如何对HttpServletRequest中的Header进行增删

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HttpServletRequest 没有提供修改/删除的Api

HttpServletRequest中定义的对Header的操作全是只读，没有修改。

public interface HttpServletRequest extends ServletRequest {    ...    public long getDateHeader(String name);    public String getHeader(String name);    public Enumeration getHeaders(String name);    public Enumeration getHeaderNames();    public int getIntHeader(String name);    ...}

HttpServletRequest 只是一个接口，实现由Servlet容器提供。不管是任何容器，实现类，肯定是要把请求的Header存储在某个地方，于是可以通过反射来对存储Header的容器进行增删。

先定义一个测试的Controller

这个Controller很简单，把客户端的所有Header，以JSON形似响应给客户端。

import java.util.ArrayList;import java.util.Enumeration;import java.util.LinkedHashMap;import java.util.List;import java.util.Map;import javax.servlet.http.HttpServletRequest;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;@RestController@RequestMapping("/demo")public class DemoController {                // 遍历所有请求Header，响应给客户端。 map        @GetMapping        public Object demo (HttpServletRequest request) {                Map> headers = new LinkedHashMap<>();                Enumeration nameEnumeration = request.getHeaderNames();                while (nameEnumeration.hasMoreElements()) {                        String name = nameEnumeration.nextElement();                        List values = headers.get(name);                        if (values == null) {                                values = new ArrayList<>();                                headers.put(name, values);                        }                        Enumeration valueEnumeration = request.getHeaders(name);                        while (valueEnumeration.hasMoreElements()) {                                values.add(valueEnumeration.nextElement());                        }                }                return headers;        }}

使用Tomcat作为容器

Tomcat对HttpServletRequest的实现

Tomcat使用了外观模式（Facade），这个实现稍微有一点点复杂

org.apache.catalina.connector.RequestFacade|-org.apache.catalina.connector.Request  |-org.apache.coyote.Request    |-org.apache.tomcat.util.http.MimeHeaders

首先是 org.apache.catalina.connector.RequestFacade 实现，它有一个org.apache.catalina.connector.Request 的对象。这个对象又有一个org.apache.coyote.Request的对象，这个对象又有一个org.apache.tomcat.util.http.MimeHeaders 字段，它就是存储了客户端请求头的容器，只要通过反射获取到这个MimeHeaders，对它进行修改即可。

org.apache.catalina.connector.RequestFacade

public class RequestFacade implements HttpServletRequest {    protected org.apache.catalina.connector.Request request = null;    ...}

org.apache.catalina.connector.Request

public class Request implements HttpServletRequest {    protected org.apache.coyote.Request coyoteRequest;    ...}

org.apache.coyote.Request coyoteRequest

public final class Request {    private final org.apache.tomcat.util.http.MimeHeaders headers = new MimeHeaders();}

在Filter中通过反射对请求Header进行增删

假设的场景是，需要对请求Header统一添加一个x-request-id，通过这个ID来从日志中定位每一个请求。

import java.io.IOException;import java.lang.reflect.Field;import java.util.UUID;import javax.servlet.FilterChain;import javax.servlet.ServletException;import javax.servlet.annotation.WebFilter;import javax.servlet.http.HttpFilter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.catalina.connector.Request;import org.apache.catalina.connector.RequestFacade;import org.apache.tomcat.util.http.MimeHeaders;import org.springframework.core.annotation.Order;import org.springframework.stereotype.Component;import org.springframework.util.ReflectionUtils;@WebFilter(urlPatterns = "/*")@Component@Order(-999)public class RequestIdGenFilter extends HttpFilter {        /**         *          */        private static final long serialVersionUID = 1787347739651657706L;                @Override        protected void doFilter(HttpServletRequest req, HttpServletResponse res, FilterChain chain) throws IOException, ServletException {                try {                        // 从 RequestFacade 中获取 org.apache.catalina.connector.Request                        Field connectorField = ReflectionUtils.findField(RequestFacade.class, "request", Request.class);                        connectorField.setAccessible(true);                        Request connectorRequest = (Request) connectorField.get(req);                                                // 从 org.apache.catalina.connector.Request 中获取 org.apache.coyote.Request                        Field coyoteField = ReflectionUtils.findField(Request.class, "coyoteRequest", org.apache.coyote.Request.class);                        coyoteField.setAccessible(true);                        org.apache.coyote.Request coyoteRequest = (org.apache.coyote.Request) coyoteField.get(connectorRequest);                                                // 从 org.apache.coyote.Request 中获取 MimeHeaders                        Field mimeHeadersField =  ReflectionUtils.findField(org.apache.coyote.Request.class, "headers", MimeHeaders.class);                        mimeHeadersField.setAccessible(true);                        MimeHeaders mimeHeaders =  (MimeHeaders) mimeHeadersField.get(coyoteRequest);                                                this.mineHeadersHandle(mimeHeaders);                } catch (Exception e) {                        throw new RuntimeException(e);                }                super.doFilter(req, res, chain);        }                protected void mineHeadersHandle (MimeHeaders mimeHeaders) {                // 添加一个Header，随机生成请求ID                mimeHeaders.addValue("x-request-id").setString(UUID.randomUUID().toString());;                // 移除一个header                mimeHeaders.removeHeader("User-Agent");        }}

