AJAX interacts with the database to determine whether the user is registered

This time I will bring you AJAX to interact with the database to determine whether the user is registered, and AJAX to interact with the database to determine whether the user is registered. What are the precautions? Here is a practical case, let's take a look.

On many registration pages, we may encounter the following situation. When we register a user name, we may be prompted that the user name has been registered. The implementation is to apply AJAX technology.

First write a login page

用户ID 

姓名：

密码：

Then write a servlet Java code

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CheckServlet extends HttpServlet{
public static final String DBDRIVER = "oracle.jdbc.OracleDriver";
public static final String DBURL = "jdbc:oracle:thin:@59.173.240.149:1521:heer";
public static final String DBUSER = "hnsyu_dev";
public static final String DBPASS = "hnsyuok";
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException{
this.doPost(request, response);
}
public void doPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException{
request.setCharacterEncoding("gbk");
response.setContentType("text/html");
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
PrintWriter out = response.getWriter();
String userid = request.getParameter("userid");
try {
Class.forName(DBDRIVER);
connection = DriverManager.getConnection(DBURL, DBUSER, DBPASS);
String sql = "select count(userid) from userdemo where userid=?";
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1,userid);
resultSet = preparedStatement.executeQuery();
if (resultSet.next()) {
if(resultSet.getInt(1)>0){
out.print("false");
System.out.println("true");
}else {
out.print("false");
}
}
out.close();
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
connection.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}

It also needs to be configured in web.xml

  
 
  index.jsp
 
  
 CheckServlet
 CheckServlet
 
 
 CheckServlet
 /CheckServlet
  

Believe it After reading the case in this article, you have mastered the method. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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