第一种：在jsp中用语句块<%%>写java代码，最后用表达式<%=%>展示出来。这种方式耦合性太高了，不利于维护。
calculator.jsp：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
计算器
<%
String firstNum=request.getParameter("firstNum");
String secondNum=request.getParameter("secondNum");
String str=request.getParameter("operator");
if(firstNum==null||secondNum==null)
{firstNum="0";secondNum="0";
str="+";
}
float first=Float.parseFloat(firstNum);
float second=Float.parseFloat(secondNum);
char operator=str.charAt(0);
String result="";
switch (operator) {
case '+':{
result=(first+second)+"";
break;
}
case '-':{
result=(first-second)+"";
break;
}
case '*':{
result=(first*second)+"";
break;
}
case '/':{
if(second==0){
out.println("被除数不能为0；");//throw new RuntimeException("被除数不能为0；");
}
else
result=(first/second)+"";
break;
}
default:
throw new RuntimeException("运算符有误！");
}
%>
*********************************
计算结果是：
<%=first %><%=operator %><%=second %>
=
<%=result %>
*********************************
第二种方式：jsp+javajean 这种方式会进一步降低耦合性。
实体类：CalBeans:
package com.ag;
public class CalBeans {
private String firstNum = "0";
private char operator = '+';
private String secondNum = "0";
private String result = "0";
public CalBeans() {
super();
}
public CalBeans(String firstNum, char operator, String secondNum) {
super();
this.firstNum = firstNum;
this.operator = operator;
this.secondNum = secondNum;
}
public String getFirstNum() {
return firstNum;
}
public void setFirstNum(String firstNum) {
this.firstNum = firstNum;
}
public char getOperator() {
return operator;
}
public void setOperator(char operator) {
this.operator = operator;
}
public String getSecondNum() {
return secondNum;
}
public void setSecondNum(String secondNum) {
this.secondNum = secondNum;
}
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
//
public void calculate() {
float first = Float.parseFloat(this.firstNum);
float second = Float.parseFloat(this.secondNum);
switch (this.operator) {
case '+':
this.result = (first + second) + "";
break;
case '-':
this.result = (first - second) + "";
break;
case '*':
this.result = (first * second) + "";
break;
case '/':
if (second == 0) {
throw new RuntimeException("被除数不能为0！");
} else {
this.result = (first / second) + "";
break;
}
default:
throw new RuntimeException("运算符有误！");
}
}
}
Cal.jsp:
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
Insert title here
*********************************
计算结果是：
*********************************
第三种：jsp+javaBean+Servlet
即MVC模式，MVC模式（Model-view-controller）是软件工程中的一种软件架构模式，把软件系统分为三个基本部分：模型（Model）、视图（View）和控制器（Controller）。这种方式jsp只是用于前端的页面的展示，后端实现计算的功能，很好地分离了前后端。
CalBeans和第二种是相同的：
代码如下：
package com.ag;
public class CalBeans {
private String firstNum = "0";
private char operator = '+';
private String secondNum = "0";
private String result = "0";
public CalBeans() {
super();
}
public CalBeans(String firstNum, char operator, String secondNum) {
super();
this.firstNum = firstNum;
this.operator = operator;
this.secondNum = secondNum;
}
public String getFirstNum() {
return firstNum;
}
public void setFirstNum(String firstNum) {
this.firstNum = firstNum;
}
public char getOperator() {
return operator;
}
public void setOperator(char operator) {
this.operator = operator;
}
public String getSecondNum() {
return secondNum;
}
public void setSecondNum(String secondNum) {
this.secondNum = secondNum;
}
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
//
public void calculate() {
float first = Float.parseFloat(this.firstNum);
float second = Float.parseFloat(this.secondNum);
switch (this.operator) {
case '+':
this.result = (first + second) + "";
break;
case '-':
this.result = (first - second) + "";
break;
case '*':
this.result = (first * second) + "";
break;
case '/':
if (second == 0) {
throw new RuntimeException("被除数不能为0！");
} else {
this.result = (first / second) + "";
break;
}
default:
throw new RuntimeException("运算符有误！");
}
}
}
前端展示：cal1.jsp：
用el表达式展示：
代码如下：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
Insert title here
*********************************
计算结果是： ${calBeans_firstNum} ${calBeans_b} ${calBeans_secondNum}${calBeans_a} ${calBean_result}
*********************************
calServlet的编写：
package web;
import com.ag.CalBeans;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet("/calServlet")
public class calServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//接受数据
String firstNum = request.getParameter("firstNum");
String operator = request.getParameter("operator");
String secondNum = request.getParameter("secondNum");
char b=operator.charAt(0);
//封装对象
CalBeans calBeans = new CalBeans();
calBeans.setFirstNum(firstNum);
calBeans.setOperator(b);
calBeans.setSecondNum(secondNum);
//调用方法
calBeans.calculate();
String result = calBeans.getResult();
request.setCharacterEncoding("utf-8");
//把数据存到request域中
request.setAttribute("calBeans_firstNum",firstNum);
request.setAttribute("calBeans_b",b);
request.setAttribute("calBeans_secondNum",secondNum);
request.setAttribute("calBeans_a","=");
request.setAttribute("calBean_result",result);
//转发
request.getRequestDispatcher("/cal1.jsp").forward(request,response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request, response);
}
}
最后附上结果图：
需要源码的朋友，可以点击这个https://gitee.com/zhu-yiwen-667/Calculator，是一个maven项目，导入之后，可能会下载一些插件和jar包，里面已经配好了Tomcat7的插件，（现在tomcat插件最高只有7的版本），可以直接配置使用，我配置的80端口，如果需要修改可以在pom.xml中修改，如果觉得慢，提前在pom.xml中加入如下代码：
nexus-aliyun nexus-aliyun http://maven.aliyun.com/nexus/content/groups/public/ true false
配置图：idea上面偏右一点
最后，如有问题或者不懂的地方，希望大家评论指出和提问。
欢迎分享，转载请注明来源：内存溢出
微信扫一扫
支付宝扫一扫
评论列表（0条）