[原创]java WEB学习笔记23：MVC案例完整实践(part 4)---模糊查询的设计与实现

时间：2021-08-04 14:19:08

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1.查询操作：

　　1）思路：

　　　 Servlet:在查询方法中，创建CustomerDAO 对象，调用getAll() 方法，获得List<Customer> 集合，利用保证为requset，转发，获取，遍历

　　 　　　　

　　　　　　//1. 调用 CustomerDAO 的 getAll() 得到 Customer 的集合 List<Customer> customers = customerDAO.getAll();

　　 　　　　//2. 把 Customer 的集合放入 request 中 request.setAttribute("customers", customers);

　　 　　　　//3. 转发页面到 index.jsp(不能使用重定向) request.getRequestDispatcher("/index.jsp").forward(request, response);

　　   JSP

　　　　　　获取 request 中的 customers 属性

　　　　　　遍历显示

　　2）代码：

　　　CustomerServlet2.java

　　　Servlet中的 private void query(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException{} 方法

 package com.jason.mvcapp.servlet;

 import java.io.IOException;

 import java.lang.reflect.Method;

 import java.util.List;

 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 com.jason.mvcapp.dao.CustomerDAO;

 import com.jason.mvcapp.dao.impl.CustomerDAOJdbcImpl;

 import com.jsaon.mvcapp.domain.CriteriaCustomer;

 import com.jsaon.mvcapp.domain.Customer;

     /**

      * Servlet implementation class CustomerServlet2

      */

     @WebServlet("*.do")

     public class CustomerServlet2 extends HttpServlet {

         private static final long serialVersionUID = 1L;

         //创建一个CustomerDAO对象，多态

         private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();

         protected void doGet(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             doPost(request, response);

         }

         protected void doPost(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             //1.获取servletPath：/add.do 或者 query.do

             String serveltPath = request.getServletPath();

         //     System.out.println(serveltPath);

             //2.去除/ 和 .do 得到对应的方法，如 add  query

             String methodName = serveltPath.substring(1);

             methodName = methodName.substring(0, methodName.length() - 3);

             // System.out.println(methodName);

             try {

                 //3.利用反射获取methodName对应的方法

                 Method method = getClass().getDeclaredMethod(methodName,

                         HttpServletRequest.class, HttpServletResponse.class);

                 //4.利用反射调用方法

                 method.invoke(this, request, response);

             } catch (Exception e) {

                 e.printStackTrace();

             }

         }

         private void update(HttpServletRequest request, HttpServletResponse response)

                 throws ServletException, IOException {

             System.out.println("update");

         }

         private void editeCustomer(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             System.out.println("edit");

         }

         private void deleteCustomer(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             System.out.println("delete");

         }

         private void query(HttpServletRequest request, HttpServletResponse response)

78                 throws ServletException, IOException {

79

80 //            //1.调用CustomerDAO 的getAll()方法的到Customer 集合

81 //            List<Customer> lists = customerDAO.getAll();

82             //2.把Customer 集合放入request

83             request.setAttribute("list", lists);

84             //3.转发页面到index.jsp

85             request.getRequestDispatcher("/index.jsp").forward(request, response);

86

87         }


         private void addCustomer(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             System.out.println("add");

         }

     }

index.jsp：获取list, 通过脚本遍历list集合，输出到表格中

　　

 <%@ page language="java" contentType="text/html; charset=UTF-8"

     pageEncoding="UTF-8"%>

 <%@ page import="com.jsaon.mvcapp.domain.Customer" %>

 <%@ page import="java.util.List" %>

 <!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>mve_index</title>

 </head>

 <body>

     <form action="query.do" method="post">

         <table>

             <tr>

                  <td>CustomerName:</td>

                  <td><input type="text" name="name"/></td>

             </tr>

             <tr>

                  <td>Address:</td>

                  <td><input type="text" name="address"/></td>

             </tr>

             <tr>

                  <td>Phone:</td>

                  <td><input type="text" name="phone"/></td>

             </tr>

             <tr>

                  <td><input type="submit" value="Query"/></td>

                  <td><a href="">Add New Customer</a></td>

             </tr>

         </table>

     </form>

     <br><br>

     <%

         List<Customer> lists = (List<Customer>)request.getAttribute("list");

