How to add a filter in Spring Boot

Spring-Boot/spring-boot-example/.gitignore

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+/target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/build/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/

Spring-Boot/spring-boot-example/pom.xml

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+<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.javadevjournal</groupId>
+    <artifactId>spring-boot-example</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <packaging>jar</packaging>
+
+    <name>spring-boot-example</name>
+    <description>Spring Boot Generic examples</description>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.0.3.RELEASE</version>
+        <relativePath/> <!-- lookup parent from repository -->
+    </parent>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+        <java.version>1.8</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>

Spring-Boot/spring-boot-example/src/main/java/com/javadevjournal/SpringBootExampleApplication.java

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+package com.javadevjournal;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SpringBootExampleApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(SpringBootExampleApplication.class, args);
+    }
+}

Spring-Boot/spring-boot-example/src/main/java/com/javadevjournal/config/AppConfig.java

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+package com.javadevjournal.config;
+
+import com.javadevjournal.filters.CustomURLFilter;
+import org.springframework.boot.web.servlet.FilterRegistrationBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class AppConfig {
+
+    @Bean
+    public FilterRegistrationBean<CustomURLFilter> filterRegistrationBean() {
+        FilterRegistrationBean<CustomURLFilter> registrationBean = new FilterRegistrationBean();
+        CustomURLFilter customURLFilter = new CustomURLFilter();
+
+        registrationBean.setFilter(customURLFilter);
+        registrationBean.addUrlPatterns("/greeting/*");
+        registrationBean.setOrder(2);  //set precedence
+        return registrationBean;
+    }
+}

Spring-Boot/spring-boot-example/src/main/java/com/javadevjournal/controller/FilterExampleController.java

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+package com.javadevjournal.controller;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class FilterExampleController {
+
+    @GetMapping
+    public String greeting(){
+        return "Hello World";
+    }
+
+    @GetMapping(value = "/greeting")
+    public String customGreetings(){
+        return "Hello From Custom Greetings";
+    }
+}

Spring-Boot/spring-boot-example/src/main/java/com/javadevjournal/filters/CustomFilter.java

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+package com.javadevjournal.filters;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
+
+import javax.servlet.*;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+@Configuration
+@Order(Ordered.HIGHEST_PRECEDENCE)
+public class CustomFilter implements Filter {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(CustomFilter.class);
+
+    @Override
+    public void init(FilterConfig filterConfig) throws ServletException {
+        LOGGER.info("########## Initiating Custom filter ##########");
+    }
+
+    @Override
+    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
+
+        HttpServletRequest request = (HttpServletRequest) servletRequest;
+        HttpServletResponse response = (HttpServletResponse) servletResponse;
+
+        LOGGER.info("Logging Request  {} : {}", request.getMethod(), request.getRequestURI());
+
+        //call next filter in the filter chain
+        filterChain.doFilter(request, response);
+
+        LOGGER.info("Logging Response :{}", response.getContentType());
+    }
+
+    @Override
+    public void destroy() {
+        // TODO: 7/4/18
+    }
+}

Spring-Boot/spring-boot-example/src/main/java/com/javadevjournal/filters/CustomURLFilter.java

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+package com.javadevjournal.filters;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.servlet.*;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+public class CustomURLFilter implements Filter {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(CustomURLFilter.class);
+
+    @Override
+    public void init(FilterConfig filterConfig) throws ServletException {
+        LOGGER.info("########## Initiating CustomURLFilter filter ##########");
+    }
+
+    @Override
+    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
+
+        HttpServletRequest request = (HttpServletRequest) servletRequest;
+        HttpServletResponse response = (HttpServletResponse) servletResponse;
+
+        LOGGER.info("This Filter is only called when request is mapped for /customer resource");
+
+        //call next filter in the filter chain
+        filterChain.doFilter(request, response);
+    }
+
+    @Override
+    public void destroy() {
+
+    }
+}

Spring-Boot/spring-boot-example/src/test/java/com/javadevjournal/SpringBootExampleApplicationTests.java

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+package com.javadevjournal;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class SpringBootExampleApplicationTests {
+
+    @Test
+    public void contextLoads() {
+    }
+
+}