二、处理AJAX请求的servlet

package classmate;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class SignUpAction extends HttpServlet {
   public void init(ServletConfig config) throws ServletException {
  }
    /*
     *  处理<GET> 请求方法.
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
     //设置接收信息的字符集
     request.setCharacterEncoding("UTF-8");
     //接收浏览器端提交的信息
  String uname = request.getParameter("uname");
  String psw = request.getParameter("psw");  
  //设置输出信息的格式及字符集       
        response.setContentType("text/xml; charset=UTF-8");
        response.setHeader("Cache-Control", "no-cache");
        //创建输出流对象
        PrintWriter out = response.getWriter();
        //依据验证结果输出不同的数据信息
        out.println("<response>");  
       
        //数据库操作
        DB db = new DB();
  ResultSet rs;
  int insRes = 0;
        String strSql=null;
        //判断用户名是否重复
        strSql = "select * from classuser where username='"
   + uname + "'";
  rs = db.executeQuery(strSql);
  boolean bnoRepeat = false;
  try {
   if ( !rs.next()) {
    bnoRepeat = true;
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }
        //用户名不重复,插入记录
  if (bnoRepeat){
            strSql = "Insert Into classuser values('"+ uname + "','" + psw + "')";
   insRes = db. executeUpdate(strSql);
        }
        if(!bnoRepeat){
   out.println("<res>" + "注册失败!用户名已存在，重新输入用户名" + "</res>");
  }else if(insRes>0){
   out.println("<res>" + "注册成功！" + "</res>");
  }else{
   out.println("<res>" + "注册失败！" + "</res>");
  } 
 
  out.println("</response>");
  out.close();
    }
}

三、数据库操作类：

package classmate;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DB {
 Connection connect = null;
 ResultSet rs = null;
 public DB() {
  try {
   Class.forName("org.gjt.mm.mysql.Driver");  //设置驱动程序类型  
  }
  catch(java.lang.ClassNotFoundException e) {
   e.printStackTrace();
  }
 }
 //执行查询语句的方法
 public ResultSet executeQuery(String sql) {
  try {
//建立与数据库服务器的连接
     onnect = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test1", "root", "");<br>     tatement stmt = connect.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
   rs = stmt.executeQuery(sql);//执行指定的数据查询语句
  }
  catch(SQLException ex) {
   ex.printStackTrace();
  }
  return rs;
 }
    //执行增、删改语句的方法
 public int executeUpdate(String sql) {
  int result = 0;
  try {
   connect = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test1", "root", "");
   Statement stmt = connect.createStatement();
   result = stmt.executeUpdate(sql);//执行指定的数据操作语句
  }
  catch(SQLException ex) {
   System.err.println(ex.getMessage());  
  }
  return result;
 }
 //关闭数据库连接的方法
 public void close(){
  if(connect!=null){
   try{
    connect.close();
    connect = null; 
   }catch(SQLException ex) {
    System.err.println(ex.getMessage());
   }
  } 
 }
 
}

四、web.xml文件中配置servlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<servlet>
<servlet-name>ms1</servlet-name>
<servlet-class>classmate.SignUpAction</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ms1</servlet-name>
<url-pattern>/signUp</url-pattern>
</servlet-mapping>

<!-- The Welcome File List -->
<welcome-file-list>
<welcome-file>signUp.jsp</welcome-file>
</welcome-file-list>
</web-app>
 

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