What is filter what is its use list different filter interfaces with their important methods?

Asked By: Valerijus Zhang | Last Updated: 12th February, 2020
Category: technology and computing web development
4/5 (155 Views . 10 Votes)
It is mainly used to perform filtering tasks such as conversion, logging, compression, encryption and decryption, input validation etc.

1) Filter interface.
Method Description
public void init(FilterConfig config) init() method is invoked only once. It is used to initialize the filter.

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Correspondingly, what is the use of filter in Web XML?

Filters are used for filtering functionality of the Java web application. They manipulate the responses from the server and sent to the client.

Secondly, what is a filter chain? javax.servlet public interface FilterChain. A FilterChain is an object provided by the servlet container to the developer giving a view into the invocation chain of a filtered request for a resource.

Then, what is the sequence of method execution in filter?

This method is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain. This method is called by the web container to indicate to a filter that it is being placed into service.

How do I map a filter in Web XML?

The filter-mapping element maps a URL pattern or servlet name to an instance of a filter. The filter-mapping always contains a filter-name element and a url-pattern element. The filter-name element must match a filter-name defined in a filter element elsewhere in the web. xml file.

29 Related Question Answers Found

Why do we use filters?

A filter is a circuit capable of passing (or amplifying) certain frequencies while attenuating other frequencies. DC power supplies: Filters are used to eliminate undesired high frequencies (i.e., noise) that are present on AC input lines. Additionally, filters are used on a power supply's output to reduce ripple.

Why servlet filter is used?

Servlet Filter. A filter is an object that is invoked at the preprocessing and postprocessing of a request. It is mainly used to perform filtering tasks such as conversion, logging, compression, encryption and decryption, input validation etc. The servlet filter is pluggable, i.e. its entry is defined in the web.

What is JSP filter?

JSP Filters are Java classes that can be used for intercepting requests from a client or manipulating responses from server. The filters can be used to do Authentication, Encryption, Logging, Auditing. A filter is a Java class that implements the javax. servlet. Filter interface.

How can we configure the filter in Web application?

To configure a filter:
  1. Open the web. xml deployment descriptor in a text editor or use the Administration Console.
  2. Add a filter declaration.
  3. Specify one or more initialization attributes inside a <filter> element.
  4. Add filter mappings.
  5. To create a chain of filters, specify multiple filter mappings.

What is the difference between servlet and filter?


What is the difference between Servlet and Filter ? A filter is an object that can transform content and header of a request or response. Filter provides functionality which can be “attached” to any web resource. Filter serve different purpose and servlet serve different purpose.

What is HTTP filter?

HTTP Filter. HTTP filters help to limit the amount of output data. A filter can be created for a particular application, protocol and/or IP address.

How does servlet filter work?

The target servlet is requested. The container detects that there are two filters and creates the filter chain. The first filter in the chain is invoked by its doFilter() method. The first filter completes any preprocessing, then calls the doFilter() method of the filter chain.

What is Servlet listener?

Listener. Servlet Listener is used for listening to events in a web container, such as when you create a session or place an attribute in a session or if you passivate and activate in another container, to subscribe to these events you can configure listener in web. xml, for example, HttpSessionListener.

What is servlet filter with an example?

That's why we have a servlet filter. Servlet Filters are pluggable java components that we can use to intercept and process requests before they are sent to servlets and response after servlet code is finished and before container sends the response back to the client.

When filter destroy method is called?


destroy. public void destroy() The destroy method is called by the web container to indicate to a filter that it is being taken out of service. This method is only called once all threads within the filter's doFilter method have exited, or after a timeout period has passed.

What is filter servlet?

A Servlet filter is an object that can intercept HTTP requests targeted at your web application. A servlet filter can intercept requests both for servlets, JSP's, HTML files or other static content, as illustrated in the diagram below: A Servlet Filter in a Java Web Application.

What are Spring Filters?

Spring Boot - Servlet Filter. Advertisements. A filter is an object used to intercept the HTTP requests and responses of your application. By using filter, we can perform two operations at two instances − Before sending the request to the controller.

What does Chain doFilter do?

The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain. The FilterChain passed in to this method allows the Filter to pass on the request and response to the next entity in the chain.

What is authentication filter in MVC?

ASP.NET MVC filters are used to add extra logic at the different levels of MVC Framework request processing. Authentication Filter runs before any other filter or action method. Authentication confirms if you are a valid or invalid user.

What is dispatcher in filter mapping?


The dispatcher type of a request is used by the container to select the filters that need to be applied to the request: Only filters with matching dispatcher type and url patterns will be applied.

Which element declares a filter inside deployment descriptor?

Similar to servlets, you configure a filter in the deployment descriptor by declaring the filter with the <filter> element, then mapping it to a URL pattern with the <filter-mapping> element. You can also map filters directly to other servlets.

What is filters in Java?

A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both. Filters perform filtering in the doFilter method.