javaBean组件

1. javaBean组件

0) 不使用Javabean组件

javabean01.jsp

<%@ page import="com.andrew.model.Student" %>
<%
    Student student=new Student();
    student.setName("王二小");
    student.setAge(12);
%>
<h1>姓名：<%=student.getName() %></h1>
<h1>年龄：<%=student.getAge() %></h1>

1) Javabean组件引入

JavaBean是使用Java语言开发的一个可重用的组件，在JSP开发中可以使用JavaBean减少重复代码，使整个JSP代码的开发更简洁。

Student.java

package com.andrew.model;
public class Student {
    private String name;
    private int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}

2) jsp:useBean创建javabean

<jsp:useBean id="实例化对象名称" scope="保存范围" class="类完整名称"/>
Scope，一共有page, request, session和application 4个属性范围，默认是page；

javabean02.jsp

<jsp:useBean id="student" scope="page" class="com.andrew.model.Student"/>
<%
    student.setName("王二小2");
    student.setAge(12);
%>
<h1>姓名：<%=student.getName() %></h1>
<h1>年龄：<%=student.getAge() %></h1>

3) jsp:setProperty设置javabean属性值

<jsp:setProperty property="属性名称" name="实例化对象的名称" value="属性值" param="参数名称"/>
property="*"自动匹配所有

未使用property情况 javabean03.jsp

<%@ page import="com.andrew.model.Student" %>
<%
    request.setCharacterEncoding("utf-8");
    String name=request.getParameter("name");
    String age=request.getParameter("age");
    Student student=new Student();
    student.setName(name);
    student.setAge(Integer.parseInt(age));
%>
<h1>姓名：<%=student.getName() %></h1>
<h1>年龄：<%=student.getAge() %></h1>

student.jsp
    action="javabean03-1.jsp"
    action="javabean03-2.jsp"
    action="javabean03-3.jsp"

<form action="javabean03-3.jsp" method="post">
<table>
    <tr><td>姓名：</td><td><input type="text" name="name"/></td></tr>
    <tr><td>年龄：</td><td><input type="text" name="age"/></td></tr>
    <tr><td colspan="2"><input type="submit" value="提交"/></td></tr>
</table>
</form>

javabean03-1.jsp

<%
    request.setCharacterEncoding("utf-8");
%>
<jsp:useBean id="student" scope="page" class="com.andrew.model.Student"/>
<jsp:setProperty property="*" name="student"/>
<h1>姓名：<%=student.getName() %></h1>
<h1>年龄：<%=student.getAge() %></h1>

javabean03-2.jsp

<%
    request.setCharacterEncoding("utf-8");
%>
<jsp:useBean id="student" scope="page" class="com.andrew.model.Student"/>
<jsp:setProperty property="name" name="student"/>
<jsp:setProperty property="age" name="student" value="100"/>
<h1>姓名：<%=student.getName() %></h1>
<h1>年龄：<%=student.getAge() %></h1>

javabean03-3.jsp

<%
    request.setCharacterEncoding("utf-8");
%>
<jsp:useBean id="student" scope="page" class="com.andrew.model.Student"/>
<jsp:setProperty property="name" name="student" param="userName"/>
<jsp:setProperty property="age" name="student" value="100"/>
<h1>姓名：<%=student.getName() %></h1>
<h1>年龄：<%=student.getAge() %></h1>

4) jsp:getProperty获取javabean属性值

<jsp:getProperty property="属性名称" name="实例化对象的名称"/>

javabean04.jsp

<jsp:useBean id="student" scope="page" class="com.andrew.model.Student"/>
<%
    student.setName("王二小2");
    student.setAge(12);
%>
<h1>姓名：<jsp:getProperty property="name" name="student"/></h1>
<h1>年龄：<jsp:getProperty property="age" name="student"/></h1>

5) javabean的保存范围

Javabean的保存范围有page,request,session,application，默认是page；

javabean04-2.jsp

<jsp:useBean id="student" scope="request" class="com.andrew.model.Student"/>
<jsp:setProperty property="name" name="student" value="王八蛋"/>
<jsp:setProperty property="age" name="student" value="12"/>
<jsp:forward page="target01.jsp"/>

target01.jsp

<jsp:useBean id="student" scope="request" class="com.andrew.model.Student"/>
<h1>姓名：<jsp:getProperty property="name" name="student"/></h1>
<h1>年龄：<jsp:getProperty property="age" name="student"/></h1>

javabean04-3.jsp

<jsp:useBean id="student" scope="session" class="com.andrew.model.Student"/>
<jsp:setProperty property="name" name="student" value="王八蛋"/>
<jsp:setProperty property="age" name="student" value="12"/>
<h1>Session数据设置完毕！</h1>

target02.jsp

<h1>Session中取值</h1>
<jsp:useBean id="student" scope="session" class="com.andrew.model.Student"/>
<h1>姓名：<jsp:getProperty property="name" name="student"/></h1>
<h1>年龄：<jsp:getProperty property="age" name="student"/></h1>

javabean04-4.jsp

<jsp:useBean id="student" scope="application" class="com.andrew.model.Student"/>
<jsp:setProperty property="name" name="student" value="李四"/>
<jsp:setProperty property="age" name="student" value="13"/>
<h1>Application数据设置完毕！</h1>

target03.jsp

<h1>Application中取值</h1>
<jsp:useBean id="student" scope="application" class="com.andrew.model.Student"/>
<h1>姓名：<jsp:getProperty property="name" name="student"/></h1>
<h1>年龄：<jsp:getProperty property="age" name="student"/></h1>

6) javabean删除

page范围：pageContext.removeAttribute("javaBean Name");
request范围：request.removeAttribute("javaBean Name");
session范围：session.removeAttribute("javaBean Name");
application范围：application.removeAttribute("javaBean Name");

javabeanDelete.jsp

<%
    session.removeAttribute("student");
%>
<h1>javabean已删除！</h1>

javabean04-3.jsp --> target02.jsp --> javabeanDelete.jsp --> target02.jsp