求助！！！ 关于filter对request头的修改
我现在有一个需求，就是在jsp调到servlet之前，用filter进行拦截，然后在request的header中追加一项内容。

现在的进度：可以使用filter在对应的位置进行拦截，但是知道如何在header中追加内容。

需求是硬性的，必须在header中追加内容。

从网上查到可以利用filter对request头进行修改。

请问有人做过类似的机能嘛？跪等！！！！
[最优解释]
可以在Filter对Request做包装

上代码:
Filter部分

package test;

import java.io.IOException;
import java.util.Enumeration;
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;

public class TestFilter implements Filter{

public void destroy() {

}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain fc) throws IOException, ServletException {
HttpServletRequest oldRequest = (HttpServletRequest) request;
// 打印原始数据
System.out.println("OLD REQUEST HEADER:");
Enumeration enumeration = oldRequest.getHeaderNames();
while(enumeration.hasMoreElements()) {
String name = (String) enumeration.nextElement();
System.out.println(name + "=" + oldRequest.getHeader(name));
}
// 包装新的客户化Request
ChangedRequest newRequest = new ChangedRequest(oldRequest);

// 添加新的HEADER
newRequest.addHeader("TestMyHeader", "This is a test");
fc.doFilter(newRequest, response);
}

public void init(FilterConfig arg0) throws ServletException {

}



}

Request包装类:

package test;

import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

/**
 * 用于包装REQUEST
 * @author ALLEN
 *
 */
public class ChangedRequest extends HttpServletRequestWrapper implements Enumeration<String>{

private Map<String,String> headerMap;

public ChangedRequest(HttpServletRequest request) {
super(request);

// 提取原本的HEADER内容
Enumeration enumeration = request.getHeaderNames();
headerMap = new HashMap<String, String>();
while(enumeration.hasMoreElements()) {
String name = (String) enumeration.nextElement();
headerMap.put(name, request.getHeader(name));
}
}

public Map<String, String> getHeaderMap() {
return headerMap;
}

public void setHeaderMap(Map<String, String> headerMap) {
this.headerMap = headerMap;
}

public void addHeader(String name,String value) {
headerMap.put(name, value);
}

/**
 * 从自己的MAP中返回HEADER内容
 * 这里只实现了getHeader,可以根据需要重写这2个函数
 */
@Override
public String getHeader(String name) {
return headerMap.get(name); 
 
}

@Override
public Enumeration getHeaderNames() {
return this;
}

/**
 * 未实现,根据需要重写
 */
@Override
public Enumeration getHeaders(String name) {
return null;
};

/**
 * 用于实现getHeaderNames
 * 只是简单实现,仅提供单次检索功能
 */
Set<String> mapKeySet;
Iterator<String> mapKeySetIt;
public boolean hasMoreElements() {
if(mapKeySet == null) {
mapKeySet = headerMap.keySet();
mapKeySetIt = mapKeySet.iterator();
}

return mapKeySetIt.hasNext();
}

public String nextElement() {
return mapKeySetIt.next();
}
}

servlet测试代码:

package test;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Test extends HttpServlet {

public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println();
System.out.println("CHANGED REQUEST HEADER:");
Enumeration enumeration = request.getHeaderNames();
while(enumeration.hasMoreElements()) {
String name = (String) enumeration.nextElement();
System.out.println(name + "=" + request.getHeader(name));
}
}

}

忽略了servlet和Filter配置

在你的servlet上采用这个Filter,就可以自己去添加Header部分
以下是测试打印内容

OLD REQUEST HEADER:
accept=text/html, application/xhtml+xml, */*
accept-language=zh-CN
user-agent=Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
accept-encoding=gzip, deflate
host=localhost:8080
connection=Keep-Alive

CHANGED REQUEST HEADER:
connection=Keep-Alive
host=localhost:8080
accept-language=zh-CN
accept=text/html, application/xhtml+xml, */*
user-agent=Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
accept-encoding=gzip, deflate
TestMyHeader=This is a test