JSP声明、表达式

JSP声明的基本语法是：<%! 变量定义/方法定义/类%>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page language="java" import="java.util.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP声明例子</title>
<%!int x, y = 60, z;
    String name = "John";
    Date date = new Date();%>
<%!int add(int m, int n) {
        int result = 0;
        result = m + n;
        return result;
    }%>
<%!int chengji(int m, int n) {
        int result = 0;
        result = m + n;
        return result;
    }%>
<%!class Circle {
        double r;

        Circle(double r) {
            super();
            this.r = r;
        }

        double area() {
            return Math.floor(Math.PI * r * r);
        }
    }%>
</head>
<body>
    <%
        out.print("我的名字：" + name);
        out.print("<br/><br/>");
        out.print("x的值为：" + x);
        out.print("<br/><br/>");
        out.print("y的值为：" + y);
        out.print("<br/><br/>");
        out.print("z的值为：" + z);
        out.print("<br/><br/>");
        out.print("现在的时间为：" + date);
        out.print("<br/><br/>");
        out.print("10与20的和为：" + add(10, 20));
        out.print("<br/><br/>");
        out.print("10与20的积为：" + chengji(10, 20));
    %>
    <br />
    <br />
    <%
        Circle c = new Circle(6);
        out.print("半径为6的圆面积为：" + c.area());
    %>
</body>
</html>

JSP表达式的作用是将动态信息显示在页面中，语法：<%=变量或者表达式%>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page language="java" import="java.util.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP声明例子</title>
<%!int x, y = 60, z;
    String name = "John";
    Date date = new Date();%>
<%!int add(int m, int n) {
        int result = 0;
        result = m + n;
        return result;
    }%>
<%!int chengji(int m, int n) {
        int result = 0;
        result = m + n;
        return result;
    }%>
<%!class Circle {
        double r;

        Circle(double r) {
            super();
            this.r = r;
        }

        double area() {
            return Math.floor(Math.PI * r * r);
        }
    }%>
</head>
<body>
    <%
        out.print("我的名字：" + name);
        out.print("<br/><br/>");
        out.print("x的值为：" + x);
        out.print("<br/><br/>");
        out.print("y的值为：" + y);
        out.print("<br/><br/>");
        out.print("z的值为：" + z);
        out.print("<br/><br/>");
        out.print("10与20的和为：" + add(10, 20));
        out.print("<br/><br/>");
        out.print("10与20的积为：" + chengji(10, 20));
    %>
    <br /><br />
    当前的时间为：<%= date%>
    <br /><br />
    <%
        Circle c = new Circle(6);
        out.print("半径为6的圆面积为：" + c.area());
    %>
</body>
</html>