一、契子
很早以前就开始构思可动态部署的Web应用,模块化应用无疑是一种趋势,Portal应用可谓是一个小革新,它的功能引起了很多人的注意,OSGi 无疑会为这带来本质上的升级。
二、目标
这篇blog中的例子从JPetStoreOsgi衍生,通过扩展(修改)Spring mvc中的某些对象,实现模块的动态部署,当然,这只是很简单的案例,不过足以达到我的预期目标:有2个非常简单的模块module1和module2,它们都有自己的Spring mvc配置文件,可以在运行时简单的通过OSGi控制台,安装它们,并完成它们各自的功能。
三、准备工作
[点击这里下载 DynamicModule 工程包]
由于整个Workspace太大,所以仅仅只是把更新的5个Bundle的Project上传了,先 下载JPetStoreOsgi ,然后将所有关于JPetStore的Project删除,导入这5个Project
四、Spring MVC
目前还没有用于OSGi环境的MVC框架,所以选用Spring MVC做为演示框架
org.phrancol.osgi.demo.mvc.springmvc 是整个应用的MVC Bundle,以下简称 MVCBundle
- org.phrancol.osgi.demo.mvc.springmvc.core.HandlerRegister
public interface HandlerRegister {
/** *//**
* 当bundle的ApplicationContext生成后,获取HandlerMapping,并注册
* @param context Spring为Bundle生成的ApplicationContext
* @param bundle
*/
public void registerHandler(ApplicationContext context, Bundle bundle);
/** *//**
* 当Bundle被停止或是卸载的时候,注销这个bundle的HandlerMapping
* 当然这个功能没有实现(它可以实现),因为他不属于演示范围
* @param bundle
*/
public void unRegisterHandler(Bundle bundle);
}
- 扩展DispatcherServlet - org.phrancol.osgi.demo.mvc.springmvc.core.OsgiDispatcherServlet
同时,它还充当一个HandlerMapping注册管理器的角色,通过一个BundleHandlerMappingManager来管理bundle的HandlerMapping,包括动态添加/删除等,它会重写DispatcherServlet 的getHandler方法,从BundleHandlerMappingManager获取Handler.....这里的代码比较简单,一看就能明白。BundleHandlerMappingManager只是一个Map的简单操作,代码省略
public class OsgiDispatcherServlet extends DispatcherServlet implements
HandlerRegister {
private static final Log log = LogFactory
.getLog(OsgiDispatcherServlet.class);
/**//* HandlerMapping管理对象 */
private BundleHandlerMappingManager bundleHandlerMappingManager;
private BundleContext bundleContext;
public OsgiDispatcherServlet(BundleContext bundleContext) {
this.bundleContext = bundleContext;
this.bundleHandlerMappingManager = new BundleHandlerMappingManager();
}
protected WebApplicationContext createWebApplicationContext(
WebApplicationContext parent) throws BeansException {
ClassLoader contextClassLoader = Thread.currentThread()
.getContextClassLoader();
try {
ClassLoader cl = BundleDelegatingClassLoader
.createBundleClassLoaderFor(bundleContext.getBundle(),
getClass().getClassLoader());
Thread.currentThread().setContextClassLoader(cl);
LocalBundleContext.setContext(bundleContext);
ConfigurableWebApplicationContext wac = new OSGiXmlWebApplicationContext(
bundleContext);
wac.setParent(parent);
wac.setServletContext(getServletContext());
wac.setServletConfig(getServletConfig());
wac.setNamespace(getNamespace());
if (getContextConfigLocation() != null) {
wac
.setConfigLocations(StringUtils
.tokenizeToStringArray(
getContextConfigLocation(),
ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
wac.addApplicationListener(this);
wac.refresh();
return wac;
} finally {
Thread.currentThread().setContextClassLoader(contextClassLoader);
}
}
/** *//**
* 重写这个方法是很有必要的
*/
protected HandlerExecutionChain getHandler(HttpServletRequest request,
boolean cache) throws Exception {
HandlerExecutionChain handler = (HandlerExecutionChain) request
.getAttribute(HANDLER_EXECUTION_CHAIN_ATTRIBUTE);
if (handler != null) {
if (!cache) {
request.removeAttribute(HANDLER_EXECUTION_CHAIN_ATTRIBUTE);
}
return handler;
}
for (Iterator _it = this.bundleHandlerMappingManager
.getBundlesHandlerMapping().values().iterator(); _it.hasNext();) {
List _handlerMappings = (List) _it.next();
for (Iterator it = _handlerMappings.iterator(); it.hasNext();) {
HandlerMapping hm = (HandlerMapping) it.next();
if (logger.isDebugEnabled()) {
logger.debug("Testing handler map [" + hm
+ "] in OsgiDispatcherServlet with name '"
