自定义mvc(2)

最新推荐文章于 2023-06-29 21:43:07 发布

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最新推荐文章于 2023-06-29 21:43:07 发布

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本文链接：https://blog.youkuaiyun.com/lei_lin/article/details/93792805

本文详细介绍了一次自定义MVC框架的升级过程，包括工具类封装为JAR包、DAO层通用方法实现、Web层Action设计及视图层JSP页面展示。通过反射优化，实现了通用的增删改查功能。

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自定义mvc的最后一次升级

1、把所写好的工具类导成jar包
在这里插入图片描述
找到JAR file选择你要导出的文件路径:

最后点击finish,就把文件成功的导出来了

2、dao层通用的增删改方法
BaseDao

package com.leiyuanlin.dao;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.leiyuanlin.util.DBAccess;
import com.leiyuanlin.util.PageBean;

/**
 * T代表你要对哪个实体类对应表进行分页查询
 * @author 2018101801
 *
 * @param <T>
 */
public class BaseDao<T> {
	/**
	 * 
	 * @param sql	查询不同的实体类，那么对应的sql不同，所以需要传递
	 * @param clz	生产出不同的实体类对应的实例，然后装进list容器中返回
	 * @param pageBean	决定是否分页
	 * @return
	 * @throws SQLException
	 * @throws IllegalAccessException 
	 * @throws InstantiationException 
	 */
	public List<T> executeQuery(String sql,Class clz,PageBean pageBean) throws SQLException, InstantiationException, IllegalAccessException{
		Connection con = DBAccess.getConnection();
		PreparedStatement pst = null;
		ResultSet rs = null;
		
		if(pageBean != null && pageBean.isPagination()) {
//			3、考虑该方法可以进行分页
//			需要分页
//			3.1	算符合总记录数
			String countSql = getCountSql(sql);
			pst = con.prepareStatement(countSql);
			rs = pst.executeQuery();
			if(rs.next()) {
				pageBean.setTotal(rs.getLong(1)+"");
			}
			
//			3.2	查询出符合条件的结果集
			String pageSql = getPageSql(sql,pageBean);
			pst = con.prepareStatement(pageSql);
			rs = pst.executeQuery();
		}else {
			pst = con.prepareStatement(sql);
			rs = pst.executeQuery();
		}
		
		
		List<T> list = new ArrayList<>();
		T t;
		while(rs.next()) {
			/*
			 * 1、实例化一个book对象（该对象是空的，里面的属性没有值）
			 * 2、取book的所有属性，然后给其赋值
			 * 	2.1	获取所有属性对象
			 * 	2.2	给属性对象赋值
			 * 3、赋完值的book对象装进list容器中
			 */
//			list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
			t = (T) clz.newInstance();
			Field[] fields = clz.getDeclaredFields();
			for (Field field : fields) {
				field.setAccessible(true);
				field.set(t, rs.getObject(field.getName()));
			}
			list.add(t);
		}
		DBAccess.close(con, pst, rs);
		return list;
	}
	
	/**
	 * 利用原生sql拼接出符合条件的结果集的查询sql
	 * @param sql
	 * @param pageBean
	 * @return
	 */
	private String getPageSql(String sql, PageBean pageBean) {
		return sql+" limit "+pageBean.getStartIndex()+","+pageBean.getRows();
	}

	/**
	 * 获取符合条件的总记录数的sql语句
	 * @param sql
	 * @return
	 */
	private String getCountSql(String sql) {
		return "select count(1) from ("+sql+") t";
	}
	
	/**
	 * 
	 * @param sql	决定增删改的一种
	 * @param attrs	决定?的位置	new String[]{"bid","bname",...}
	 * @param t	要操作的实体类
	 * @return
	 * @throws SQLException 
	 * @throws SecurityException 
	 * @throws NoSuchFieldException 
	 * @throws IllegalAccessException 
	 * @throws IllegalArgumentException 
	 */
	public int executeUpdate(String sql, String[] attrs ,T t) throws SQLException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException{
		Connection con = DBAccess.getConnection();
		PreparedStatement pst = con.prepareStatement(sql);
		for (int i = 1; i <= attrs.length; i++) {
			Field field = t.getClass().getDeclaredField(attrs[i-1]);
			field.setAccessible(true);
			pst.setObject(i, field.get(t));
		}
		int num = pst.executeUpdate();
		DBAccess.close(con, pst, null);
		return num;
	}
}

