java web app 导出csv excel 文件

叁歲伎倆 2022-08-27 15:53 210阅读 0赞

here is a class you can using to export to CSV:

import java.io.FileWriter; import java.io.IOException; import User; public class GenerateCsv { private static void generateCsvFile(ArrayList<User> users) { String output = "Email, Name\n"; for (User user in users) { output += user.getEmail() + ", " + user.getName() + "\n"; } return output; } }

Working the MVC way

Here is how your code should be written:

Let's say you have a class called. *User.java* inside of which there is a static function called get all users

public class User { String name; String email; public static ArrayList<User> getAllUsers() { // returns all users ... } }

Then let's say you have a servlet called UsersServlet which get these users:

import javax.servlet.*; import javax.servlet.http.*; public class UsersServlet extends HttpServlet { public void doGet (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("application/csv"); PrintWriter w = res.getWriter(); ArrayList<User> users = Users.getAllUsers(); w.prinln(GenerateCsv.generateCsvFile(users)); w.flush(); w.close(); } public void doPost (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { ... } }

in your jsp, for example, you will have a simple anchor tag which calls the servlet (the servlets calls User.java, get data, forms them into a CSV and then outputs it to the browser...). Something like this would work:

<a href='/getCSV' > Export CSV </a>

but please note that you have to link the servlet to the *url* using web.xml:

<web-app> <servlet> <servlet-name>UsersServlet</servlet-name> <servlet-class>__package__.UsersServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>UsersServlet</servlet-name> <url-pattern>getCSV</url-pattern> </servlet-mapping> </web-app>

EDIT: Writing to disk instead of sending to browser

import java.io.FileWriter; import java.io.IOException; import User; public class GenerateCsv { private static void generateCsvFile(String fileName, ArrayList<User> users) { try { FileWriter writer = new FileWriter(fileName); writer.append("Email"); writer.append(','); writer.append("Name"); writer.append('\n'); for (User user in users) { writer.append(user.getEmail()); writer.append(','); writer.append(user.getName()); writer.append('\n'); } writer.flush(); writer.close(); } catch(IOException e) { e.printStackTrace(); } } }