在servlet過濾器中向請求添加HTTP標頭

Question

我正在與現有的servlet進行集成，該servlet從HTTP標頭中取出一些屬性。基本上，我正在實現一個無法訪問實際請求的接口，它只能訪問HTTP標頭的k-> v映射。

我需要傳入請求參數。該計劃是使用servlet過濾器從參數傳遞到標頭值，但是當然HttpServletRequest對象沒有addHeader（）方法。

任何想法？

Answer 1

擴展HttpServletRequestWrapper，覆蓋頭部的getter返回的參數，以及：

public class AddParamsToHeader extends HttpServletRequestWrapper { 
    public AddParamsToHeader(HttpServletRequest request) { 
     super(request); 
    } 

    public String getHeader(String name) { 
     String header = super.getHeader(name); 
     return (header != null) ? header : super.getParameter(name); // Note: you can't use getParameterValues() here. 
    } 

    public Enumeration getHeaderNames() { 
     List<String> names = Collections.list(super.getHeaderNames()); 
     names.addAll(Collections.list(super.getParameterNames())); 
     return Collections.enumeration(names); 
    } 
} 

..和包裹它的原始請求：

chain.doFilter(new AddParamsToHeader((HttpServletRequest) request), response); 

---

這麼說，我個人發現這是一個壞主意。而是讓它直接訪問參數或將參數傳遞給參數。

Answer 2

你將不得不使用HttpServletRequestWrapper：

public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain) throws IOException, ServletException { 
    final HttpServletRequest httpRequest = (HttpServletRequest) request; 
    HttpServletRequestWrapper wrapper = new HttpServletRequestWrapper(httpRequest) { 
     @Override 
     public String getHeader(String name) { 
      final String value = request.getParameter(name); 
      if (value != null) { 
       return value; 
      } 
      return super.getHeader(name); 
     } 
    }; 
    chain.doFilter(wrapper, response); 
} 

取決於你想做的事，你可能需要實現像getHeaderNames例如包裝的其他方法是什麼。請注意，這是相信客戶端並允許他們操縱任何HTTP標頭。您可能需要對其進行沙箱處理，並且只允許以這種方式修改某些標題值。

Answer 3

as https://stackoverflow.com/users/89391/miku指出這將是一個完整的ServletFilter示例，該示例使用也適用於Jersey的代碼來添加remote_addr標頭。

package com.bitplan.smartCRM.web; 

import java.io.IOException; 
import java.util.Collections; 
import java.util.Enumeration; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 

import javax.servlet.Filter; 
import javax.servlet.FilterChain; 
import javax.servlet.FilterConfig; 
import javax.servlet.ServletException; 
import javax.servlet.ServletRequest; 
import javax.servlet.ServletResponse; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletRequestWrapper; 

/** 
* 
* @author wf 
* 
*/ 
public class RemoteAddrFilter implements Filter { 

    @Override 
    public void destroy() { 

    } 

    @Override 
    public void doFilter(ServletRequest request, ServletResponse response, 
      FilterChain chain) throws IOException, ServletException { 
     HttpServletRequest req = (HttpServletRequest) request; 
     HeaderMapRequestWrapper requestWrapper = new HeaderMapRequestWrapper(req); 
     String remote_addr = request.getRemoteAddr(); 
     requestWrapper.addHeader("remote_addr", remote_addr); 
     chain.doFilter(requestWrapper, response); // Goes to default servlet. 
    } 

    @Override 
    public void init(FilterConfig filterConfig) throws ServletException { 

    } 

    // https://stackoverflow.com/questions/2811769/adding-an-http-header-to-the-request-in-a-servlet-filter 
    // http://sandeepmore.com/blog/2010/06/12/modifying-http-headers-using-java/ 
    // http://bijubnair.blogspot.de/2008/12/adding-header-information-to-existing.html 
    /** 
    * allow adding additional header entries to a request 
    * 
    * @author wf 
    * 
    */ 
    public class HeaderMapRequestWrapper extends HttpServletRequestWrapper { 
     /** 
     * construct a wrapper for this request 
     * 
     * @param request 
     */ 
     public HeaderMapRequestWrapper(HttpServletRequest request) { 
      super(request); 
     } 

     private Map<String, String> headerMap = new HashMap<String, String>(); 

     /** 
     * add a header with given name and value 
     * 
     * @param name 
     * @param value 
     */ 
     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; 
     } 

     /** 
     * get the Header names 
     */ 
     @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); 
     } 

    } 

} 

的web.xml片段：

<!-- first filter adds remote addr header --> 
<filter> 
    <filter-name>remoteAddrfilter</filter-name> 
    <filter-class>com.bitplan.smartCRM.web.RemoteAddrFilter</filter-class> 
</filter> 
<filter-mapping> 
    <filter-name>remoteAddrfilter</filter-name> 
    <url-pattern>/*</url-pattern> 
</filter-mapping>