bookDao(继承于BaseDao)

package com.leiyuanlin.dao;
/**
 * 目的：做一个通用的分页的查询方法
 * 	1、利用s2的知识完成一个普通的查询方法
 * 	2、将原有的查询方法进行反射优化，转变成一个可以被所有实体类dao层所继承的通用查询方法
 * 	3、考虑该方法可以进行分页
 * 		3.1	算总记录数
 * 		3.2	查询出当前页的结果集
 * 
 * @author 2018101801
 *
 */

import java.sql.SQLException;
import java.util.List;

import com.leiyuanlin.entity.Book;
import com.leiyuanlin.util.PageBean;
import com.leiyuanlin.util.StringUtils;

public class BookDao extends BaseDao<Book>{
	/**
	 * 查询方法
	 * @param book	封装着jsp传递过来的查询参数
	 * @param pageBean	决定dao层的list调用时是否分页
	 * @return
	 * @throws SQLException 
	 * @throws IllegalAccessException 
	 * @throws InstantiationException 
	 */
	public List<Book> list(Book book,PageBean pageBean) throws SQLException, InstantiationException, IllegalAccessException{
		String sql = "select * from t_mvc_book where true ";
		String bname = book.getBname();
		int bid = book.getBid();
		
		if(StringUtils.isNotBlank(bname)) {
			sql += " and bname like '%"+bname+"%'";
		}
		if(bid != 0) {
			sql += " and bid ="+bid;
		}
		return super.executeQuery(sql, Book.class, pageBean);
	}
	
	/**
	 * 新增
	 * @param book
	 * @return
	 * @throws SQLException
	 * @throws NoSuchFieldException
	 * @throws SecurityException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public int add(Book book) throws SQLException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
		String sql = "insert into t_mvc_book values(?,?,?)";
		return super.executeUpdate(sql, new String[] {"bid","bname","price"}, book);
	}
	
	/**
	 * 删除
	 * @param book
	 * @return
	 * @throws SQLException
	 * @throws NoSuchFieldException
	 * @throws SecurityException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public int del(Book book) throws SQLException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
		String sql = "delete from t_mvc_book where bid=?";
		return super.executeUpdate(sql, new String[] {"bid"}, book);
	}
	
	/**
	 * 修改
	 * @param book
	 * @return
	 * @throws SQLException
	 * @throws NoSuchFieldException
	 * @throws SecurityException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public int edit(Book book) throws SQLException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
		String sql = "update t_mvc_book set bname=?,price=? where bid=?";
		return super.executeUpdate(sql, new String[] {"bname","price","bid"}, book);
	}
	
	
}

3、web层(BookAction)

package com.leiyuanlin.web;

import java.sql.SQLException;
import java.util.List;

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

import com.leiyuanlin.dao.BookDao;
import com.leiyuanlin.entity.Book;
import com.leiyuanlin.framework.ActionSupport;
import com.leiyuanlin.framework.ModelDrivern;
import com.leiyuanlin.util.PageBean;

public class BookAction extends ActionSupport implements ModelDrivern<Book>{
	private Book book = new Book();
	private BookDao bookDao = new BookDao();
	
	/**
	 * 分页查询
	 * @param req
	 * @param resp
	 * @return
	 */
	public String list(HttpServletRequest req,HttpServletResponse resp) {
		PageBean pageBean = new PageBean();
		pageBean.setRequest(req);
		try {
			List<Book> list = this.bookDao.list(book, pageBean);
			req.setAttribute("bookList", list);
			req.setAttribute("pageBean", pageBean);
		} catch (InstantiationException | IllegalAccessException | SQLException e) {
			e.printStackTrace();
		}
		return "list";
	}
	
	/**
	 * 跳转到增加或者修改页面
	 * @param req
	 * @param resp
	 * @return
	 */
	public String preSave(HttpServletRequest req,HttpServletResponse resp) {
//		bid的类型是int类型，而int类型的默认值是0，如果jsp未传递bid的参数值，那么bid=0
		if(book.getBid() == 0) {
			System.out.println("增加逻辑...");
		}else {
			try {
//				修改数据回显逻辑
				Book b = this.bookDao.list(book, null).get(0);
				req.setAttribute("book", b);
			} catch (InstantiationException | IllegalAccessException | SQLException e) {
				e.printStackTrace();
			}
		}
//		新增页面与修改页面是同一个jsp
		return "edit";
	}
	
