創建組件：

Servlet

public class TxServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("hello txjava");
    }
}

Filter

public class TxFilter implements Filter {
    @Override
    
 
public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("執行前");
        filterChain.doFilter(servletRequest, servletResponse);
        System.out.println(
 
"執行後");
    }

    @Override
    public void destroy() {

    }
}

Listener

public class TxListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("web容器啟動了");
    }

    @Override
    
 
public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

註冊：

@Configuration
public class WebConfig {

    @Bean
    public ServletRegistrationBean<TxServlet> getTxServlet(){
        ServletRegistrationBean<TxServlet> txs = new ServletRegistrationBean<>(new TxServlet());
        txs.setUrlMappings(Arrays.asList("/servlet/servlet1"));
        return txs;
    }

    @Bean
    public FilterRegistrationBean<TxFilter> getFilter(){
        FilterRegistrationBean<TxFilter> filter = new FilterRegistrationBean<TxFilter>();
        filter.setFilter(new TxFilter());
        filter.setUrlPatterns(Arrays.asList("/book/filter"));
        return filter;
    }

    @Bean
    public ServletListenerRegistrationBean<TxListener> getListener(){
        ServletListenerRegistrationBean<TxListener> listener = new ServletListenerRegistrationBean<>();
        listener.setListener(new TxListener());
        return listener;
    }
}

SpringBoot-註冊web三大組件