Servlet如何返回XML类型的数据

package com.panlong.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AjaxXmlServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {

try {
//1.取参数
resp.setContentType("text/xml;charset=UTF-8");
PrintWriter out = resp.getWriter();
StringBuilder builder = new StringBuilder();

String old = req.getParameter("name");

//2、检查参数是否有问题
String name = old;

builder.append("<message>");
if("".equals(old) || old == null){
builder.append("用户名必须输入").append("</message>");

}
else
{

if("lila".equals(name)){
builder.append("该用户名已经注册").append("</message>");
}else{
builder.append("该用户名未注册，您可以注册["+name+"]这个用户名").append("</message>");

}
}
out.println(builder.toString());

}catch (Exception e) {
e.printStackTrace();
//3.检验操作
}
}

protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doGet(req, resp);
}

}