This article describes the functions and simple usage of jsp filter. Share it for your reference, as follows:
What is the function of a filter?
Filters can dynamically intercept requests and responses to transform or use information contained in the request or response.
One or more filters can be attached to a Servlet or a group of Servlets. Filters can also be attached to JavaServer Pages (JSP) files and HTML pages.
- Intercept the client's requests before accessing the backend resource.
- Process these responses before the server's response is sent back to the client.
The filter implementation needs to implement this interface class
A simple filter class example
package demo;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
public class DemoFilter implements Filter
{
private String name=null;
@Override
public void destroy()
{
}
@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException
{
("name", "init text string : " + name);
(arg0, arg1);
}
@Override
public void init(FilterConfig arg0) throws ServletException
{
//Get the configuration in filter init-param name = ("name");
}
}
Just writing this filter class is not OK. We want to declare which requests require filter calls
<!--Declare afilter-->
<filter>
<!--filterName of-->
<filter-name>demoFilter</filter-name>
<!--filter kind-->
<filter-class></filter-class>
<!--Shouldfilterkind需要的配置-->
<init-param>
<param-name>name</param-name>
<param-value>my name is tanyong</param-value>
</init-param>
</filter>
<!--forurl-pattern Matched inurlLink Map to correspondingfilter filter pass filter-nameTo identify-->
<filter-mapping>
<filter-name>demoFilter</filter-name>
<!--Match mapping rules，I'm using all requests heredemoFilter filter Go around inside-->
<url-pattern>/*</url-pattern>
</filter-mapping>
I hope this article will be helpful to everyone's jsp programming.