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import com.google.gson.GsonBuilder;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;

@WebServlet( name = "UploadServlet", urlPatterns = {"/uploadFile"} )
public class UploadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;
    private static final String UPLOAD_DIR_REL_PATH = "uploads";

	private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3;
	private static final int MAX_FILE_SIZE = 1024 * 1024 * 40;
	private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        if (ServletFileUpload.isMultipartContent(request)) {
	
		    DiskFileItemFactory factory = new DiskFileItemFactory();
		    factory.setSizeThreshold(MEMORY_THRESHOLD);
		    factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
		
		    ServletFileUpload upload = new ServletFileUpload(factory);
		    upload.setHeaderEncoding("UTF-8");
		    upload.setFileSizeMax(MAX_FILE_SIZE);
		    upload.setSizeMax(MAX_REQUEST_SIZE);
		
		    String ROOT_ABS_PATH = request.getSession().getServletContext().getRealPath("");
		    String UPLOAD_DIR_ABS_PATH = ROOT_ABS_PATH + File.separator + UPLOAD_DIR_REL_PATH;
		
		    makeDirectory(UPLOAD_DIR_ABS_PATH);
		
		    String storeFileName = "";
		    try {
		        List<FileItem> formItems = upload.parseRequest(request);
		
		        if (formItems != null && formItems.size() > 0) {
		            for (FileItem item : formItems) {
		                if (!item.isFormField()) {
		                    String ext = item.getName().substring(item.getName().lastIndexOf('.'));
		                    storeFileName = UUID.randomUUID().toString() + ext;
		                    String storeFileAbsPath = UPLOAD_DIR_ABS_PATH + File.separator + storeFileName;
		
		                    item.write(new File(storeFileAbsPath)); // 파일 저장
		                }
		            }
		        }
		    } catch (Exception ex) {
		        ex.printStackTrace();
		    }
		
		    Map map = new HashMap();
		    map.put("uploadPath", "uploads/" + storeFileName);
		
		    PrintWriter out = response.getWriter();
		    response.setContentType("application/json");
		    response.setCharacterEncoding("UTF-8");
		
		    out.print(new GsonBuilder().create().toJson(map));
		    out.flush();
		}
    }


	/**
	 * 디렉토리가 없는 경우 디렉토리를 생성합니다.
	 */
	private static void makeDirectory(String dirPath) {
	    File dir = new File(dirPath);
	    if (!dir.exists()) {
	        dir.mkdir();
	    }
	}
}