前言

• spring 4.3.4.RELEASE
• CharacterEncodingFilter ： Spring MVC 提供的字符集過濾器，用于處理項目中的亂碼問題
• 項目比較老，大部分url使用的是GBK編碼，少量url使用UTF-8編碼。
• 需要對 CharacterEncodingFilter 設置例外。即，少量url不要進行 CharacterEncodingFilter 過濾。

CharacterEncodingFilter設置

<filter><filter-name>characterEncodingFilter</filter-name><filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>GBK</param-value></init-param><init-param><param-name>forceEncoding</param-name><param-value>true</param-value></init-param></filter><filter-mapping><filter-name>characterEncodingFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping>

url-pattern很霸氣，過濾所有。
forceEncoding更霸氣，強制編碼格式為GBK。
為什么這么設置不說了（很顯然這樣讓charset為UTF-8的JS很受傷），就說怎么辦吧。

受傷的JS

<script type="text/javascript" language="javascript" src="../codebase/laydate/laydate.js" charset="UTF-8"></script>

CharacterEncodingFilter添加例外

方法1（推薦）：filter-mapping添加例外

嗯~，filter-mapping添加例外是個好辦法。

<!-- 解決編碼問題過濾器 --><filter><filter-name>characterEncodingFilter</filter-name><filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>GBK</param-value></init-param><init-param><param-name>forceEncoding</param-name><param-value>true</param-value></init-param></filter><filter-mapping><filter-name>characterEncodingFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping><!-- CharacterEncodingFilter過濾器添加例外 --><filter><filter-name>characterEncodingFilter_utf8</filter-name><filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>UTF-8</param-value></init-param><init-param><param-name>forceEncoding</param-name><param-value>true</param-value></init-param></filter><filter-mapping><filter-name>characterEncodingFilter_utf8</filter-name><url-pattern>/codebase/laydate/laydate.js</url-pattern></filter-mapping>

方法2：告知CharacterEncodingFilter不用再處理了

根據CharacterEncodingFilter代碼顯示，在request的Attribute中，增加名為filter-name.FILTERED，值為TRUE的Attribute時，會跳過過濾器。
本文中需要增加名為characterEncodingFilter.FILTERED的Attribute。
增加名為characterEncodingFilter.FILTERED的Attribute的方法則是：在characterEncodingFilter執行前，再增加一個Filter。該Filter向request增加名為characterEncodingFilter.FILTERED的Attribute。（該Filter需要自己寫，此處暫不提供）

CharacterEncodingFilter的相關代碼如下：

CharacterEncodingFilter的相關代碼：

public class CharacterEncodingFilter extends OncePerRequestFilter {... }

OncePerRequestFilter的相關代碼：

public abstract class OncePerRequestFilter extends GenericFilterBean {/*** Suffix that gets appended to the filter name for the* "already filtered" request attribute.* @see #getAlreadyFilteredAttributeName*/public static final String ALREADY_FILTERED_SUFFIX = ".FILTERED";/*** This {@code doFilter} implementation stores a request attribute for* "already filtered", proceeding without filtering again if the* attribute is already there.* @see #getAlreadyFilteredAttributeName* @see #shouldNotFilter* @see #doFilterInternal*/@Overridepublic final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)throws ServletException, IOException {if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {throw new ServletException("OncePerRequestFilter just supports HTTP requests");}HttpServletRequest httpRequest = (HttpServletRequest) request;HttpServletResponse httpResponse = (HttpServletResponse) response;String alreadyFilteredAttributeName = getAlreadyFilteredAttributeName();boolean hasAlreadyFilteredAttribute = request.getAttribute(alreadyFilteredAttributeName) != null;if (hasAlreadyFilteredAttribute || skipDispatch(httpRequest) || shouldNotFilter(httpRequest)) {// Proceed without invoking this filter...filterChain.doFilter(request, response);}else {// Do invoke this filter...request.setAttribute(alreadyFilteredAttributeName, Boolean.TRUE);try {doFilterInternal(httpRequest, httpResponse, filterChain);}finally {// Remove the "already filtered" request attribute for this request.request.removeAttribute(alreadyFilteredAttributeName);}}}/*** Return the name of the request attribute that identifies that a request* is already filtered.* <p>The default implementation takes the configured name of the concrete filter* instance and appends ".FILTERED". If the filter is not fully initialized,* it falls back to its class name.* @see #getFilterName* @see #ALREADY_FILTERED_SUFFIX*/protected String getAlreadyFilteredAttributeName() {String name = getFilterName();if (name == null) {name = getClass().getName();}return name + ALREADY_FILTERED_SUFFIX;}... }

GenericFilterBean的相關代碼：

public abstract class GenericFilterBean implements Filter, BeanNameAware, EnvironmentAware,EnvironmentCapable, ServletContextAware, InitializingBean, DisposableBean {/*** Make the name of this filter available to subclasses.* Analogous to GenericServlet's {@code getServletName()}.* <p>Takes the FilterConfig's filter name by default.* If initialized as bean in a Spring application context,* it falls back to the bean name as defined in the bean factory.* @return the filter name, or {@code null} if none available* @see javax.servlet.GenericServlet#getServletName()* @see javax.servlet.FilterConfig#getFilterName()* @see #setBeanName*/@Nullableprotected String getFilterName() {return (this.filterConfig != null ? this.filterConfig.getFilterName() : this.beanName);}... } 與50位技術專家面對面20年技術見證，附贈技術全景圖

總結

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