java - 清理 @RequestScoped 对象？

Question

我正在使用 guice-servlet (2.0) 在每个 HTTP 请求开始时注入(inject)一个数据库连接，但是我怎样才能知道请求何时结束以便关闭连接？

web.xml

<filter>
    <filter-name>Guice Filter</filter-name>
    <filter-class>com.google.inject.servlet.GuiceFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>Guice Filter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

GuiceServletContextListener

/**
 * Creates a new Database connection.
 */
@RequestScoped
@Provides
private Connection getConnection();

Answer 1

这在 Guice 2.0 中是不可能的。一种解决方法是注册一个自定义 servlet 监听器，在每个请求结束时关闭连接:

/**
 * Closes SQL connections at the end of an HTTP request.
 * 
 * @author Gili Tzabari
 */
public class ConnectionFilter implements Filter
{
    private final Injector injector;

    @Inject
    public ConnectionFilter(Injector injector)
    {
        this.injector = injector;
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException
    {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
                                             FilterChain chain)
        throws IOException, ServletException
    {
        Session session = injector.getInstance(Session.class);

        try
        {
            chain.doFilter(servletRequest, servletResponse);
        }
        finally
        {
            session.close();
        }
    }

    @Override
    public void destroy()
    {
    }
}