[Java知识库]JavaWEB十：Servlet优化1 实现将各种请求由一个组件进行统一调度后响应

Servlet优化1 实现将各种请求由一个组件进行统一调度后响应

1. 截取各种post/get请求，在一个组件种进行统一调配

2. servlet组件

   // 所有的html内post请求的action值和get请求中的href值，全部变更为customers.do
   @WebServlet("/customers.do")
   public class CustomersServlet extends ViewBaseServlet {
       // 属性
       private ListIpm listIpm = new ListIpm();
       // service方法，将所有的get/post请求统一拦截，然后调配至相应do方法
       @Override
       protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
           req.setCharacterEncoding("UTF-8");
           // 将各html文件与js文件中请求标记的值赋给operate变量
           String operate = req.getParameter("operate");
           if (StringUtil.isEmpty(operate)) {
               operate = "index";
           }
           // 使用反射，获取该对象对应的运行时类内的所有方法，使方法名与operate代表请求信息一一对应
           Method[] methods = this.getClass().getDeclaredMethods();
           for (Method m : methods) {
               String methodName = m.getName();
               if (operate.equals(methodName)) {
                   try {
                       m.invoke(this, req, resp);
                       break;
                   } catch (IllegalAccessException e) {
                       e.printStackTrace();
                   } catch (InvocationTargetException e) {
                       e.printStackTrace();
                   }
               }
               throw new RuntimeException("operate值非法");
           }
       }
   	
       // 下面的index、delete、edit、update、add方法，是各请求的具体实现方法
       protected void index(HttpServletRequest req, HttpServletResponse resp) {
           Connection conn = null;
           try {
               // 1.连接数据库，实例化DAO中的实现类，得到session
               conn = JdbcUtils.getConnection();
               ListIpm ipm = new ListIpm();
               HttpSession session = req.getSession();
               // 2.分页功能
               // 2.1 给pageOn赋初始值，用于在js无返回页面值时，html可以明确显示哪个分页
               int pageOn = 1;
               // 3.确认是否为查询按钮提交的数据
               // 3.1 获取表单中隐藏域的关键字
               String oper = req.getParameter("oper");
               String key = null;
               // 3.2 判断获取的oper中的值，从而确定查询按钮被触发,显示的就是查询后的结果，页面调整到从首页显示
               if (StringUtil.isNotEmpty(oper) && "search".equals(oper)) {
                   pageOn = 1;
                   // key是查询得到的关键字
                   key = req.getParameter("keyword");
                   if (StringUtil.isEmpty(key)) {
                       key = "";
                   }
                   // 如果查询输入栏中有值，那么就将这个值保存在作用域中，可以被组件或html调用
                   session.setAttribute("k",key);
               }else {
   
                   // 2.3获取js文件中的page,如果html页面的控制页面按钮被触动，就将页面值赋给pageOn
                   String pageStr = req.getParameter("page");
                   if (StringUtil.isNotEmpty(pageStr)) {
                       pageOn = Integer.parseInt(pageStr);
                   }
                   // 如果是其它按钮被触发，那么key要从保存作用域中读值，这时可能时查询之后的翻页，key值还应该时查询时输入的值。
                   Object keyObj = session.getAttribute("k");
                   if (keyObj == null) {
                       key =  "";
                   }else {
                       key = (String) keyObj;
                   }
               }
               // 2.2 将pageOn保存到作用域中
               session.setAttribute("pageOn",pageOn);
               List<Customers> custList = ipm.getList(conn,"%"+ key +"%",pageOn);
               session.setAttribute("cl",custList);
   
               // 4 获取客户个数，用于优化html中分页按钮功能
               long count = 0L;
               count = ipm.getCount(conn,"%"+key+"%");
               int max = (int) (count+2-1)/2;
               session.setAttribute("max",max);
               // 5.调用父类的模板处理方法
               super.processTemplate("index",req,resp);
           } catch (Exception e) {
               e.printStackTrace();
           } finally {
               JdbcUtils.closeResource(conn,null);
           }
       }
       
       private void add(HttpServletRequest req, HttpServletResponse resp)  {
           Connection conn = null;
           try {
               String name = req.getParameter("name");
               String email = req.getParameter("email");
               String birth = req.getParameter("birth");
               SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
               Date date = format.parse(birth);
               conn = JdbcUtils.getConnection();
               listIpm.addCustomer(conn,name,email,date);
               resp.sendRedirect("customers.do");
   
