【JAVA】拦截请求参数并设置请求头

今天药忘吃喽~ 2022-03-25 09:08 1708阅读 1赞

业务中遇到了一些场景，需要对请求做统一拦截，用请求参数计算新的变量设置到请求头中。

以下分别用Filter和Interceptor两种方式实现，（建议使用Filter的方法，因为Interceptor的方法仅仅对Post和GET方法有效，并不支持PUT等其他方法，主要原因是因为HttpServletRequest接口的实现类不同，以下仅支持了POST和GET方法）

场景：

我们有两类用户，一类用户的请求中头部header中有用户名字参数（userName），另一类用户的请求并无请求header，但是请求参数requestParam中有userId参数，我们可以通过userId查库等计算出userName。

需求：

我们想统一两类用户，使请求达到我们的controller层的时候头部统一都有userName。

具体：

以下的两种方式实现了这个需求，controller层获取userName，将优先使用从requestParam中的userId计算出来的userName。

### 1、Filter实现     ###

package com.paomo.filter;
    
    import org.springframework.context.annotation.Configuration;
    
    import javax.servlet.*;
    import javax.servlet.annotation.WebFilter;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletRequestWrapper;
    import java.io.IOException;
    import java.util.*;
    
    @Configuration
    @WebFilter(value = "/*")
    public class ParamFilter implements Filter {
    
        private static final String USER_PARAM = "userId";
        
        private static final String USER_HEADER = "userName";
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
        }
    
        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
            HttpServletRequest req = (HttpServletRequest) request;
            HeaderMapRequestWrapper requestWrapper = new HeaderMapRequestWrapper(req);
            String userId = request.getParameter(USER_PARAM);
    
    
            //依据你自己的业务通过userId获取userName
            String userName = getUserNameById(userId);
    
            requestWrapper.addHeader(USER_HEADER, userName);
            chain.doFilter(requestWrapper, response);
        }
    
        @Override
        public void destroy() {
        }
    
        public class HeaderMapRequestWrapper extends HttpServletRequestWrapper {
    
            public HeaderMapRequestWrapper(HttpServletRequest request) {
                super(request);
            }
    
            private Map<String, String> headerMap = new HashMap<String, String>();
    
            public void addHeader(String name, String value) {
                headerMap.put(name, value);
            }
    
            @Override
            public String getHeader(String name) {
                String headerValue = super.getHeader(name);
                if (headerMap.containsKey(name)) {
                    headerValue = headerMap.get(name);
                }
                return headerValue;
            }
    
            @Override
            public Enumeration<String> getHeaderNames() {
                List<String> names = Collections.list(super.getHeaderNames());
                for (String name : headerMap.keySet()) {
                    names.add(name);
                }
                return Collections.enumeration(names);
            }
    
            @Override
            public Enumeration<String> getHeaders(String name) {
                List<String> values = Collections.list(super.getHeaders(name));
                if (headerMap.containsKey(name)) {
                    values.add(headerMap.get(name));
                }
                return Collections.enumeration(values);
            }
        }
    
    }

### 2、Interceptor实现 ###

@Component
    public class ParamInterceptor extends HandlerInterceptorAdapter {
    
        private static final Logger logger = LoggerFactory.getLogger(ParamInterceptor.class);
    
        private static final String USER_PARAM = "userId";
    
        private static final String USER_HEADER = "userName";
    
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
            if (handler instanceof HandlerMethod) {
                String userId = request.getParameter(USER_PARAM);
                if (StringUtils.isNotBlank(userId)) {
    
                    //依据你自己的业务通过userId获取userName
                    String userName = getUserNameById(userId);
    
                    reflectSetHeader(request, USER_HEADER, userName);
                }
            }
            return true;
        }
    
        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
            super.postHandle(request, response, handler, modelAndView);
        }
    
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
            super.afterCompletion(request, response, handler, ex);
        }
    
        private void reflectSetHeader(HttpServletRequest request, String key, String value){
            Class<? extends HttpServletRequest> requestClass = request.getClass();
            logger.info("request实现类={}", requestClass.getName());
            try {
                Field request1 = requestClass.getDeclaredField("request");
                request1.setAccessible(true);
                Object o = request1.get(request);
                Field coyoteRequest = o.getClass().getDeclaredField("coyoteRequest");
                coyoteRequest.setAccessible(true);
                Object o1 = coyoteRequest.get(o);
                Field headers = o1.getClass().getDeclaredField("headers");
                headers.setAccessible(true);
                MimeHeaders o2 = (MimeHeaders)headers.get(o1);
                o2.removeHeader(key);
                o2.addValue(key).setString(value);
            } catch (Exception e) {
                logger.info("reflect set header error {}", e);
            }
        }
    }