+ getServletName() + "'");
}
handler = hm.getHandler(request);
if (handler != null) {
if (cache) {
request.setAttribute(HANDLER_EXECUTION_CHAIN_ATTRIBUTE,
handler);
}
return handler;
}
}
}
return null;
}
/** *//**
* 这个功能实现起来有点牵强,但是以演示为主,一笑而过
*/
protected View resolveViewName(String viewName, Map model, Locale locale,
HttpServletRequest request) throws Exception {
long bundleId = this.bundleHandlerMappingManager.getBundleId(request);
Bundle bundle = this.bundleContext.getBundle(bundleId);
ViewResolver viewResolver = new OsgiInternalResourceViewResolver(
bundle, getWebApplicationContext(), viewName);
View view = viewResolver.resolveViewName(viewName, locale);
return view;
}
public void registerHandler(ApplicationContext context, Bundle bundle) {
Map matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(
context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
List _list = new ArrayList(matchingBeans.values());
String bundleId = new Long(bundle.getBundleId()).toString();
this.bundleHandlerMappingManager.registerHandlerMapping(bundleId,
_list);
}
}
public void unRegisterHandler(Bundle bundle){
String bundleId = new Long(bundle.getBundleId()).toString();
this.bundleHandlerMappingManager.unRegisterHandlerMapping(bundleId);
}
}
- 扩展InternalResourceViewResolver - org.phrancol.osgi.demo.mvc.springmvc.core.OsgiInternalResourceViewResolver
为了方便,这部份的代码写得有些不地道(演示为主~),重写getPrefix()方法,主要是为了获取jsp文件
public class OsgiInternalResourceViewResolver extends
InternalResourceViewResolver {
private static final Log log = LogFactory.getLog(OsgiInternalResourceViewResolver.class);
private static final String PREFIX = "/web/jsp/spring/";
private static final String SUFFIX = ".jsp";
private String viewName;
private Bundle bundle;
public OsgiInternalResourceViewResolver(Bundle bundle, ApplicationContext applicationContext , String viewName){
this.bundle = bundle;
setPrefix(PREFIX);
setSuffix(SUFFIX);
setViewClass(new JstlView().getClass());
setApplicationContext(applicationContext);
this.bundle = bundle;
this.viewName = viewName;
}
protected String getPrefix() {
String _prefix= "/"+bundle.getSymbolicName()+PREFIX;
return _prefix;
}
}
- MVCBundle需要设置一个Activator,用于将OsgiDispatcherServlet注册为OSGi Service
public void start(BundleContext bundleContext) throws Exception {
DispatcherServlet ds = new OsgiDispatcherServlet(bundleContext);
bundleContext.registerService(DispatcherServlet.class.getName(), ds,
null);
}
- MVCBundle中的SpringmvcHttpServiceRegister还是需要的,它需要生成一个所谓的容器Context
public class SpringmvcHttpServiceRegister implements HttpServiceRegister {
public void serviceRegister(BundleContext context,
ApplicationContext bundleApplicationContext) {
try {
ServiceReference sr = context.getServiceReference(HttpService.class
.getName());
HttpService httpService = (HttpService) context.getService(sr);
HttpContext defaultContext = httpService.createDefaultHttpContext();
Dictionary<String, String> initparams = new Hashtable<String, String>();
initparams.put("load-on-startup", "1");
/** *//**/
ContextLoaderServlet contextloaderListener = new BundleContextLoaderServlet(
context, bundleApplicationContext);
httpService.registerServlet("/initContext", contextloaderListener,
initparams, defaultContext);
/**/
DispatcherServlet dispatcherServlet = (DispatcherServlet) context
.getService(context
.getServiceReference(DispatcherServlet.class
.getName()));
/**//* 这里给了 DispatcherServlet 一个空的配置文件,可以节省好多代码*/
dispatcherServlet
.setContextConfigLocation("META-INF/dispatcher/DynamicModule-servlet.xml");
initparams = new Hashtable<String, String>();
