Add PviAttributeBindingFilter

AttributeBindingFilter is a filter that is used along with rest-proxy to add headers to a request based on the attributes added with the filter.

WIP for suggestions/critiques on the design and implementation.

Please review: @paul.erickson @ahoffmann @bjsousa

uw-spring-security-web/src/main/java/edu/wisc/uwss/web/PviAttributeBindingFilter.java

+package edu.wisc.uwss.web;
+
+import edu.wisc.uwss.UWUserDetails;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.web.filter.GenericFilterBean;
+
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+/**
+ * Filter to a UW user's PVI to a request. This sets an attribute named "wiscedupvi" to the value
+ * of the currently authenticated user.
+ */
+public class PviAttributeBindingFilter extends GenericFilterBean {
+
+    private static final Logger logger = LoggerFactory.getLogger(PviAttributeBindingFilter.class);
+
+    /**
+     * Add an attribute to the request with the currently authenticated user's PVI.
+     *
+     * @param servletRequest the request
+     * @param servletResponse the response
+     * @param filterChain the filter chain
+     * @throws IOException
+     * @throws ServletException
+     */
+    @Override
+    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
+        HttpServletRequest req = (HttpServletRequest)servletRequest;
+        HttpServletResponse res = (HttpServletResponse)servletResponse;
+
+        Authentication auth = SecurityContextHolder.getContext().getAuthentication();
+
+        if (auth != null) {
+            Object principal = auth.getPrincipal();
+            if (principal instanceof UWUserDetails) {
+                UWUserDetails userDetails = (UWUserDetails)principal;
+                logger.debug("adding PVI attribute with value {} to request", userDetails.getPvi());
+                req.setAttribute("wiscedupvi", userDetails.getPvi());
+            }
+        }
+
+        filterChain.doFilter(req, res);
+    }
+
+}