java web app 导出csv excel 文件


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();
}
}
}