         if(lists != null && lists.size() > 0 ){

     %>

     <hr>

     <br><br>

     <table border="1" cellpadding="10" cellspacing="0">

             <tr>

                 <th>ID</th>

                 <th>CustomerName</th>

                 <th>Address</th>

                 <th>Phone</th>

                 <th>Update\Delete</th>

             </tr>

             <%

                 for(Customer customer : lists){

             %>

             <tr>

                 <td><%= customer.getId() %></td>

                 <td><%= customer.getName() %></td>

                 <td><%= customer.getAddress() %></td>

                 <td><%= customer.getPhone() %></td>

                 <td>

                     <a href="">Update</a>

                     <a href="">Delete</a>

                 </td>

             </tr>

             <%

                 }

             %>

     </table>

     <%

         }

     %>

 </body>

 </html>

2.模糊查询的设计和 实现

　　1）思路：

　　　　后端：

　　　　> 条件：根据传入的 name, address, phone 进行模糊查询.

　　　　　　　　 例子: name: a、address: b、phone: 3 则 SQL 语句的样子为: SELECT id, name, address, phone FROM customers WHERE name LIKE ‘%a%’ AND address LIKE ‘%b%’ AND phone LIKE ‘%3%

　　　　> 需要在 CustomerDAO接口中定义一个 getForListWithCriteriaCustomer(CriteriaCustomer criteriaCustomer)。　　　　　　

　　其中 CriteriaCustomer 用于封装查询条件：name, address, phone。因为查询条件很多时候和 domain 类并不相同，所以要做成一个单独的类　　　　

 package com.jsaon.mvcapp.domain;

 /**

  * @author: jason

  * @time:2016年5月27日上午9:31:46

  * @description:封装查询信息的类

  */

 public class CriteriaCustomer {

     private String name;

     private String address;

     private String phone;

     public String getName() {

         if(name == null){

             name = "%%";

         }else{

             name = "%"+ name +"%";

         }

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getAddress() {

         if(address == null){

             address = "%%";

         }else{

             address = "%"+ address +"%";

         }

         return address;

     }

     public void setAddress(String address) {

         this.address = address;

     }

     public String getPhone() {

         if(phone == null){

             phone = "%%";

         }else{

             phone = "%"+ phone +"%";

         }

         return phone;

     }

     public void setPhone(String phone) {

         this.phone = phone;

     }

     public CriteriaCustomer(String name, String address, String phone) {

         super();

         this.name = name;

         this.address = address;

         this.phone = phone;

     }

     public CriteriaCustomer() {

         super();

     }

 }

　　　　>在CustomerDAOJdbcImpl 中重写CustomerDAO 中的getForListWithCriteriaCustomer(CriteriaCustomer criteriaCustomer)

 @Override

     public List<Customer> getForListWithCriteriaCustomer(

             CriteriaCustomer criteriaCustomer) {

         //sql语句

         String sql = "SELECT id,name,address,phone FROM customers WHERE name LIKE ? AND  address LIKE ? AND phone LIKE ?";

         //调用DAO<T> 中的方法getForList(),并且为占位符设置参数

         return getForList(sql, criteriaCustomer.getName(),criteriaCustomer.getAddress(),criteriaCustomer.getPhone());

     }

　　　　> 拼 SQL： "SELECT id, name, address, phone FROM customers WHERE " + "name LIKE ? AND address LIKE ? ANDphone LIKE ?";

　　　　

　　　　> 为了正确的填充占位符时，重写了 CriteriaCustomer 的 getter方法　　

 //获取Name

 public String getName() {

         if(name == null){

             name = "%%";

         }else{

             name = "%"+ name +"%";

         }

         return name;

     }

 //获取Address

 public String getAddress() {

         if(address == null){

             address = "%%";

         }else{

             address = "%"+ address +"%";

         }

         return address;

     }

 //获取Phone

 public String getPhone() {

         if(phone == null){

             phone = "%%";

