java web application without web.xml - servlets 3.0

javax-servlets-3/.gitignore

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+# Created by .ignore support plugin (hsz.mobi)
+.idea
+classes
+target
+*.iml
+out

javax-servlets-3/Dockerfile

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+FROM tomcat
+ADD ./target/javax-servlets-3-1.0-SNAPSHOT.war /usr/local/tomcat/webapps/

javax-servlets-3/README.md

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+## Build with maven:
+mvn package
+
+## Run with Tomcat on Docker container:
+docker build --tag my-tomcat .
+docker run -it --rm -p 8080:8080 my-tomcat
+
+### Relevant Articles:
+- [Java Web Application Without Web.xml]

javax-servlets-3/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>
+    <artifactId>javax-servlets-3</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <name>javax-servlets-3</name>
+    <packaging>war</packaging>
+    
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    
+    <dependencies>
+        <!-- Servlet -->
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>javax.servlet-api</artifactId>
+            <version>${javax.servlet-api.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-webmvc</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+    </dependencies>
+    <properties>
+        <javax.servlet-api.version>4.0.1</javax.servlet-api.version>
+        <spring.version>5.1.3.RELEASE</spring.version>
+    </properties>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-war-plugin</artifactId>
+                <version>3.1.0</version>
+                <executions>
+                    <execution>
+                        <id>default-war</id>
+                        <phase>prepare-package</phase>
+                        <configuration>
+                            <failOnMissingWebXml>false</failOnMissingWebXml>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

javax-servlets-3/src/main/java/com/baeldung/servlets3/spring/AppInitializer.java

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+package com.baeldung.servlets3.spring;
+
+import com.baeldung.servlets3.spring.config.AppConfig;
+import org.springframework.web.WebApplicationInitializer;
+import org.springframework.web.context.ContextLoaderListener;
+import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
+import org.springframework.web.servlet.DispatcherServlet;
+
+import javax.servlet.ServletContext;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRegistration;
+
+public class AppInitializer implements WebApplicationInitializer {
+    @Override
+    public void onStartup(ServletContext servletContext) throws ServletException {
+        AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
+        context.register(AppConfig.class);
+
+        servletContext.addListener(new ContextLoaderListener(context));
+
+        ServletRegistration.Dynamic dispatcher = servletContext.addServlet("spring-dispatcher",
+            new DispatcherServlet(context));
+
+        dispatcher.setLoadOnStartup(1);
+        dispatcher.addMapping("/spring/*");
+    }
+}

javax-servlets-3/src/main/java/com/baeldung/servlets3/spring/config/AppConfig.java

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+package com.baeldung.servlets3.spring.config;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+
+@Configuration
+@EnableWebMvc
+@ComponentScan("com.baeldung.servlets3.spring")
+public class AppConfig {
+}

javax-servlets-3/src/main/java/com/baeldung/servlets3/spring/controllers/UppercaseController.java

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+package com.baeldung.servlets3.spring.controllers;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping("/uppercase")
+public class UppercaseController {
+
+    @GetMapping(produces = "text/html")
+    public String getUppercase(@RequestParam(required = false)String param) {
+        String response = param != null ? param.toUpperCase() : "Missing param";
+        return "From Spring: " + response;
+    }
+}

javax-servlets-3/src/main/java/com/baeldung/servlets3/web/filters/EmptyParamFilter.java

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+package com.baeldung.servlets3.web.filters;
+
+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.annotation.WebFilter;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+@WebFilter(servletNames = { "uppercaseServlet" }, filterName = "emptyParamFilter")
+public class EmptyParamFilter implements Filter {
+
+    @Override
+    public void init(FilterConfig filterConfig) throws ServletException {
+    }
+
+    @Override
+    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
+        FilterChain filterChain) throws IOException, ServletException {
+        String inputString = servletRequest.getParameter("input");
+
+        if (inputString == null || inputString.isEmpty()) {
+            response(servletResponse);
+        } else {
+            filterChain.doFilter(servletRequest, servletResponse);
+        }
+    }
+
+    private void response(ServletResponse response) throws IOException {
+        response.setContentType("text/html");
+
+        PrintWriter out = response.getWriter();
+
+        out.println("Missing input parameter");
+    }
+
+    @Override
+    public void destroy() {
+    }
+
+}

javax-servlets-3/src/main/java/com/baeldung/servlets3/web/listeners/AppListener.java

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+package com.baeldung.servlets3.web.listeners;
+
+import javax.servlet.ServletContext;
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+import javax.servlet.annotation.WebListener;
+
+@WebListener
+public class AppListener implements ServletContextListener {
+
+    @Override
+    public void contextInitialized(ServletContextEvent event) {
+        ServletContext context = event.getServletContext();
+        context.setAttribute("counter", 0);
+    }
+
+    @Override
+    public void contextDestroyed(ServletContextEvent event) {
+
+    }
+}

javax-servlets-3/src/main/java/com/baeldung/servlets3/web/listeners/RequestListener.java

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+package com.baeldung.servlets3.web.listeners;
+
+import javax.servlet.ServletContext;
+import javax.servlet.ServletRequestEvent;
+import javax.servlet.ServletRequestListener;
+import javax.servlet.annotation.WebListener;
+import javax.servlet.http.HttpServletRequest;
+
+@WebListener
+public class RequestListener implements ServletRequestListener {
+
+    @Override
+    public void requestInitialized(ServletRequestEvent event) {
+    }
+
+    @Override
+    public void requestDestroyed(ServletRequestEvent event) {
+        HttpServletRequest request = (HttpServletRequest)event.getServletRequest();
+        if (!request.getServletPath().equals("/counter")) {
+            ServletContext context = event.getServletContext();
+            context.setAttribute("counter", (int)context.getAttribute("counter") + 1);
+        }
+    }
+}

javax-servlets-3/src/main/java/com/baeldung/servlets3/web/servlets/CounterServlet.java

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+package com.baeldung.servlets3.web.servlets;
+
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+@WebServlet(urlPatterns = "/counter", name = "counterServlet")
+public class CounterServlet extends HttpServlet {
+
+    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
+        doGet(request, response);
+    }
+
+    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
+        response.setContentType("text/html");
+
+        PrintWriter out = response.getWriter();
+
+        int count = (int)request.getServletContext().getAttribute("counter");
+
+        out.println("Request counter: " + count);
+    }
+
+}

javax-servlets-3/src/main/java/com/baeldung/servlets3/web/servlets/UppercaseServlet.java

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+package com.baeldung.servlets3.web.servlets;
+
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+@WebServlet(urlPatterns = "/uppercase", name = "uppercaseServlet")
+public class UppercaseServlet extends HttpServlet {
+
+    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
+        doGet(request, response);
+    }
+
+    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
+        String inputString = request.getParameter("input").toUpperCase();
+
+        response.setContentType("text/html");
+
+        PrintWriter out = response.getWriter();
+
+        out.println(inputString);
+    }
+}