ajax实现省市县三级联动

根据mvc分层思想

v层(视图层)

select.jsp(未封装公共方法)

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>



  
    
    My JSP 'select.jsp' starting page
    
     
     
     
     
  
  
  	
省: 市: 区\县:
select2.jsp(封装公共方法) <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> My JSP 'select.jsp' starting page
省: 市: 区\县:

m层(service业务处理层,dao层数据访问层,pojo实体类层)

dao

AreaDao.java

package com.madi.dao;

import java.util.List;

import com.madi.pojo.Area;

public interface AreaDao {
	/**
	 * 根据pid查询地区信息
	 * @param pid
	 * @return
	 */
	List getAreaInfoDao(String pid);

}
AreaDaoImpl.java

package com.madi.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.madi.dao.AreaDao;
import com.madi.pojo.Area;
import com.madi.util.DBUtil;

public class AreaDaoImpl implements AreaDao{
	//根据pid查询地区信息
	public List getAreaInfoDao(String pid) {
		//声明jdbc变量
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		//声明变量
		ArrayList la=null;
		try {
			//获取连接
			conn=DBUtil.getConnection();
			//创建SQL命令
			String sql="select * from area where parentid=?";
			//创建SQL命名对象
			ps=conn.prepareStatement(sql);
			//给占位符赋值
			ps.setString(1,pid);
			//执行sql
			rs=ps.executeQuery();
			la=new ArrayList<>();
			//遍历结果
			while (rs.next()) {
				//创建实体类对象
				Area a=new Area();
				a.setAreaid(rs.getInt("areaid"));
				a.setAreaname(rs.getString("areaname"));
				a.setParentid(rs.getInt("parentid"));
				a.setArealevel(rs.getInt("arealevel"));
				a.setStatus(rs.getInt("status"));
				
				la.add(a);
			}
			//关闭资源
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			DBUtil.closeAll(rs, ps, conn);
		}
		
		//返回
		return la;
	}

}

service层

AreaService.java

package com.madi.service;

import java.util.List;

import com.madi.pojo.Area;

public interface AreaService {
	/**
	 *根据pid查询地区信息
	 * @param pid
	 * @return
	 */
	List getAreaInfoService(String pid);

}
AreaServiceImpl.java

package com.madi.service.impl;

import java.util.List;

import com.madi.dao.AreaDao;
import com.madi.dao.impl.AreaDaoImpl;
import com.madi.pojo.Area;
import com.madi.service.AreaService;

public class AreaServiceImpl implements AreaService{
	//创建Dao层对象
	AreaDao ad=new AreaDaoImpl();
	//根据pid查询地区信息
	@Override
	public List getAreaInfoService(String pid) {
		
		return ad.getAreaInfoDao(pid);
	}
	
}

pojo层

Area.java

package com.madi.pojo;

public class Area {
	private int areaid;
	private String areaname;
	private int parentid;
	private int arealevel;
	private int status;
	public int getAreaid() {
		return areaid;
	}
	public void setAreaid(int areaid) {
		this.areaid = areaid;
	}
	public String getAreaname() {
		return areaname;
	}
	public void setAreaname(String areaname) {
		this.areaname = areaname;
	}
	public int getParentid() {
		return parentid;
	}
	public void setParentid(int parentid) {
		this.parentid = parentid;
	}
	public int getArealevel() {
		return arealevel;
	}
	public void setArealevel(int arealevel) {
		this.arealevel = arealevel;
	}
	public int getStatus() {
		return status;
	}
	public void setStatus(int status) {
		this.status = status;
	}
	@Override
	public String toString() {
		return "Area [areaid=" + areaid + ", areaname=" + areaname
				+ ", parentid=" + parentid + ", arealevel=" + arealevel
				+ ", status=" + status + "]";
	}
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + areaid;
		result = prime * result + arealevel;
		result = prime * result
				+ ((areaname == null) ? 0 : areaname.hashCode());
		result = prime * result + parentid;
		result = prime * result + status;
		return result;
	}
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Area other = (Area) obj;
		if (areaid != other.areaid)
			return false;
		if (arealevel != other.arealevel)
			return false;
		if (areaname == null) {
			if (other.areaname != null)
				return false;
		} else if (!areaname.equals(other.areaname))
			return false;
		if (parentid != other.parentid)
			return false;
		if (status != other.status)
			return false;
		return true;
	}
	public Area() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Area(int areaid, String areaname, int parentid, int arealevel,
			int status) {
		super();
		this.areaid = areaid;
		this.areaname = areaname;
		this.parentid = parentid;
		this.arealevel = arealevel;
		this.status = status;
	}
	
	
	
	
}

c层

servlet

AreaServlet.java

package com.madi.servlet;

import java.io.IOException;
import java.util.List;

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

import com.madi.pojo.Area;
import com.madi.service.AreaService;
import com.madi.service.impl.AreaServiceImpl;
import com.google.gson.Gson;

public class AreaServlet extends HttpServlet {
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//设置请求编码格式
		req.setCharacterEncoding("utf-8");
		//设置响应编码格式
		resp.setContentType("text/html;charset=utf-8");
		//获取请求信息
		String pid=req.getParameter("parentid");
		//处理请求
			//获取业务层对象
			AreaService as=new AreaServiceImpl();
			List la=as.getAreaInfoService(pid);
		//响应处理结果
			//直接响应
			resp.getWriter().write(new Gson().toJson(la));
	}
}

Dbutil.java工具类

package com.madi.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class DBUtil {
	//声明全局变量记录jdbc参数
	private static String driver;
	private static String url;
	private static String username;
	private static String password;
	//使用静态代码块,在类加载时即完成对属性文件的读取
	static{
		//动态获取属性配置文件的流对象
		InputStream in=DBUtil.class.getResourceAsStream("/db.properties");
		//创建Properties对象
		Properties p=new Properties();
		//加载
		try {
			p.load(in);//会将属性配置文件的所有数据存储到Properties对象中
			//将读取的jdbc参数赋值给全局变量
			driver=p.getProperty("driver");
			url=p.getProperty("url");
			username=p.getProperty("username");
			password=p.getProperty("password");
			//加载驱动
			Class.forName(driver);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	//创建连接对象并返回
	public static Connection getConnection(){
		Connection conn=null;
		try {
			conn = DriverManager.getConnection(url, username, password);
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		return conn;
	}
	//关闭资源
	public static void closeAll(ResultSet rs,Statement stmt,Connection conn){
		try {
			if(rs!=null){
				rs.close();
			}
		} catch (SQLException e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
		}
		try {
			stmt.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			conn.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}
	//封装增加删除修改的通用工具方法
	/**
	 * @param sql SQL语句
	 * @param objs	SQL语句占位符实参,如果没有参数则传入null
	 * @return 返回增删改的结果,类型为int
	 */
	public static int executeDML(String sql,Object...objs){
		// 声明jdbc变量
				Connection conn = null;
				PreparedStatement ps = null;
				int i = -1;
				try {
					// 获取连接对象
					conn = DBUtil.getConnection();
					// 开启事务管理
					conn.setAutoCommit(false);
					// 创建SQL命令对象
					ps = conn.prepareStatement(sql);
					// 给占位符赋值
					if(objs!=null){
						for(int j=0;j

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