httpClient 로 httpPost 보내어 로그인한후 

httpGet을 이용하여 파일을 다운로드 가능하다.

package com.lm.httpCliTest;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpRequest;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLContextBuilder;
import org.apache.http.conn.ssl.TrustSelfSignedStrategy;

public class HttpFileDown {
 
 private String usId="mankeys@test.com";
 private String usPw="password";
 private String url="http://192.168.0.119:8080/test";
 public static void main(String [] args) throws ClientProtocolException, URISyntaxException, IOException{
  HttpFileDown fileDown= new HttpFileDown();
  fileDown.getFileDown();
 }
 
 // httpPost 보내기 위한 부분 : login 이후에는 Cookies (JSESSIONID)를 헤더에 넣어 준다.
 private String getFileDown() throws URISyntaxException, ClientProtocolException, IOException {
  URI uri = new URI(url);
  int timeout = 10000; // request timeout 은 10초
  RequestConfig config = RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout)
    .setConnectionRequestTimeout(timeout).build();
  
  CloseableHttpClient httpClient = HttpClients.createDefault();
  //login 부분
  HttpPost httpPost = new HttpPost(uri+"/login.do");
  httpPost.setConfig(config);
//  httpPost.setEntity(postParams);

  List<NameValuePair> postParams = new ArrayList<>();
  postParams.add(new BasicNameValuePair("usId", usId));
  postParams.add(new BasicNameValuePair("usPw", usPw));
  httpPost.setEntity(new UrlEncodedFormEntity(postParams, "UTF-8"));
  CloseableHttpResponse response = httpClient.execute(httpPost);
  Header[] headers = response.getHeaders("Set-Cookie");
  for (Header headerElem : headers) {
   String cookies = "";
   cookies = headerElem.getValue(); // Set-Cookie의 value 가져 온다
   if (cookies != null && !cookies.equals("")) { // 로그인시에는 JSESSIONID를
               // 세션obj 에 넣어 준다.
    System.out.println("getFileDown > setLoginVO :" + cookies);
   }
   System.out.println("getFileDown > Header :" + headerElem.getValue());
   System.out.println("getFileDown > cookies:" + cookies);
  }

  // get file  from 서버
  String[] fileNms={ "9dcf053c160149119c790066fd5fa7e5.png", 
    "3ac06e6b2e1a469db21539f7db818bf0.png",
    "dd34eefe500c46c5a97980d35f0dc8da.png",
    "15fbf1edc8324119b021296484beee97.png"
    };
  String filePath="e:\\java_down\\";
  for(String fileNm: fileNms){
   String finalUri = url + "/download/img/"+fileNm;
   HttpGet httpGetFl = new HttpGet(finalUri);
   CloseableHttpResponse responseFl = httpClient.execute(httpGetFl);
   BufferedInputStream bInStr = new BufferedInputStream(responseFl.getEntity().getContent()); // Buffered Stream 이용: fast down
   System.out.println("getFileDown> finalPath:" + finalUri);
   BufferedOutputStream bOutStr = new BufferedOutputStream(new FileOutputStream(new File(filePath+fileNm))); // Buffered  Stream
   int inpByte;
   while ((inpByte = bInStr.read()) != -1) {
    bOutStr.write(inpByte);
   }
   bInStr.close();
   bOutStr.close();
  }
  response.close();
  return "ok";
 }
}