Ajax实现下拉列表联动

最新推荐文章于 2021-08-06 02:12:36 发布

wj603201

最新推荐文章于 2021-08-06 02:12:36 发布

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分类专栏： AJAX 文章标签： Ajax Java Servlet XML Netbeans

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本文介绍了一种使用Ajax实现的下拉列表联动效果，当用户选择一级列表项时，会触发Ajax请求，从服务器获取相应的二级列表选项并更新页面。

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Ajax实现下拉列表联动
1.取得一级列表中的值，通过XMLHttpRequest发送给服务器；
2.服务器根据传入参数在内存或数据库中找到相应信息，返回给客户端；
3.客户端根据返回值更新二级列表。

select.html:
程序代码

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Select</title>
<script type="text/javascript" src="js/select.js"></script>
</head>
<body>
<h2>Select</h2>
<select id="first" onChange="change();">
<option value="">Please select</option>
<option value="J2EE">J2EE</option>
<option value="DataBase">DataBase</option>
<option value="Tools">Tools</option>
</select>
<select id="second">
<option value="">Please select</option>
</select>
</body>
</html>

select.js:
程序代码

var xmlHttp;

function createXMLHttpRequest() {
if (window.ActiveXObject) {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
} else if (window.XMLHttpRequest) {
xmlHttp = new XMLHttpRequest();
}
}

function change() {
createXMLHttpRequest();
var first = document.getElementById("first").value;
var timeStamp = new Date().getTime();
var url = "select.mgc?first=" + first + "×tamp=" + timeStamp;
xmlHttp.onreadystatechange = callback;
xmlHttp.open("GET", url, true);
xmlHttp.send(null);
}

function callback() {
if (xmlHttp.readyState == 4) {
if (xmlHttp.status == 200) {
parseResult();
}
}
}

function parseResult() {
var xmlDoc = xmlHttp.responseXML;
var javas = xmlDoc.getElementsByTagName("java");
var second = document.getElementById("second");
second.length = 1;
for (var i = 0; i < javas.length; i++) {
var java = javas[i].childNodes[0].nodeValue;
var len = second.length;
second.options[len] = new Option(java, java);
}
}

select.html:
程序代码

package cn.edu.ahau.mgc.ajax.select;

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

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

public class Select extends HttpServlet {

private List<Java> javas = new ArrayList<Java>();

@Override
public void init() throws ServletException {
super.init();
this.initData();
}

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("UTF-8");
String first = request.getParameter("first");
List<Java> rsJavas = query(first);
String xml = "<javas>";
for (Iterator<Java> iter = rsJavas.iterator(); iter.hasNext();) {
Java java = (Java) iter.next();
xml += "<java>" + java.getSecond() + "</java>";
}
xml += "</javas>";
response.setContentType("text/xml");
PrintWriter out = response.getWriter();
out.print(xml);
out.close();
}

private List<Java> query(String first) {
List<Java> rsJavas = new ArrayList<Java>();
for (Iterator<Java> iter = javas.iterator(); iter.hasNext();) {
Java java = (Java) iter.next();
if (java.getFirst().equals(first)) {
rsJavas.add(java);
}
}
return rsJavas;
}

private void initData() {
javas.add(new Java("J2EE", "JSP"));
javas.add(new Java("J2EE", "Servlet"));
javas.add(new Java("J2EE", "Struts"));
javas.add(new Java("J2EE", "Hibernate"));
javas.add(new Java("J2EE", "Spring"));
javas.add(new Java("DataBase", "SQL Server"));
javas.add(new Java("DataBase", "MySQL"));
javas.add(new Java("DataBase", "Oracle"));
javas.add(new Java("DataBase", "DB2"));
javas.add(new Java("Tools", "NetBeans"));
javas.add(new Java("Tools", "MyEclipse"));
javas.add(new Java("Tools", "JBuild"));
}

class Java {
private String first;
private String second;

Java(String first, String second) {
this.first = first;
this.second = second;
}

public String getFirst() {
return first;
}

public void setFirst(String first) {
this.first = first;
}

public String getSecond() {
return second;
}

public void setSecond(String second) {
this.second = second;
}
}

}

web.xml:
程序代码

<?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>
<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>Select</servlet-name>
<servlet-class>cn.edu.ahau.mgc.ajax.select.Select</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>Select</servlet-name>
<url-pattern>/select.mgc</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>