作用域对象ServletContext（添加、删除和修改，模糊查询）

ゝ一纸荒年。 2024-03-26 13:06 73阅读 0赞

1.  ## ServletContext ##

ServetContext官方叫servlet上下文。服务器会为每一个工程创建一个对象，这个对象就是ServletContext对象。这个对象全局唯一，而且工程内部的所有servlet都共享这个对象。所以叫全局应用程序共享对象。

一个web应用对应一个ServletContext实例，这个实例是应用部署启动后，servlet容器为应用创建的。ServletContext实例包含了所有servlet共享的资源信息。通过提供一组方法给servlet使用，用来和servlet容器通讯。

> ServletContext 被 Servlet 程序用来与 Web 容器通信。例如写日志，转发请求。每一个 Web 应用程序含有一个Context，被Web应用内的各个程序共享。因为Context可以用来保存资源并且共享，所以我所知道的 ServletContext 的最大应用是Web缓存----把不经常更改的内容读入内存，所以服务器响应请求的时候就不需要进行慢速的磁盘I/O了。

![780a565052c9865ee7f9e9331997cb18.png][]

session默认的生存时间是1800秒。

有没有生存时间更长的对象来实现页面间或不同的Servlet间的数据共享呢？

在Servet AP操供了ServletContext接口来实现上述功能，运行在同一个容器中的Servlet使用ServletContext来共享存在于其中的信息和属性。

ServletContext接口中定义了用于处理上下文的方法

<table style=""> 
 <tbody> 
  <tr> 
   <td style="width:272px;vertical-align:top;height:51px;"><p style="">方法</p></td> 
   <td style="width:500px;vertical-align:top;height:51px;"><p style="">说明</p></td> 
  </tr> 
  <tr> 
   <td style="width:272px;vertical-align:top;height:51px;"><p style="">Object getAttribute(String</p><p style="">name)</p></td> 
   <td style="width:500px;vertical-align:top;height:51px;"><p style="">根据name属性返回在上下文中绑定的对象，如果指定的属性不存在，则返回null</p></td> 
  </tr> 
  <tr> 
   <td style="width:272px;vertical-align:top;height:51px;"><p style="">void setAttribute(Stringname, Object object)</p></td> 
   <td style="width:500px;vertical-align:top;height:51px;"><p style="">把一个对象和属性名绑定在一起，并保存到Servlet上下文中。如果名字属性已经存在，则先把它从上下文中删除，并将名字同新属性值绑定在一起</p></td> 
  </tr> 
  <tr> 
   <td style="width:272px;vertical-align:top;height:51px;"><p style="">void removeAttribute(String</p><p style="">name)</p></td> 
   <td style="width:500px;vertical-align:top;height:51px;"><p style="">根据name属性从Servlet上下文中删除对象</p></td> 
  </tr> 
  <tr> 
   <td style="width:272px;vertical-align:top;height:51px;"><p style="">Enumeration</p><p style="">getAttributeNames()</p></td> 
   <td style="width:500px;vertical-align:top;height:51px;"><p style="">返回一个Enumeration对象，包含了所有存储在Servelt上下文中的属性名</p></td> 
  </tr> 
 </tbody> 
</table>

1.  **上下文的作用**

web容器在启动时，它会为每个web程序都创建一个对应的ServletContext对象，它代表当前的web应用。 事实上SpringMVC封装的ApplicationContext 以及Struts2封装的ApplicationContext里面都是保存着原本的ServletContext

**作用：**Web应用范围内存取共享数据；访问web应用的静态资源；Servlet对象之间通过ServletContext对象来实现通讯。

1.  **下文接口的方法**

在Servlet中通过

final ServletContext application = request.getServletContext();

获取上下文对象application

上下文的常用方法如下：

> getInitParameter(String name) 获取name名称的初始化参数的值  
> getResourceAsStream(String path) 输入流的形式返回path对应的资源，path参数必须以“/”  
> getInitParameterNames() 获取所有初始化参数的名称，返回的结果是一个枚举值  
> getRequestDispatcher(String name) 根据转发的地址获取 RequestDispatcher对象  
> setAttribute() 设置属性值  
> getAttributeNames() 获取所有属性值名称

1.  **上下文参数**

在web.xml中配置初始化参数：

<context-param>
       <param-name>adminEmail</param-name>
       <param-value>webmaster</param-value>
    <context-param>

