struts源码2

看struts2源码感之一：struts.action.excludePattern属性

1、问题发现

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,如果我们想有一些特殊的请求不经过该struts2框架处理，我们该怎么办？

如使用DWR，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.

当然struts2本身肯定已经想到到了这样的问题，那就我们看下struts2的源码吧。

2.通过struts2源码发现问题

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,是不是找到了答案?原来,
StrutsConstants.STRUTS_ACTION_EXCLUDE_PATTERN常量保存了不经过struts2处理的路径,我们在struts2.properties中配置即可.

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