StrutsPrepareAndExecuteFilter

struts2

要使用struts2必须在web.xml中配置filter
<filter>
<filter-name>struts2</filter-name>
<filter-

class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

 

public class StrutsPrepareAndExecuteFilter implements StrutsStatics, Filter
StrutsPrepareAndExecuteFilter是一个过滤器，它会对filtre-mapping中的所有请求进行处理，

protected PrepareOperations prepare; protected ExecuteOperations execute;protected List<Pattern> excludedPatterns = null; public void init(FilterConfig filterConfig) throws ServletException { InitOperations init = new InitOperations(); try { FilterHostConfig config = new FilterHostConfig(filterConfig); init.initLogging(config); Dispatcher dispatcher = init.initDispatcher(config); init.initStaticContentLoader(config, dispatcher); prepare = new PrepareOperations(filterConfig.getServletContext(), dispatcher); execute = new ExecuteOperations(filterConfig.getServletContext(), dispatcher);this.excludedPatterns = init.buildExcludedPatternsList(dispatcher); postInit(dispatcher, filterConfig); } finally { init.cleanup(); } }

StrutsPrepareAndExecuteFilter在初始化的时候会读取配置文件的信息，在初始化的时候根据FilterConfig的信息来构建InitOperations，PrepareOperations,ExecuteOperations，List<Pattern> excludedPatterns，其中InitOperations是容器初始化操作，例如构建Dispatcher，日志LoggerFactory，静态资源加载器StaticContentLoader，构建Struts2不处理的URL列表也就是List<Pattern> excludedPatterns（这个可以通过struts.action.excludePattern进行设定）等

 

 

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) res; try { prepare.setEncodingAndLocale(request, response); prepare.createActionContext(request, response); prepare.assignDispatcherToThread();if ( excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) {chain.doFilter(request, response);} else {request = prepare.wrapRequest(request);ActionMapping mapping = prepare.findActionMapping(request, response, true);if (mapping == null) {boolean handled = execute.executeStaticResourceRequest(request, response);if (!handled) {chain.doFilter(request, response);}} else {execute.executeAction(request, response, mapping);}} } finally { prepare.cleanupRequest(request); } }

 

PrepareOperations是在doFilter的时候进行一些操作，
1.prepare.setEncodingAndLocale(request, response); 为request和response进行encoding和Locale,
2.prepare.createActionContext(request, response);为当前线程创建ActionContext,ActionContext是

ThreadLocal的，ActionContent其实就是一个线程安全的HashMap,它内部使用一个HashMap来储存相关信息，这个

map的构造是使用dispatcher.createContextMap(request, response, null, servletContext)来形成的，这个

map包括的信息有session,request,response，ServletContext，RequestMap，SessionMap等各种信息，可以通

个这个ActionContent取得各种信息，例如ActionContext.getContext().getSession()来获得当前的Session,

如果要获得request或者response必须用ServletActionContext它是ActionContent的子类，提供更多的方法，如

果是forward那也会新建一个新的ActionContent,这个新的ActionContent直接使用旧的ActionContent的数据来构造

3.prepare.assignDispatcherToThread();把dispatcher绑定到当前线程上，这样就可以通过

Dispatcher.getInstance()来获得当前线程的dispatcher，这样dispatcher就可以被所有请求共享

以上操作完成后就根据excludedPatterns来判断这个请求是否应该交给当前这个filter进行处理，如果不需要就调

用chain.doFilter(request, response);交给其他filter进行处理，如果需要，那么PrepareOperations就执行

 

4.request = prepare.wrapRequest(request);对request进行包装，包装成StrutsRequestWrapper或者

MultiPartRequestWrapper（请求类型是multipart/form-data的情况）

5 ActionMapping mapping = prepare.findActionMapping(request, response, true);根据request的请求找

到对应的ActionMapping,如果返回的是null，那就当做静态资源进行处理boolean handled = execute.executeStaticResourceRequest(request, response);处理失败就交给其他的filter,如果返回的不是null，那么就调用execute.executeAction(request, response, mapping);处理完成之后 prepare.cleanupRequest(request);会把当前线程的ActionContext和Dispatcher设置为null

 

ActionMapping的构造：

 

public class ActionMapping { private String name;//action的名字 private String namespace;//所属package的namespace private String method;//action的方法 private String extension;//请求的url中的额外信息 private Map<String, Object> params;//action名字之前的信息 private Result result;//视图}

prepare.findActionMapping(request, response, true)根据请求获得ActionMapping ，struts2默认使用

DefaultActionMapper来进行查找