jQuery+ajax+servlet实现4级联动

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Servlet：
package com.servlet.ajax;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class AjaxServlet
 */
@WebServlet("/ajax.do")
public class AjaxServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

    /**
     * Default constructor. 
     */
    public AjaxServlet() {
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		this.doPost(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		String type = request.getParameter("type");
		String value = request.getParameter("value");
		PrintWriter pw = response.getWriter();
		System.out.println(type);
		
		if ("1".equals(type) && value != null && !"".equals(value)) { // 根据省获取市
			// 这里可以从数据库获取
			if ("hubei".equals(value)) {
				StringBuilder citys = new StringBuilder();
				citys.append("[");
				citys.append("{name:'武汉',value:'hubei001'},");
				citys.append("{name:'襄阳',value:'hubei002'}");
				citys.append("]");
				System.out.println(citys.toString());
				pw.print(citys.toString());
			}
		}
		else if ("2".equals(type) && value != null && !"".equals(value)) { // 根据省获取县
			// 这里可以从数据库获取
			StringBuilder countries = new StringBuilder();
			if ("hubei001".equals(value)) {
				countries.append("[");
				countries.append("{name:'AAA县',value:'wuhan001'},");
				countries.append("{name:'BBB县',value:'wuhan002'},");
				countries.append("{name:'CCC县',value:'wuhan003'}");
				countries.append("]");
			}
			else if ("hubei002".equals(value)) {
				countries.append("[");
				countries.append("{name:'南漳县',value:'xiangyang001'},");
				countries.append("{name:'古城县',value:'xiangyang002'}");
				countries.append("]");
			}
			
			System.out.println(countries.toString());
			pw.print(countries.toString());
		}
		else if ("3".equals(type) && value != null && !"".equals(value)) {
			StringBuilder towns = new StringBuilder();

			if ("wuhan001".equals(value)) {
				towns.append("[");
				towns.append("{name:'AAA镇',value:'wuhan001'},");
				towns.append("{name:'BBB镇',value:'wuhan002'},");
				towns.append("{name:'CCC镇',value:'wuhan003'}");
				towns.append("]");
				
			}
			else if ("wuhan002".equals(value)) {
				towns.append("[");
				towns.append("{name:'CCC镇',value:'wuhan001'},");
				towns.append("{name:'DDD镇',value:'wuhan002'},");
				towns.append("{name:'EEE镇',value:'wuhan003'}");
				towns.append("]");
			}
			else if ("wuhan003".equals(value)) {
				towns.append("[");
				towns.append("{name:'FFF镇',value:'wuhan001'},");
				towns.append("{name:'GGG镇',value:'wuhan002'}");
				towns.append("]");
			}
			else if ("xiangyang001".equals(value)) {
				towns.append("[");
				towns.append("{name:'WWW镇',value:'wuhan001'},");
				towns.append("{name:'RRR镇',value:'wuhan002'}");
				towns.append("]");
			}
			else if ("xiangyang002".equals(value)) {
				towns.append("[");
				towns.append("{name:'XXX镇',value:'wuhan001'},");
				towns.append("{name:'YYY镇',value:'wuhan002'}");
				towns.append("]");
			}
			
			System.out.println(towns.toString());
			pw.print(towns.toString());
		}
	}

}

JSP：
<%@ page language="java" contentType="text/html; charset=GB18030"
    pageEncoding="GB18030"%>










	省：
			请选择一个省
			湖北
		
	市：
	县：
	镇：
	
	




注意：需引入servlet3.0的jar