           } catch (Exception e) {
               e.printStackTrace();
           } finally {
               JdbcUtils.closeResource(conn,null);
           }
       }
       
       private void delete(HttpServletRequest req, HttpServletResponse resp)  {
           String idStr = req.getParameter("sid");
           if (StringUtil.isNotEmpty(idStr)) {
               Connection conn = null;
               try {
                   int id = Integer.parseInt(idStr);
                   conn = JdbcUtils.getConnection();
                   listIpm.delById(conn,id);
                   resp.sendRedirect("customers.do");
               } catch (Exception e) {
                   e.printStackTrace();
               } finally {
                   JdbcUtils.closeResource(conn,null);
               }
           }
       }
       
       private void edit(HttpServletRequest req, HttpServletResponse resp)  {
           Connection conn = null;
           try {
               conn = JdbcUtils.getConnection();
               // 1.去数据库中查询某一个库存记录，根据thymeleaf在html中的超链接标签中提供的id
               String idStr = req.getParameter("cid");
               // 2.将判断idStr不是空字符串且不为null的语句写成一个工具类内的方法，可以方便后续频繁调用
               if (StringUtil.isNotEmpty(idStr)) {
                   int id = Integer.parseInt(idStr);
                   System.out.println(id);
                   Customers customer = listIpm.getCustomerById(conn, id);
                   System.out.println(customer);
                   // 3.将获取到的对象变量以键值对的形式保存到作用域中
                   req.setAttribute("cu" ,customer);
                   // 4.调用模板处理方法，连接到edit.html文件中(如果该页面不存在，就创建一个)
                   super.processTemplate("edit",req,resp);
               }
           } catch (Exception e) {
               e.printStackTrace();
           } finally {
               JdbcUtils.closeResource(conn,null);
           }
   
       }
       
       private void update(HttpServletRequest req, HttpServletResponse resp) {
           Connection conn = null;
           try {
               String idStr = req.getParameter("id");
               int id = Integer.parseInt(idStr);
               String name = req.getParameter("name");
               String email = req.getParameter("email");
               String birth = req.getParameter("birth");
               SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
               Date date = format.parse(birth);
               conn = JdbcUtils.getConnection();
               listIpm.updateById(conn,name,email,date,id);
               resp.sendRedirect("customers.do");
           } catch (Exception e) {
               e.printStackTrace();
           } finally {
               JdbcUtils.closeResource(conn,null);
           }
       }
   }
   

3. html文件

   index.html

   <!DOCTYPE html>
   <html xmlns:th="http://www.thymeleaf.org">
   <html>
   <head>
       <meta charset="UTF-8">
       <link rel="stylesheet" th:href="@{CSS/index.css}">
       <script language="JavaScript" th:src="@{js/index.js}" ></script>
   </head>
   <body>
   <div id="div_contain">
       <div id="div_fruit_list">
           <p class="center f32">欢迎使用客户后台管理系统</p>
           
           <!-- 查询层 -->
           <div style="float: left; margin-left: 20%;width: 60%" >
               <form th:action="@{/customers.do}" method="post">
                   <!-- 增加隐藏域，给operate赋值，对应index方法 -->
                   <input type="hidden" name="operate" value="index">
                   <input type="hidden" name="oper" value="search">                
                   请输入查询关键字<input type="text" name="keyword"/>
                   <input type="submit" value="查询" />
               </form>
           </div>
           
           <!-- 添加层 -->
           <div style=" width:60% ; margin-left: 20%; float: right">
               <a th:href="@{/add.html}"  style=" margin-bottom: 10px"> 新添加客户 </a>
           </div>
           
           <!-- thymeleaf渲染表格 -->
           <table id="tbl_fruit">
               <tr>
                   <th>cust_id</th>
                   <th>cust_name</th>
                   <th>cust_email</th>
                   <th>cust_birth</th>
               </tr>
               <tr th:if="${#lists.isEmpty(session.cl)}">
                   <td colspan="4">无客户名单！</td>
               </tr>
               <tr th:unless="${#lists.isEmpty(session.cl)}" 
                   th:each="cust:${session.cl}">
                   <td>
                       <!-- get请求，给operate赋值，对应edit方法 -->
                       <a th:text="${cust.id}"                        
                          th:href="@{/customers.do(cid=${cust.id},operate='edit')}">1</a>
                   </td>
                   <td th:text="${cust.name}">太白金星</td>
                   <td th:text="${cust.email}" 
                       th:onclick="|delCust(${cust.id})|">tbstart@163.com</td>
                   <td th:text="${cust.birth}">1000-1-1</td>
               </tr>
           </table>
           
