サーブレットダウンロードファイル

import org.apache.commons.io.IOUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * @author Prannt
 * @throws Exception
 * @param req
 * @param resp
 */
public class Download extends HttpServlet {
     
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     
        //          （  servletContext      ）
        ServletContext servletContext = getServletContext();
        InputStream resourceAsStream = servletContext.getResourceAsStream("/file/aaa.docx");
        //          
        String mimeType = servletContext.getMimeType("/file/aaa.docx");
        System.out.println("        ：" + mimeType);
        resp.setContentType(mimeType);
        //        
        OutputStream outputStream = resp.getOutputStream();
        //              
        //          ，      ，       
        IOUtils.copy(resourceAsStream,outputStream);//copy      resourceAsStream outputStream    
        //                   ，          （       ）
        resp.setHeader("Content-Disposition","attachment;filename=   .docx");
    }
}

    <servlet>
        <servlet-name>Downloadservlet-name>
        <servlet-class>ProjectTest.Downloadservlet-class>
    servlet>
    <servlet-mapping>
        <servlet-name>Downloadservlet-name>
        <url-pattern>/downloadurl-pattern>
    servlet-mapping>