java - 如何编写 CSV 文件并在浏览器中打开它

Question

我正在尝试在新浏览器中打开文件，而不是将其保存在本地。

下面是我的 servlet，它保存到我的本地驱动器中，但我想在浏览器中打开它。我认为我应该使用 OutPutStream 而不是 FileWriter，但我了解如何使用它。

  protected void doGet(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
   Connection conn = null;
    ResultSet result = null;
    PreparedStatement selectStmt = null;
    try {
        conn = DBUtil.getConnection();
        if(request.getParameter("param1").equals("RED9")){
            selectStmt = conn.prepareStatement("select * from TableName");
        }else if(request.getParameter("param1").equals("RED921")){
            selectStmt = conn.prepareStatement("select * from TableName");
    result = selectStmt.executeQuery();
       FileWriter f = new FileWriter("c://myFile.cvs);
      while(result.next()){

        writer.append(result.getString("PARTC_SSN"));
        writer.append(',');

        writer.append("\n");
            }
            writer.flush();
    writer.close();
            }catch(Exception e){
        e.printStackTrace();
    }finally {
        try {
            if (result != null) {
                result.close();
                result = null;
            }
            if (selectStmt != null) {
                selectStmt.close();
                selectStmt = null;
            }
            if (conn != null) {
                conn.close();
                conn = null;
            }

        } catch (SQLException e) {
            DBUtil
                    .log("Exception from ExcelReportServlet class, Method -createNoEcmatsRegDoc "
                            + e);
        }
    }

}

Answer 1

有两件事。首先，将文件编写器替换为响应编写器，并确保告诉响应期望正确的输出格式。另外，如果发生异常，请务必关闭编写器。不管怎样，这是我对你的代码应该是什么样子的猜测:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package gov.ca.water.preciptemp;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author hdunsford
 */
public class DailyHydroServlet1 extends HttpServlet {

    private static final Logger logger = Logger.getLogger(DailyHydroServlet1.class.getName());

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {


        response.setContentType("text/html;charset=UTF-8");
        Connection conn = null;
        ResultSet result = null;
        PreparedStatement selectStmt = null;
        PrintWriter out;
        try {
            out = response.getWriter();
            conn = DBUtil.getConnection();
            if (request.getParameter("param1").equals("RED9")) {
                selectStmt = conn.prepareStatement("select * from TableName");
            } else if (request.getParameter("param1").equals("RED921")) {
                selectStmt = conn.prepareStatement("select * from TableName");
                result = selectStmt.executeQuery();

                while (result.next()) {

                    out.append(result.getString("PARTC_SSN"));
                    out.append(',');

                    out.append("\n");
                }
                out.flush();
                out.close();
            }
        } catch (Exception ex) {
            try{
                out.close();
            }catch(Exception e){
                //ignore
            }
            logger.log(Level.SEVERE, ex.getMessage(), ex);
        } finally {
            try {
                if (result != null) {
                    result.close();
                    result = null;
                }
                if (selectStmt != null) {
                    selectStmt.close();
                    selectStmt = null;
                }
                if (conn != null) {
                    conn.close();
                    conn = null;
                }

            } catch (SQLException e) {
                DBUtil.log("Exception from ExcelReportServlet class, Method -createNoEcmatsRegDoc "
                                + e);
            }
        }

    }


    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}