JAVA-EE使用EL表达式在域中取值实现改造JSP页面------计算机网络经典

水深无声 2024-03-27 00:36 62阅读 0赞

>     EL表达式
>     EL表达式是为了代替JSP的java代码,让JSP看起来更加整洁美观,JSP中夹杂着各种java代码就会让文件混乱不好维护
>     第一功效:从某个域中取数据,将取出的数据转成字符串,将字符串输出到浏览器
>     EL表达式是属于JSP语法的一种
>     JSTL标签库,Filter过滤器,Listener监听器
> 
>     EL表达式
>     EL表达式是为了代替JSP的java代码,让JSP看起来更加整洁美观,JSP中夹杂着各种java代码就会让文件混乱不好维护
>     第一功效:从某个域中取数据,将取出的数据转成字符串,将字符串输出到浏览器
>     EL表达式是属于JSP语法的一种
>     JSTL标签库,Filter过滤器,Listener监听器

>     package com.bjpowernode.oa.web.Pojo;
>     
>     public class Address
>     {
>         private String city;
>         private String loc;
>     
>         @Override
>         public String toString() {
>             return "Address{" +
>                     "city='" + city + '\'' +
>                     ", loc='" + loc + '\'' +
>                     '}';
>         }
>     
>         public String getCity() {
>             return city;
>         }
>     
>         public void setCity(String city) {
>             this.city = city;
>         }
>     
>         public String getLoc() {
>             return loc;
>         }
>     
>         public void setLoc(String loc) {
>             this.loc = loc;
>         }
>     
>         public Address() {
>         }
>     
>         public Address(String city, String loc) {
>             this.city = city;
>             this.loc = loc;
>         }
>     }
> 
>     package com.bjpowernode.oa.web.Pojo;
>     
>     public class Address
>     {
>         private String city;
>         private String loc;
>     
>         @Override
>         public String toString() {
>             return "Address{" +
>                     "city='" + city + '\'' +
>                     ", loc='" + loc + '\'' +
>                     '}';
>         }
>     
>         public String getCity() {
>             return city;
>         }
>     
>         public void setCity(String city) {
>             this.city = city;
>         }
>     
>         public String getLoc() {
>             return loc;
>         }
>     
>         public void setLoc(String loc) {
>             this.loc = loc;
>         }
>     
>         public Address() {
>         }
>     
>         public Address(String city, String loc) {
>             this.city = city;
>             this.loc = loc;
>         }
>     }

>     <%@ page import="com.bjpowernode.oa.web.Pojo.Dept" %>
>     <%@ page import="com.bjpowernode.oa.web.Pojo.Address" %>
>     <%@ page contentType="text/html;charset=UTF-8" language="java" %>
>     <!DOCTYPE html>
>     <html>
>     <head>
>         <meta charset="utf-8">
>         <title>欢迎页</title>
>     </head>
>     <body>
>         <h1>用户登录</h1>
>         <hr>
>         <form action="<%=request.getContextPath()%>/user/login" method="post">
>             username:<input type="text" name="username"><br>
>             password:<input type="password" name="password"><br>
>             10天免登录:<input type="checkbox" name="flag" value="1"><br>
>             <input type="submit" value="login">
>         </form>
>         <h1>
>             <a href="<%=request.getContextPath()%>/cookie/generate">
>                 服务器生成Cookie,然后把Cookie传给浏览器,浏览器收到,再放到客户端上
>             </a>
>         </h1>
>         <h1>
>             <a href="<%=request.getContextPath()%>/sendCookie">
>                 浏览器发送Cookie给服务器
>             </a>
>         </h1>
>         <%request.setAttribute("name","zhangSan");%>
>         <%request.setAttribute("OBJ",new Object());%>
>     <%--    这里的EL表达式起到的作用就是从域中取出数据,并将它以字符串的形式输出到浏览器--%>
>     <%--    使用EL表达式时,它会自动从某个域取数据,将其转为字符串,如果是Object类就调用toString方法--%>
>     <%--    并将它输出到浏览器--%>
>         <%session.setAttribute("dept1",new Dept("3","2","1",new Address("阿斯顿","马丁")));%>
>         <%request.setAttribute("dept",new Dept("1","2","3"));%>
>         <%request.setAttribute("1",new Dept("1","2","3"));%>
>         ${name}
>         ${OBJ}
>     <%--    EL表达式的.属性名取值实际调用的是该对象的get方法--%>
>         ${dept.dname}
>     <%--    有同名的对象在不同的域的时候,优先从小的域取值--%>
>         ${dept}
>         ${dept1.address.city}
>         ${dept1.address.loc}
>         ${dept1.address.toString()}
>     <%--    前端发送请求路径的时候,如果请求路径是绝对路径,要以/开始,加项目名--%>
>     <%--    <h1><a href="<%=(request.getContextPath())%>/dept/list">查看部门列表</a></h1>--%>
>     </body>
>     </html>
> 
>     <%@ page import="com.bjpowernode.oa.web.Pojo.Dept" %>
>     <%@ page import="com.bjpowernode.oa.web.Pojo.Address" %>
>     <%@ page contentType="text/html;charset=UTF-8" language="java" %>
>     <!DOCTYPE html>
>     <html>
>     <head>
>         <meta charset="utf-8">
>         <title>欢迎页</title>
>     </head>
>     <body>
>         <h1>用户登录</h1>
>         <hr>
>         <form action="<%=request.getContextPath()%>/user/login" method="post">
>             username:<input type="text" name="username"><br>
>             password:<input type="password" name="password"><br>
>             10天免登录:<input type="checkbox" name="flag" value="1"><br>
>             <input type="submit" value="login">
>         </form>
>         <h1>
>             <a href="<%=request.getContextPath()%>/cookie/generate">
>                 服务器生成Cookie,然后把Cookie传给浏览器,浏览器收到,再放到客户端上
>             </a>
>         </h1>
>         <h1>
>             <a href="<%=request.getContextPath()%>/sendCookie">
>                 浏览器发送Cookie给服务器
>             </a>
>         </h1>
>         <%request.setAttribute("name","zhangSan");%>
>         <%request.setAttribute("OBJ",new Object());%>
>     <%--    这里的EL表达式起到的作用就是从域中取出数据,并将它以字符串的形式输出到浏览器--%>
>     <%--    使用EL表达式时,它会自动从某个域取数据,将其转为字符串,如果是Object类就调用toString方法--%>
>     <%--    并将它输出到浏览器--%>
>         <%session.setAttribute("dept1",new Dept("3","2","1",new Address("阿斯顿","马丁")));%>
>         <%request.setAttribute("dept",new Dept("1","2","3"));%>
>         <%request.setAttribute("1",new Dept("1","2","3"));%>
>         ${name}
>         ${OBJ}
>     <%--    EL表达式的.属性名取值实际调用的是该对象的get方法--%>
>         ${dept.dname}
>     <%--    有同名的对象在不同的域的时候,优先从小的域取值--%>
>         ${dept}
>         ${dept1.address.city}
>         ${dept1.address.loc}
>         ${dept1.address.toString()}
>     <%--    前端发送请求路径的时候,如果请求路径是绝对路径,要以/开始,加项目名--%>
>     <%--    <h1><a href="<%=(request.getContextPath())%>/dept/list">查看部门列表</a></h1>--%>
>     </body>
>     </html>