如何使用jdbc将数据从Postgresql导出到.csv文件？

我想按日期导出表中的数据，因此我使用jdbc编写了一个Java程序。

  public void exportData(Connection conn,String filename) {

        Statement stmt;
        String query;
        try {
            stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                    ResultSet.CONCUR_UPDATABLE); 

            SimpleDateFormat dateFormat = new SimpleDateFormat ("yyyy-MM-dd hh:mm:ss");
            Date startDate = dateFormat.parse("2014-08-21 00:00:00");
            Date endDate = dateFormat.parse("2014-08-22 00:00:00");

            Calendar startCalendar = Calendar.getInstance();
            startCalendar.setTime(startDate);

            Calendar endCalendar = Calendar.getInstance();
            endCalendar.setTime(endDate);

            Calendar thisDayCalendar = startCalendar;

            while(!thisDayCalendar.after(endCalendar)){
                Date thisDayDate = thisDayCalendar.getTime();
                thisDayCalendar.add(Calendar.DATE, 1);
                Date nextDayDate = thisDayCalendar.getTime();

                String thisDayString = dateFormat.format(thisDayDate);
                String nextDayString = dateFormat.format(nextDayDate);

                SimpleDateFormat dateFormat1 = new SimpleDateFormat ("yyyy-MM-dd");
                String fileDateString = dateFormat1.format(thisDayDate);

                //For comma separated file
                query ="COPY (SELECT * FROM signals WHERE date_time >= '" + thisDayString + 
                        "' AND date_time < '" +nextDayString + "' ) TO " +filename + fileDateString + ".csv  delimiter ','";

                stmt.executeQuery(query);  
            //System.out.println(query);

            }

        } catch(Exception e) {
            e.printStackTrace();
            stmt = null;
        }
    }

该程序在服务器上运行，而数据库又是另一个服务器，我在该程序中连接到数据库。但是，当我在服务器上运行该程序时，出现了一个错误，只有超级用户才能从文件中复制或复制文件：

org.postgresql.util.PSQLException: ERROR: must be superuser to COPY to or from a file
  Hint: Anyone can COPY to stdout or from stdin. psql's \copy command also works for anyone.
        at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2161)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1890)
        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:560)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:403)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:283)
        at DBase.exportData(ExportSignal.java:85)
        at ExportSignal.main(ExportSignal.java:23)

我在线搜索了解决方案，并尝试使用psql'\ copy'命令，但是在编译时，另一个错误提示'\'是Java中的无效转义符，因此我写了“双斜杠COPY”，这在运行程序时出现语法错误。

query ="\COPY (SELECT * FROM signals WHERE date_time >= '" + thisDayString + 
                            "' AND date_time < '" +nextDayString + "' ) TO " +filename + fileDateString + ".csv  delimiter ','";

有谁知道如何使程序执行或解决“ \ copy”中无效转义符的问题？