HttpServletRequestWrapper干預Request處理流程解析

更新時間：2023年09月21日 09:59:37 作者：晴天哥_王志

這篇文章主要分析在?Tomcat的處理?http?請求的流程中干預?Request對象,?通過基于HttpServletRequestWrapper和?Filter組合進行干預,有需要的朋友可以借鑒參考下,希望能夠有所幫助

開篇

Tomcat 處理 http 請求的過程中 Request 對象是RequestFacade對象（可以通過 springBoot 中跟蹤tomcat-embed-core 的包進行跟蹤），干預后會設配成HttpServletRequestWrapper的子類對象進行傳遞。

HttpServletRequestWrapper和RequestFacade都實現(xiàn) HttpServletRequest 接口。

Tomcat 處理流程

Tomcat 的針對 http請求的處理流程如上圖所示，在org.apache.catalina.core.ApplicationFilterChain#doFilter的方法中將org.apache.catalina.connector.Request封裝成了org.apache.catalina.connector.RequestFacade對象。
在后續(xù)的ApplicationFilterChain之后的執(zhí)行鏈路中使用的是RequestFacade對象。

Request 分析

Request

package org.apache.catalina.connector;
public class Request implements org.apache.catalina.servlet4preview.http.HttpServletRequest {
}
------------------------------
package org.apache.catalina.servlet4preview.http;
public interface HttpServletRequest extends javax.servlet.http.HttpServletRequest {
    public ServletMapping getServletMapping();
    public PushBuilder newPushBuilder();
}
------------------------------
package javax.servlet.http;
public interface HttpServletRequest extends ServletRequest {
}
----------------------------------------
package javax.servlet;
public interface ServletRequest {
}

Request 實現(xiàn)了javax.servlet.ServletRequest接口
Request 實現(xiàn)了javax.servlet.http.HttpServletRequest接口

RequestFacade

package org.apache.catalina.connector;
public class RequestFacade implements HttpServletRequest {
    public RequestFacade(Request request) {
        this.request = request;
    }
    protected Request request = null;
}
-------------------------------------
package org.apache.catalina.servlet4preview.http;
public interface HttpServletRequest extends javax.servlet.http.HttpServletRequest {
    public ServletMapping getServletMapping();
    public PushBuilder newPushBuilder();
}
-------------------------------------
package javax.servlet.http;
public interface HttpServletRequest extends ServletRequest {
}
----------------------------------------
package javax.servlet;
public interface ServletRequest {
}

RequestFacade 實現(xiàn)了javax.servlet.ServletRequest接口
RequestFacade 實現(xiàn)了javax.servlet.http.HttpServletRequest接口

HttpServletRequestWrapper

package javax.servlet.http;
public class HttpServletRequestWrapper extends ServletRequestWrapper implements
        HttpServletRequest {
    public HttpServletRequestWrapper(HttpServletRequest request) {
        super(request);
    }
}
----------------------------------------
package javax.servlet;
public class ServletRequestWrapper implements ServletRequest {
    private ServletRequest request;
    public ServletRequestWrapper(ServletRequest request) {
        if (request == null) {
            throw new IllegalArgumentException("Request cannot be null");
        }
        this.request = request;
    }
}
----------------------------------------
package javax.servlet;
public interface ServletRequest {
}

HttpServletRequestWrapper 實現(xiàn)了javax.servlet.ServletRequest接口

Request 改寫 Demo

import org.springframework.stereotype.Component;
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;
import java.io.IOException;
@Component
public class WrapperFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("wrapper filter init");
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        WrapperDemo wrapperDemo = new WrapperDemo((HttpServletRequest)servletRequest);
        filterChain.doFilter(wrapperDemo, servletResponse);
    }
    @Override
    public void destroy() {
        System.out.println("wrapper filter init");
    }
}
---------------------------------
class WrapperDemo extends HttpServletRequestWrapper {
    public WrapperDemo(HttpServletRequest request) {
        super(request);
    }
}

自定義類WrapperDemo繼承HttpServletRequestWrapper，改寫getParameter相關的方法。
自定義WrapperFilter，在doFilter方法內部將servletRequest（RequestFacade對象）強轉成HttpServletRequest后創(chuàng)建WrapperDemo對象后進行 Filter 的后續(xù)過濾，后續(xù) Filter 操作的 Request 對象是WrapperDemo對象。
servletRequest（RequestFacade對象）能夠強轉成HttpServletRequest的原因是RequestFacade 實現(xiàn)了javax.servlet.http.HttpServletRequest接口。
HttpServletRequestWrapper屬于HttpServletRequest的封裝類，內部實現(xiàn)了所有HttpServletRequest的方法。

ServletWebRequest參數(shù)獲取

at org.apache.catalina.connector.Request.getParameter(Request.java:1140)
at org.apache.catalina.connector.RequestFacade.getParameter(RequestFacade.java:381)
at javax.servlet.ServletRequestWrapper.getParameter(ServletRequestWrapper.java:153)
at org.springframework.web.context.request.ServletWebRequest.getParameter(ServletWebRequest.java:154)

ServletWebRequest獲取參數(shù)的流程本質上執(zhí)行的是org.apache.catalina.connector.Request.getParameter的實現(xiàn)。
不管是 RequestFacade 或 ServletRequestWrapper等對請求的操作都是由org.apache.catalina.connector.Request.getParameter實現(xiàn)的。

以上就是HttpServletRequestWrapper干預Request處理流程解析的詳細內容，更多關于HttpServletRequestWrapper干預Request的資料請關注腳本之家其它相關文章！

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