jsp技术：day3#1---JavaBean的使用

客官°小女子只卖身不卖艺 2022-09-24 12:15 151阅读 0赞

# 1 、jsp:userBean相关 #

## 声明一个javaBean –new一个javabean对象 ##

<jsp:useBean id="user" class="cn.hncu.regServletPojo.domain.User"></jsp:useBean>

等价于Java脚本:

User user = new  cn.hncu.regServletPojo.domain.User()

给user对象设置属性，即setName(),setPwd()

<jsp:setProperty property="name" name="user" value="张三"/>
            <jsp:setProperty property="pwd" name="user" value="qwert"/>

读取user对象的属性，即getName(),getPwd()

<jsp:getProperty property="name" name="user"/>,
    <jsp:getProperty property="pwd" name="user"/>

## 用EL表达式获取 ##

${user}<br/>
    ${user.name },${user.pwd }<br/>

## 声明一个javabean的时候，要将它放在指定的容器中即设置**scope** 默认是page也可以指定request、session、application，本质上是new一个对象，将它放到指定容器中去。拿的时候还是用的前面学过的pageContext.findAttribute()方法一次从page、request、session、application对象去读取对应函数，读取到返回相应对象，否则返回空字符串 ##

<jsp:useBean id="user2" class="cn.hncu.regServletPojo.domain.User" scope="request"></jsp:useBean>
    <jsp:setProperty property="name" name="user2" value="张三"/>
    <jsp:setProperty property="pwd" name="user2" value="qwert"/>

out.print(request.getAttribute("user2"));

下面的el表达式等价于上面的输出代码

${user2 }

## 表单提交时候，property设为“\*”，就是让系统自动根据提交上来的参数去找对应的属性赋值 找到就赋值相应值 否则返回空字符串 ##

<jsp:useBean id="user4" class="cn.hncu.regServletPojo.domain.User" ></jsp:useBean>
    <jsp:setProperty property="*" name="user4"/>

## 当javaBean的属性名与setter-getter方法比较特殊时的jsp:useBean用法 ##

特殊的属性(不是基本数据时,标记无法 直接使用)  
解决方案：不写它自己默认的setter-getter—setBirth(Date)  
而是写一结替代该属性的setter-getter —setBirthday(String)  
另外，在页面使用时，属性应该用替代setter-getter方法反推出的属性名—-birthday

# 本文完整代码如下： #

## index.jsp ##

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    <%
    String path = request.getContextPath();
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
    %>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
      </head>
    
      <body>
          <h2>演示javaBean的使用： jsp:userBean相关</h2>
              <a href="jsps/javaBean.jsp">演示javaBean的使用： jsp:userBean相关</a>
              <br/>
              <br/>
              <br/>
              <br/>
              <br/>
              <br/>
              <br/>
      </body>
    </html>

## javaBean.jsp ##

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
      </head>
    
      <body>
            
            <jsp:useBean id="user" class="cn.hncu.regServletPojo.domain.User"></jsp:useBean>
            
            
            <jsp:setProperty property="name" name="user" value="张三"/>
            <jsp:setProperty property="pwd" name="user" value="qwert"/>
            
            <jsp:getProperty property="name" name="user"/>,
            <jsp:getProperty property="pwd" name="user"/>
    
            <br/>
            <br/>
            
            ${user}<br/>
            ${user.name },${user.pwd }<br/>
            <br/>
            <br/>
    
            
            <jsp:useBean id="user2" class="cn.hncu.regServletPojo.domain.User" scope="request"></jsp:useBean>
            <jsp:setProperty property="name" name="user2" value="张三"/>
            <jsp:setProperty property="pwd" name="user2" value="qwert"/>
            <%
                out.print(request.getAttribute("user2"));
             %>
            <br/>
            
            ${user2 }
    
            <br/>
            <br/>
            <br/>
            <form action="/jspDemo2_jun/jsps/doBeanForm.jsp" method="post">
                姓名:<input type="text" name="name" /><br>
                密码:<input type="password" name="pwd" /><br>
                <input type="submit" value="提交" />
            </form>
    
            <br/>
            <hr/>
            
            <jsp:useBean id="p" class="cn.hncu.regServletPojo.domain.Person"></jsp:useBean>
            <jsp:setProperty property="name" name="p" value="张三"/>
            <jsp:setProperty property="age" name="p" value="25"/>
            <jsp:setProperty property="birthday" name="p" value="1995-04-12"/>
            
    
            ${p}
            <br/>
            <br/>
            <br/>
            <br/>
            <br/>
            <br/>
            <br/>
            <br/>
    
    
      </body>
    </html>

## cn.hncu.regServletPojo.domain.Person ##

package cn.hncu.regServletPojo.domain;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    public class Person {
        
        private String name;
        private Integer age;
        private Date birth;
        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 getBirthday() {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            return sdf.format(birth);
        }
        public void setBirthday(String strDate) {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            try {
                Date d = sdf.parse(strDate);
                this.birth=d;
            } catch (ParseException e) {
                throw new RuntimeException("日期格式错误");
            }
        }
        @Override
        public String toString() {
            return "Person [name=" + name + ", age=" + age + ", birth=" + getBirthday()
                    + "]";
        }
    
    
    }

## cn.hncu.regServletPojo.domain.User ##

package cn.hncu.regServletPojo.domain;
    
    public class User {
        
        private String name;
        private String pwd;
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getPwd() {
            return pwd;
        }
        public void setPwd(String pwd) {
            this.pwd = pwd;
        }
        @Override
        public String toString() {
            return "User [name=" + name + ", pwd=" + pwd + "]";
        }
    
    }

## doBeanForm.jsp ##

<%@page import="java.io.PrintWriter"%>
    <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
      </head>
    
      <body>
        <h1>处理注册界面</h1>
        <jsp:useBean id="user3" class="cn.hncu.regServletPojo.domain.User" ></jsp:useBean>
        
        <jsp:setProperty property="name" name="user3" param="name"/>
        <jsp:setProperty property="pwd" name="user3" param="pwd"/>
        ${user3 }<br/>
    
        <jsp:useBean id="user4" class="cn.hncu.regServletPojo.domain.User" ></jsp:useBean>
        
        <jsp:setProperty property="*" name="user4"/>
        ${user4 }
    
      </body>
    </html>