[英]Adding an HTTP Header to the request in a servlet filter
我正在与现有的servlet集成,从而将一些属性从HTTP头中拉出来。 基本上,我正在实现一个无法访问实际请求的接口,它只能访问HTTP头的k-> v映射。
我需要传入一个请求参数。 计划是使用servlet过滤器从参数到标头值,但当然HttpServletRequest对象没有addHeader()方法。
有任何想法吗?
扩展HttpServletRequestWrapper
,覆盖标头getter以返回参数:
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);
}
}
..并用它包装原始请求:
chain.doFilter(new AddParamsToHeader((HttpServletRequest) request), response);
也就是说,我个人认为这是一个坏主意。 而是让它直接访问参数或将参数传递给它。
正如https://stackoverflow.com/users/89391/miku所指出的那样,这将是一个完整的ServletFilter示例,该示例使用也适用于Jersey的代码来添加remote_addr标头。
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);
}
}
}
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>
您将不得不使用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);
}
根据您的要求,您可能需要实现包装器的其他方法,例如getHeaderNames
。 请注意,这是信任客户端并允许它们操纵任何HTTP头。 您可能希望对其进行沙箱处理,并且仅允许以这种方式修改某些标头值。
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