SpringBoot-Web开发之Web原生组件注入

使用Servlet API

Web三大原生组件：Servlet、Filter、Listener
启动类上使用注解@ServletComponentScan(basePackages = "com.my.admin")
- 使用注解的方式注入，需要开启扫描
@WebServlet()
- 执行后会发现直接响应，没有经过Spring的拦截器

java 复制代码

//处理/my请求
@WebServlet(urlPatterns = "/my")
public class MyServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
                throws ServletException, IOException {
        resp.getWriter().write("66666");
    }
}

@WebFilter

java 复制代码

@Slf4j
//拦截所有请求在servlet中是/*，spring中是/**
@WebFilter(urlPatterns={"/css/*","/images/*"}) 
public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        log.info("MyFilter初始化完成");
    }

    @Override
    public void doFilter(ServletRequest request, 
                         ServletResponse response, 
                         FilterChain chain) throws IOException, ServletException {
        log.info("MyFilter工作");
        chain.doFilter(request,response);
    }

    @Override
    public void destroy() {
        log.info("MyFilter销毁");
    }
}

@WebListener

java 复制代码

@Slf4j
@WebListener
public class MyServletContextListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        log.info("MySwervletContextListener监听到项目初始化完成");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        log.info("MySwervletContextListener监听到项目销毁");
    }
}

RegistrationBean

不使用注解注入，使用配置类
ServletRegistrationBean
FilterRegistrationBean
ServletListenerRegistrationBean

java 复制代码

@Configuration(proxyBeanMethods = true)
public class MyRegistConfig {

    @Bean
    public ServletRegistrationBean myServlet(){

        MyServlet myServlet = new MyServlet();
        return new ServletRegistrationBean(myServlet,"/my","/my02");
    }

    @Bean
    public FilterRegistrationBean myFilter(){

        MyFilter myFilter = new MyFilter();
		//myServlet()可以将servlet处理的请求进行过滤
        //return new FilterRegistrationBean(myFilter,myServlet());

        FilterRegistrationBean filterRegistrationBean = 
									new FilterRegistrationBean(myFilter);
		//自定义过滤的路径
        filterRegistrationBean.setUrlPatterns(Arrays.asList("/my","/css/*"));
        return filterRegistrationBean;
    }

    @Bean
    public ServletListenerRegistrationBean myListener(){

        MySwervletContextListener mySwervletContextListener = 
									new MySwervletContextListener();
        return new ServletListenerRegistrationBean(mySwervletContextListener);
    }
}

DispatcherServlet注入原理

容器中自动配置了 DispatcherServlet，属性绑定到 WebMvcProperties；对应的配置文件配置项是 spring.mvc

通过ServletRegistrationBean把 DispatcherServlet 配置进来。默认映射的是以/开头的路径

多个Servlet都能处理到同一层路径，精确路径优先原则，故解释了上述自定义servlet直接响应，不经过spring