How to use Servlet in SpringBoot

1. Method 1 (using annotations)

First, we write a Servlet. The requirement is to simply print a sentence.

Use the @WebServlet annotation above the MyServlet class to create a Servlet.

package com.songzihao.springboot.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
/**
 *
 */
@WebServlet(urlPatterns = "/myservlet")
public class MyServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().println("My SpringBoot Servlet-1");
        resp.getWriter().flush();
        resp.getWriter().close();
    }
 
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

Then use the annotation @ServletComponentScan annotation above the entry class of the SpringBoot project to scan the annotations in the Servlet.

package com.songzihao.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
 
@SpringBootApplication //开启spring配置
@ServletComponentScan(basePackages = "com.songzihao.springboot.servlet")
public class Application {
 
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Finally start the test.

#2. Method 2 (define configuration class)

Still write a Servlet first. No annotations are used this time.

package com.songzihao.springboot.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
/**
 *
 */
public class MyServlet extends HttpServlet {
 
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().println("My SpringBoot Servlet-2");
        resp.getWriter().flush();
        resp.getWriter().close();
    }
 
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

Then write a configuration class! ! !

The @Configuration annotation is used above this class. The table name of this class is a configuration class, which is equivalent to various previous xml configuration files.

Use the @Bean annotation above the method in the class. ServletRegistrationBean is equivalent to a Servlet registration class, similar to the previous and tags.

package com.songzihao.springboot.config;
import com.songzihao.springboot.servlet.MyServlet;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
/**
 *
 */
@Configuration //该注解将此类定义为一个配置类（相当于一个xml配置文件）
public class ServletConfig {
 
    /**
     * @Bean 是一个方法级别上的注解，主要用在配置类里
     * 相当于一个 <beans>
     *              <bean id="..." class="..." />
     *          </beans>
     * @return
     */
    @Bean
    public ServletRegistrationBean myServletRegistrationBean() {
        ServletRegistrationBean servletRegistrationBean=new ServletRegistrationBean(
                new MyServlet(),"/myservlet"
        );
        return servletRegistrationBean;
    }
}

Finally start the test.

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

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