javaee学习之路(十四)JSP编程实例
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例1、输出当前时间值。
1.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>jsp入门案例（输出时间）</title> </head> <body> 当前时间值是： <% Date date=new Date(); out.write(date.toLocaleString()); %> </body></html>找到tomcat服务器当中对应的Servlet文件C:\tomcat\work\Catalina\localhost\day08\org\apache\jsp\ _1_jsp.java
……
out.write("\r\n"); out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n"); out.write("<html>\r\n"); out.write(" <head>\r\n"); out.write(" <title>jsp入门案例（输出时间）</title> \r\n"); out.write("</head>\r\n"); out.write("<body>\r\n"); out.write("当前时间值是：\r\n"); out.write(" "); Date date=new Date(); out.write(date.toLocaleString()); out.write("\r\n"); out.write(" </body>\r\n"); out.write("</html>\r\n");<% %>之间的内容被原封不动地嵌套在了servlet当中
例2、Page指令之errorPage，怎样处理JSP当中的异常—实际开发当中案例1。
Step1、1.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>jsp入门案例（输出时间）</title> </head> <body> <% int x=1/0; out.print(x); %> </body></html>Step2、web.xml
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <error-page> <exception-type>java.lang.ArithmeticException</exception-type> <location>/errors/error.jsp</location> </error-page> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list></web-app>Step3、error.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>My JSP 'error.jsp' starting page</title> </head> <body> 对不起，出错了！！！ <br> </body></html>例3、Page指令之errorPage，怎样处理JSP当中的异常—实际开发当中案例1
Step1、
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <error-page> <exception-type>java.lang.ArithmeticException</exception-type> <location>/errors/error.jsp</location> </error-page> <error-page> <error-code>404</error-code> <location>/errors/404.jsp</location> </error-page> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list></web-app>Step2、404.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>My JSP '404.jsp' starting page</title> </head> <body> 对不起，您访问的资源不存在！！！ <br> </body></html>Step3、在IE中键入htpp://localhost:8080/day08/fandong
例3、JSP乱码问题。 
在Eclipse当中只需要这只PageEncoding就行了
例4、include指令实例代码
Step1、在WebRoot目录之下建立目录public,在其中放入head.jsp和foot.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>head.jsp</title> </head> <body> 这是页头！！！ <br> </body></html><%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>foot.jsp</title> </head> <body> 这是页脚！！！ <br> </body></html>Step2、在WebRoot目录下创建页面2.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>include指令(静态包涵)</title> </head> <body> <%@include file="/public/head.jsp"%> aaaa<br> <%@include file="/public/foot.jsp"%> </body></html>Step3、在ie中键入: http://localhost:8080/day08/2.jsp可得
这是页头！！！ aaaa这是页脚！！！1、 在实际开发当中通常将head.jsp和foot.jsp等被包涵的文件写为一下格式:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 这是页头！！！<br> (即只留下声明和与当中的内容即可)
2、include指令（静态包涵，编译时包含，被包涵的JSP文件与包涵的Jsp文件一起编译成一个servlet）
3、动态包涵：3.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>动态包涵(这种情况是运行时包含)</title> </head> <body> <% request.getRequestDispatcher("/public/head.jsp").include(request,response); %> <% response.getWriter().write("aaaaaaaaaaa <br>"); %> <% request.getRequestDispatcher("/public/foot.jsp").include(request,response); %> </body></html>在实际开发当中尽量用静态包含！！！！！
例5、out隐式对象
问题演示：4.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>My JSP '4.jsp' starting page</title> </head> <body> Aaaaaaa//编译之后用out输出 <% out.write("hahahahahha"); response.getWriter().write("wuuwuwuwuuwu"); %> </body></html>在IE中键入:http://localhost:8080/day08/4.jsp可以看到：
wuuwuwuwuuwu aaaaaaaa hahahahahha
问题在于并没有出想ha在前wu在后的情况,原因:out有缓存
例6、PageContext对象访问其他域对象(4.jsp)
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>pageContext对象访问其他域</title> </head> <body> <% request.setAttribute("data","fandong"); String data=(String)pageContext.getAttribute("data",PageContext.REQUEST_SCOPE); out.write(data); %> </body></html>在IE中可以得到:fandong
例7、pageContext域对象之findAttribute方法之应用。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>pageContext对象访问其他域</title> </head> <body> <% request.setAttribute("data","fandong"); String data=(String)pageContext.getAttribute("data",PageContext.REQUEST_SCOPE); out.write(data+"<br/>"); String data2=(String)pageContext.findAttribute("data"); out.write(data2); %> </body></html>在IE中可以得到:fandong
fandong
例8、标签的作用
Step1、5.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>JSP常用标签</title> </head> <body> <% String x="12"; %> <jsp:forward page="/servlet/ServletDemo1"> <jsp:param value="<%= x %>" name="password"/> <jsp:param value="fandong" name="username"/> </jsp:forward> </body></html>Step2、ServletDemo1.java