元素是针对整个应用的，所以并不嵌套在某个<servlet>元素中，该元素是<web-app>元素的直接子元素。

从Servlet中访问初始化参数：

final ServletContext application=this.getServletContext();
    application.getInitParameter("email");

1.  **上下文属性**

ServletContext application=this.getServletContext();
    application.setAttribute("name","value");
    application.getAttribute("name"); 
    Enumberation p=application.getAttributeNames();

1.  ## 作用域对象 ##

### 2.1pageContext ###

pageContext对象:它的生命周期即page域，指存储在pageContext对象的数据只在当前页面有效，当发生页面跳转时，则在pageContext域的数据进行销毁。

### 2.2request ###

request对象主要用于处理客户端请求，同时request对象也是作用域对象，它的作用域范围是同一个请求。

![dd637fb22602d170768198d8f3f13ef4.png][]

<table style=""> 
 <tbody> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style=""><span style="font-weight:bold;">方法</span></p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style=""><span style="font-weight:bold;">说明</span></p></td> 
  </tr> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style="">void setAttribute(String name, Object value)</p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style="">把name属性储存到request对象</p></td> 
  </tr> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style="">Object getAttribute(String name)</p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style="">返回name属性的值</p></td> 
  </tr> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style="">void removeAttribute(String name)</p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style="">从request对象中移除name属性</p></td> 
  </tr> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style="">String getParameter(String name)</p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style="">返回指定name的参数值</p></td> 
  </tr> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style="">Enumeration getParameterNames()</p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style="">以枚举类型返回所有的参数名称</p></td> 
  </tr> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style="">String []getParameterValues(String name)</p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style="">以字符数组类型返回所有指定name参数值</p></td> 
  </tr> 
  <tr> 
   <td style="width:357px;vertical-align:top;height:51px;"><p style="">Map getParameterMap( )</p></td> 
   <td style="width:299px;vertical-align:top;height:51px;"><p style="">以java.util.Map类型返回请求参数</p></td> 
  </tr> 
 </tbody> 
</table>

### 2.3session ###

session对象用来存储有关用户会话的所有信息，它的作用域范围是同一个会话。

session对象常用方法：

> void setAttribute(String key,object value):以键/值的方式，将一个对象的值存放到session中

session.setAttribute("name"，"admin")；

Object getAttribute(String key)；根据名称去获取session中存放对象的值

string name =(string) session.getAttribute("name");

### 2.4 application ###

application类似于系统的“全局变量”，用于实现用户之间的数据共享,它的作用域范围是在服务器一开始执行服务，到服务器关闭为止。

application对象实现了javax.servlet.ServletContext接口

application对象的常用方法:

void setAttribute(String key, Object value): 以键/值的方式，将一个对象的值存放到application中

void getAttribute(String key)通过键的方式，把对应的值取出来。

<%
    //设置
    pageContext,setAttribute("name1","zhangshan001");
    request.setAttribute("name2"zhangshan001");
    session.setAttribute("name3""zhangshan001");
    applicationsetAttribute("name4""zhangshan001");
    //取值
    string namel=(string)pageContext.getAttribute("namel");
    string name2=(String)request.getAttribute("name2”);
    String name3=(string)session.getAttribute("name3”);
    string name4=(string)application.getAttribute("name4");
    %>
    
    pageContext域:<%=name1 %><br/>
    request域:<%=name2 %><br/>
    session域:<%=name3 %><br/>
    application域:<%=name4 %><br/>

## **3.作用域对象测试** ##

package com.zhao.servlet;
    
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    public class Test01 extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doPost(request, response);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1.pageContext
            //2.request
            request.setAttribute("name","request");
            //3.session
            HttpSession session=request.getSession();
            session.setAttribute("name","session");
            //4.application
            ServletContext application = request.getServletContext();
            application.setAttribute("name","application");
    
            //重定向
    
        }
    }

<%--
      Created by IntelliJ IDEA.
      User: lenovo
      Date: 2023/2/23
      Time: 11:05
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>作用域对象测试</title>
    </head>
    <body>
    <%--
    EL表达式获取作用域对象得顺序是:pageContext(当前页面)、request（请求问）、session（当前会话）、application（应用程序）
    --%>
    <h2>
        pageContext只能当前页面定义数据，当前页面使用
        request后端程序和页面有情关系，则数据可以共享
        session是当前会话有效（同一个人使用同一个浏览器在任何页面都可以数据共享）
        application是整个服务器有效，所有用户得请求可以数据共享
    </h2>
    ${name}
    </body>
    </html>

