191122-SpringBoot系列教程web篇Servlet 注册的四种姿势

    org.springframework.boot
    spring-boot-starter-parent
    2.2.1.RELEASE
     



    UTF-8
    UTF-8
    1.8



    
        org.springframework.boot
        spring-boot-starter-web
    



    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    


    
        spring-snapshots
        Spring Snapshots
        https://repo.spring.io/libs-snapshot-local
        
            true
        
    
    
        spring-milestones
        Spring Milestones
        https://repo.spring.io/libs-milestone-local
        
            false
        
    
    
        spring-releases
        Spring Releases
        https://repo.spring.io/libs-release-local
        
            false
        
    

/**
 * 使用注解的方式来定义并注册一个自定义Servlet
 * Created by @author yihui in 19:08 19/11/21.
 */
@WebServlet(urlPatterns = "/annotation")
public class AnnotationServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("name");
        PrintWriter writer = resp.getWriter();
        writer.write("[AnnotationServlet] welcome " + name);
        writer.flush();
        writer.close();
    }
}

@ServletComponentScan
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class);
    }
}

➜  ~ curl http://localhost:8080/annotation\?name\=yihuihui
# 输出结果
[AnnotationServlet] welcome yihuihui%

/**
 * Created by @author yihui in 19:17 19/11/21.
 */
public class RegisterBeanServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("name");
        PrintWriter writer = resp.getWriter();
        writer.write("[RegisterBeanServlet] welcome " + name);
        writer.flush();
        writer.close();
    }
}

@Bean
public ServletRegistrationBean servletBean() {
    ServletRegistrationBean registrationBean = new ServletRegistrationBean();
    registrationBean.addUrlMappings("/register");
    registrationBean.setServlet(new RegisterBeanServlet());
    return registrationBean;
}

➜  ~ curl 'http://localhost:8080/register?name=yihuihui'
# 输出结果
[RegisterBeanServlet] welcome yihuihui%

/**
 * Created by @author yihui in 19:49 19/11/21.
 */
public class ContextServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("name");
        PrintWriter writer = resp.getWriter();
        writer.write("[ContextServlet] welcome " + name);
        writer.flush();
        writer.close();
    }
}


/**
 * Created by @author yihui in 19:50 19/11/21.
 */
@Component
public class SelfServletConfig implements ServletContextInitializer {
    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        ServletRegistration initServlet = servletContext.addServlet("contextServlet", ContextServlet.class);
        initServlet.addMapping("/context");
    }
}

➜  ~ curl 'http://localhost:8080/context?name=yihuihui'
# 输出结果
[ContextServlet] welcome yihuihui%

@Component
public class BeanServlet1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("name");
        PrintWriter writer = resp.getWriter();
        writer.write("[BeanServlet1] welcome " + name);
        writer.flush();
        writer.close();
    }
}

// org.springframework.boot.web.servlet.ServletContextInitializerBeans#addAsRegistrationBean(org.springframework.beans.factory.ListableBeanFactory, java.lang.Class, java.lang.Class, org.springframework.boot.web.servlet.ServletContextInitializerBeans.RegistrationBeanAdapter)

@Override
public RegistrationBean createRegistrationBean(String name, Servlet source, int totalNumberOfSourceBeans) {
    String url = (totalNumberOfSourceBeans != 1) ? "/" + name + "/" : "/";
    if (name.equals(DISPATCHER_SERVLET_NAME)) {
        url = "/"; // always map the main dispatcherServlet to "/"
    }
    ServletRegistrationBean bean = new ServletRegistrationBean<>(source, url);
    bean.setName(name);
    bean.setMultipartConfig(this.multipartConfig);
    return bean;
}