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 {    private OutputStream stream;    private Map<String,String> fields;    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();  }    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);    }  }}