           <!-- 分页按钮层 -->
           <div style="width:60% ; margin-left: 20%">
               <input th:type="button" th:value="首页" th:onclick="|pageControl(1)|"
                      th:disabled="${session.pageOn==1}"/>
               <input th:type="button" th:value="上一页" 
                      th:onclick="|pageControl(${session.pageOn-1})|"
                      th:disabled="${session.pageOn==1}"/>
               <input th:type="button" th:value="下一页" 
                      th:onclick="|pageControl(${session.pageOn+1})|"
                      th:disabled="${session.pageOn==session.max}"/>
               <input th:type="button" th:value="尾页" 
                      th:onclick="|pageControl(${session.max})|"
                      th:disabled="${session.pageOn==session.max}"/>
           </div>
       </div>
   </div>
   </body>
   </html>
   

   add.html

   <!DOCTYPE html>
   <html>
   <head>
       <meta charset="UTF-8">
       <base href="http://localhost:8080/optimization_1/" >
       <link rel="stylesheet" href="CSS/edit.css" >
   
   </head>
   <body>
   <div id="div_contain">
       <div id="div_fruit_list">
           <p class="center f32">修改/编辑库存信息</p>
           <form action="customers.do" method="post">
                <!-- 增加隐藏域，给operate赋值，对应add方法 -->
               <input type="hidden" name="operate" value="add" />
               <table id="tbl_fruit">
                   <tr>
                       <th>cust_name</th>
                       <td><input type="text" name="name" /></td>
                   </tr>
                   <tr>
                       <th>cust_email</th>
                       <td><input type="text" name="email" /></td>
                   </tr>
                   <tr>
                       <th>cust_birth</th>
                       <td><input type="text" name="birth" /></td>
                   </tr>
                   <tr>
                       <th colspan="2">
                           <input type="submit" value="添加" />
                       </th>
                   </tr>
               </table>
           </form>
       </div>
   </div>
   </body>
   </html>
   

   edit.html

   <!DOCTYPE html>
   <html xmlns:th="http://www.thymeleaf.org">
   <html>
   <head>
       <meta charset="UTF-8">
       <link th:rel="stylesheet" th:href="@{CSS/index.css}">
   </head>
   <body>
   <div id="div_contain">
       <div id="div_fruit_list">
           <p class="center f32">修改/编辑库存信息</p>
           <form th:action="@{/customers.do}" method="post">
               <!-- 新增了隐藏域，为operate赋值，du -->
               <input  type="hidden" name="operate" value="update"/>
               <table id="tbl_fruit" th:object="${cu}">
                   <tr>
                       <th>cust_id</th>
                       <td><input type="text" name="id" th:value="*{id}"/></td>
                   </tr>
                   <tr>
                       <th>cust_name</th>
                       <td><input type="text" name="name" th:value="*{name}"/></td>
                   </tr>
                   <tr>
                       <th>cust_email</th>
                       <td><input type="text" name="email" th:value="*{email}"/></td>
                   </tr>
                   <tr>
                       <th>cust_birth</th>
                       <td><input type="text" name="birth" th:value="*{birth}"/></td>
                   </tr>
                   <tr>
                       <th colspan="2">
                           <input th:type="submit" th:value="提交" />
                       </th>
                   </tr>
               </table>
           </form>
       </div>
   </div>
   </body>
   </html>
   

4. js文件

   function delCust(s) {
       if (confirm('是否确认删除')) {
           <!-- 在url上添加operate的值，对应到delete方法 -->
           window.location.href = 'customers.do?sid=' + s +'&operate=delete';
       }
   }
   
   function pageControl(page) {
       if (confirm("确认")) {
           <!-- 在url上添加operate的值，对应到index方法 -->
           window.location.href = 'customers.do?page=' + page +'&operate=index';
       }
   }