Unit05： WEB项目的开发模式 、转发 和 Unit09： EL、JSTL
dao
package dao; import java.io.Serializable; import java.util.ArrayList; import java.util.List; import entity.Emp; public class EmpDao implements Serializable { public List<Emp> findAll() { List<Emp> list = new ArrayList<Emp>(); Emp e1 = new Emp(); e1.setEmpno(1); e1.setEname("唐僧"); e1.setJob("师父"); e1.setSal(9000.0); list.add(e1); Emp e2 = new Emp(); e2.setEmpno(2); e2.setEname("悟空"); e2.setJob("徒弟"); e2.setSal(5000.0); list.add(e2); Emp e3 = new Emp(); e3.setEmpno(3); e3.setEname("八戒"); e3.setJob("徒弟"); e3.setSal(6000.0); list.add(e3); return list; } public void save(Emp e) { System.out.println( "增加员工:" + e.getEname()); } }
entity
package entity; import java.io.Serializable; public class Course implements Serializable { //对象的属性 private Integer courseId; private String name; private Integer days; //Bean的属性 //1.通过get/set方法所观察出来的属性 //2.将get/set去掉后得到的单词首字母小写 public Integer getId() { return courseId; } public void setId(Integer courseId) { this.courseId = courseId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getDays() { return days; } public void setDays(Integer days) { this.days = days; } }
package entity; import java.io.Serializable; public class Emp implements Serializable { private Integer empno; private String ename; private String job; private Double sal; public Integer getEmpno() { return empno; } public void setEmpno(Integer empno) { this.empno = empno; } public String getEname() { return ename; } public void setEname(String ename) { this.ename = ename; } public String getJob() { return job; } public void setJob(String job) { this.job = job; } public Double getSal() { return sal; } public void setSal(Double sal) { this.sal = sal; } }
package entity; import java.io.Serializable; public class Student implements Serializable { private String name; private Integer age; private String sex; private String[] interests; private Course course; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public String[] getInterests() { return interests; } public void setInterests(String[] interests) { this.interests = interests; } public Course getCourse() { return course; } public void setCourse(Course course) { this.course = course; } }
WEB组件：Servlet/JSP
使用一个组件处理请求，处理业务，返回响应信息，耦合度过高，不利于代码维护
<%@page pageEncoding="utf-8" import="dao.*,entity.*,java.util.*"%> <!doctype html> <html> <head> <meta charset="utf-8"/> <title>查询员工</title> <style> table { border: 1px solid red; border-collapse: collapse; width: 30%; } td { border: 1px solid red; } </style> </head> <body> <table> <tr> <td>编号</td> <td>姓名</td> <td>职位</td> <td>薪资</td> </tr> <% EmpDao dao = new EmpDao(); List<Emp> list = dao.findAll(); if(list != null) { for(Emp e : list) { %> <tr> <td><%=e.getEmpno() %></td> <td><%=e.getEname() %></td> <td><%=e.getJob() %></td> <td><%=e.getSal() %></td> </tr> <% } } %> </table> </body> </html>
Model2引用了MVC模式对代码解耦。(重要)
MVC模式是经典的设计模式，是代码的分层思想：
1.M：model，即业务层，用来处理业务；
2.V：View，即视图层，用来显示数据；
3.C：controller，即控制层，负责调度，是M和V的桥梁，其作用是对代码解耦，便于团队开发及维护；
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"> <display-name>jsp2</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>findEmp</servlet-name> <servlet-class>web.FindEmpServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>findEmp</servlet-name> <url-pattern>/findEmp</url-pattern> </servlet-mapping> <servlet> <servlet-name>findStudent</servlet-name> <servlet-class>web.FindStudentServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>findStudent</servlet-name> <url-pattern>/findStudent</url-pattern> </servlet-mapping> </web-app>
package web; import java.io.IOException; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import dao.EmpDao; import entity.Emp; public class FindEmpServlet extends HttpServlet { @Override protected void service( HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { //查询所有员工 EmpDao dao = new EmpDao(); List<Emp> list = dao.findAll(); //转发到JSP //1)将数据绑定到request上 req.setAttribute("emps", list); //2)将请求转发给JSP //当前:/jsp2/findEmp //目标:/jsp2/emps.jsp req.getRequestDispatcher("emps.jsp") .forward(req, res); } }
<%@page pageEncoding="utf-8" import="entity.*,java.util.*"%> <!doctype html> <html> <head> <meta charset="utf-8"/> <title>查询员工</title> <style> table { border: 1px solid red; border-collapse: collapse; width: 30%; } td { border: 1px solid red; } </style> </head> <body> <table> <tr> <td>编号</td> <td>姓名</td> <td>职位</td> <td>薪资</td> </tr> <% List<Emp> list = (List<Emp>) request.getAttribute("emps"); if(list != null) { for(Emp e : list) { %> <tr> <td><%=e.getEmpno() %></td> <td><%=e.getEname() %></td> <td><%=e.getJob() %></td> <td><%=e.getSal() %></td> </tr> <% } } %> </table> </body> </html>
package web; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import entity.Course; import entity.Student; public class FindStudentServlet extends HttpServlet { @Override protected void service( HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { //模拟查询一个学生 Student stu = new Student(); stu.setName("zhangsan"); stu.setAge(23); stu.setSex("M"); stu.setInterests( new String[]{"篮球","足球","排球"}); Course c = new Course(); c.setId(1); c.setName("Java"); c.setDays(82); stu.setCourse(c); //转发 req.setAttribute("stu", stu); req.getRequestDispatcher("student.jsp") .forward(req, res); } }
<%@page pageEncoding="utf-8"%> <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <!doctype html> <html> <head> <meta charset="utf-8"/> <title>查询学生</title> </head> <body> <!-- 2.JSTL标签 --> <!-- 2.1 if标签 --> <p> <c:if test="${stu.sex==‘M‘ }">男</c:if> <c:if test="${stu.sex==‘F‘ }">女</c:if> </p> <!-- 2.2 choose标签 --> <p> <c:choose> <c:when test="${stu.sex==‘M‘ }">男</c:when> <c:otherwise>女</c:otherwise> </c:choose> </p> <!-- 2.3 forEach标签 --> <p> <c:forEach items="${stu.interests }" var="i"> ${i } </c:forEach> </p> <!-- 1.EL表达式 --> <!-- 1.1访问Bean属性 --> <!-- request.getAttribute("stu").getName() --> <p>姓名:${stu.name }</p> <p>年龄:${stu.age }</p> <!-- 等价于stu.sex --> <p>性别:${stu["sex"] }</p> <!-- request.getAttribute("stu") .getCourse().getId() --> <p>课程ID:${stu.course.id }</p> <!-- EL表达式的取值范围: 1)EL默认从4个隐含对象中依次取值 page->request->session->application 2)默认依次取值的规则,其意义在于简化EL 表达式,在取值时可以不用写对象名. 3)若希望打破默认规则,明确从某对象中取值, 则需要在表达式前面增加对象名. requestScope.stu.name sessionScope.stu.name --> <p>兴趣:${requestScope.stu.interests }</p> <!-- 1.2访问时可以直接运算 --> <p>年龄+5:${stu.age+5 }</p> <p>介于20-30间:${stu.age>20 && stu.age<30 }</p> <p>是否为空:${empty stu.interests }</p> <!-- 1.3直接获取请求参数 --> <p>参数:${param.user }</p> </body> </html>
Unit05： WEB项目的开发模式 、转发 和 Unit09： EL、JSTL
原文：http://www.cnblogs.com/tangshengwei/p/6431532.html
