added support for web.xml context-param "springJspExpressionSupport" (explicit "true"/"false")

Author: jhoeller

org.springframework.web/src/main/java/org/springframework/web/util/ExpressionEvaluationUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2011 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.web.util;
 
+import javax.servlet.ServletContext;
 import javax.servlet.jsp.JspException;
 import javax.servlet.jsp.PageContext;
 import javax.servlet.jsp.el.ELException;
@@ -30,18 +31,53 @@
  * invoking the EL evaluator, treating the value as "normal" expression
  * (i.e. a literal String value) else.
  *
+ * <p><b>See {@link #isSpringJspExpressionSupportActive} for guidelines
+ * on when to use Spring's JSP expression support as opposed to the
+ * built-in expression support in JSP 2.0+ containers.</b>
+ *
  * @author Juergen Hoeller
  * @author Alef Arendsen
  * @since 11.07.2003
  * @see javax.servlet.jsp.el.ExpressionEvaluator#evaluate
  */
 public abstract class ExpressionEvaluationUtils {
 
+	/**
+	 * Expression support parameter at the servlet context level
+	 * (i.e. a context-param in <code>web.xml</code>): "springJspExpressionSupport".
+	 */
+	public static final String EXPRESSION_SUPPORT_CONTEXT_PARAM = "springJspExpressionSupport";
+
 	public static final String EXPRESSION_PREFIX = "${";
 
 	public static final String EXPRESSION_SUFFIX = "}";
 
 
+	/**
+	 * Check whether Spring's JSP expression support is actually active.
+	 * <p>Note that JSP 2.0+ containers come with expression support themselves:
+	 * However, it will only be active for web applications declaring Servlet 2.4
+	 * or higher in their <code>web.xml</code> deployment descriptor.
+	 * <p>If a <code>web.xml</code> context-param named "springJspExpressionSupport" is
+	 * found, its boolean value will be taken to decide whether this support is active.
+	 * If not found, for backwards compatibility with Servlet 2.3 applications,
+	 * Spring's expression support will remain active by default.
+	 * <p><b>Recommendations:</b> Explicitly set "springJspExpressionSupport" to "false"
+	 * in order to prevent double evaluation for Servlet 2.4+ based applications.
+	 * @param pageContext current JSP PageContext
+	 * @return <code>true</code> if active (ExpressionEvaluationUtils will actually evaluate expressions);
+	 * <code>false</code> if not active (ExpressionEvaluationUtils will return given values as-is,
+	 * relying on the JSP container pre-evaluating values before passing them to JSP tag attributes)
+	 */
+	public static boolean isSpringJspExpressionSupportActive(PageContext pageContext) {
+		ServletContext sc = pageContext.getServletContext();
+		String springJspExpressionSupport = sc.getInitParameter(EXPRESSION_SUPPORT_CONTEXT_PARAM);
+		if (springJspExpressionSupport != null) {
+			return Boolean.valueOf(springJspExpressionSupport);
+		}
+		return true;
+	}
+
 	/**
 	 * Check if the given expression value is an EL expression.
 	 * @param value the expression to check
@@ -67,7 +103,7 @@ public static boolean isExpressionLanguage(String value) {
 	public static Object evaluate(String attrName, String attrValue, Class resultClass, PageContext pageContext)
 			throws JspException {
 
-		if (isExpressionLanguage(attrValue)) {
+		if (isSpringJspExpressionSupportActive(pageContext) && isExpressionLanguage(attrValue)) {
 			return doEvaluate(attrName, attrValue, resultClass, pageContext);
 		}
 		else if (attrValue != null && resultClass != null && !resultClass.isInstance(attrValue)) {
@@ -90,7 +126,7 @@ else if (attrValue != null && resultClass != null && !resultClass.isInstance(att
 	public static Object evaluate(String attrName, String attrValue, PageContext pageContext)
 			throws JspException {
 
-		if (isExpressionLanguage(attrValue)) {
+		if (isSpringJspExpressionSupportActive(pageContext) && isExpressionLanguage(attrValue)) {
 			return doEvaluate(attrName, attrValue, Object.class, pageContext);
 		}
 		else {
@@ -109,7 +145,7 @@ public static Object evaluate(String attrName, String attrValue, PageContext pag
 	public static String evaluateString(String attrName, String attrValue, PageContext pageContext)
 			throws JspException {
 
-		if (isExpressionLanguage(attrValue)) {
+		if (isSpringJspExpressionSupportActive(pageContext) && isExpressionLanguage(attrValue)) {
 			return (String) doEvaluate(attrName, attrValue, String.class, pageContext);
 		}
 		else {
@@ -128,7 +164,7 @@ public static String evaluateString(String attrName, String attrValue, PageConte
 	public static int evaluateInteger(String attrName, String attrValue, PageContext pageContext)
 			throws JspException {
 
-		if (isExpressionLanguage(attrValue)) {
+		if (isSpringJspExpressionSupportActive(pageContext) && isExpressionLanguage(attrValue)) {
 			return (Integer) doEvaluate(attrName, attrValue, Integer.class, pageContext);
 		}
 		else {
@@ -147,15 +183,14 @@ public static int evaluateInteger(String attrName, String attrValue, PageContext
 	public static boolean evaluateBoolean(String attrName, String attrValue, PageContext pageContext)
 			throws JspException {
 
