我们发送一个请求时，服务端的javax.servlet.http.HttpServletRequest帮我们做了什么？-白红宇

我们发送一个请求时，服务端的javax.servlet.http.HttpServletRequest帮我们做了什么？

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发布时间：2019-05-25

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在web应用程序中，后台仅仅获取请求参数是远远不够的。比如，spring的controller层，我们可以通过@RequestMapping注解一个方法使其成为web借口，我们可以通过方法参数来获取匹配获取请求的参数。但是，如果我们想要获取更多的信息怎么办呢？
没错，用javax.servlet.http.HttpServletRequest，HttpServletRequest帮我们将请求解析封装好了已经，我们只需要拿来直接用即可。

举个例子

(HttpServletRequest在springMVC/springBoot Controller层的应用)

@RequestMapping(value = "/**")public ResponseEntity

在方法mockEntry中，可以通过httpServletRequest实例提供的方法获取到各种请求数据。

我们来看不同请求下，HttpServletRequest将请求封装成什么样子了。我们将验证一下请求：

1、 GET方法，不带queryParams；

curl 'http://localhost:8089/my/url'

2、GET方法，带queryParams；

curl 'http://localhost:8089/my/url?key1=value1&key2=vlaue2'

3、POST方法，bodyType为application/x-www-form-urlencoded，不带queryParams，不带bodyParams；

curl -H 'Content-Type:application/x-www-form-urlencoded' -d '' 'http://localhost:8089/my/url'

4、POST方法，bodyType为application/x-www-form-urlencoded，不带queryParams，带bodyParams；

curl -H 'Content-Type:application/x-www-form-urlencoded' -d 'key=value' 'http://localhost:8089/my/url'

5、POST方法，bodyType为application/x-www-form-urlencoded，带queryParams，不带bodyParams；

curl -H 'Content-Type:application/x-www-form-urlencoded' -d '' 'http://localhost:8089/my/url?key=value'

6、POST方法，bodyType为application/x-www-form-urlencoded，带queryParams，带bodyParams；

curl -H 'Content-Type:application/x-www-form-urlencoded' -d 'key1=value1' 'http://localhost:8089/my/url?key2=value2'

7、POST方法，bodyType为application/json，不带queryParams，不带bodyParams；

curl -H 'Content-Type:application/json' -d '' 'http://localhost:8089/my/url'

8、POST方法，bodyType为application/json，不带queryParams，带bodyParams；

curl -H 'Content-Type:application/json' -d '{"key": "value"}' 'http://localhost:8089/my/url'

9、POST方法，bodyType为application/json，带queryParams，不带bodyParams；

curl -H 'Content-Type:application/json' -d '' 'http://localhost:8089/my/url?key=value'

10、POST方法，bodyType为application/json，带queryParams，带bodyParams；

curl -H 'Content-Type:application/json' -d '{"key": "value"}' 'http://localhost:8089/my/url?key2=value2'

准备工作

我们写一个Filter，并且写一个RequestMetadata作为数据承载类，为我们直观的输出HttpServletRequest封装了什么。

import java.io.Serializable;import java.util.Map;public class RequestMetadata implements Serializable {
       private static final long serialVersionUID = 4756023942925621584L;    private String protocol;    private String scheme;    private String serverName;    private String serverPort;    private String servletPath;    private String method;    private String uri;    private String url;    private String contentType;    private int contentLength;    private Map
   
     headerNames;    private String queryString;    private Map
    
      parameterMap;    private String body;    public RequestMetadata() {    }    public String getProtocol() {        return protocol;    }    public void setProtocol(String protocol) {        this.protocol = protocol;    }    public String getScheme() {        return scheme;    }    public void setScheme(String scheme) {        this.scheme = scheme;    }    public String getServerName() {        return serverName;    }    public void setServerName(String serverName) {        this.serverName = serverName;    }    public String getServerPort() {        return serverPort;    }    public void setServerPort(String serverPort) {        this.serverPort = serverPort;    }    public String getServletPath() {        return servletPath;    }    public void setServletPath(String servletPath) {        this.servletPath = servletPath;    }    public String getMethod() {        return method;    }    public void setMethod(String method) {        this.method = method;    }    public String getUri() {        return uri;    }    public void setUri(String uri) {        this.uri = uri;    }    public String getUrl() {        return url;    }    public void setUrl(String url) {        this.url = url;    }    public String getContentType() {        return contentType;    }    public void setContentType(String contentType) {        this.contentType = contentType;    }    public int getContentLength() {        return contentLength;    }    public void setContentLength(int contentLength) {        this.contentLength = contentLength;    }    public Map
     
