Create custome filter in spring boot

Posted By : Rahbar Ali | 28-May-2018

Java

Sometimes we need to integrate some validation before request object goes to Controller.

So, in this case, we need Filter that invoke request object & perform some validation about data.

We are going to describe how to use a custom filter in spring boot.

The Spring give an interface Filter that has 3 methods. we will override both 3 methods because of its an interface.

destroy

doFilter - in this method we get request & response object of current request & perform our operation related to request object or (both) response

object.

init

package com.pkg.checkrequest;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CheckRequest implements Filter{

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {	
		HttpServletRequest httpRequest = (HttpServletRequest) servletRequest;
		HttpServletResponse httpResponse = (HttpServletResponse) servletResponse;
		System.out.println("httpRequest.getLocalAddr() "+httpRequest.getLocalAddr());
		filterChain.doFilter(httpRequest, httpResponse);
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
		
	}

	
}

In another class we will create bean of that class

Here we are creating a bean of class that given by spring & add URL of that controller that we want perform an operation of some kind of validation.

package com.pkg.configuration;

import javax.servlet.Filter;

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.pkg.checkrequest.CheckRequest;

@Configuration
public class FilterConfig {

	@Bean
	public FilterRegistrationBean<Filter> userSecurityFilterRegistartion() {
		CheckRequest checkRequest = new CheckRequest();
		FilterRegistrationBean<Filter> registration = new FilterRegistrationBean<>(checkRequest);
		registration.setFilter(checkRequest);
		registration.addUrlPatterns("/api/v1/*");
		return registration;
	}
}

In the above example, we are intercepting an HTTP request object.

if we want to add some kind of validation like token varify or adding cookies or check cookies or perform any operations before request object goes to controller

then we can intercept httpRequest object like above & perform our custom validation on above object & then pass that object into controller if our condition is verified in filter

otherwise we will stop that request in filter & give validation message from filter.

Thanks.