OSGi Embedded HttpService

1  概述
    Equinox 提供了两种OSGi embedded HttpSerivce的实现，如下：

 

• org.eclipse.equinox.http。适合资源受限的环境。兼容Servlet 2.4，但是对Servlet 2.1以外的API提供了有限的支持。
• org.eclipse.equinox.http.jetty。使用Jetty 作为引擎，支持Servlet 2.4。

    本文以使用org.eclipse.equinox.http.jetty为例，介绍一下通过Eclipse3.3.1.1编写基于bundles的web应用程序。有两种方式在Equinox中运行HTTP Server，如下（本文采用第一种方式）：

• Embed a server in Equinox。
• Embed Equinox in an existing servlet container。

2  创建工程
    首先在Eclipse中新建一个新工程，New->Project->Plug-in Development->Plug-in Project，单击Next按钮；输入工程名：HttpServiceExample。在Target Platform中选择an OSGi framework单选按钮，同时在右边的下拉框中选择standard，单击Next按钮；在Classpath中输入bin，在Activator 中输入com.example.http.service.Activator，单击Next按钮；单击Finish按钮。
    用Plug-in Manifest Editor打开工程META-INF目录下的MANIFEST.MF文件。选择Dependencies标签，单击Required Plug-ins下的Add按钮。在弹出的对话框中选择以下plug-in：

• javax.servlet
• javax.servlet.jsp
• org.eclipse.osgi.services
• org.eclipse.equinox.http.jetty
• org.eclipse.equinox.http.servlet
• org.eclipse.equinox.http.registry
• org.eclipse.equinox.jsp.jasper
• org.eclipse.equinox.jsp.jasper.registry
• org.mortbay.jetty
• org.apache.jasper
• org.apache.commons.el
• org.apache.commons.logging

3 新建web资源
    在工程的com.example.http.service包中应该已经生成了一个Activator类，为其添加两条控制台输出并注册资源。需要注意的是，BundleEntryHttpContext.java和ContextPathServletAdaptor.java是在名为org.eclipse.equinox.http.helper的bundle中，而这个bundle需要到eclipse cvs下载。为了方便读者，笔者将两个类的源码下载并保存到com.example.http.service.helper包中。

package com.example.http.service;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.eclipse.equinox.jsp.jasper.JspServlet;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.service.http.HttpContext;
import org.osgi.service.http.HttpService;

import com.example.http.service.helper.BundleEntryHttpContext;
import com.example.http.service.helper.ContextPathServletAdaptor;
import com.example.http.service.helper.FilterServletAdaptor;

public class Activator implements BundleActivator {

	public void start(BundleContext context) throws Exception {
		System.out.println("starting bundle...");
		
		ServiceReference sr = context.getServiceReference(HttpService.class.getName());
		HttpService hs = (HttpService) context.getService(sr);
		
		HttpContext hc = new BundleEntryHttpContext(context.getBundle(), "/web");
        hs.registerResources("/jsp", "/", hc);
         
		Servlet jspServlet = new ContextPathServletAdaptor( new JspServlet(context.getBundle(), "/web/"), "/jsp");
        hs.registerServlet("/jsp/*.jsp", jspServlet, null, hc);
        
        // Filter
        Filter filter = new Filter() {
        	public void init(FilterConfig arg0) throws ServletException {
			}
        	
			public void destroy() {
			}

			public void doFilter(ServletRequest request, ServletResponse response, FilterChain fc) 
			throws IOException, ServletException {
				System.out.println("in filter.doFilter()");
				fc.doFilter(request, response);
			}
        };
        hs.registerServlet("/jsp/hello.jsp", new FilterServletAdaptor(filter, null, jspServlet), null, null);
	}

	public void stop(BundleContext context) throws Exception {
		System.out.println("stoping bundle...");
		ServiceReference sr = context.getServiceReference(HttpService.class.getName());
		HttpService hs = (HttpService) context.getService(sr);
        hs.unregister("/web");
        hs.unregister("/jsp");
	}
}

   另外再新建一个LoginServlet，如下：

package com.example.http.service;

import java.io.IOException;

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

public class LoginServlet extends HttpServlet {
	/**
	 * 
	 */
	private static final long serialVersionUID = -1300648117298008054L;

	/**
	 * 
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response) 
	throws ServletException, IOException {
		doPost(request, response);
	}
	
	public void doPost(HttpServletRequest request, HttpServletResponse response) 
	throws ServletException, IOException {
		//
		String user = request.getParameter("user");
		String password = request.getParameter("password");
		if("user".equals(user) && "123456".equals(password)) {
			request.setAttribute("message", "hello " + user);
			RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/jsp/hello.jsp");
			dispatcher.forward(request, response);
		} else {
			RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/web/login.html");
			dispatcher.forward(request, response);
		}
	}
}

    在工程根目录下新建一个web目录，在其中新建一个login.html如下：

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login</title>
</head>
<body>
  <br>
  <form name="loginForm" method="post" action="/login">
  	<table>
  		<tr>
  			<td><div align="right">User Name:</div></td>
  			<td><input type="text" name="user"></td>
  		</tr>
  		<tr>
  			<td><div align="right">Password:</div></td>
  			<td><input type="password" name="password"></td>
  		</tr>
  		<tr>
  			<td></td>
  			<td><input type="Submit" name="Submit" value="Submit"></td>
  		</tr>
  </form>
</body>
</html>

    再新建一个hello.jsp，如下：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!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=ISO-8859-1">
<title>hello</title>
</head>
<body>
<h2><%=request.getAttribute("message") %></h2>
</body>
</html>

 

4 扩展点
    在工程根目录下新建一个plugin.xml文件，内容如下：

<plugin>

  <extension point="org.eclipse.equinox.http.registry.resources">
    <resource
      alias="/web"
      base-name="/web"/>
  </extension>
  
  <extension point="org.eclipse.equinox.http.registry.servlets">
    <servlet
      alias="/login"
      class="com.example.http.service.LoginServlet"/>
  </extension>
  
</plugin>

   修改MANIFEST.MF文件，在Bundle-SymbolicName: HttpServiceExample后边加上;singleton:=true，如下

   Bundle-SymbolicName: HttpServiceExample;singleton:=true 

5 运行
    Run->Open Run Dialog，首先在弹出对话框中，单击右侧的Deselect All。然后选择：

• HttpServiceExample
• javax.servlet
• org.eclipse.osgi.services
• org.eclipse.equinox.http.jetty
• org.eclipse.equinox.http.servlet
• org.eclipse.equinox.http.registry
• org.eclipse.equinox.jsp.jasper
• org.eclipse.equinox.jsp.jasper.registry
• org.mortbay.jetty
• org.apache.jasper
• org.apache.commons.el
• org.apache.commons.logging

   再单击Validate Bundles按钮，如果提示还缺少bundles，那么就根据提示添加bundles。直到提示No problems were detected，单击Run。    

   控制台中除了其它bundles的输出外，还应该有HttpServiceExample的输出：starting bundle...。在控制台输入ss并回车，应该看到所有的state都是ACTIVE。打开浏览器访问http://localhost/web/login.html，输入用户名user，密码123456后会进入显示hello.jsp的内容，否则会提示重新输入用户名和密码。