请求Controller获取响应结果

可以看到成功添加了x-request-id header，并且删除了User-Agent header。

SpringBoot默认的Servlet容器就是Tomcat

使用Undertow作为容器

越来越多人使用Undertow作为Servlet容器，据说性能比Tomcat要好很多

SpringBoot替换Tomcat为Undertow

只需要把spring-boot-starter-web中的spring-boot-starter-tomcat排除，然后手动添加spring-boot-starter-undertow即可

                                         org.springframework.boot                        spring-boot-starter-web                                                                                                org.springframework.boot                                        spring-boot-starter-tomcat                                                                                                                org.springframework.boot                        spring-boot-starter-undertow                        

Undertow中的HttpServletRequest实现

它的实现就比较简单

io.undertow.servlet.spec.HttpServletRequestImpl|-io.undertow.server.HttpServerExchange  |-io.undertow.util.HeaderMap

io.undertow.servlet.spec.HttpServletRequestImpl实现类中有一个属性对象io.undertow.server.HttpServerExchange，这个属性对象又包含了一个io.undertow.util.HeaderMap，HeaderMap就是请求Header的存储容器，反射获取它就行。

io.undertow.servlet.spec.HttpServletRequestImpl

public final class HttpServletRequestImpl implements HttpServletRequest {    private final io.undertow.server.HttpServerExchange exchange;}

io.undertow.server.HttpServerExchange

public final class HttpServerExchange extends AbstractAttachable {    private final HeaderMap requestHeaders;}

在Filter中通过反射对请求Header进行增删

import java.io.IOException;import java.lang.reflect.Field;import java.util.UUID;import javax.servlet.FilterChain;import javax.servlet.ServletException;import javax.servlet.annotation.WebFilter;import javax.servlet.http.HttpFilter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.core.annotation.Order;import org.springframework.stereotype.Component;import org.springframework.util.ReflectionUtils;import io.undertow.server.HttpServerExchange;import io.undertow.servlet.spec.HttpServletRequestImpl;import io.undertow.util.HeaderMap;import io.undertow.util.HttpString;@WebFilter(urlPatterns = "/*")@Component@Order(-999)public class RequestIdGenFilter extends HttpFilter {        /**         *          */        private static final long serialVersionUID = 1787347739651657706L;                @Override        protected void doFilter(HttpServletRequest req, HttpServletResponse res, FilterChain chain) throws IOException, ServletException {                try {                        // 从HttpServletRequestImpl中获取HttpServerExchange                        Field exchangeField = ReflectionUtils.findField(HttpServletRequestImpl.class, "exchange", HttpServerExchange.class);                        exchangeField.setAccessible(true);                        HttpServerExchange httpServerExchange = (HttpServerExchange) exchangeField.get(req);                                                // 从HttpServerExchange中获取HeaderMap                        Field headerMapField = ReflectionUtils.findField(HttpServerExchange.class, "requestHeaders", HeaderMap.class);                        headerMapField.setAccessible(true);                                                HeaderMap requestHeaderMap = (HeaderMap) headerMapField.get(httpServerExchange);                        this.handleRequestHeaderMap(requestHeaderMap);                } catch (Exception e) {                        throw new RuntimeException(e);                }                super.doFilter(req, res, chain);        }        private void handleRequestHeaderMap(HeaderMap requestHeaderMap) {                // 添加Header                requestHeaderMap.add(new HttpString("x-request-id"), UUID.randomUUID().toString());                // 移除Header                requestHeaderMap.remove("User-Agent");        }}

请求Controller获取结果

感谢各位的阅读，以上就是"如何对HttpServletRequest中的Header进行增删"的内容了，经过本文的学习后，相信大家对如何对HttpServletRequest中的Header进行增删这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是，小编将为大家推送更多相关知识点的文章，欢迎关注！