Spring boot servlet,filter,Listener,Interceptor

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文章目录

Spring boot servlet,filter,Listener,Interceptor

上一节

Spring boot restTemplate

源码

源码地址


Spring boot 使用servlet

第一种方式:使用注解@WebServlet

@WebServlet 是java Servlet 3.0 提供的注解,标注在类上声明这是一个servlet, 类需要继承servlet

使用示例

@WebServlet(value = "/test/servlet", name = "myServlet1", asyncSupported = true,
        loadOnStartup = 0,
        initParams = 
        @WebInitParam(name = "param1", value = "value1")
)
public class MyServlet1 extends HttpServlet 

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
        System.out.println("reqeust myServlet1");
        // 获取 init-param
        String param1 = getServletConfig().getInitParameter("param1");
        System.out.println("myServlet1  listener = " + getServletContext().getAttribute("myListener"));
        super.service(req, resp);
    

属性简介
@WebServlet 中的每个属性都基本对应我们在web.xml中的配置

属性web.xml备注
name<servlet-name>servlet 名称
value<url-pattern>匹配的url
urlPatterns<url-pattern>匹配的url正则,和value必须二选一有值
loadOnStartup<load-on-startup>启动加载顺序
initParams<init-param>初始化参数
description<description>描述
displayName<display-name>显示的名称
    <servlet>
        <servlet-name></servlet-name>
        <servlet-class></servlet-class>
        <init-param>
            <param-name></param-name>
            <param-value></param-value>
        </init-param>
        <description></description>
        <load-on-startup></load-on-startup>
        <async-supported></async-supported>
    </servlet>
    <servlet-mapping>
        <servlet-name></servlet-name>
        <url-pattern></url-pattern>
    </servlet-mapping>

若在springboot 项目中使用的 嵌入Web容器;则需要使用@ServletComponentScan 扫描;
@WebFilter 过滤器和@WebLIstener 监听器使用同理也需要扫描

@SpringBootApplication
@ServletComponentScan(value = "com.xiaodu.servlet", "com.xiaodu.filter", "com.xiaodu.listener")
public class StartApplication 

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


第二种方式:使用spring 提供的方式ServletRegistrationBean

在配置类中加入ServletRegistrationBean ; 即可使用

   @Bean
    public ServletRegistrationBean<MyServlet2> servletRegistrationBean() 
        ServletRegistrationBean<MyServlet2> servletRegistrationBean = new ServletRegistrationBean<>();
        servletRegistrationBean.setServlet(new MyServlet2()); // 设置servlet
        servletRegistrationBean.addUrlMappings("/test/servlet2"); // url
        servletRegistrationBean.setLoadOnStartup(0); // 启动加载顺序
        servletRegistrationBean.setAsyncSupported(true); // 是否支持异步
        servletRegistrationBean.setName("myServlet2"); // servlet-name
        // init-param
        Map<String, String> initParam = new HashMap<>();
        initParam.put("param", "value");
        servletRegistrationBean.setInitParameters(initParam);
        return servletRegistrationBean;
    

spring boot 使用 filter

第一种方式:注解 @WebFilter

@webFilter 标注在类上,类需要继承Filter 实现doFilter 方法

@WebFilter(value = "/test/*", filterName = "myServletFilter1",
        initParams =
        @WebInitParam(name = "filer1", value = "filer1-Value")
        
)
public class MyServletFilter1 implements Filter 
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException 
        System.out.println("myFilter 1");

        chain.doFilter(request, response);
    

    @Override
    public void init(FilterConfig filterConfig) throws ServletException 
        String filer1 = filterConfig.getInitParameter("filer1");
        System.out.println("myFilter1 initParam = " + filer1);
    


属性简介

属性web.xml备注
description<description>描述
displayName<display-name>显示名称
initParams<init-param>初始参数
filterName<filter-name>filter-name
servletNames<servlet-name>过滤那些servlet,通过servletName指定
value</url-pattern>url
urlPatterns</url-pattern>url
asyncSupported<async-supported>是否支持异步
 <filter>
        <filter-name></filter-name>
        <filter-class></filter-class>
        <async-supported></async-supported>
        <description></description>
        <init-param>
            <param-name></param-name>
            <param-value></param-value>
        </init-param>
        <display-name></display-name>
    </filter>
    <filter-mapping>
        <filter-name></filter-name>
        <url-pattern></url-pattern>
        <servlet-name></servlet-name>
    </filter-mapping>

第二种方式: 使用 FilterRegistrationBean

    @Bean
    public FilterRegistrationBean<MyServletFilter2> filterRegistrationBean() 
        FilterRegistrationBean<MyServletFilter2> registrationBean = new FilterRegistrationBean<>();
        registrationBean.setFilter(new MyServletFilter2());
        // 指定过滤路径
        registrationBean.addUrlPatterns("/test/*");
        // 指定过滤servletRegistrantionBean
//        registrationBean.addServletRegistrationBeans(servletRegistrationBean());// 可以过滤那个servlet
        // 指定过滤servlet
//        registrationBean.addServletNames("myServlet2");
        // init filter param
        registrationBean.addInitParameter("filter2", "filter2-value");
        return registrationBean;
    

spring boot 使用 Listener

第一种方式:注解@WebListener

@WebListener(value = "testListener")
public class MyServletContentListener implements ServletContextListener 

    private ServletContext servletContext;

    @Override
    public void contextInitialized(ServletContextEvent sce) 
        System.out.println("listener init");
        this.servletContext = sce.getServletContext();
        servletContext.setAttribute("myListener", "attribute");
    

    @Override
    public void contextDestroyed(ServletContextEvent sce) 
        System.out.println("listener destroy");
    

第二种方式:spring 提供的ServletListenerRegistrationBean

   @Bean
    public ServletListenerRegistrationBean<MyServletContentListener2> servletListenerRegistrationBean() 
        ServletListenerRegistrationBean<MyServletContentListener2> servletListenerRegistrationBean = new ServletListenerRegistrationBean<>();
        servletListenerRegistrationBean.setListener(new MyServletContentListener2());
        return servletListenerRegistrationBean;
    

springboot 使用interceptor

interceptor 是spring 提供的拦截器,作用类似servlet Filter 的作用;不过他们使命不相同; filter 对 request 和 response 进行过滤任务,例如字符集设置; interceptor 则是更进一步能够拦截到具体方法执行前,可以对方法中的参数进行校验和权限认证等

创建拦截器

@Component
public class MyInterceptor1 implements HandlerInterceptor 

    // 方法执行前拦截
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception 
        System.out.println("interceptor preHandle");
        return true;
    

    // 方法处理后拦截
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception 
        System.out.println("interceptor postHandle");

    

    // 处理完成后,报错不报错都走
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception 
        System.out.println("interceptor afterCompletion");
    

加入和配置拦截器

@Configuration
public class WebMvcConfig implements WebMvcConfigurer 

    @Autowired
    @Qualifier("myInterceptor1")
    private HandlerInterceptor handlerInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) 
    // 添加拦截器
        registry.addInterceptor(handlerInterceptor)
        // 拦截url 配置
                .addPathPatterns("/test/**");

    

filer 和 interceptor 的区别和执行顺序

区别:
filter:
1. filter 是Java提供的servlet 技术规范中的;是在servlet 前后执行;是一种函数回调
interceptor:
interceptor 是 spring 框架提供的基于aop 和Java反射机制在方法执行前后进行拦截;

执行顺序:
filter前 -> interceptor.preHandle -> servlet(controller) -> interceptor.postHandle -> filter后


下一节

Spring boot test

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