java web开发中大量数据导出Excel超时(504)问题解决

import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Field;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang3.StringUtils;
import org.joda.time.DateTime;
import com.travelzen.framework.net.http.TZHttpClient;
import com.travelzen.tops.front.ota.member.item.CustomerItem;
public class CSV {
  /**
   * 目标输出流
   */
  private OutputStream stream;
  /**
   * 表头
   */
  private Map<String,String> fields;

  /**
   * 数据源model所有字段map
   */
  private static Map<String, Field> fieldMap = new HashMap<>();
  public CSV(HttpServletResponse response,Map<String,String> fields,String fileName,Class<?> clz) throws IOException{
    if(response == null || fields == null || fileName == null || clz == null)
      throw new IllegalArgumentException();
    getFieldMap(clz,fieldMap);
    this.stream = response.getOutputStream();
    this.fields = fields;
    response.setContentType("application/octet-stream;charset=GBK");
    response.setHeader("Content-Disposition", "attachment;fileName="+ fileName);
    //写表头，生成指定名字的文件，返回客户端
    StringBuilder hb = new StringBuilder();
    for(Entry<String, String> e : fields.entrySet())
      hb.append(e.getValue()+",");
    stream.write(hb.substring(0, hb.length() - 1).getBytes("GBK"));
    stream.flush();
  }
  /**
   * 往表格中插入记录
   */
  public void write(List<Object> data) throws IllegalArgumentException, IllegalAccessException, IOException{
    for(Object o : data){
      StringBuilder sb = new StringBuilder();
      sb.append("\n");
      for(String field : fields.keySet()){
        Field f = fieldMap.get(field);
        f.setAccessible(true);
        Object value = f.get(o);
        if(value == null || StringUtils.isBlank(value.toString())){
          sb.append(" ,");
        } else if (f.getType() == Date.class) {
          sb.append(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(value) + ",");
        } else if (f.getType() == DateTime.class) {
          sb.append(((DateTime)value).toString("yyyy-MM-dd HH:mm:ss") + ",");
        } else {
          String tmp = value.toString();
          if(tmp.contains(","))
            tmp = tmp.replace(",", "\",\"");
          sb.append(value.toString() + ",");
        }
      }
      stream.write(sb.substring(0, sb.length() - 1).getBytes("GBK"));
      stream.flush();
    }
  }
  public void close() throws IOException{
    stream.close();
  }
  private static <T extends Object> void getFieldMap(Class<T> clz, Map<String, Field> result) {
    for (Field field : clz.getDeclaredFields()) {
      result.put(field.getName(), field);
    }
    if (clz.getSuperclass() != null) {
      getFieldMap(clz.getSuperclass(), result);
    }
  }
}