过滤器
实现过滤器需要实现 javax.servlet.Filter
接口。重写三个方法。其中 init()
方法在服务启动时执行,destroy()
在服务停止之前执行。
可用两种方式注册过滤器:
- 使用
FilterRegistrationBean
来注入。可使用setOrder(0)
设置过滤器的优先级,越小优先级越高。 - 使用
@WebFilter(filterName = "myFilter2" ,urlPatterns = "/*")
配合@ServletComponentScan()
实现注入。(@Order
注解无效)
编写过滤器
package com.example.recorddemo.filters; import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import java.io.IOException; public class MyFilter1 implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { System.out.println("初始化过滤器:" + filterConfig.getFilterName()); } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println("在请求之前做处理"); if (servletRequest instanceof HttpServletRequest) { System.out.println(" URL:" + ((HttpServletRequest)servletRequest).getRequestURL()); } // 调用filter链中的下一个filter filterChain.doFilter(servletRequest, servletResponse); System.out.println("在请求之后做处理"); } @Override public void destroy() { System.out.println("销毁:MyFilter1"); } }
注册过滤器
基于 FilterRegistrationBean
在配置类中注册一个 FilterRegistrationBean
类型的Bean。
- 如果没有设置
UrlPatterns
, 那么会自动关联到/*
上。 - 如果没有设置过滤器的名字,那么会自动推理出一个过滤器名称(bean的名字)
When no URL pattern or servlets are specified the filter will be associated to ‘/*’. The filter name will be deduced if not specified.
- fileter默认是enable的,将其设置为false表示关闭当前过滤器。
- 可通过
setOrder(0)
方法设置过滤器的优先级,如果优先级相同,则先定义的优先级更高。
@Configuration public class FilterConfiguration { @Bean public FilterRegistrationBean myFilter1(){ MyFilter1 filter = new MyFilter1(); FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(filter); // filterRegistrationBean.addUrlPatterns("/*"); // filterRegistrationBean.setEnabled(true); return filterRegistrationBean; } }
基于 @WebFilter
- 使用
@WebFilter
修饰filter。 - 在任意configuration类中添加
@ServletComponentScan("com.example.recorddemo.filters")
,包名可以不填。
import javax.servlet.*; import javax.servlet.annotation.WebFilter; import javax.servlet.http.HttpServletRequest; import java.io.IOException; @WebFilter(filterName = "myFilter2" ,urlPatterns = "/*") public class MyFilter2 implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException {} @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { // 调用filter链中的下一个filter filterChain.doFilter(servletRequest, servletResponse); } @Override public void destroy() {} }
拦截器
拦截器会在处理指定请求之前和之后进行相关操作,配置拦截器需要两步
- 编写拦截器类(实现
HandlerInterceptor
接口) - 添加已实现的拦截器(实现
WebMvcConfigurer
接口,并重写addInterceptors()
方法) - 添加
addPathPatterns()
规定拦截哪些请求。(/*
表示只拦截/
下的所有目录,但是不包括子目录,/**
表示拦截/
下的所有目录,及其子目录)
拦截器类:
package com.example.recorddemo.interceptor; import org.springframework.stereotype.Component; import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @author wangchao */ @Component public class MyInterceptor implements HandlerInterceptor { @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { // handle可拿到执行方法的反射对象。 System.out.println("preHandle: MyInterceptor"); return true; } @Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { // 对于RESTful 接口用处不大 } @Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { // 可捕捉异常,但是springboot已经有了全局异常捕捉 } }
配置拦截器:
package com.example.recorddemo.configuration; import com.example.recorddemo.interceptor.MyInterceptor; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.config.annotation.InterceptorRegistration; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; import javax.annotation.Resource; @Configuration public class InterceptorConfiguration implements WebMvcConfigurer { @Resource MyInterceptor myInterceptor; /** * 添加拦截器 * @param registry */ @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(myInterceptor).addPathPatterns("/**"); } }
registry.addInterceptor()
方法会返回当前的 interceptor
, 因此可直接执行 addPathPatterns()
方法
public InterceptorRegistration addInterceptor(HandlerInterceptor interceptor) { InterceptorRegistration registration = new InterceptorRegistration(interceptor); this.registrations.add(registration); return registration; }
拦截器的执行顺序类似于栈,按照如下顺序执行:
preHandle-1, preHandle-2, postHandle-2, postHandle-1, afterCompletion-2, afterCompletion-1
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