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JSP内置对象及翻译过程:
隐含(内置)对象
1. request(*)
- HttpServletRequest
2. response
- HttpServletResponse
3. out
- JSPWriter
- 等价于PrintWriter
4. config
- ServletConfig
5. application
- ServletContext
6. exception
- Throwable
- 当页面发生异常时才能使用
7. session(*)
- HttpSession
- 将来再讲
8. page
- Object
- 指代当前的页面,相当于this
9. pageContext(*)
- PageContext
- 页面的环境,可以给页面提供数据
- 通过该对象可以获取其他8个隐含对象
隐含对象使用示例
<%Object obj = request.getAttribute("");%>
<%=request.getAttribute("")%>
案例演示JSP简单使用图示:
案例演示:
工程案例目录结构
pom.xml:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.study</groupId>
<artifactId>Jsp02</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<dependencies>
<dependency>
<groupId>javaee</groupId>
<artifactId>javaee-api</artifactId>
<version>5</version>
</dependency>
</dependencies>
</project>
find_emp.jsp:
<%@page pageEncoding="utf-8"
import="entity.Emp,dao.EmpDao,java.util.*"
%>
<!doctype html>
<html>
<head>
<title>员工列表</title>
<meta charset="utf-8">
</head>
<body>
<table border="1" width="40%" cellspacing="0">
<!-- th就是特殊的td,自带加粗和居中 -->
<tr>
<th>编号</th>
<th>姓名</th>
<th>职位</th>
<th>薪资</th>
</tr>
<!-- 查询所有的员工,拼对应的数据行 -->
<%
EmpDao dao = new EmpDao();
List<Emp> list = dao.findAll();
for(Emp e :list){
%>
<tr>
<td><%=e.getEmpno() %></td>
<td><%=e.getName() %></td>
<td><%=e.getJob() %></td>
<td><%=e.getSal() %></td>
</tr>
<%
}
%>
</table>
</body>
</html>
Emp.java:
package entity;
import java.io.Serializable;
public class Emp implements Serializable {
private Integer empno;
private String name;
private String job;
private Double sal;
public Integer getEmpno() {
return empno;
}
public void setEmpno(Integer empno) {
this.empno = empno;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
public Double getSal() {
return sal;
}
public void setSal(Double sal) {
this.sal = sal;
}
}
EmpDao.java:
package dao;
import java.util.ArrayList;
import java.util.List;
import entity.Emp;
public class EmpDao {
public void save(Emp e) {
System.out.println(
"向DB插入员工数据:" + e);
}
public List<Emp> findAll() {
List<Emp> list = new ArrayList<Emp>();
Emp e1 = new Emp();
e1.setEmpno(1);
e1.setName("唐僧");
e1.setJob("领导");
e1.setSal(9000.0);
list.add(e1);
Emp e2 = new Emp();
e2.setEmpno(2);
e2.setName("悟空");
e2.setJob("保镖");
e2.setSal(6000.0);
list.add(e2);
Emp e3 = new Emp();
e3.setEmpno(3);
e3.setName("八戒");
e3.setJob("徒弟");
e3.setSal(7000.0);
list.add(e3);
return list;
}
}
将Jsp02工程部署到Tomcat上,运行Tomcat启动案例工程,
浏览器录入http://localhost:8080/Jsp02//find_emp.jsp 即可:如果没有错误,最终页面显示效果应如下图: