SpringBoot注册三大Web组件

我会带着你远行 2023-07-06 09:00 33阅读 0赞

### 文章目录 ###

*  一、SpringBoot 提供的方式
 *  二、Servlet3.0 提供的注解
 *  三、拦截器 interceptor 的使用
 *  四、使用拦截器解决跨域问题

# 一、SpringBoot 提供的方式 #

使用`@Bean`注解将组件添加到`Web`容器中

@Component
    public class WebComponentRegister { 
        
        /** * 注册servlet */
        @Bean
        public ServletRegistrationBean myServlet() { 
            ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(), "/myServlet");
            return registrationBean;
        }
        
         /** * 注册filter */
        @Bean
        public FilterRegistrationBean myFilter() { 
            FilterRegistrationBean registrationBean = new FilterRegistrationBean();
            registrationBean.setFilter(new MyFilter());
            registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
            return registrationBean;
        }
    
        /** * 注册listener */  
        @Bean
        public ServletListenerRegistrationBean myListener() { 
    	ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<>(new MyListener());
    	return registrationBean;
    	}
    }

# 二、Servlet3.0 提供的注解 #

主启动类上需要添加注解`@ServletComponentScan`扫描`Servlet3.0`注解

**① 注册 Servlet**

@WebServlet(name = "userServlet",urlPatterns = "/test/customs")
    public class UserServlet extends HttpServlet{ 
    
        @Override
        public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            resp.getWriter().print("custom sevlet");
            resp.getWriter().flush();
            resp.getWriter().close();
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            this.doGet(req, resp);
        }
    }

**② 注册 filter**

@WebFilter(urlPatterns = "/*",filterName = "TestFilter")
    public class TestFilter implements Filter { 
        /** * 容器初始化时调用 */
        @Override
        public void init(FilterConfig filterConfig) throws ServletException { 
            System.out.println("-------------init--------------");
        }
    
        /** * 拦截请求 */
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { 
            boolean flag = true;
            if (flag){ 
                filterChain.doFilter(servletRequest,servletResponse);
            }else { 
                //进行页面调用什么
                HttpServletResponse response = (HttpServletResponse) servletResponse;
                response.sendRedirect("/index.html");
            }
        }
    
        /** * 容器销毁时执行 */
        @Override
        public void destroy() { 
            System.out.println("-------------destory--------------");
        }
    }

**③ 注册 listener**

常用的监听器：`servletContextListener`、`httpSessionListener`、`servletRequestListener`

@WebListener
    public class RequestListener implements ServletRequestListener { 
    
        @Override
        public void requestDestroyed(ServletRequestEvent sre) { 
            // TODO Auto-generated method stub
            System.out.println("======requestDestroyed========");
        }
    
        @Override
        public void requestInitialized(ServletRequestEvent sre) { 
            System.out.println("======requestInitialized========");
    
        }

**④ 异常映射**

在`templates`目录下创建`error`目录，下面放`4XX`、`5XX`页面，对应的错误会对应；

**⑤ 视图控制器**

编写一个配置类继承`WebMvcConfigurerAdapter`，然后代码中编写：

registry.addViewController("/atguigu").setViewName("success");

# 三、拦截器 interceptor 的使用 #

实现HandlerInterceptor或者继承HandlerInterceptorAdapter

@Component
    public class AuthInterceptor extends HandlerInterceptorAdapter { 
    
        @Autowired
        UserService userService;
    
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { 		
            //这个handler可以被拦截请求的信息
            return true;
        }
    }lan

注册拦截器的方法见下：

**拦截器和过滤器的区别？**

*  **Filter**：`chain.doFileter(request,response);` **基于Servlet**
 *  **Interceptor**：`return true;`**SpringMVC提供**

# 四、使用拦截器解决跨域问题 #

创建并注册拦截器

@Component
    public class AllowOriginIntercepter extends HandlerInterceptorAdapter { 
    	@Override
    	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { 
    		response.addHeader("Access-Control-Allow-Origin", "*");
    		response.addHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    		return true;
    	}
    }

@Configuration
    	public class WebMvcConfiguration extends WebMvcConfigurerAdapter { 
    		@Autowired
    		AllowOriginIntercepter allowOriginIntercepter;
    		
    		@Override
    		public void addInterceptors(InterceptorRegistry registry) { 
    			registry.addInterceptor(allowOriginIntercepter).addPathPatterns("/**");
    			super.addInterceptors(registry);
    		}
    }