package cn.itcast.web.servlet;import *;public class ServletDemo1 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String username=request.getParameter("username"); System.out.println(username); String x = (String)request.getParameter("password"); System.out.println(x); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}Step3、在IE中键入：htpp://localhost:8080/day08/5.jsp可以看到：fandong 12
例9、应用实例之一。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>jsp:usebean</title> </head> <body> <%--创建一个Person对象,这个对象的名字叫做person,(如果在page域中有了一个Person就直接拿过来用，不另外创建)--%><%-- useBean标签的标签提只在useBean标签实例化bean时才执行--%> <jsp:useBean id="person" class="cn.itcast.domain.Person" scope="page"> Fandong!!!!</jsp:useBean> <%=person.getName() %> </body></html> 上面的过程中，当浏览器第一次访问1.jsp时，useBean标签会实例化Person对象，此时标签之间的Fandong!!!!会执行下去，会在浏览其中显示，但是，当第二次访问1.jsp时就不会执行了，因为已经在page域当中创建了persion的对象了！
例10、2.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>jsp:setProperty标签</title> </head> <body> <jsp:useBean id="person" class="cn.itcast.domain.Person" scope="page"/> <%--手工为bean赋值 --%> <jsp:setProperty name="person" property="name" value="xxx"/> <%--赋当前时间值给属性birthday --%> <jsp:setProperty name="person" property="birthday" value="<%=new Date()%>"/> <%=person.getName() %><br/> <%=person.getBirthday() %><br/> <%--用请求参数给bean的属性赋值 --%> <jsp:setProperty property="name" name="person" param="name"/> <jsp:setProperty property="age" name="person" param="age"/> <%=person.getName() %><br/> <%=person.getAge() %><br/> </body></html> 在IE中键入http://localhost:8080/day09/2.jsp?name=fandong&age=12可以得到结果:
xxx
Sat Sep 15 17:52:51 CST 2012
fandong
12
例11、为所有参数赋值。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>jsp:setProperty标签</title> </head> <body> <jsp:useBean id="person" class="cn.itcast.domain.Person" scope="page"/> <%--用所有的请求参数为bean赋值 --%> <jsp:setProperty property="*" name="person"/> <%=person.getName()%>上面这一句代码等同于<jsp:getProperty name=”person” ptoperty=”name”/> <%=person.getAge()%> </body></html> 在IE中键入http://localhost:8080/day09/2.jsp?name=fandong&age=12可以得到结果:
fandong
12
（注意IE栏中带过来的参数名称应该与bean中的属性名一样）
说明：在servlet当中自动将”12”转为了整形。这个标签支持8中数据类型的转换（把客户机提交的字符串转为8中基本数据类型赋值到jean当中）。
例13、使用Jsp+javabean编写一个计算器页面，javaBean具有firstNum、secondNum、result、operator属性，并提供一个calculate方法.
补充:实现各种数的精确运算：
package cn.itcast.domain;import java.math.BigDecimal;public class Demo1 { public static void main(String[] args){ BigDecimal a=new BigDecimal("0.1"); BigDecimal b=new BigDecimal("0.006"); BigDecimal c=new BigDecimal("0.3"); System.out.println(a.add(b).toString()); System.out.println(a.multiply(b).toString()); System.out.println(a.divide(c, 10,BigDecimal.ROUND_HALF_UP)); //表示保留小数点后面10位 }}输出结果为:
0.106
0.0006
0.3333333333
Step1、calculator.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>计算器</title> </head> <body style="text-align: center"> <jsp:useBean id="calculatorBean" class="cn.itcast.domain.CalculatorBean"></jsp:useBean> <jsp:setProperty property="*" name="calculatorBean"/> <% try{ calculatorBean.calculator(); }catch(Exception e) { out.write(e.getMessage());//把异常给用户友好提示 } %> <br/>--------------------------------------------------------<br/> 计算结果是: <jsp:getProperty property="firstNum" name="calculatorBean"/> <jsp:getProperty property="operator" name="calculatorBean"/> <jsp:getProperty property="secondNum" name="calculatorBean"/> = <jsp:getProperty property="result" name="calculatorBean"/> <br/>--------------------------------------------------------<br/> <form action="/day09/calculator.jsp" method="post"> <table width="40%" border="1"> <tr> <td colspan="2">简单的计算器</td> </tr> <tr> <td>第一个参数</td> <td> <input type="text" name="firstNum"/> </td> </tr> <tr> <td>运算符</td> <td> <select name="operator"> <option value="+">+</option> <option value="-">-</option> <option value="*">*</option> <option value="/">/</option> </select> </td> </tr> <tr> <td>第二个参数</td> <td><input type="text" name="secondNum"/> </td> </tr> <tr> <td colspan="2"> <input type="submit" value="计算"/> </td> </tr> </table> </form> </body></html>Step2、CalculatorBean.java