### 主页信息 ###

<%@ page import="java.util.List" %><%--
      Created by IntelliJ IDEA.
      User: hcyns
      Date: 2023/2/17
      Time: 19:34
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%--在页面导入jstl的核心类库--%>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <html>
    <head>
        <title>主页</title>
    </head>
    <body>
    <h2>欢迎来到主页!</h2>
    <a href="addGoods.jsp">添加商品</a>
    <table>
        <thead>
        <tr>
            <th>商品编号</th>
            <th>商品名称</th>
            <th>商品价格</th>
            <th>商品说明</th>
            <th>操作</th>
        </tr>
        </thead>
    
        <tbody>
        <c:forEach items="${goodsList}" var="goods">
            <tr>
                <td>${goods.gid}</td>
                <td>${goods.gname}</td>
                <td>${goods.price}</td>
                <td>${goods.mark}</td>
                <td>
                    <a href="#">修改</a>
                    <a href="del?gid=${goods.gid}">删除</a>
                </td>
            </tr>
        </c:forEach>
        </tbody>
      </table>
    </body>
    </html>

## **4.添加信息操作** ##

![65937d9670b71504d2097bdd2646b08e.png][]

<%--
      Created by IntelliJ IDEA.
      User: hcyns
      Date: 2023/2/23
      Time: 18:42
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>商品信息添加</title>
    </head>
    <body>
    <h2>商品信息录入</h2>
    <form action="addGoods" method="post">
        商品名称:<input type="text" name="gname" value="" placeholder="商品名称"><br/>
        商品价格:<input type="number" step="0.01" name="price" value="" placeholder="商品价格"><br/>
        商品说明:<input type="text" name="mark" value="" placeholder="商品说明"><br/>
        <input type="submit" value="提交">
    </form>
    </body>
    </html>

package com.zhao.servlet;
    
    
    import com.zhao.bean.Goods;
    import com.zhao.dao.GoodsDao;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    @WebServlet("/addGoods")
    public class AddGoods extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            doPost(req,resp);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            req.setCharacterEncoding("utf-8");//设置请求的编码
            resp.setCharacterEncoding("utf-8");//设置响应的编码
    
            Goods goods=new Goods();
            goods.setGname(req.getParameter("gname"));
            goods.setPrice(Double.parseDouble(req.getParameter("price")));//获取字符串数字转换为double数据
            goods.setMark(req.getParameter("mark"));
    
            GoodsDao goodsDao=new GoodsDao();
            int row=goodsDao.add(goods);
    
            if(row>0){
                req.getRequestDispatcher("selectAllGoods").forward(req,resp);
            }else {
                req.setAttribute("error_msg","添加商品信息失败!");
                req.getRequestDispatcher("error.jsp").forward(req,resp);
            }
        }
    }

### 1.展示页面效果 ###

#### 登录账号 ####

![de095f97470bbcee751fd874eeffd0a4.png][]

#### 跳转到商品信息页面 ####

![a30efc6bdcbcefdf2e515f7a59f87c25.png][]

#### 然后点击添加商品 ####

![abfe77008c148e01bff312a2c692a33a.png][]

#### 录入商品信息 ####

![6525eab5a19bb51b857d50b10ea1a617.png][]

#### 然后点击提交，跳转到主页 ####

![f12707d4596c50357f49d5235ea7cb97.png][]

#### 控制台添加信息成功 ####

![0c1c83134d6deb082697cb5fd2ad5252.png][]

## **5.删除信息操作** ##

### 1.在主页点击删除跳转到servlet，后端根据id查询到该商品的信息； ###

### 2.把商品信息添加到request作用域中请求转发到信息展示页面； ###

package com.zhao.servlet;
    
    
    import com.zhao.dao.GoodsDao;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    @WebServlet("/del")
    public class DelGoods extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            doPost(req,resp);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            int gid=Integer.parseInt(req.getParameter("gid"));
            //根据id执行数据库的删除
            GoodsDao goodsDao=new GoodsDao();
            int row=goodsDao.deleteById(gid);
            if(row>0){
                //请求转发，查询所有商品信息（刷新）
                    req.getRequestDispatcher("selectAllGoods").forward(req,resp);
                }else {
                    req.setAttribute("error_msg","删除出现了问题!!");
                    req.getRequestDispatcher("error.jsp").forward(req,resp);
            }
        }
    }

