On this page, we'll look at an example of a Spring Boot Servlet mapping. Servlet mapping can be achieved by using ServletRegistrationBean or by using @ServletComponentScan annotation of Spring Boot. The ServletRegistrationBean registers the Servlet as a Spring Bean. @ServletComponentScan scans Servlets annotated with @WebServlet. The annotation @ServletComponentScan only works with Spring Boot's built-in server. On this page, we will create two Servlets and one Spring Controller class. The following is an example of using Servlet in stages using ServletRegistrationBean and @ServletComponentScan.
pom.xml
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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.concretepage</groupId>
<artifactId>spring-boot-app</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>spring-boot-app</name>
<description>Spring Boot Application</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.3.RELEASE</version>
<relativePath/>
</parent>
<properties>
<java.version>9</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-devtools</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
The ServletRegistrationBean is used to register a Servlet in a Servlet 3.0 or later container. You need to create a Bean for the ServletRegistrationBean in JavaConfig. Find some methods of the ServletRegistrationBean used to configure the Servlet.
** setServlet () **: Set the Servlet to be registered. ** addUrlMappings () **: Add URL mappings for the Servlet. ** setLoadOnStartup **: Sets the priority for loading Servlets at startup.
I have two Servlets, HelloCountryServlet and HelloStateServlet, and I use the ServletRegistrationBean to register them in Spring Boot as follows:
WebConfig.java
package com.concretepage;
import javax.servlet.http.HttpServlet;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.concretepage.servlets.HelloCountryServlet;
import com.concretepage.servlets.HelloStateServlet;
@Configuration
public class WebConfig {
@Bean
public ServletRegistrationBean<HttpServlet> countryServlet() {
ServletRegistrationBean<HttpServlet> servRegBean = new ServletRegistrationBean<>();
servRegBean.setServlet(new HelloCountryServlet());
servRegBean.addUrlMappings("/country/*");
servRegBean.setLoadOnStartup(1);
return servRegBean;
}
@Bean
public ServletRegistrationBean<HttpServlet> stateServlet() {
ServletRegistrationBean<HttpServlet> servRegBean = new ServletRegistrationBean<>();
servRegBean.setServlet(new HelloStateServlet());
servRegBean.addUrlMappings("/state/*");
servRegBean.setLoadOnStartup(1);
return servRegBean;
}
}
Create a ServletRegistrationBean bean for all Servlets. The Servlets HelloCountryServlet and HelloStateServlet can be accessed using the URLs ** / country ** and ** / state **, respectively. Find the Servlet used in this example.
HelloCountryServlet.java
package com.concretepage.servlets;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloCountryServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
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();
out.println("<h3>Hello India!</h3>");
}
}
HelloStateServlet.java
package com.concretepage.servlets;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloStateServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
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();
out.println("<h3>Hello Uttar Pradesh!</h3>");
}
}
The controller used in this example.
HelloWorldController.java
package com.concretepage.controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloWorldController {
@RequestMapping("/world")
public String helloMsg() {
String msg = "Hello World!";
return msg;
}
}
Main class for launching applications.
SpringBootAppStarter.java
package com.concretepage;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class SpringBootAppStarter {
public static void main(String[] args) {
SpringApplication.run(SpringBootAppStarter.class, args);
}
}
Spring Boot's @ServletComponentScan scans @WebServlet-annotated Servlets, @WebFilter-annotated filters, and @WebListener-annotated Listeners. The annotation @ServletComponentScan is used at the JavaConfig class level. @ServletComponentScan scans Servlets, filters, and listeners only using an embedded web server. It is a Servlet with @WebServlet annotation.
HelloCountryServlet.java
package com.concretepage.servlets;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(urlPatterns = "/country/*", loadOnStartup = 1)
public class HelloCountryServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
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();
out.println("<h3>Hello India!</h3>");
}
}
HelloStateServlet.java
package com.concretepage.servlets;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(urlPatterns = "/state/*", loadOnStartup = 1)
public class HelloStateServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
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();
out.println("<h3>Hello Uttar Pradesh!</h3>");
}
}
You can use @ServletComponentScan as follows:
SpringBootAppStarter.java
package com.concretepage;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
@ServletComponentScan
@SpringBootApplication
public class SpringBootAppStarter {
public static void main(String[] args) {
SpringApplication.run(SpringBootAppStarter.class, args);
}
}
You can run the Spring Boot application in the following ways:
mvn spring-boot:run
mvn clean eclipse：eclipse
Click and then update the project in eclipse. Click Run as-> Java Application to run the main class SpringBootAppStarter. Then the Tomcat server is started.
mvn clean package
Get the executable JAR ** spring-boot-app-0.0.1-SNAPSHOT.jar ** in the target folder. Run this JAR as follows:
java -jar target / spring-boot-app-0.0.1-SNAPSHOT.jar
The Tomcat server is started.
Now you are ready to test your application.
The URL to execute HelloCountryServlet.
http://localhost:8080/country
The URL to execute HelloStateServlet.
http://localhost:8080/state
The URL to execute the HelloWorldController method.
http://localhost:8080/world
Spring Boot Reference Guide ServletRegistrationBean ＠ServletComponentScan
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