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从servlet演进到springMVC

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2018年2月25日 下午8:08

JavaWeb三大组件（Servlet、Filter、Listener） - CSDN博客

阶段概述：

  1. servlet阶段：将URL请求能够通过web.xml的配置，映射URL到一个具体的servlet类，但是他不能映射到方法，所以，在selvet中我们还得通过具体的URL参数去手工敲码，跳向某个方法
  2. 基于servlet的MVC模式实现
    1. 这个主要是想用于和SpringMVC进行比较，就能清晰的知道SpringMVC到底做了什么。
    2. 代码在附录中
  3. SpringMVC牛逼的地方有：
    1. URL直接映射到方法，而不是仅仅是类，并且这个类也不是servlet了，就是一个普通给的类，只不过加上了@controller
    2. controller中操作service对象的方式：
      1. 在商品管理第四个知识点
    3. 从controller对于的方法执行完之后，跳转到jsp页面的方式
      1. 通过modelAndView
      2. 可以和基于servlet的MVC模式实现对比
    4. 代码实例：
      1. SpringMVC 基础教程 简单入门实例 - CSDN博客

附录：servlet的MVC模式实现

servlet的MVC模式实现目录结构：

EmployeeServlet.java

EmployeeServiceImpl.java

EmployeeService.java:就是接口而已

SuperDaoImpl.java:老师封装好的dao

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package com.shanxi.weixin.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Types;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.shanxi.weixin.dbUtils.DbUtils;

public class SuperDaoImpl implements SuperDao {


	@Override
	public List<Map<String, Object>> queryForList(String sql) {
		List<Map<String,Object>> list =  new ArrayList<Map<String, Object>>();
		try {
			Connection conn = DbUtils.getConnection();
			Statement sta = conn.createStatement();
			ResultSet rs = sta.executeQuery(sql);
			list = rsToList(rs);
			DbUtils.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return list;
	}
	

	@Override
	public int batchDelete(String sql, String[] ID) {
		Connection conn = DbUtils.getConnection();
		try {
			PreparedStatement ps = conn.prepareStatement(sql);
			if (ID.length>0){
	            for(int i=0;i<ID.length;i++){
	                ps.setInt(1,Integer.parseInt(ID[i]));   
	                ps.addBatch();             
	            }
	        }
			ps.executeBatch();  
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return 0;
	}


	@Override
	public List<Map<String, Object>> queryForList(String sql, int[] types, Object[] obj) {
		List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
		try {
			Connection conn = DbUtils.getConnection();
			PreparedStatement ps = conn.prepareStatement(sql);
			for (int i = 0; i < obj.length; i++) {
				switch (types[i]) {
				case Types.INTEGER:
					ps.setInt(i+1,Integer.parseInt(obj[i].toString()));
					break;
				case Types.VARCHAR:
					ps.setString(i+1,obj[i].toString());
					break;
				default:
					ps.setString(i+1,obj[i].toString());
				}
			}
			ResultSet rs = ps.executeQuery();
			list = rsToList(rs);
			DbUtils.close();
		
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		return list;
	}

	@Override
	public Map<String, Object> queryForMap(String sql) {
		List<Map<String,Object>> list =  new ArrayList<Map<String, Object>>();
		try {
			
			Connection conn = DbUtils.getConnection();
			Statement sta = conn.createStatement();
			ResultSet rs = sta.executeQuery(sql);
			list = rsToList(rs);
			DbUtils.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		if(!list.isEmpty()){
			return list.get(0);
		}
		return null;
	}
	@Override
	public Map<String, Object> queryForMap(String sql, int[] types, Object[] obj) {
		List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
		try {
			Connection conn = DbUtils.getConnection();
			PreparedStatement ps = conn.prepareStatement(sql);
			for (int i = 0; i < obj.length; i++) {
				switch (types[i]) {
				case Types.INTEGER:
					ps.setInt(i+1,Integer.parseInt(obj[i].toString()));
					break;
				case Types.VARCHAR:
					ps.setString(i+1,obj[i].toString());
					break;
				default:
					ps.setString(i+1,obj[i].toString());
				}
			}
			ResultSet rs = ps.executeQuery();
			list = rsToList(rs);
			DbUtils.close();
		
		} catch (SQLException e) {
			e.printStackTrace();
		}
		if(!list.isEmpty()){
			return list.get(0);
		}
		return null;
	}

	@Override
	public int excuteUpdate(String sql) {
		try {
			Connection conn = DbUtils.getConnection();
			Statement sta = conn.createStatement();
			int count = sta.executeUpdate(sql);
			DbUtils.close();
			return count;
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return 0;
	}

	@Override
	public int[] deleteDept(String sql1, String sql2) {
		try {
			int[] count = new int[2];
			Connection conn = DbUtils.getConnection();
			conn.setAutoCommit(false);
			Statement sta = conn.createStatement();
			int count1 = sta.executeUpdate(sql1);
			count[0] = count1;
			int count2 = sta.executeUpdate(sql2);
			count[1] = count2;
			conn.commit();
			DbUtils.close();
			return count;
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return null;
	}

	@Override
	public int excuteUpdate(String sql, int[] types, Object[] obj) {
		try {
			Connection conn = DbUtils.getConnection();
			PreparedStatement ps = conn.prepareStatement(sql);
			for (int i = 0; i < obj.length; i++) {
				switch (types[i]) {
				case Types.INTEGER:
					ps.setInt(i+1,Integer.parseInt(obj[i].toString()));
					break;
				case Types.VARCHAR:
					ps.setString(i+1,obj[i].toString());
					break;
				default:
					ps.setString(i+1,obj[i].toString());
				}
			}
			int count = ps.executeUpdate();
			DbUtils.close();
			return count;
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return 0;
	}

	@Override
	public int queryForCount(String sql) {
		try {
			Connection conn = DbUtils.getConnection();
			Statement sta = conn.createStatement();
			ResultSet rs = sta.executeQuery(sql);
			int count = 0 ;
			while(rs.next()){
				count = rs.getInt(1);
			}
			DbUtils.close();
			return count;
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return 0;
	}

	@Override
	public int queryForCount(String sql, int[] types, Object[] obj) {
		try {
			Connection conn = DbUtils.getConnection();
			PreparedStatement ps = conn.prepareStatement(sql);
			for (int i = 0; i < obj.length; i++) {
				switch (types[i]) {
				case Types.INTEGER:
					ps.setInt(i+1,Integer.parseInt(obj[i].toString()));
					break;
				case Types.VARCHAR:
					ps.setString(i+1,obj[i].toString());
					break;
				default:
					ps.setString(i+1,obj[i].toString());
				}
			}
			ResultSet rs = ps.executeQuery();
			int count = 0;
			while(rs.next()){
				count = rs.getInt(1);
			}
			DbUtils.close();
			return count;
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return 0;
	}

	private List<Map<String, Object>> rsToList(ResultSet rs) {
		List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
		try {
			while(rs.next()){
				Map<String, Object>  map =  new HashMap<String,Object>();
				for (int i = 1; i <= rs.getMetaData().getColumnCount(); i++) {
					switch (rs.getMetaData().getColumnType(i)) {
					case Types.INTEGER:
						map.put(rs.getMetaData().getColumnName(i),rs.getInt(i));
						break;
					case Types.VARCHAR:
						map.put(rs.getMetaData().getColumnName(i),rs.getString(i));
						break;
					default:
						map.put(rs.getMetaData().getColumnName(i),rs.getObject(i));
					}
				}
				list.add(map);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return list;
	}
	

	
}