-		if (isExpressionLanguage(attrValue)) {
+		if (isSpringJspExpressionSupportActive(pageContext) && isExpressionLanguage(attrValue)) {
 			return (Boolean) doEvaluate(attrName, attrValue, Boolean.class, pageContext);
 		}
 		else {
 			return Boolean.valueOf(attrValue);
 		}
 	}
 
-
 	/**
 	 * Actually evaluate the given expression (be it EL or a literal String value)
 	 * to an Object of a given type. Supports concatenated expressions,

org.springframework.web/src/test/java/org/springframework/web/util/ExpressionEvaluationUtilsTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2011 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,25 +24,39 @@
 import javax.servlet.jsp.el.FunctionMapper;
 import javax.servlet.jsp.el.VariableResolver;
 
-import junit.framework.TestCase;
+import org.junit.Test;
 
 import org.springframework.mock.web.MockExpressionEvaluator;
 import org.springframework.mock.web.MockPageContext;
+import org.springframework.mock.web.MockServletContext;
+
+import static org.junit.Assert.*;
 
 /**
  * @author Aled Arendsen
  * @author Juergen Hoeller
  * @since 16.09.2003
  */
-public class ExpressionEvaluationUtilsTests extends TestCase {
+public class ExpressionEvaluationUtilsTests {
+
+	@Test
+	public void testIsSpringJspExpressionSupportActive() {
+		MockServletContext sc = new MockServletContext();
+		PageContext pc = new MockPageContext(sc);
+		assertTrue(ExpressionEvaluationUtils.isSpringJspExpressionSupportActive(pc));
+		sc.addInitParameter("springJspExpressionSupport", "false");
+		assertFalse(ExpressionEvaluationUtils.isSpringJspExpressionSupportActive(pc));
+	}
 
+	@Test
 	public void testIsExpressionLanguage() {
 		assertTrue(ExpressionEvaluationUtils.isExpressionLanguage("${bla}"));
 		assertTrue(ExpressionEvaluationUtils.isExpressionLanguage("bla${bla}"));
 		assertFalse(ExpressionEvaluationUtils.isExpressionLanguage("bla{bla"));
 		assertFalse(ExpressionEvaluationUtils.isExpressionLanguage("bla$b{"));
 	}
 
+	@Test
 	public void testEvaluate() throws Exception {
 		PageContext ctx = new MockPageContext();
 		ctx.setAttribute("bla", "blie");
@@ -59,6 +73,7 @@ public void testEvaluate() throws Exception {
 		}
 	}
 
+	@Test
 	public void testEvaluateWithConcatenation() throws Exception {
 		PageContext ctx = new MockPageContext();
 		ctx.setAttribute("bla", "blie");
@@ -98,6 +113,7 @@ public void testEvaluateWithConcatenation() throws Exception {
 		}
 	}
 
+	@Test
 	public void testEvaluateString() throws Exception {
 		PageContext ctx = new MockPageContext();
 		ctx.setAttribute("bla", "blie");
@@ -106,6 +122,7 @@ public void testEvaluateString() throws Exception {
 		assertEquals("blie", ExpressionEvaluationUtils.evaluateString("test", "blie", ctx));
 	}
 
+	@Test
 	public void testEvaluateStringWithConcatenation() throws Exception {
 		PageContext ctx = new MockPageContext();
 		ctx.setAttribute("bla", "blie");
@@ -137,6 +154,7 @@ public void testEvaluateStringWithConcatenation() throws Exception {
 
 	}
 
+	@Test
 	public void testEvaluateInteger() throws Exception {
 		PageContext ctx = new MockPageContext();
 		ctx.setAttribute("bla", new Integer(1));
@@ -145,6 +163,7 @@ public void testEvaluateInteger() throws Exception {
 		assertEquals(21, ExpressionEvaluationUtils.evaluateInteger("test", "21", ctx));
 	}
 
+	@Test
 	public void testEvaluateBoolean() throws Exception {
 		PageContext ctx = new MockPageContext();
 		ctx.setAttribute("bla", new Boolean(true));
@@ -153,6 +172,7 @@ public void testEvaluateBoolean() throws Exception {
 		assertTrue(ExpressionEvaluationUtils.evaluateBoolean("test", "true", ctx));
 	}
 
+	@Test
 	public void testRepeatedEvaluate() throws Exception {
 		PageContext ctx = new CountingMockPageContext();
 		CountingMockExpressionEvaluator eval = (CountingMockExpressionEvaluator) ctx.getExpressionEvaluator();
@@ -172,6 +192,7 @@ public void testRepeatedEvaluate() throws Exception {
 		assertEquals(4, eval.evaluateCount);
 	}
 
+	@Test
 	public void testEvaluateWithComplexConcatenation() throws Exception {
 		PageContext ctx = new CountingMockPageContext();
 		CountingMockExpressionEvaluator eval = (CountingMockExpressionEvaluator) ctx.getExpressionEvaluator();