Struts2与DWR在项目中的共处解决方案(转载)

Struts2与DWR在项目中的共存解决方案(转载)
1.struts2和dwr为什么会冲突?

最近很多同学都在问同样一个问题,struts2和dwr该如何共存?我们先分析一下为什么会出现冲突.

struts2通过StrutsPrepareAndExecuteFilter过滤器来处理请求,常见的配置如下:

 <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>

问题就在这里,<url-pattern>/*</url-pattern>配置过滤了所有的请求,当用户提交的请求是/dwr/*时,也同样被StrutsPrepareAndExecuteFilter处理了,根本达不到DWR框架,这就是为什么二者不能共存的原因.


2.通过struts2源码发现问题

网上我没找到问题的解决方案,所以,只能通过阅读源代码来查找问题的根源了.在StrutsPrepareAndExecuteFilter类中,重写了doFilter方法:

    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);        }    }

注意看粗体部分,如果excludedPatterns不为null且prepare.isUrlExcluded方法的返回值为true,则该请求不交给struts框架处理,那么,sUrlExcluded是如何定义的呢?我们跟踪找到下面的代码:

    public boolean isUrlExcluded( HttpServletRequest request, List<Pattern> excludedPatterns ) {        if (excludedPatterns != null) {            String uri = getUri(request);            for ( Pattern pattern : excludedPatterns ) {                if (pattern.matcher(uri).matches()) {                    return true;                }            }        }        return false;    }

我们看到,  isUrlExcluded 方法中 excludedPatterns参数是一个List集合, String uri = getUri(request);代码获取请求路径,然后通过一个for循环将请求路径与 excludedPatterns进行匹(,注意,这里是通过正则表达式进行匹配的),如果匹配成功,则返回true,否则返回false.

那么, excludedPatterns的值从哪里来呢?下面的代码是也:

    public List<Pattern> buildExcludedPatternsList( Dispatcher dispatcher ) {        return buildExcludedPatternsList(dispatcher.getContainer().getInstance(String.class, StrutsConstants.STRUTS_ACTION_EXCLUDE_PATTERN));    }                private List<Pattern> buildExcludedPatternsList( String patterns ) {        if (null != patterns && patterns.trim().length() != 0) {            List<Pattern> list = new ArrayList<Pattern>();            String[] tokens = patterns.split(",");            for ( String token : tokens ) {                list.add(Pattern.compile(token.trim()));            }            return Collections.unmodifiableList(list);        } else {            return null;        }    }

看了上面的代码,是不是豁然开朗?原来, StrutsConstants.STRUTS_ACTION_EXCLUDE_PATTERN常量保存了不由struts2处理的路径,我们在struts2.properties中配置即可.

struts.action.excludePattern=/dwr/.*,/dwr/test/.*

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