### 3.展示页面效果 ###

#### 原来的商品信息 ####

![141c5119881ec0a35c8b4f858d295cc8.png][]

#### 现在的商品信心 ####

![1daa700f284f678a48111b2031a66b78.png][]

#### 数据库中的表删除成功 ####

![006763b8b07d31202c7117d9ce88145f.png][]

## 6.修改信息操作 ##

**修改逻辑：**

> 1.点击修改跳转到servlet，后端根据id查询到该商品的信息；  
> 2.把商品信息添加到request作用域中请求转发到信息展示页面；  
> 3.用户根据需求修改表单中的字段，重新提交表单；  
> 4.编写后端servlet获取用户最新修订的商品信息，执行数据库的修改操作；  
> 5.重新请求查询所有商品，跳转到商品信息主页；

### 1.在主页点击修改跳转到servlet，后端根据id查询到该商品的信息； ###

<%@ page import="java.util.List" %><%--
      Created by IntelliJ IDEA.
      User: hcyns
      Date: 2023/2/17
      Time: 19:34
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%--在页面导入jstl的核心类库--%>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <html>
    <head>
        <title>主页</title>
    </head>
    <body>
    <h2>欢迎来到主页!</h2>
    <a href="addGoods.jsp">添加商品</a>
    <table>
        <thead>
        <tr>
            <th>商品编号</th>
            <th>商品名称</th>
            <th>商品价格</th>
            <th>商品说明</th>
            <th>操作</th>
        </tr>
        </thead>
    
        <tbody>
        <c:forEach items="${goodsList}" var="goods">
            <tr>
                <td>${goods.gid}</td>
                <td>${goods.gname}</td>
                <td>${goods.price}</td>
                <td>${goods.mark}</td>
                <td>
                    <a href="findById?gid=${goods.gid}">修改</a>
                    <a href="del?gid=${goods.gid}">删除</a>
                </td>
            </tr>
        </c:forEach>
        </tbody>
      </table>
    </body>
    </html>

### 2.把商品信息添加到request作用域中请求转发到信息展示页面； ###

package com.zhao.dao;
    
    import com.zhao.bean.Goods;
    import com.zhao.util.JDBCUtil;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.util.ArrayList;
    import java.util.List;
    
    public class GoodsDao {
        private Connection con=null;//数据库连接对象
        private PreparedStatement pstm=null;//预处理对象
        private ResultSet rs=null;//结果集对象
    
        private int row=0;//增删改受影响的行数
    
        public List<Goods> selectAll(){
            List<Goods> goodsList=new ArrayList<>();
            try {
                con= JDBCUtil.getCon();
                String sql="select * from t_goods";
                pstm=con.prepareStatement(sql);
                rs=pstm.executeQuery();
                while (rs.next()){
                    //把当前数据行中的数据取出来，存储到Goods对象中
                    Goods goods=new Goods();
                    goods.setGid(rs.getInt("gid"));
                    goods.setGname(rs.getString("gname"));
                    goods.setPrice(rs.getDouble("price"));
                    goods.setMark(rs.getString("mark"));
                    //把Goods对象存储到集合中
                    goodsList.add(goods);
                }
    
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                JDBCUtil.close(rs,pstm,con);
    
            }
            return goodsList;
        }
    
        public int add(Goods goods){
            try {
                con= JDBCUtil.getCon();
                String sql="insert into t_goods(gname,price,mark) values(?,?,?)";
                pstm=con.prepareStatement(sql);
                pstm.setObject(1,goods.getGname());
                pstm.setObject(2,goods.getPrice());
                pstm.setObject(3,goods.getMark());
                row=pstm.executeUpdate();
    
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                JDBCUtil.close(pstm,con);
            }
            return row;
        }
    
        public int deleteById(int gid){
            try {
                con= JDBCUtil.getCon();
                String sql="delete from t_goods where gid=?";
                pstm=con.prepareStatement(sql);
                pstm.setObject(1,gid);
                row=pstm.executeUpdate();
    