	/**
	 * 新增
	 * @param req
	 * @param resp
	 * @return
	 */
	public String add(HttpServletRequest req,HttpServletResponse resp) {
		try {
			this.bookDao.add(book);
		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException
				| SQLException e) {
			e.printStackTrace();
		}
		return "toList";
	}
	
	/**
	 * 修改
	 * @param req
	 * @param resp
	 * @return
	 */
	public String edit(HttpServletRequest req,HttpServletResponse resp) {
		try {
			this.bookDao.edit(book);
		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException
				| SQLException e) {
			e.printStackTrace();
		}
		return "toList";
	}
	
	/**
	 * 删除
	 * @param req
	 * @param resp
	 * @return
	 */
	public String del(HttpServletRequest req,HttpServletResponse resp) {
		try {
			this.bookDao.del(book);
		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException
				| SQLException e) {
			e.printStackTrace();
		}
		return "toList";
	}
	
	
	@Override
	public Book getModel() {
		return book;
	}
}

对mvc.xml进行配置

<?xml version="1.0" encoding="UTF-8"?>

<config>
	<action path="/cal" type="com.leiyuanlin.web.CalAction">
		<forward name="res" path="/res.jsp" redirect="false" />
	</action>
	
</config>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>web_mvc</display-name>
  <filter>
  	<filter-name>encodingFiter</filter-name>
  	<filter-class>com.leiyuanlin.util.EncodingFiter</filter-class>
  </filter>
  
  <filter-mapping>
  	<filter-name>encodingFiter</filter-name>
  	<url-pattern>*.action</url-pattern>
  </filter-mapping>
  
  <servlet>
  	<servlet-name>dispatcherServlet</servlet-name>
  	<servlet-class>com.leiyuanlin.framework.DispatcherServlet</servlet-class>
  	<init-param>
  		<param-name>xmlPath</param-name>
  		<param-value>/mvc.xml</param-value>
  	</init-param>
  </servlet>
  
  <servlet-mapping>
  	<servlet-name>dispatcherServlet</servlet-name>
  	<url-pattern>*.action</url-pattern>
  </servlet-mapping>
  
</web-app>

4、jsp
bookList.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@taglib uri="/leiyuanlin" prefix="z" %>
<!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>Insert title here</title>
</head>
<body>
	<h2>小说目录</h2>
	<br>

	<form action="${pageContext.request.contextPath}/book.action?methodName=list"
		method="post">
		书名：<input type="text" name="bname"> <input type="submit"
			value="确定">
			<input type="hidden" name="rows" value="15">
	</form>
	<a href="${pageContext.request.contextPath}/book.action?methodName=preSave">增加</a>
	<table border="1" width="100%">
		<tr>
			<td>编号</td>
			<td>名称</td>
			<td>价格</td>
			<td>操作</td>
		</tr>
		<c:forEach items="${bookList }" var="b">
			<tr>
				<td>${b.bid }</td>
				<td>${b.bname }</td>
				<td>${b.price }</td>
				<td>
					<a href="${pageContext.request.contextPath}/book.action?methodName=preSave&&bid=${b.bid}">修改</a>&nbsp;
					<a href="${pageContext.request.contextPath}/book.action?methodName=del&&bid=${b.bid}">删除</a>
				</td>
			</tr>
		</c:forEach>
	</table>
	<z:page pageBean="${pageBean }"></z:page>
</body>
</html>

bookEdit.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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>Insert title here</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/book.action" method="post">
	<input type="hidden" name="methodName" value="${book.bname == null ? 'add' : 'edit' }">
	书籍ID：<input type="text" name="bid" value="${book.bid }"><br>
	书籍名称：<input type="text" name="bname" value="${book.bname }"><br>
	书籍价格：<input type="text" name="price" value="${book.price }"><br>
	<input type="submit">
</form>
</body>
</html>

注意：
在做增删改操作的时候用重定向，查询时用转发
在这里插入图片描述
这样做的目的是阻止多次上传请求带来数据重复的影响
感谢观看！