SWF-485 Introduce a "currentUser" EL variable that resolves to the principal in the security context.

spring-webflow/src/main/java/org/springframework/webflow/expression/el/SpringSecurityELResolver.java

@@ -0,0 +1,68 @@
+package org.springframework.webflow.expression.el;
+
+import java.util.Iterator;
+
+import javax.el.ELContext;
+import javax.el.ELResolver;
+import javax.el.PropertyNotWritableException;
+
+import org.springframework.security.Authentication;
+import org.springframework.security.context.SecurityContextHolder;
+
+/**
+ * Custom EL resolver that resolves to the Spring Security Principal object for binding expressions prefixed with
+ * {@link #SECURITY_PRINCIPAL_VARIABLE_NAME}. For instance "#{currentUser}".
+ * 
+ * @author Scott Andrews
+ */
+public class SpringSecurityELResolver extends ELResolver {
+
+	/**
+	 * Name of the security principal variable.
+	 */
+	public static final String SECURITY_PRINCIPAL_VARIABLE_NAME = "currentUser";
+
+	public Class getCommonPropertyType(ELContext elContext, Object base) {
+		return Object.class;
+	}
+
+	public Iterator getFeatureDescriptors(ELContext elContext, Object base) {
+		return null;
+	}
+
+	public Class getType(ELContext elContext, Object base, Object property) {
+		if (base == null && SECURITY_PRINCIPAL_VARIABLE_NAME.equals(property)) {
+			elContext.setPropertyResolved(true);
+			return Authentication.class;
+		} else {
+			return null;
+		}
+	}
+
+	public Object getValue(ELContext elContext, Object base, Object property) {
+		if (base == null && SECURITY_PRINCIPAL_VARIABLE_NAME.equals(property)) {
+			elContext.setPropertyResolved(true);
+			return SecurityContextHolder.getContext().getAuthentication();
+		} else {
+			return null;
+		}
+	}
+
+	public boolean isReadOnly(ELContext elContext, Object base, Object property) {
+		if (base == null && SECURITY_PRINCIPAL_VARIABLE_NAME.equals(property)) {
+			elContext.setPropertyResolved(true);
+			return true;
+		} else {
+			return false;
+		}
+	}
+
+	public void setValue(ELContext elContext, Object base, Object property, Object value) {
+		if (base == null && SECURITY_PRINCIPAL_VARIABLE_NAME.equals(property)) {
+			elContext.setPropertyResolved(true);
+			throw new PropertyNotWritableException("The " + SECURITY_PRINCIPAL_VARIABLE_NAME
+					+ " cannot be set with an expression.");
+		}
+	}
+
+}

spring-webflow/src/main/java/org/springframework/webflow/expression/el/WebFlowELExpressionParser.java

@@ -14,6 +14,7 @@ import org.springframework.beans.BeanUtils;
 import org.springframework.binding.expression.el.DefaultELResolver;
 import org.springframework.binding.expression.el.ELContextFactory;
 import org.springframework.binding.expression.el.ELExpressionParser;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.webflow.core.collection.MutableAttributeMap;
 import org.springframework.webflow.execution.RequestContext;
@@ -23,6 +24,7 @@ import org.springframework.webflow.execution.RequestContext;
  * FlowDefinition.
  * 
  * @author Jeremy Grelle
+ * @author Scott Andrews
  */
 public class WebFlowELExpressionParser extends ELExpressionParser {
 
@@ -59,6 +61,9 @@ public class WebFlowELExpressionParser extends ELExpressionParser {
 		public ELContext getELContext(Object target) {
 			List customResolvers = new ArrayList();
 			customResolvers.add(new RequestContextELResolver());
+			if (ClassUtils.isPresent("org.springframework.security.context.SecurityContextHolder")) {
+				customResolvers.add(new SpringSecurityELResolver());
+			}
 			customResolvers.add(new ImplicitFlowVariableELResolver());
 			customResolvers.add(new SpringBeanWebFlowELResolver());
 			customResolvers.add(new ActionMethodELResolver());

spring-webflow/src/main/java/org/springframework/webflow/mvc/MvcViewFactoryCreator.java

@@ -14,6 +14,7 @@ import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.core.io.ContextResource;
 import org.springframework.core.io.ResourceLoader;
+import org.springframework.security.context.SecurityContextHolder;
 import org.springframework.util.ClassUtils;
 import org.springframework.web.servlet.ViewResolver;
 import org.springframework.web.servlet.view.InternalResourceView;
@@ -37,10 +38,13 @@ import org.springframework.webflow.execution.ViewFactory;
  * infrastructure is configured, JSP resources relative to the flow definition being built.
  * 
  * @author Keith Donald
+ * @author Scott Andrews
  */
 public class MvcViewFactoryCreator implements ViewFactoryCreator, ApplicationContextAware {
 
 	private static final boolean jstlPresent = ClassUtils.isPresent("javax.servlet.jsp.jstl.fmt.LocalizationContext");
+	private static final boolean springSecurityPresent = ClassUtils
+			.isPresent("org.springframework.security.context.SecurityContextHolder");
 
 	private List viewResolvers;
 
@@ -183,6 +187,9 @@ public class MvcViewFactoryCreator implements ViewFactoryCreator, ApplicationCon
 					.union(context.getRequestScope()).asMap());
 			model.put("flowExecutionRequestContext", context);
 			model.put("flowExecutionUrl", context.getFlowExecutionUrl());
+			if (springSecurityPresent && !model.containsKey("currentUser")) {
+				model.put("currentUser", SecurityContextHolder.getContext().getAuthentication());
+			}
 			try {
 				view.render(model, (HttpServletRequest) context.getExternalContext().getNativeRequest(),
 						(HttpServletResponse) context.getExternalContext().getNativeResponse());