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                JDBCUtil.close(pstm,con);
            }
            return row;
        }
    
    
        public Goods selectById(int gid) {
            Goods goods=null;
            try {
                con= JDBCUtil.getCon();
                String sql="select * from t_goods where gid=?";
                pstm=con.prepareStatement(sql);
                pstm.setObject(1,gid);
                rs=pstm.executeQuery();
                if (rs.next()){
                    //把当前数据行中的数据取出来，存储到Goods对象中
                    goods=new Goods();
                    goods.setGid(rs.getInt("gid"));
                    goods.setGname(rs.getString("gname"));
                    goods.setPrice(rs.getDouble("price"));
                    goods.setMark(rs.getString("mark"));
                }
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                JDBCUtil.close(pstm,con);
            }
            return goods;
        }
    }

package com.zhao.servlet;
    
    import com.zhao.bean.Goods;
    import com.zhao.dao.GoodsDao;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet("/findById")
    public class FindById extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doPost(request, response);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            int gid = Integer.parseInt(request.getParameter("gid"));
            //根据gid查询商品信息
            GoodsDao goodsDao=new GoodsDao();
            Goods goods=goodsDao.selectById(gid);
            if (goods!=null){
                //查询商品信息成功，存入request域中，然后请求转发到页面展示数据
                request.setAttribute("goods",goods);
                request.getRequestDispatcher("showGoods.jsp").forward(request,response);
            }else {
                request.setAttribute("error_msg","修改出了异常!");
                request.getRequestDispatcher("error.jsp").forward(request,response);
            }
    
        }
    }

### 3.在商品信息中点击update跳转到serlvet,用户根据需求修改表单中的字段，重新提交表单； ###

<%--
      Created by IntelliJ IDEA.
      User: lenovo
      Date: 2023/2/25
      Time: 10:09
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>商品信心修改</title>
    </head>
    <body>
    <h2>商品信息修改</h2>
    <form action="update" method="post">
        商品编号:<input type="text" name="gid" value="${goods.gid}" readonly="readonly" placeholder="商品编号"><br/>
        商品名称:<input type="text" name="gname" value="${goods.gname}" placeholder="商品名称"><br/>
        商品价格:<input type="number" step="0.01" name="price" value="${goods.price}" placeholder="商品价格"><br/>
        商品说明:<input type="text" name="mark" value="${goods.mark}" placeholder="商品说明"><br/>
        <input type="submit" value="修改">
    </form>
    </body>
    </html>

package com.zhao.servlet;
    
    import com.zhao.bean.Goods;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet("/update")
    public class UpdateGoods extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doPost(request, response);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            response.setCharacterEncoding("utf-8");
    
            //获取表单提交的数据，封装到goods对象中
            Goods goods=new Goods();
            goods.setGid(Integer.parseInt(request.getParameter("gid")));
            goods.setGname(request.getParameter("gname"));
            goods.setPrice(Double.parseDouble(request.getParameter("price")));
            goods.setMark(request.getParameter("mark"));
    
            System.out.println(goods);
            //执行数据库JDBC的修改操作
    
        }
    }

### 4.编写后端servlet获取用户最新修订的商品信息，执行数据库的修改操作； ###

### 5.重新请求查询所有商品，跳转到商品信息主页； ###

package com.zhao.servlet;
    
    import com.zhao.bean.Goods;
    import com.zhao.dao.GoodsDao;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet("/update")
    public class UpdateGoods extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doPost(request, response);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            response.setCharacterEncoding("utf-8");
    
            //获取表单提交的数据，封装到goods对象中
            Goods goods=new Goods();
            goods.setGid(Integer.parseInt(request.getParameter("gid")));
            goods.setGname(request.getParameter("gname"));
            goods.setPrice(Double.parseDouble(request.getParameter("price")));
            goods.setMark(request.getParameter("mark"));
    
            System.out.println(goods);
            //执行数据库JDBC的修改操作
            GoodsDao goodsDao=new GoodsDao();
            int row = goodsDao.update(goods);
    
            if (row>0){
                request.getRequestDispatcher("selectAllGoods").forward(request,response);
            }else {
                request.setAttribute("error_msg","修改时出现了问题!!");
                request.getRequestDispatcher("error.jsp").forward(request,response);
            }
    
        }
    }

### 6.展示页面效果 ###

#### 点击去登录 ####

![e85a74b787644c90a6a7f822046f66e8.png][]

#### 点击登录 ####

![44cfd18ded278b780220138f708f874b.png][]

#### 跳转到商品信息页面 ####

![04d1411e1ef1b750b93f80b6e44b5639.png][]

#### 然后点击id1修改，跳转到修改页面 ####

![cb663e489d40eb05f1c5c8217f528aeb.png][]

