【Java】走得越遠就越以爲不瞭解

2014-6-2

Filter是個好東西，除了在請求過程當中作些處理以外，甚至能夠定義一個Filter專門用於收集Filter Chain中本身後面的Filter拋出的異常(try catch)。

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        //作try catch
        try {
            chain.doFilter(request, response);

            logger.debug("Chain processed normally");
        }
        catch (IOException ex) {
            throw ex;
        }
        catch (Exception ex) {
            // Try to extract a SpringSecurityException from the stacktrace
            Throwable[] causeChain = throwableAnalyzer.determineCauseChain(ex);
            RuntimeException ase = (AuthenticationException)
                    throwableAnalyzer.getFirstThrowableOfType(AuthenticationException.class, causeChain);

            if (ase == null) {
                ase = (AccessDeniedException)throwableAnalyzer.getFirstThrowableOfType(AccessDeniedException.class, causeChain);
            }

            if (ase != null) {
                handleSpringSecurityException(request, response, chain, ase);
            } else {
                // Rethrow ServletExceptions and RuntimeExceptions as-is
                if (ex instanceof ServletException) {
                    throw (ServletException) ex;
                }
                else if (ex instanceof RuntimeException) {
                    throw (RuntimeException) ex;
                }

                // Wrap other Exceptions. This shouldn't actually happen
                // as we've already covered all the possibilities for doFilter
                throw new RuntimeException(ex);
            }
        }
    }

 上面的栗子就是Spring Security的Filter Chain中的ExceptionTranslateFilter的處理邏輯。以後本身也能夠借鑑。對該類的分析連接：http://dead-knight.iteye.com/blog/1518463