HTTP Status 500 - Cannot call sendRedirect() after the response has been committ
package package1;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
import javax.servlet.ServletConfig;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RegisterProcessAction
 */
public class RegisterProcessAction extends HttpServlet {
private static final long serialVersionUID = 1L;
  private Connection cn = null;
  private String drivername = null;
  private String url = null;
  private String user = null;
  private String password = null;
  public void init(ServletConfig config) throws ServletException
  {
  super.init(config);
  drivername = config.getInitParameter("drivername");
  url = config.getInitParameter("url");
  try{
  Class.forName(drivername);
  cn = DriverManager.getConnection(url,user,password);
  }catch(Exception e){
  System.out.println("取得数据库连接错误："+e.getMessage());
  }
  }
   

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String userid = request.getParameter("userid");
String password = request.getParameter("password");
String repassword = request.getParameter("repassword");
String name = request.getParameter("name");
if(userid==null||userid.trim().length()==0){
response.sendRedirect("register.jsp");
}
if(password==null||password.trim().length()==0){
response.sendRedirect("register.jsp");
}
if(repassword==null||repassword.trim().length()==0){
response.sendRedirect("register.jsp");
}
if(!password.equals(repassword)){
response.sendRedirect("register.jsp");
}
if(name!=null&&name.trim().length()>0){
name = new String(name.getBytes("UTF-8"));
}
String sql = "insert into register(userid,name,password)values(?,？,？)";
try{
PreparedStatement ps = cn.prepareStatement(sql);
ps.setString(1, userid);
ps.setString(2, name);
ps.setString(3, password);
ps.executeUpdate();
ps.close();
response.sendRedirect("success.jsp");
}catch(Exception e){
System.out.println("错误："+e.getMessage());
response.sendRedirect("register.jsp");
}
}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}
public void destroy(){
super.destroy();
try{
cn.close();
}catch(Exception e){
System.out.println("关闭数据库错误："+e.getMessage());
}
}

}

运行之后老是出现HTTP Status 500 - Cannot call sendRedirect() after the response has been committed

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