HttpServletRequest添加header

做法如下：

import java.util.Collections;import java.util.Enumeration;import java.util.HashMap;import java.util.HashSet;import java.util.Map;import java.util.Set; import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletRequestWrapper; final class MutableHttpServletRequest extends HttpServletRequestWrapper {    // holds custom header and value mapping    private final Map<String, String> customHeaders;     public MutableHttpServletRequest(HttpServletRequest request){        super(request);        this.customHeaders = new HashMap<String, String>();    }        public void putHeader(String name, String value){        this.customHeaders.put(name, value);    }     public String getHeader(String name) {        // check the custom headers first        String headerValue = customHeaders.get(name);                if (headerValue != null){            return headerValue;        }        // else return from into the original wrapped object        return ((HttpServletRequest) getRequest()).getHeader(name);    }     public Enumeration<String> getHeaderNames() {        // create a set of the custom header names        Set<String> set = new HashSet<String>(customHeaders.keySet());                // now add the headers from the wrapped request object        @SuppressWarnings("unchecked")        Enumeration<String> e = ((HttpServletRequest) getRequest()).getHeaderNames();        while (e.hasMoreElements()) {            // add the names of the request headers into the list            String n = e.nextElement();            set.add(n);        }         // create an enumeration from the set and return        return Collections.enumeration(set);    }}

使用方法：

public class SecurityFilter implements javax.servlet.Filter {     @Override    public void destroy() {            }     @Override    public void doFilter(ServletRequest request, ServletResponse response,            FilterChain chain) throws IOException, ServletException {        HttpServletRequest req = (HttpServletRequest) request;        MutableHttpServletRequest mutableRequest = new MutableHttpServletRequest(req);        ...        mutableRequest.putHeader("x-custom-header", "custom value");        chain.doFilter(mutableRequest, response);    }     @Override    public void init(FilterConfig filterConfig) throws ServletException {            }}