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从数据库中读取数据（AJAX版本）

    博客分类：
  • J2EE
AjaxJavaServletSQL ServerMySQL 
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现在是用ajax 做从数据库读取数据的例子

1个jsp
Reg。jsp 
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head>
<script>
	var xmlHttp;//不能用数字，标识符的定义
	
		function creatXML(){//建立异步请求的对象,为了jsp和servlet的交互,固定写法,名字固定

		if(window.ActiveXObject){
			xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
		}else if(window.XMLHttpRequest){
			xmlHttp=new XMLHttpRequest();
		}
	}
	//调用的主要的方法
	function a(){
		creatXML();
		xmlHttp.open("GET","http://127.0.0.1:9999/test730/servlet/zf");
		xmlHttp.onreadystatechange=call;
		xmlHttp.send(null);
	}
	//
	function call(){
		if(xmlHttp.readyState==4){//固定写法 4 代表完成 
			if(xmlHttp.status==200){//固定写法  200 代表 网页正常
				var b=xmlHttp.responseXML.getElementsByTagName("rr");//按照标签的名字对应的是servlet里面的out.println("<rr>"+b.getCity()+"</rr>");
				var c=document.getElementById("city");// <select name="city" id="city">里面的id="city"
				for(var i=0;i<b.length;i++){//把b里面的数组做循环
				
					var d=document.createElement("option");//option是固定的html标签
					d.innerText=b[i].firstChild.nodeValue;//把城市输出的结果显示出来
					d.setAttribute("value",b[i].firstChild.nodeValue);//输入value值
					c.appendChild(d);//把option里面的东西放入到select标签里面
					
				}
			}
		}
	}
	//测试用的方法
	function c(){
		alert("gag");
	}
</script>
<body onload="a()">
<form id="form1" name="form1" method="post" action="reg.do">
  用户名：
  <label>
  <input name="username" type="text" id="username" />
  </label>
  <p>电话：
    <label>
    <input name="tel" type="text" id="tel" />
    </label>
  </p>
  <p>城市：
    <label>
    <select name="city" id="city">
			  
    </select>
    </label>
  </p>
  <p>
    <label>
    <input type="submit" name="Submit" value="提交" />
    </label>
  </p>
</form>
<input type="button" value="gaoying" onclick="a()"/>

</body>
</html>


1个servlet 
package sl;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;

import javabean.yonghu;

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

import db.DB;

public class zf extends HttpServlet {

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/xml");//设置返回的信息的类型
		PrintWriter out = response.getWriter();//为了显示输出。
		
		ArrayList a =new DB().yonghu();
		
		/**
		 * 做循环输出
		 */
		
		out.println("<citys>");
		for(int i=0;i<a.size();i++){
			yonghu b=(yonghu)a.get(i);
			out.println("<rr>"+b.getCity()+"</rr>");
		}
		out.println("</citys>");
		out.flush();//把流中的东西刷出去
		out.close();//关闭
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		
	}

}

DB包 
package db;

import java.sql.*;
import java.text.SimpleDateFormat;
import java.util.*;

import javabean.yonghu;


public class DB {
	private Connection conn;//用来连接数据库的“数据库连接对象”

	private PreparedStatement stmt;//数据库操作对象

	private ResultSet rs;

	public DB() {
		try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(
					"jdbc:mysql://localhost:3306/test728", "root", "1234");
					} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public boolean adduser(String username,String tel,String city) {
		try {

			stmt = conn
					.prepareStatement("insert into test728.user(username,tel,city) values(?,?,?)");
			//stmt.setInt(1, name);
			stmt.setString(1, username);
			stmt.setString(2, tel);
			stmt.setString(3, city);

			stmt.execute();

		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return false;

	}

		 public ArrayList yonghu(){
			ArrayList a=new ArrayList();
			try {
				
				stmt=conn.prepareStatement("select distinct city from test728.user");
	
				
				rs=stmt.executeQuery();
				while(rs.next()){

					yonghu c=new yonghu();
					//c.setId(Integer.parseInt(rs.getString("id")));
					//c.setUsername(rs.getString("username"));
					//c.setTel("tel");
					c.setCity(rs.getString("city"));
					a.add(c);
					
				}
			
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
			return a;
		}
}

1 个javabean 
package javabean;

public class yonghu {
	private int id;
	private String username;
	private String tel;
	private String city;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getTel() {
		return tel;
	}
	public void setTel(String tel) {
		this.tel = tel;
	}
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}

}

Web.xml 
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.4" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee   http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
  <servlet>
    <servlet-name>action</servlet-name>
    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
    <init-param>
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>debug</param-name>
      <param-value>3</param-value>
    </init-param>
    <init-param>
      <param-name>detail</param-name>
      <param-value>3</param-value>
    </init-param>
    <load-on-startup>0</load-on-startup>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>zf</servlet-name>
    <servlet-class>sl.zf</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>zf</servlet-name>
    <url-pattern>/servlet/zf</url-pattern>
  </servlet-mapping>
</web-app>


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