package cn.itcast.domain;import java.math.BigDecimal;//封转计算器数据的beanpublic class CalculatorBean { private String firstNum="0"; private String secondNum="0"; private char operator='+'; private String result; public String getFirstNum() { return firstNum; } public void setFirstNum(String firstNum) { this.firstNum = firstNum; } public String getSecondNum() { return secondNum; } public void setSecondNum(String secondNum) { this.secondNum = secondNum; } public char getOperator() { return operator; } public void setOperator(char operator) { this.operator = operator; } public String getResult() { return result; } public void setResult(String result) { this.result = result; } public void calculator(){ BigDecimal first=new BigDecimal(this.firstNum); BigDecimal second=new BigDecimal(this.secondNum); switch (this.operator) { case '+':{ this.result=first.add(second).toString(); break;} case '-':{ this.result=first.subtract(second).toString(); break;} case '*':{ this.result=first.multiply(second).toString(); break;} case '/':{ if(second.doubleValue()==0){ throw new RuntimeException("被除数不能为0"); } this.result=first.divide(second,10,BigDecimal.ROUND_HALF_UP).toString(); break;} default:{ throw new RuntimeException("运算符错误!"); } } }}例14、EL表达式例程。（3.jsp）
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>EL表达式例程</title> </head> <body> <% String data="fandong"; request.setAttribute("data",data); %> ${data}<%--相当于pageContext.findAttribute(“data”);--%> </body></html>在IE中键入:http:localhost:8080/day09/3.jsp便可以看到：
fandong
例15、EL表达式快速入门。
Step1、Person.java
package cn.itcast.domain;import java.util.Date;public class Person { private String name;private Address address; public Person() { super(); } public Person(String name) { super(); this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; }}Step2、Address.java
package cn.itcast.domain;public class Address { private String city; public String getCity() { return city; } public void setCity(String city) { this.city = city; }}Step3、3.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%%@page import="cn.itcast.domain.Person"%%><%@page import="cn.itcast.domain.Address"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>EL表达式例程</title> </head> <body> <% String data="fandong"; request.setAttribute("data",data); %> ${data}<%--相当于pageContext.findAttribute(“data”);--%> <br> <% Person p=new Person(); p.setName("denghongmei!"); request.setAttribute("person",p); %> ${person.name} <br> <% Person p1=new Person(); Address a=new Address(); a.setCity("上海"); p1.setAddress(a); request.setAttribute("p1",p1); %> ${p1.address.city} <br> <%-- p1上面的request设置的属性名称，而后面的为bean封装的属性--%> <%--EL表达式读取集合当中的内容--%> <% List list=new ArrayList(); list.add(new Person("aaa")); list.add(new Person("bbb")); list.add(new Person("ccc")); request.setAttribute("list",list); %> ${list[0].name} <br> <% Map map=new HashMap(); map.put("aa",new Person("aaaa")); map.put("bb",new Person("bbbb")); map.put("cc",new Person("cccc")); map.put("dd",new Person("dddd")); map.put("1111",new Person("eeee")); request.setAttribute("map123",map); %> ${map123.bb.name} <br> <%--用${map123.1111.name}取不出来数据的,这是要用[]来取 --%> ${map123['1111'].name} <br> <%--得到当前web应用的名称,用在超链接等地方 --%> ${pageContext.request.contextPath} <br> <a href="${pageContext.request.contextPath}/index.jsp">点击</a> </body></html>例16、使用jstl和EL完成集合的迭代。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@page import="cn.itcast.domain.Person"%><%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><%--上面一行的作用是导入标签库,上面的uri怎么来的? 在eclipse左侧目录点击day09项目->Reference Libraries->standard.jar->META-INF->c.tld->找到映射的<uri>http://java.sun.com/jsp/jstl/core</uri>--%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>使用jstl+EL完成集合迭代</title> </head> <body> <% List list=new ArrayList(); list.add(new Person("aaa")); list.add(new Person("bbb")); list.add(new Person("ccc")); request.setAttribute("list",list); %> <c:forEach var="person" items="${list }"> <%--将迭代的每个元素放在person变量当中 --%> ${person.name }<br/> </c:forEach> <br> <% Map map=new HashMap(); map.put("aa",new Person("aaaa")); map.put("bb",new Person("bbbb")); map.put("cc",new Person("cccc")); map.put("dd",new Person("dddd")); map.put("1111",new Person("eeee")); request.setAttribute("map123",map); %> <c:forEach var="entry" items="${map123}"> <%--对map的迭代实际上是对map.entrySet返回的set<Map.entry>结合进行迭代 --%> ${entry.key} : ${entry.value.name} <br/> <%--判断标签 --%> </c:forEach> <c:if test="${user!=null}"> 欢迎您:${user.username} </c:if> <c:if test="${user==null}"> 用户名：<input type="text"/> 密码：<input type="password"/> </c:if> </body></html> 0 0
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