Servlet3.0

一、要求

MyEclipes10.0或以上版本!

发布到Tomcat7.0或以上版本!

二、步骤

创建JavaEE6.0应用


-------------------------------------------

三、概述

*注解代替web.xml配置文件

*异步处理

*对上传的支持


Servlet3.0在市场上没有应用!


--------------------------------------------

四、注解替代配置文件

1、删除web.xml

2、在servlet类上添加@WebServlet(urlPatterns={"/AServlet"})


初次接触Servlet3.0_html初次接触Servlet3.0_html_02


package cn.itcast.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/*
<servlet>
<servlet-name>AServlet</servlet-name>
<servlet-class>cn.itcast.web.servlet.AServlet</servlet-class>
<init-param>
<param-name>p1</param-name>
<param-value>v1</param-value>
</init-param>
<init-param>
<param-name>p2</param-name>
<param-value>v2</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>AServlet</servlet-name>
<url-pattern>/AServlet</url-pattern>
<url-pattern>/AAServlet</url-pattern>
</servlet-mapping>
*/
@WebServlet(urlPatterns="/AServlet",
initParams={ //这个既然修改不了,为什么不直接在servlet对应地方书写呢,所以无太大意义,一般不适用
@WebInitParam(name="p1",value="v1"),
@WebInitParam(name="p2",value="v2"),
},
loadOnStartup=1
)
public class AServlet extends HttpServlet{

public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
System.out.println("hello servlet3.0!");
resp.getWriter().print("hello 3.0!!");
}
}

View Code

总结:

注解的优缺点:配置信息少,不方便修改

3、在Filter类上面添加@WebFilter(urlPattern="/AFilter")


初次接触Servlet3.0_上传文件_03初次接触Servlet3.0_上传文件_04


package cn.itcast.web.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;

@WebFilter(urlPatterns="/*")
public class AFilter implements Filter{

@Override
public void destroy() {

}

@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
System.out.println("哈哈,看到我了没有!");
arg2.doFilter(arg0, arg1);
}

@Override
public void init(FilterConfig arg0) throws ServletException {

}

}

View Code

4、在Listener类上添加@WebListener


初次接触Servlet3.0_上传_05初次接触Servlet3.0_上传_06


package cn.itcast.web.listener;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class AListener implements ServletContextListener{

@Override
public void contextDestroyed(ServletContextEvent arg0) {
System.out.println("死掉了!");
}

@Override
public void contextInitialized(ServletContextEvent arg0) {
System.out.println("出生了!");
}

}

View Code

五、异步处理

1、什么是异步处理

原来,在服务器没有结束响应之前,客户端浏览器是看不到响应内容的,只有响应结束时候,浏览器才能显示结果!

现在异步处理的而作用:在服务器开始响应后,浏览器就可以看到响应内容,不用等待响应结束


2、实现异步的步骤

*得到AsyncContext,它是异步上下文对象

AsyncContext ac=request.startAsync(request,response);

*给上下文一个Runnable对象,启动它!(给上下文一个任务,让它完成!)

ac.start(new Runnable(){

public void run(){

...

}

});


*@WebServlet(urlPattern="/AServlet",asyncSupported=true)

*resp.setContentType("text/html;charset=utf-8");

*IE如果不能正常输出,这说明响应体大小不足521B,那么你多补充一点废话就可以了

*AstnContext#complete():通知Tomcat我们异步线程已经执行完毕了


初次接触Servlet3.0_上传文件_07初次接触Servlet3.0_上传文件_08


package cn.itcast.web.servlet;

import java.io.IOException;

import javax.servlet.AsyncContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(urlPatterns="/AServlet",asyncSupported=true)
public class AServlet extends HttpServlet{

/* 不异步
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.getWriter().print("hello");
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
}
resp.getWriter().print("word");
resp.getWriter().flush();
}
*/
public void doGet(HttpServletRequest req, final HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=utf-8");
for(int i=0;i<=512;i++){
resp.getWriter().print("a");
}
/*
* 得到异步上下文对象
*/
final AsyncContext ac=req.startAsync(req, resp);
/*
* 给上下文对象一个Runnable对象,让它执行这个任务
*/
ac.start(new Runnable(){
public void run(){
println("现在马上开始!<br/>",resp);
sleep(2000);
for(char c='A';c<'Z';c++){
println(c+"",resp);
sleep(250);
}
//通知Tomcat该线程已经结束了
ac.complete();
}
});
}
public void println(String text,HttpServletResponse resp){
try {
resp.getWriter().print(text);
resp.getWriter().flush();
} catch (IOException e) {
}

}
public void sleep(long ms){
try {
Thread.sleep(ms);
} catch (InterruptedException e) {
}
}
}

View Code

 

----------------------------------------

六、上传支持

1、上传

*上传时对表单的要求

method="post"

enctype="multipart/form-data",它的默认值是:application/x-www-form-urlencoded

<input type="file" name="必须给"/>


*上传Servlet的使用

request.getParameter()相关不能再使用

request.getInputStream()使用它来获取整个表单的数据


*commons-fileupload

创建工厂

解析器

使用解析器得到List<FileItem>


=====================

Servlet3.0对上传提供了支持:

*表单不变

*在Servlet中不需要再使用commons-fileupload,而是使用Servlet3.0提供的上传接口


=====================

上传的步骤:

*使用request.getPart("字段名"),得到Part实例

*Part:

>String getContentType():获取上传文件的MIME类型

>String getName():获取表单项的名称,不是文件名称

>String getHeader(String header):获取指定头的值

>long getSize():获取上传文件的大小

>InputStream getInputStream():获取上传文件的内容

>void write(String fileName):把上传文件保存到指定路径下

*默认Servlet是不支持使用上传组件:需要给Servlet添加一个注解:@MultipartConfig


它没有提供获取上传文件名称的方法

这需要我们自己从Content-Disposition中截取


初次接触Servlet3.0_ide_09初次接触Servlet3.0_上传_10


<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
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>
<base href="<%=basePath%>">

<title>My JSP 'form.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->

</head>

<body>
<h1>注册</h1>
<form action="<c:url value='/AServlet'/>" method="post" enctype="multipart/form-data">
用户名:<input type="text" name="username"/><br/>
简 历:<input type="file" name="resume"/><br/>
<input type="submit" value="注册"/>
</form>
</body>
</html>

form.jsp

初次接触Servlet3.0_ide_11初次接触Servlet3.0_上传_12


package cn.itcast.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

@WebServlet(urlPatterns="/AServlet")
@MultipartConfig
public class AServlet extends HttpServlet{

public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
/*
* getParameter()可以使用了
*/
String username=req.getParameter("username");
/*
* 获取文件表单字段
*/
Part part=req.getPart("resume");
/*
* 从Part中获取需要的数据
*/
//获取上传文件的MIME类型
System.out.println(part.getContentType());
//获取上传文件的字节数
System.out.println(part.getSize());
//获取文件字段名称
System.out.println(part.getName());
//获取头,这个头包含了上传文件名称
System.out.println(part.getHeader("Content-Disposition"));
String filename=part.getHeader("Content-Disposition");
// filename=filename.split("filename=")[1].split("\"")[1];
int start=filename.lastIndexOf("filename=\"");
int end=filename.length()-1;
filename=filename.substring(start,end);
System.out.println(filename);
//保存上传文件
part.write("C:/"+filename);

}
}

AServlet.java