Add servletRelativeAction form tag attribute

A recent change in FormTag to prepend the context and servlet paths if
not present, causes issues when used in portlet applications.
This change introduces a servletRelativeAction form tag attribute that
must be used for the context and servlet paths to be prepended.

Issue: SPR-10382

spring-webmvc/src/main/java/org/springframework/web/servlet/tags/form/FormTag.java

@@ -17,6 +17,7 @@
 package org.springframework.web.servlet.tags.form;
 
 import java.util.Map;
+
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
@@ -104,6 +105,8 @@ public class FormTag extends AbstractHtmlElementTag {
 
 	private String action;
 
+	private String servletRelativeAction;
+
 	private String method = DEFAULT_METHOD;
 
 	private String target;
@@ -189,6 +192,21 @@ public class FormTag extends AbstractHtmlElementTag {
 		return this.action;
 	}
 
+	/**
+	 * Set the value of the '{@code action}' attribute.
+	 * <p>May be a runtime expression.
+	 */
+	public void setServletRelativeAction(String servletRelativeaction) {
+		this.servletRelativeAction = (servletRelativeaction != null ? servletRelativeaction : "");
+	}
+
+	/**
+	 * Get the value of the '{@code action}' attribute.
+	 */
+	protected String getServletRelativeAction() {
+		return this.servletRelativeAction;
+	}
+
 	/**
 	 * Set the value of the '{@code method}' attribute.
 	 * <p>May be a runtime expression.
@@ -395,22 +413,30 @@ public class FormTag extends AbstractHtmlElementTag {
 
 	/**
 	 * Resolve the value of the '{@code action}' attribute.
-	 * <p>If the user configured an '{@code action}' value then
-	 * the result of evaluating this value is used. Otherwise, the
-	 * {@link org.springframework.web.servlet.support.RequestContext#getRequestUri() originating URI}
-	 * is used.
+	 * <p>If the user configured an '{@code action}' value then the result of
+	 * evaluating this value is used. If the user configured an
+	 * '{@code servletRelativeAction}' value then the value is prepended
+	 * with the context and servlet paths, and the result is used. Otherwise, the
+	 * {@link org.springframework.web.servlet.support.RequestContext#getRequestUri()
+	 * originating URI} is used.
+	 *
 	 * @return the value that is to be used for the '{@code action}' attribute
 	 */
 	protected String resolveAction() throws JspException {
 		String action = getAction();
+		String servletRelativeAction = getServletRelativeAction();
 		if (StringUtils.hasText(action)) {
-			String pathToServlet = getRequestContext().getPathToServlet();
-			if (action.startsWith("/") && !action.startsWith(getRequestContext().getContextPath())) {
-				action = pathToServlet + action;
-			}
 			action = getDisplayString(evaluate(ACTION_ATTRIBUTE, action));
 			return processAction(action);
 		}
+		else if (StringUtils.hasText(servletRelativeAction)) {
+			String pathToServlet = getRequestContext().getPathToServlet();
+			if (servletRelativeAction.startsWith("/") && !servletRelativeAction.startsWith(getRequestContext().getContextPath())) {
+				servletRelativeAction = pathToServlet + servletRelativeAction;
+			}
+			servletRelativeAction = getDisplayString(evaluate(ACTION_ATTRIBUTE, servletRelativeAction));
+			return processAction(servletRelativeAction);
+		}
 		else {
 			String requestUri = getRequestContext().getRequestUri();
 			ServletResponse response = this.pageContext.getResponse();

spring-webmvc/src/main/resources/META-INF/spring-form.tld

@@ -142,6 +142,12 @@
 			<required>false</required>
 			<rtexprvalue>true</rtexprvalue>
 		</attribute>
+		<attribute>
+			<description>HTML Required Attribute</description>
+			<name>servletRelativeAction</name>
+			<required>false</required>
+			<rtexprvalue>true</rtexprvalue>
+		</attribute>
 		<attribute>
 			<description>HTML Optional Attribute</description>
 			<name>method</name>

spring-webmvc/src/test/java/org/springframework/web/servlet/tags/form/FormTagTests.java

@@ -179,7 +179,7 @@ public class FormTagTests extends AbstractHtmlElementTagTests {
 		String onreset = "onreset";
 
 		this.tag.setCommandName(commandName);
-		this.tag.setAction(action);
+		this.tag.setServletRelativeAction(action);
 		this.tag.setMethod(method);
 		this.tag.setEnctype(enctype);
 		this.tag.setOnsubmit(onsubmit);