       getHeaderNames() {        return headerNames;    }    public void setHeaderNames(Map
      
        headerNames) {        this.headerNames = headerNames;    }    public String getQueryString() {        return queryString;    }    public void setQueryString(String queryString) {        this.queryString = queryString;    }    public Map
       
         getParameterMap() {        return parameterMap;    }    public void setParameterMap(Map
        
          parameterMap) { this.parameterMap = parameterMap; } public String getBody() { return body; } public void setBody(String body) { this.body = body; } @Override public String toString() { return "RequestMetadata{" + "protocol='" + protocol + '\'' + ", scheme='" + scheme + '\'' + ", serverName='" + serverName + '\'' + ", serverPort='" + serverPort + '\'' + ", servletPath='" + servletPath + '\'' + ", method='" + method + '\'' + ", uri='" + uri + '\'' + ", url='" + url + '\'' + ", contentType='" + contentType + '\'' + ", contentLength=" + contentLength + ", headerNames=" + headerNames + ", queryString='" + queryString + '\'' + ", parameterMap=" + parameterMap + ", body='" + body + '\'' + '}'; }}

import java.io.IOException;import java.util.Enumeration;import java.util.Iterator;import java.util.Map;import javax.servlet.FilterChain;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.annotation.WebFilter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.web.filter.OncePerRequestFilter;import wiremock.com.google.common.collect.Maps;/** * Filter all requests. Extract useful information from the request (for example: method, parameter, uri, etc.) and * store it in a map. An http request will first go to this Filter, and then go to the Controller class, so this map is * stored in the ThreadLocal in order to obtain the details of the request at the Controller level. */@WebFilter(filterName = "requestFilter", urlPatterns = "/*")public class RequestFilter extends OncePerRequestFilter {    private static final Logger logger      = LoggerFactory.getLogger(RequestFilter.class);    public static ThreadLocal   threadLocal = new ThreadLocal();    @Override    protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse,                                    FilterChain filterChain) throws ServletException, IOException {        RequestMetadata requestMetadata = new RequestMetadata();        ServletRequest requestWrapper = null;        requestMetadata.setProtocol(httpServletRequest.getProtocol());        requestMetadata.setScheme(httpServletRequest.getScheme());        requestMetadata.setServerName(httpServletRequest.getServerName());        requestMetadata.setServerPort(String.valueOf(httpServletRequest.getServerPort()));        requestMetadata.setServletPath(httpServletRequest.getServletPath());        requestMetadata.setMethod(httpServletRequest.getMethod());        requestMetadata.setUri(httpServletRequest.getRequestURI());        requestMetadata.setUrl(httpServletRequest.getRequestURL().toString());        requestMetadata.setContentType(httpServletRequest.getContentType());        requestMetadata.setContentLength(httpServletRequest.getContentLength());        requestMetadata.setQueryString(httpServletRequest.getQueryString());        // headerNames        Map
   
     headersMap = Maps.newHashMap();        Enumeration
    
      headerNamesEnumeration = httpServletRequest.getHeaderNames();        while (headerNamesEnumeration.hasMoreElements()) {            String key = headerNamesEnumeration.nextElement();            headersMap.put(key, httpServletRequest.getHeader(key));        }        requestMetadata.setHeaderNames(headersMap);        // parameterMap        Map
     
       parameterMap = Maps.newHashMap();        Iterator iterator = httpServletRequest.getParameterMap().entrySet().iterator();        while (iterator.hasNext()) {            Map.Entry
      
        entry = (Map.Entry
       
        ) iterator.next();            parameterMap.put(entry.getKey(), entry.getValue()[0]);        }        requestMetadata.setParameterMap(parameterMap);        requestWrapper = new BodyReaderHttpServletRequestWrapper(httpServletRequest);        byte[] body = ((BodyReaderHttpServletRequestWrapper) requestWrapper).getBody();        requestMetadata.setBody(new String(body));        // Save the requestMetadata containing the request details in threadLocal        threadLocal.set(requestMetadata);        if (null == requestWrapper) {            filterChain.doFilter(httpServletRequest, httpServletResponse);        } else {            filterChain.doFilter(requestWrapper, httpServletResponse);        }    }}