored in (and accessed from) a number of different collections of “attributes”. Each collection has different rules for the lifetime of that collection, and the visibility of the beans stored there. Together, the rules defining lifetime and visibility are called the scope of those beans. The JavaServer Pages (JSP) Specification defines scope choices using the following terms (with the equivalent servlet API concept defined in parentheses):