         }else{

             phone = "%"+ phone +"%";

         }

         return phone;

     }

　　　　　　　　

　　> 修改 Servlet：获取请求参数；把请求参数封装为 CriteriaCustomer 对象，再调用 getForListWithCriteriaCustomer(CriteriaCustomer cc) 方法

　　　

 private void query(HttpServletRequest request, HttpServletResponse response)

                 throws ServletException, IOException {

             //设置编码格式

             request.setCharacterEncoding("UTF-8");

             //获取相应的参数

             String name = request.getParameter("name");

             String address = request.getParameter("address");

             String phone = request.getParameter("phone");

             //封装请求参数

             CriteriaCustomer criteriaCustomer = new CriteriaCustomer(name,address,phone);

     //1.调用CustomerDAO 的getForListWithCriteriaCustomer(criteriaCustomer)方法的到Customer 集合

     List<Customer> lists = customerDAO.getForListWithCriteriaCustomer(criteriaCustomer);

             //2.把Customer 集合放入request

             request.setAttribute("list", lists);

             //3.转发页面到index.jsp

             request.getRequestDispatcher("/index.jsp").forward(request, response);

         }

　　　前台：同上述的JSP

　　　　　　获取 request 中的 customers 属性

　　　　　　遍历显示

　　2）代码：

CriteriaCustomer.java
 package com.jsaon.mvcapp.domain;

 /**

  * @author: jason

  * @time:2016年5月27日上午9:31:46

  * @description:封装查询信息的类

  */

 public class CriteriaCustomer {

     private String name;

     private String address;

     private String phone;

     public String getName() {

         if(name == null){

             name = "%%";

         }else{

             name = "%"+ name +"%";

         }

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getAddress() {

         if(address == null){

             address = "%%";

         }else{

             address = "%"+ address +"%";

         }

         return address;

     }

     public void setAddress(String address) {

         this.address = address;

     }

     public String getPhone() {

         if(phone == null){

             phone = "%%";

         }else{

             phone = "%"+ phone +"%";

         }

         return phone;

     }

     public void setPhone(String phone) {

         this.phone = phone;

     }

     public CriteriaCustomer(String name, String address, String phone) {

         super();

         this.name = name;

         this.address = address;

         this.phone = phone;

     }

     public CriteriaCustomer() {

         super();

     }

 }

CustomerServlet2.java

 package com.jason.mvcapp.servlet;

 import java.io.IOException;

 import java.lang.reflect.Method;

 import java.util.List;

 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 com.jason.mvcapp.dao.CustomerDAO;

 import com.jason.mvcapp.dao.impl.CustomerDAOJdbcImpl;

 import com.jsaon.mvcapp.domain.CriteriaCustomer;

 import com.jsaon.mvcapp.domain.Customer;

     /**

      * Servlet implementation class CustomerServlet2

      */

     @WebServlet("*.do")

     public class CustomerServlet2 extends HttpServlet {

         private static final long serialVersionUID = 1L;

         //创建一个CustomerDAO对象，多态

         private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();

         protected void doGet(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             doPost(request, response);

         }

         protected void doPost(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             //1.获取servletPath：/add.do 或者 query.do

             String serveltPath = request.getServletPath();

         //     System.out.println(serveltPath);

             //2.去除/ 和 .do 得到对应的方法，如 add  query

             String methodName = serveltPath.substring(1);

             methodName = methodName.substring(0, methodName.length() - 3);

             // System.out.println(methodName);

             try {

                 //3.利用反射获取methodName对应的方法

                 Method method = getClass().getDeclaredMethod(methodName,

                         HttpServletRequest.class, HttpServletResponse.class);

                 //4.利用反射调用方法

                 method.invoke(this, request, response);

             } catch (Exception e) {

                 e.printStackTrace();

             }

         }

         private void update(HttpServletRequest request, HttpServletResponse response)

                 throws ServletException, IOException {

             System.out.println("update");

         }

         private void editeCustomer(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             System.out.println("edit");

         }

         private void deleteCustomer(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             System.out.println("delete");

