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：
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。@WebFilter(filterName = "myFilter2" ,urlPatterns = "/*") 配合 @ServletComponentScan() 实现注入。（@Order 注解无效）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");
}
}在配置类中注册一个 FilterRegistrationBean 类型的Bean。
UrlPatterns ， 那么会自动关联到 /* 上。When no URL pattern or servlets are specified the filter will be associated to ‘/*’. The filter name will be deduced if not specified.
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;
}
}
@WebFilter 修饰filter。@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
HandlerInterceptor 接口）WebMvcConfigurer 接口，并重写 addInterceptors() 方法）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
