在 Web 中，我们通常需要获取 URL 相对于 Webapp 的路径，主要是下面的几个方法：

request.getServletPath()
request.getPathInfo()
request.getContextPath()
request.getRequestURI()

其中 request.getRequestURI() 的返回值包含了 request.getContextPath()，所以是相对于网站的根目录的。

下面我们分析 request.getServletPath() 和 request.getPathInfo()

1. 如果我们的 servlet-mapping 如下配置：

<servlet-mapping><servlet-name>jetbrick-template</servlet-name><url-pattern>*.jetx</url-pattern>
</servlet-mapping>

那么访问: /context/templates/index.jetx

request.getServletPath() == "/templates/index.jetx"
request.getPathInfo() == <null>

2. 如果我们的 servlet-mapping 如下配置：

<servlet-mapping><servlet-name>jetbrick-template</servlet-name><url-pattern>/*</url-pattern>
</servlet-mapping>

那么访问: /context/templates/index.jetx

request.getServletPath() == ""
request.getPathInfo() == "/templates/index.jetx"

3. 如果我们的 servlet-mapping 如下配置：

<servlet-mapping><servlet-name>jetbrick-template</servlet-name><url-pattern>/template/*</url-pattern>
</servlet-mapping>

那么访问: /context/templates/index.jetx

request.getServletPath() == "/templates"
request.getPathInfo() == "/index.jetx"

总结 ：

所以，我们要获取相对于 request.getContextPath() 的路径，我们可以使用如下的代码：

String uri = request.getServletPath();
String pathInfo = request.getPathInfo();
if (pathInfo != null && pathInfo.length() > 0) {uri = uri + pathInfo;
}

或者：

String uri = request.getRequestURI();
String contextPath = request.getContextPath();
if (contextPath != null && contextPath.length() > 0) {uri = uri.substring(contextPath.length());
}

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2013-02-08 补上一个 Tomcat 自身的实现:

catalina.jar,  DefaultServlet.java

protected String getRelativePath(HttpServletRequest request){if (request.getAttribute("javax.servlet.include.request_uri") != null){String result = (String)request.getAttribute("javax.servlet.include.path_info");if (result == null) {result = (String)request.getAttribute("javax.servlet.include.servlet_path");} else {result = (String)request.getAttribute("javax.servlet.include.servlet_path") + result;}if ((result == null) || (result.equals(""))) {result = "/";}return result;}String result = request.getPathInfo();if (result == null) {result = request.getServletPath();} else {result = request.getServletPath() + result;}if ((result == null) || (result.equals(""))) {result = "/";}return result;}