Spring Boot - Servlet Filter

---

---

A filter is an object used to filter 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
• Before sending a response to the client.

The following code shows the sample code for a Servlet Filter implementation class with @Component annotation.

@Component
public class SimpleFilter implements Filter {
   @Override
   public void destroy() {}

   @Override
   public void doFilter
      (ServletRequest request, ServletResponse response, FilterChain filterchain) 
      throws IOException, ServletException {}

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

Example - Usage of Filter

The following example shows the code for reading the remote host and remote address from the ServletRequest object before sending the request to the controller.

In doFilter() method, we have added the System.out.println statements to print the remote host and remote address.

SimpleFilter.java

package com.tutorialspoint.demo;

import java.io.IOException;

import jakarta.servlet.Filter;
import jakarta.servlet.FilterChain;
import jakarta.servlet.FilterConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;

import org.springframework.stereotype.Component;

@Component
public class SimpleFilter implements Filter {
   @Override
   public void destroy() {}

   @Override
   public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterchain) 
      throws IOException, ServletException {
      
      System.out.println("Remote Host:"+request.getRemoteHost());
      System.out.println("Remote Address:"+request.getRemoteAddr());
      filterchain.doFilter(request, response);
   }

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

In the Spring Boot main application class file, we have added the simple REST endpoint that returns the "Welcome to Tutorialspoint!" string.

DemoApplication.java

package com.tutorialspoint.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class DemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
   }
   @GetMapping(value = "/")
   public String hello() {
      return "Welcome to Tutorialspoint!";
   }
}

The code for Maven build pom.xml is given below −

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
   <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>3.5.6</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.tutorialspoint</groupId>
   <artifactId>demo</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>demo</name>
   <description>Demo project for Spring Boot</description>
   <url/>
   <licenses>
      <license/>
   </licenses>
   <developers>
      <developer/>
   </developers>
   <scm>
      <connection/>
      <developerConnection/>
      <tag/>
      <url/>
   </scm>
   <properties>
      <java.version>21</java.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>
   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>
</project>

The code for Gradle Build build.gradle is given below −

build.gradle

buildscript {
   ext {
      springBootVersion = '3.5.6'
   }
   repositories {
      mavenCentral()
   }
   dependencies {
      classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
   }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'

group = 'com.tutorialspoint'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 21

repositories {
   mavenCentral()
}
dependencies {
   compile('org.springframework.boot:spring-boot-starter-web')
   testCompile('org.springframework.boot:spring-boot-starter-test')
}

You can create an executable JAR file, and run the Spring Boot application by using the Maven or Gradle commands shown below −

For Maven, use the command as shown below −

mvn clean install

After BUILD SUCCESS, you can find the JAR file under the target directory.

For Gradle, use the command as shown below −

gradle clean build

After BUILD SUCCESSFUL, you can find the JAR file under the build/libs directory.

Now, run the JAR file by using the following command

java jar <JARFILE> 

You can see the application has started on the Tomcat port 8080.

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

 :: Spring Boot ::                (v3.5.6)

[2025-09-28T16:32:58Z] [org.springframework.boot.StartupInfoLogger] [main] [53] [INFO ] Starting DemoApplication using Java 21.0.6 with PID 41312 (D:\Projects\demo\target\classes started by mahes in D:\Projects\demo)
[2025-09-28T16:32:58Z] [org.springframework.boot.SpringApplication] [main] [652] [INFO ] No active profile set, falling back to 1 default profile: "default"
[2025-09-28T16:32:59Z] [org.springframework.boot.web.embedded.tomcat.TomcatWebServer] [main] [111] [INFO ] Tomcat initialized with port 8080 (http)
[2025-09-28T16:32:59Z] [org.apache.juli.logging.DirectJDKLog] [main] [168] [INFO ] Initializing ProtocolHandler ["http-nio-8080"]
[2025-09-28T16:32:59Z] [org.apache.juli.logging.DirectJDKLog] [main] [168] [INFO ] Starting service [Tomcat]
[2025-09-28T16:32:59Z] [org.apache.juli.logging.DirectJDKLog] [main] [168] [INFO ] Starting Servlet engine: [Apache Tomcat/10.1.46]
[2025-09-28T16:32:59Z] [org.apache.juli.logging.DirectJDKLog] [main] [168] [INFO ] Initializing Spring embedded WebApplicationContext
[2025-09-28T16:32:59Z] [org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext] [main] [301] [INFO ] Root WebApplicationContext: initialization completed in 1162 ms
[2025-09-28T16:33:00Z] [org.apache.juli.logging.DirectJDKLog] [main] [168] [INFO ] Starting ProtocolHandler ["http-nio-8080"]
[2025-09-28T16:33:00Z] [org.springframework.boot.web.embedded.tomcat.TomcatWebServer] [main] [243] [INFO ] Tomcat started on port 8080 (http) with context path '/'
[2025-09-28T16:33:00Z] [org.springframework.boot.StartupInfoLogger] [main] [59] [INFO ] Started DemoApplication in 2.177 seconds (process running for 2.722)

Now hit the URL http://localhost:8080/ and see the output Hello World. It should look as shown below −

Then, you can see the Remote host and Remote address on the console log as shown below −

Remote Host:0:0:0:0:0:0:0:1
Remote Address:0:0:0:0:0:0:0:1
Pre Handle method is Calling
Post Handle method is Calling
Request and Response is completed