         }

         private void query(HttpServletRequest request, HttpServletResponse response)

 78                 throws ServletException, IOException {

 79             request.setCharacterEncoding("UTF-8");

 80             String name = request.getParameter("name");

 81             String address = request.getParameter("address");

 82             String phone = request.getParameter("phone");

 83

 84

 85

 86             CriteriaCustomer criteriaCustomer = new CriteriaCustomer(name,address,phone);

 87             List<Customer> lists = customerDAO.getForListWithCriteriaCustomer(criteriaCustomer);

 88

 89

 90 //            //1.调用CustomerDAO 的getAll()方法的到Customer 集合

 91 //            List<Customer> lists = customerDAO.getAll();

 92             //2.把Customer 集合放入request

 93             request.setAttribute("list", lists);

 94             //3.转发页面到index.jsp

 95             request.getRequestDispatcher("/index.jsp").forward(request, response);

 96

 97         }

         private void addCustomer(HttpServletRequest request,

                 HttpServletResponse response) throws ServletException, IOException {

             System.out.println("add");

         }

     }

　

　　　CustomerDAOJdbcImpl.java

 package com.jason.mvcapp.dao.impl;

 import java.util.List;

 import com.jason.mvcapp.dao.CustomerDAO;

 import com.jason.mvcapp.dao.DAO;

 import com.jsaon.mvcapp.domain.CriteriaCustomer;

 import com.jsaon.mvcapp.domain.Customer;

 /**

  * @author: jason

  * @time:2016年5月25日下午3:45:06

  * @description:对CustomerDAO 的实现

  */

 public class CustomerDAOJdbcImpl extends DAO<Customer> implements CustomerDAO {

     @Override

     public List<Customer> getAll() {

         String sql = "SELECT * FROM customers";

         return getForList(sql);

     }

     @Override

     public void save(Customer customer) {

         String sql = "INSERT INTO customers(name, address, phone) VALUES(?,?,? )";

         update(sql,customer.getName(),customer.getAddress(),customer.getPhone());

     }

     @Override

     public Customer get(Integer id) {

         String sql = "SELECT id, name, address, phone FROM customers WHERE id = ?";

         return get(sql,id);

     }

     @Override

     public void delete(Integer id) {

         String sql = "DELETE FROM customers WHERE id = ?";

         update(sql, id);

     }

     @Override

     public long getCountWithName(String name) {

         String sql = "SELECT count(id) FROM customers WHERE name = ?";

         return getForValue(sql, name);

     }

     @Override

50     public List<Customer> getForListWithCriteriaCustomer(

51             CriteriaCustomer criteriaCustomer) {

52         //sql语句

53         String sql = "SELECT id,name,address,phone FROM customers WHERE name LIKE ? AND  address LIKE ? AND phone LIKE ?";

54         //调用DAO<T> 中的方法getForList(),并且为占位符设置参数

55         return getForList(sql, criteriaCustomer.getName(),criteriaCustomer.getAddress(),criteriaCustomer.getPhone());

56     }

 }
CustomerDAO.java

 package com.jason.mvcapp.dao;

 import java.util.List;

 import com.jsaon.mvcapp.domain.CriteriaCustomer;

 import com.jsaon.mvcapp.domain.Customer;

 /**

  * @author: jason

  * @time:2016年5月25日下午3:28:00

  * @description:

  */

 public interface CustomerDAO {

     //带参数的模糊查询

18     public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer criteriaCustomer);

       //查询所有

     public List<Customer> getAll();

     //保存操作

     public void save(Customer coustomer);

     //更新前，先查询

     public Customer get(Integer id);

     //删除用户

     public void delete(Integer id);

     //查看与参数相同的名字有多少个记录数

     public long getCountWithName(String name);

 }

index.jsp　同上面的一样

总结：

　　1）理解代码的层次

　　2）在从前台获取参数的时候，一定要设置  request.setCharacterEncoding("UTF-8"); 。我在跑测试的时候，由于没有设置编码格式，在debug 运行的时候，获取到的 name，address，phone都是乱码。一定注意

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