initparams.put("servlet-name", "DynamicModule");
initparams.put("load-on-startup", "2");
httpService.registerServlet("/*.do", dispatcherServlet, initparams,
defaultContext);
} catch (Exception e) {
e.printStackTrace(System.out);
}
}
}
通过以上工作,Spring MVC就被简单的改造完了......当然他仅仅只是能实现我所要演示的功能
五、模块
新建一个模块bundle - org.phrancol.osgi.demo.mvc.springmvc.module2 ,Bundle-SymbolicName设置为module2
先看看它的bean配置
<beans>
<bean id="module2Register"
class="org.phrancol.osgi.demo.mvc.util.BundleServiceRegister">
<constructor-arg>
<bean
class="org.phrancol.osgi.demo.mvc.springmvc.module2.SpringmvcHttpServiceRegister" />
</constructor-arg>
</bean>
<!-- ========================= DEFINITIONS OF PUBLIC CONTROLLERS ========================= -->
<bean id="module2HandlerMapping"
class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping" />
<bean name="/DynamicModule/module2.do"
class="org.phrancol.osgi.demo.mvc.springmvc.module2.TheSecondModuleController">
</bean>
</beans>
也使用了一个SpringmvcHttpServiceRegister,它就是用来注册这个bundle 中的jsp和资源的
public class SpringmvcHttpServiceRegister implements HttpServiceRegister {
public void serviceRegister(BundleContext context,
ApplicationContext bundleApplicationContext) {
try {
ServiceReference sr = context.getServiceReference(HttpService.class
.getName());
/**//* 在上一个例子中,HttpContext的用法不对,这个用法才是正确的 */
HttpService httpService = (HttpService) context.getService(sr);
HttpContext defaultContext = httpService.createDefaultHttpContext();
httpService.registerResources("/module2", "/module2",
defaultContext);
/**//*
* 这个JspServlet对象中的参数"module2/web",可以理解为 The root path of module
* application,它是干什么用的,请参考它的JavaDoc,建议从Eclipse的CVS中准备一份Equinox的源代码
*/
JspServlet jspServlet = new JspServlet(context.getBundle(),
"/module2/web");
httpService.registerServlet("/module2/*.jsp", jspServlet, null,
defaultContext);
HandlerRegister dispatcherServlet = (HandlerRegister) context
.getService(context
.getServiceReference(DispatcherServlet.class
.getName()));
dispatcherServlet.registerHandler(bundleApplicationContext, context
.getBundle());
} catch (Exception e) {
e.printStackTrace(System.out);
}
}
}
来看看org.phrancol.osgi.demo.mvc.springmvc.module2.TheSecondModuleController ,只有很简单的一个输出
public class TheSecondModuleController implements Controller {
private static final String VIEWSTRING = "Hello, this is the second module !";
public ModelAndView handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
Map model = new HashMap();
model.put("viewString", VIEWSTRING);
ModelAndView mv = new ModelAndView("Success", model);
return mv;
}
}
目录结构也有一点变化 /module1/web/jsp/spring/ *.jsp
模块1和模块2是一样的
六、运行
将模块二导出为bundle jar包,放到C盘根目录下,启动这个应用(当然不要启动modure2),在浏览器看看module1的运行情况
现在安装一下module2
试着访问一下module2
404,正常,启动一下这个bundle再看看
显示出来了,现在可以动态的操作这2个模块了......
七、扩展
通过这个演示,可以领略到OSGi带给我们的一小部分功能,做一些扩展看看
1. 当然是各种框架的支持。
2. 强大的bundle资源库
3. 绝对动态的部署框架,可以通过UI界面来操作。
4. 可以从URL来安装bundle, install http://www.domain.com/sampleBundle.jar ,如果是这样的,服务网关就能体现出来了,你提供一个服务框架,别人可以通过你的框架运行自己的服务。
5. 个人猜测,它将取代Portal的运行模式
6. ..........
八、结束语
OSGi在Web应用中还有很长的路要走,它到底会发展成什么样子,就目前的功能还真不好推测。
现在不管是MVC还是持久层都还没有框架对OSGi的支持,我个人准备用业余时间研究一下这方面,顺便也可以练练手,希望传说中的强人能开发这样的框架并不吝开源~
九、相关资源
就我目前能找到的一些资源,列出如下:
Struts2有一个OSGi的插件,但是我看了看,并不能达到预期效果,不过可以看一看
http://cwiki.apache.org/S2PLUGINS/osgi-plugin.html
在持久层方面,db4o似乎有这个打算,不做评论
http://www.db4o.com/osgi/
另外它的合作伙伴prosyst已经开发出了一个基于Equinox的OSGi Server,还有个专业版,好像要收费,所以也就没下载,不知道是个什么样子。
http://www.prosyst.com/
posted on 2007-11-01 15:09
Phrancol Yang 阅读(6273)
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