filterconfig struts2执行流程(7)

Dispatcher可以用来初始化一系列的配置文件，并且是按序加载。

request = prepare.wrapRequest(request);

wrapRequest方法的源码如下：

public HttpServletRequest wrapRequest(HttpServletRequest oldRequest) throws ServletException {
    HttpServletRequest request = oldRequest;
    try {
        // Wrap request first, just in case it is multipart/form-data
        // 为了防止这个请求是一个multipart/form-data（上传文件）类型的请求
        // parameters might not be accessible through before encoding (ww-1278)
        // 因为这种类型请求的参数如果不经过处理可能获取不到
        request = dispatcher.wrapRequest(request, servletContext);
    } catch (IOException e) {
        throw new ServletException("Could not wrap servlet request with MultipartRequestWrapper!", e);
    }
    return request;
}

为了防止这个请求是一个multipart/form-data（上传文件）类型的请求，将它包装一下。因为这种类型请求的参数如果不经过处理可能获取不到。filterconfig继续进入dispatcher.wrapRequest的源码中：

public HttpServletRequest wrapRequest(HttpServletRequest request, ServletContext servletContext) throws IOException {
    // don't wrap more than once
    // 只包装一次
    if (request instanceof StrutsRequestWrapper) {
        return request;
    }

    String content_type = request.getContentType();
    // 如果请求类型不为空并且是multipart/form-data类型的请求，那么就包装一下
    if (content_type != null && content_type.contains("multipart/form-data")) {
        MultiPartRequest mpr = getMultiPartRequest();
        LocaleProvider provider = getContainer().getInstance(LocaleProvider.class);
        request = new MultiPartRequestWrapper(mpr, request, getSaveDir(servletContext), provider);
    } else {
        request = new StrutsRequestWrapper(request, disableRequestAttributeValueStackLookup);
    }

    return request;
}

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