J2EE是什么
Java 2 Paltform Enterprise Edition(Java2企业版)
B/S模式开发应用就是J2EE最核心的功能
J2EE由13个模块组成,最主要的是Servlet(Web服务器小程序),JSP(服务器页面),JDBC(数据库交互模块),XML(XML交互模块)等12个模块
Tomcat是什么
Tomcat是Apache软件基金会旗下一款免费的开放源代码Web应用服务器程序.
Tomcat是运行Servelt(服务器小程序)的容器
J2EE与Tomcat关系
J2EE是一组技术规范与指南,具体实现由软件厂商决定.
Tomcat是J2EE Web (Servlet与JSP)标准实现者
J2EE是J2EE运行的基石,运行Tomcat离不开J2EE
标准Java Web工程结构
| 组织结构 | 描述 |
| tomcat安装目录/webapps/ | Tomcat应用根目录 |
| /web应用目录/ | Java Web应用目录 |
| /web应用目录/index.html|.jsp | 默认首页 |
| /WEB-INF | WEB应用的安全目录,用于存放配置文件 |
| /WEB-INF/web.xml | web.xml是部署描述符文件,是该项目核心配置文件 |
| /WEB-INF/classes | 存放编译后的classes文件 |
| /WEB-INF/lib | 用于存放web应用依赖的jar文件 |
| /META-INF/MANITEST.MF | 包含应用的版本等信息 |
Servlet开发步骤
1.创建Servlet类,继承HttpServlet
2.重写service方法,编写程序代码
1 import java.io.IOException;
2 import java.io.PrintWriter;
3 import javax.servlet.ServletException;
4 import javax.servlet.http.HttpServlet;
5 import javax.servlet.http.HttpServletRequest;
6 import javax.servlet.http.HttpServletResponse;
7
8 public class FirstServlet extends HttpServlet {
9
10 @Override
11 protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
12 //接收请求参数
13 String name = req.getParameter("name");
14 String html = "<h1 style='color:red'>"+name+"</h1><hr/>";
15 PrintWriter out = resp.getWriter();
16 //将html返回浏览器
17 out.print(html);
18 }
19 }
3.配置web.xml,绑定URL
1 <?xml version="1.0" encoding="UTF-8"?> 2 <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" 5 version="4.0"> 6 7 <!--声明servlet--> 8 <servlet> 9 <!-- servlet别名 --> 10 <servlet-name>first</servlet-name> 11 <servlet-class>com.mingm.FirstServlet</servlet-class> 12 </servlet> 13 14 <!--将servlet与url绑定--> 15 <servlet-mapping> 16 <servlet-name>first</servlet-name> 17 <url-pattern>/hi</url-pattern> 18 </servlet-mapping> 19 </web-app>
Servlet访问方法
http://IP地址:端口/context-path/url-mapping
context-path为"上下文路径",默认工程名
Servlet接收请求参数
request.getParameter()-接收单个请求参数
request.getParameterValues()-接收多个同名参数
Get与Post请求
Get方式是将数据通过在URL附加数据显性向服务器发送数据.
例 http://localhost:8080/FirstServer/sample?name=zhangsan
Post方法会将数据存放在"请求体"中隐性向服务器发送数据
例 http://localhost:8080/FirstServer/sample
请求体: name=zhangsan
处理方式
所有请求 - service()方法
Get请求 - doGet()方法
Post请求 - doPost()方法
1 public class RequestMethodServlet extends HttpServlet{
2 //处理get请求
3 public void doGet(HttpServletRequest request , HttpServletResponse response) throws IOException{
4 String name = request.getParameter("name");
5 response.getWriter().println("<h1 style='color:green'>" + name + "</h1>");
6 }
7 //处理post请求
8 public void doPost(HttpServletRequest request , HttpServletResponse response) throws IOException{
9 String name = request.getParameter("name");
10 response.getWriter().println("<h1 style='color:red'>" + name + "</h1>");
11 }
12 }
Servlet生命周期
1.装载 - web.xml
2.构建 - 构造函数
3.初始化 - init()
4.提供服务 - service()
5.销毁 - destroy()
使用注解简化配置
Servlet3.x引入了注解
注解用于简化Web应用程序的配置过程
Servlet核心注解: @WebServlet
1 import java.io.IOException;
2
3 import javax.servlet.ServletException;
4 import javax.servlet.annotation.WebServlet;
5 import javax.servlet.http.HttpServlet;
6 import javax.servlet.http.HttpServletRequest;
7 import javax.servlet.http.HttpServletResponse;
8
9 @WebServlet("/anno")
10 public class AnnotationServlet extends HttpServlet{
11
12 @Override
13 protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
14 // TODO Auto-generated method stub
15 resp.getWriter().println("I'm annotation servlet!");
16 }
17
18 }
启动时加载Servlet
web.xml使用<load-on-startup>设置进行加载
<load-on-startup>0~9999</load-on-startup>
启动时加载常用于系统的预处理
1 import java.io.IOException;
2 import java.io.PrintWriter;
3 import javax.servlet.ServletException;
4 import javax.servlet.http.HttpServlet;
5 import javax.servlet.http.HttpServletRequest;
6 import javax.servlet.http.HttpServletResponse;
7
8 public class FirstServlet extends HttpServlet {
9
10 @Override
11 public void init() throws ServletException {
12 System.out.println("启动时加载");
13 }
14
15 @Override
16 protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
17 //接收请求参数
18 String name = req.getParameter("name");
19 String html = "<h1 style='color:red'>"+name+"</h1><hr/>";
20 PrintWriter out = resp.getWriter();
21 //将html返回浏览器
22 out.print(html);
23 }
24 }
1 <?xml version="1.0" encoding="UTF-8"?> 2 <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" 5 version="4.0"> 6 7 <!--声明servlet--> 8 <servlet> 9 <!-- servlet别名 --> 10 <servlet-name>first</servlet-name> 11 <servlet-class>com.mingm.FirstServlet</servlet-class> 12 <load-on-startup>0</load-on-startup> 13 </servlet> 14 15 <!--将servlet与url绑定--> 16 <servlet-mapping> 17 <servlet-name>first</servlet-name> 18 <url-pattern>/hi</url-pattern> 19 </servlet-mapping> 20 21 </web-app>
注解用法
1 import java.io.IOException;
2 import java.io.PrintWriter;
3 import javax.servlet.ServletException;
4 import javax.servlet.annotation.WebServlet;
5 import javax.servlet.http.HttpServlet;
6 import javax.servlet.http.HttpServletRequest;
7 import javax.servlet.http.HttpServletResponse;
8
9 @WebServlet(urlPatterns = "/first", loadOnStartup = 1)
10 public class FirstServlet extends HttpServlet {
11
12 @Override
13 public void init() throws ServletException {
14 System.out.println("启动时加载");
15 }
16
17 @Override
18 protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
19 //接收请求参数
20 String name = req.getParameter("name");
21 String html = "<h1 style='color:red'>"+name+"</h1><hr/>";
22 PrintWriter out = resp.getWriter();
23 //将html返回浏览器
24 out.print(html);
25 }
26 }