spring - request.getServletPath() 从 Spring MVC 返回 null

Question

我做了一个过滤器来从所有请求中捕获 HttpServletRequest sevlet 路径

@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException, ServletException {

    HttpServletRequest request = (HttpServletRequest)req;
    HttpServletResponse response = (HttpServletResponse)res;

    // debug to see the output
    String path = request.getServletPath();

    filterChain.doFilter(request, response);
}

jsp 中有一个 URL 没有映射到它的 Controller 或 View

<div>
    <spring:url value="/app" var="app_url" htmlEscape="true"/>
    <a href="${app_url}"><spring:message code="label_3rd_app" /></a>
</div>

但是，当在过滤器上调试时单击 url，我看到来自两个请求的 request.getServletPath() 值:

/null
/null/app

我的问题是为什么 request.getServletPath() 从不返回 /app 而不是？

Answer 1

你得到 null 因为

request.getServletPath();

适用于 Servlet，您在过滤器中执行此操作。要在过滤器中获取它，您必须像这样手动构建它:

HttpServletRequest request = (HttpServletRequest) req;
String path = request.getRequestURI().substring(request.getContextPath().length());

更多信息为什么:

How to get request URI without context path?