JSP details-New Features of Servlet3.0

JSP details-New Features of Servlet3.0
Added comments for new features of Servlet3.0

Through annotations, you do not need to configure Servlet or filter in web. xml. Comments added to Servlet3.0 include @ WebServlet, @ WebListener, and @ WebInitParam. The following describes

1. @ WebServlet

@ WebServlet annotation is used to define Servlet components before Servlet class declaration. With this annotation, you do not need to configure the Servlet in web. xml. @ Attributes of WebServlet Annotations:

Attribute name	Type	Description
Name	String	Specify the Servlet name attribute, which is equivalent . If no display is specified, the Servlet value is the fully qualified name of the class.
Value	String []	It is equivalent to the urlPatterns attribute, but the two cannot be used at the same time.
UrlPatterns	String []	Specifies the URL matching mode for a group of servlets. Equivalent Tag
LoadOnStartup	Int	Specify the Servlet loading sequence, which is equivalent Tag
InitParams	WebInitParam []	Specify a set of Servlet initialization parameters, which is equivalent Tag
AsyncSupported	Boolean	Specifies whether the Servlet supports asynchronous operations, which is equivalent
Description	String	Servlet description, equivalent Tag
DiaplayName	Sting	Servlet display name, usually used with tools, is equivalent Tag

2. @ WebFilter

@ WebFilter annotation is used to declare a filter. The annotation will be processed by the container during deployment, and the container will deploy the corresponding class as a filter according to the specific configuration. @ WebFilter attribute list:

Attribute name	Type	Description
FilterName	String	Specify the name attribute of the filter, which is equivalent
Value	Sring []	It is equivalent to the urlPatterns attribute, but the two cannot be used at the same time.
UrlPatterns	String []	Specify the URL matching mode of the filter, which is equivalent Tag
ServletNames	String []	Specify the Servlet to which the filter will apply. It is the value of the name attribute in @ WebServlet or in web. xml. Value
InitParams	WebInitParam []	Specifies the initialization parameters of a set of filters, which is equivalent Tag
AsyncSupported	Boolean	Whether the declared filter supports asynchronous operations is equivalent
Description	String	The description of the filter, which is equivalent
DisplayName	String	The display name of the filter, usually used with tools, is equivalent Tag
DispatcherTypes	DispatcherType	Specify the forwarding mode of the filter, including ASYNC/ERROR/FORWADR/INCLUDE/REQUEST

3. @ WebListener

This annotation is used to declare listeners and act as listener classes for various Web events in a given Web application context. You can use @ WebListener to mark a class that implements ServletContextListener/ServletContextAttributeListener/ServletRequestListner/ServletRequestAttributeListener/HttpSessionListener/HttpSessionAttributeListener. @ WebListener the annotation has a value attribute, which is an optional attribute used to describe listener information. You do not need to configure this annotation in web. xml. Tag

4. @ WebInitParam

This annotation is equivalent And Of Sub-tag. This annotation cannot be used independently. It must be used with @ WebServlet or @ WebFilter. This parameter is used to specify initialization parameters for the Servlet or filter. Attributes contained in the @ WebInitParam annotation:

Attribute name	Type	Optional	Description
Name	String	No	The name of the specified parameter, which is equivalent
Value	String	No	The value of the specified parameter, which is equivalent
Description	String	Yes	The parameter description is equivalent