java web 第一个实例

按照java ee规范，一个标准的java web应用程序由以下四个部分组成：
1，项目根目录，包括各种网页文件和其他可以被用户访问的资源，如声音，图像等
2，web-inf/web.xml文件，应用程序描述符
3，web-inf/lib,所需的jar包
4,web-inf/classes，编译后的java类文件
第一个web应用程序：
在myeclipse下新建一个web项目，然后创建各种网页文件，默认位于WebRoot目录下，
结构图见下面：



主要的servlet类代码如下：

package com.qdu.sun;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginSvlt extends HttpServlet {
	private String username; //页面传过来的用户名和密码
	private String password;

	/**
	 * Constructor of the object.
	 */
	public LoginSvlt() {
		super();
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		username = request.getParameter("username"); //从请求从获取用户名参数
		password = request.getParameter("password");
		if(username.equals("zjm")&&password.equals("123")){ //简化了，未连接数据库
			HttpSession session = request.getSession(true);
			session.setAttribute("username", username);   //将信息保留到session中，以便下面的页面读取
			response.sendRedirect("welcome.jsp");
		}
		else{
			response.sendRedirect("error.jsp");
		}
		
	}

	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException if an error occurs
	 */
	public void init() throws ServletException {
		// Put your code here
	}

}

过滤器代码：

package com.qdu.sun;

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.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

//过滤器
public class FormFilter implements Filter{
	
	/**
	 * Request.java 对 HttpServletRequestWrapper 进行扩充, 不影响原来的功能并能提供所 有的
	 * HttpServletRequest 接口中的功能. 它可以统一的对 Tomcat 默认设置下的中文问题进行解决而只 需要用新的 Request
	 * 对象替换页面中的 request 对象即可.
	 */
	class Request extends HttpServletRequestWrapper {
		public Request(HttpServletRequest request) {
			super(request);
		}

		/**
		 * 转换由表单读取的数据的内码. 从 ISO 字符转到 GBK.
		 */
		public String toChi(String input) {
			try {
				byte[] bytes = input.getBytes("ISO8859-1");
				return new String(bytes, "GBK");
			} catch (Exception ex) {
			}
			return null;
		}

		/**
		 * Return the HttpServletRequest holded by this object.
		 */
		private HttpServletRequest getHttpServletRequest() {
			return (HttpServletRequest) super.getRequest();
		}

		/**
		 * 读取参数 -- 修正了中文问题.
		 */
		public String getParameter(String name) {
			return toChi(getHttpServletRequest().getParameter(name));
		}

		/**
		 * 读取参数列表 - 修正了中文问题.
		 */
		public String[] getParameterValues(String name) {
			String values[] = getHttpServletRequest().getParameterValues(name);
			if (values != null) {
				for (int i = 0; i < values.length; i++) {
					values[i] = toChi(values[i]);
				}
			}
			return values;
		}
	}
	
	
	

	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException { //过滤器主要应该实现的方法
		HttpServletRequest httpreq = (HttpServletRequest) request;
		if (httpreq.getMethod().equals("POST")) {
			request.setCharacterEncoding("GBK");
		} else {
			request = new Request(httpreq);      
		}
		chain.doFilter(request, response);
		
	}

	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
		
	}

	
}

web.xml配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 
 <!-- 以下是新建servlet后自动生成的关于servlet的配置 -->
 <servlet>
  <description>This is the description of my J2EE component</description>
  <display-name>This is the display name of my J2EE component</display-name>
  <servlet-name>LoginSvlt</servlet-name>
  <servlet-class>com.qdu.sun.LoginSvlt</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>LoginSvlt</servlet-name>
  <url-pattern>/servlet/LoginSvlt</url-pattern>
  <!-- servlet的最终访问路径是http://localhost:8080/firstWeb/servlet/LoginSvlt -->
 </servlet-mapping>
 <!-- 以上是新建servlet后自动生成的关于servlet的配置--> 
<!-- 以下是过滤器的配置 -->
 
 <filter>
  <description>过滤器</description>
  <display-name>FormFilter</display-name>
  <filter-name>FormFilter</filter-name>
  
  <filter-class>com.qdu.sun.FormFilter</filter-class>
  </filter>
  <filter-mapping>
  <filter-name>FormFilter</filter-name>
  <url-pattern>/*</url-pattern>
 </filter-mapping>
 <welcome-file-list>
  <welcome-file>index.jsp</welcome-file>
 </welcome-file-list>
 <login-config>
  <auth-method>BASIC</auth-method>
 </login-config>
</web-app>

发布和运行Web项目，有两种发布方式，散包发布和打包发布。
散包发布一般在程序开发和测试阶段使用，Myeclipse将web项目中的文件按照java ee规范的目录结构放置在服务器的发布目录下，如Tomcat/webapps。但并非所有服务器都支持散包发布java ee规范只要求所有服务器都必须支持打包发布。
打包发布一般是应用在把web应用产品化的时候，将所有的web项目中的问卷按照java ee规范打包成单个的war文件，然后放置到服务器的发布目录下。
本实例选用Tomcat 6的散包发布