springboot中使用servlet原生相关功能

写在前面

本文介绍在springboot中使用servlet原生相关功能的方式，主要有两种：

• 注解方式
  这种方式依赖于@WebServlet，@WebFilter,@WebListner等注解，需要注意，这些注意是在servlet3.0为了实现无web.xm（注意：这是个人根据学习的猜测！！！）正式引入的，因此想要使用的话必须是servlet3.0及以上版本。
• bean configuration方式
  这种方式通过springboot的XXXBean完成相关组件的注册。

好的，那我们就正式开始吧！！！

1：项目创建

• ide
  我们最爱的idea。
• 构建工具
  曾经的王者，现在逐渐被gradle取代的maven。
• jdk
  至今还没有被后来者撼动地位的jdk8。
• springboot
  2.2.10.RELEASE。

1.1：new->project

选择左侧菜单中的Spring Initilizr，starter选择default。

1.2：录入GAV

根据个人录入GAV，选择java8，项目构建为`jar,等。

1.3：选择依赖

主要选择web下spring-web。springboot版本选择2.2.10。

1.4：finish

项目名称根据个人决定是否修改，正常不用管，和ArtifactId保持一致。

2：注解方式

2.1：定义servlet

@WebServlet("/user/servlet")
public class MyAnnotationServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        resp.getWriter().write("user servlet");
    }
}

2.2：定义filter

@WebFilter("/user/servlet")
public class MyAnnotationFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
        FilterChain filterChain) throws IOException, ServletException {
        System.out.println("income log filter " + servletRequest.getRemoteHost());
        filterChain.doFilter(servletRequest, servletResponse);
    }
}

2.3：定义servletcontextlistener监听器

@WebListener
public class MyAnnotationServletContextListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("app startup at " + LocalDateTime.now().toString());
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }
}

2.4：启动类增加@ServletComponentScan注解

@SpringBootApplication
@ServletComponentScan
public class SpringbootTestservletApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootTestservletApplication.class, args);
    }

}

2.5：启动并访问测试

• 启动

2020-09-29 15:36:38.732  INFO 4720 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1957 ms
app startup at 2020-09-29T15:36:38.791

• 访问测试
  

3：bean configuration方式

3.1：定义servlet

public class MyBeanConfigurationServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        resp.getWriter().write("this is springboot servlet by bean configuration");
    }
}

3.2：定义filter

public class MyBeanConfigurationFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
        FilterChain filterChain) throws IOException, ServletException {
        System.out.println("spring boot filter by bean configuration");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void init(FilterConfig filterConfig) {
    }

    @Override
    public void destroy() {
    }
}

3.3：定义servletcontextlistener

public class MyBeanConfigurationServletContextListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("springboot servlet context listener by bean configuration started!");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }
}

3.4：定义bean configuration

@SpringBootConfiguration
public class MyBeanConfiguration {

    // 注册servlet
    @Bean
    public ServletRegistrationBean createMyBeanConfigurationServlet() {
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(
            new MyBeanConfigurationServlet(), "/book.do");
        return servletRegistrationBean;
    }

    // 注册filter
    @Bean
    public FilterRegistrationBean createMyBeanConfigurationFilter() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(new MyBeanConfigurationFilter());
        filterRegistrationBean.setUrlPatterns(Arrays.asList("/book.do"));
        return filterRegistrationBean;
    }

    // 注册监听器
    @Bean
    public ServletListenerRegistrationBean createMyBeanConfigurationServletContextListener() {
        ServletListenerRegistrationBean servletListenerRegistrationBean = new ServletListenerRegistrationBean(new MyBeanConfigurationServletContextListener());
        return servletListenerRegistrationBean;
    }
}

3.5：启动并测试

• 启动

2020-09-29 15:57:18.374  INFO 18772 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1891 ms
springboot servlet context listener by bean configuration started!

• 测试
  

4：源码

点击这里。

最后：都让开，我要喝瑞幸