#### 然后点击修改，跳转到主页，查看修改信息是否成功 ####

![61b5616486627240830c4e173f18f8ee.png][]

![063aa251d0a5550bc93e83bb328974a7.png][]

#### 控制台修改成功 ####

![4e6a7a3bd0c40e254c84b7004d85c291.png][]

#### 数据库修改成功 ####

![6d24da15882e2f0fb33bf21d058773f5.png][]

## 7.模糊查询操作 ##

### 1.在主页定义搜索的表单页面请求seach地址 ###

<%@ page import="java.util.List" %><%--
      Created by IntelliJ IDEA.
      User: hcyns
      Date: 2023/2/17
      Time: 19:34
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%--在页面导入jstl的核心类库--%>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <html>
    <head>
        <title>主页</title>
    </head>
    <body>
    <h2>欢迎来到主页!</h2>
    <form action="seach" method="post">
        <input type="text" name="keyword" value="">
        <input type="submit" value="搜索">
    </form>
    <a href="addGoods.jsp">添加商品</a>
    <table>
        <thead>
        <tr>
            <th>商品编号</th>
            <th>商品名称</th>
            <th>商品价格</th>
            <th>商品说明</th>
            <th>操作</th>
        </tr>
        </thead>
    
        <tbody>
        <c:forEach items="${goodsList}" var="goods">
            <tr>
                <td>${goods.gid}</td>
                <td>${goods.gname}</td>
                <td>${goods.price}</td>
                <td>${goods.mark}</td>
                <td>
                    <a href="findById?gid=${goods.gid}">修改</a>
                    <a href="del?gid=${goods.gid}">删除</a>
                </td>
            </tr>
        </c:forEach>
        </tbody>
      </table>
    </body>
    </html>

#### 注意事项： ####

![8722d3e1d1d11abc0e362dd8a169129c.jpeg][]

### 2.点击主页里的seach跳转到Seach类中，获取关键词并执行模糊查询 ###

package com.zhao.servlet;
    
    import com.zhao.bean.Goods;
    import com.zhao.dao.GoodsDao;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    import java.util.List;
    
    @WebServlet("/seach")
    public class Seach extends HttpServlet {
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doPost(request, response);
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            response.setCharacterEncoding("utf-8");
    
            String keyword = request.getParameter("keyword");
            //执行jdbc的模糊查询
            GoodsDao goodsDao=new GoodsDao();
            List<Goods> goodsList=goodsDao.seach(keyword);
            System.out.println(goodsList);
            //把模糊查询到的商品信息集合存储到session中
            HttpSession session=request.getSession();
            session.setAttribute("goodsList",goodsList);
            //跳转到主页进行信息显示
            response.sendRedirect("zhuye.jsp");
        }
    }

#### 注意事项： ####

![370d15300f26aec5e95cf0b1a0fd636e.jpeg][]

### 3.在GoodsDao中定义一个seach方法 ###

List<Goods> goodsList=new ArrayList<>();
        public List<Goods> seach(String keyword){
            try {
                con= JDBCUtil.getCon();
                String sql="select * from t_goods where gname like concat('%',?,'%')";//concat()函数表示字符串的拼接
                pstm=con.prepareStatement(sql);
                pstm.setObject(1,keyword);
                rs=pstm.executeQuery();
                while (rs.next()){
                    //把当前数据行中的数据取出来，存储到Goods对象中
                    Goods goods=new Goods();
                    goods.setGid(rs.getInt("gid"));
                    goods.setGname(rs.getString("gname"));
                    goods.setPrice(rs.getDouble("price"));
                    goods.setMark(rs.getString("mark"));
    
                    //把Goods对象存储到集合中
                    goodsList.add(goods);
                }
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                JDBCUtil.close(pstm,con);
            }
            return goodsList;
        }

### 4.展示页面效果 ###

#### 点击去登录 ####

![1cb548cea9a8f0e35556e0a32d1cdf25.png][]

#### 登录账号 ####

![dae89d8cf8f5f42cb1eb6ed7c54d54df.png][]

#### 在搜索框里搜索关键字，进行模糊查询 ####

![4fdeac7069ec383c4f21abf7e64251c6.png][]

#### 显示搜索后的页面，模糊查询成功！ ####

![b30b051b4cbeafa37849085dc581d8f8.png][]

#### 数据库模糊查询成功 ####

![9fc1798e696f6005aea9962547aa0832.png][]

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