Improve error reporting in ScriptTemplateView

This commit introduces a new ScriptRenderException in order to:
 - Print in the resulting error page the reason of the script failure
 - Not print the whole stacktrace in the logs

The ScriptRenderException thrown in ScriptTemplateView#renderMergedOutputModel()
is wrapped into a ServletException in order to avoid printing 2 times the messages in
the logs (throwing directly a ScriptRenderException would make it wrapped in a
NestedServletException that contains a getMessage() override not needed in this
context)

Issue: SPR-13488

spring-webmvc/src/main/java/org/springframework/web/servlet/view/script/ScriptRenderException.java

+/*
+ * Copyright 2002-2015 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.servlet.view.script;
+
+/**
+ * Exception thrown when an error occurs during script template rendering.
+ *
+ * <p>It does not print the java stacktrace in the logs, since it is not useful
+ * in this script context.
+ *
+ * @author Sebastien Deleuze
+ * @since 4.2.2
+ */
+public class ScriptRenderException extends RuntimeException {
+
+	private static final long serialVersionUID = 421565510962788082L;
+
+
+	/**
+	 * Constructs a new script rendering exception with the specified detail message.
+	 */
+	public ScriptRenderException(String msg) {
+		super(msg);
+	}
+
+	@Override
+	public synchronized Throwable fillInStackTrace() {
+		return this;
+	}
+
+}

spring-webmvc/src/main/java/org/springframework/web/servlet/view/script/ScriptTemplateView.java

@@ -29,6 +29,7 @@ import java.util.Map;
 import javax.script.Invocable;
 import javax.script.ScriptEngine;
 import javax.script.ScriptEngineManager;
+import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
@@ -357,7 +358,7 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 			response.getWriter().write(String.valueOf(html));
 		}
 		catch (Exception ex) {
-			throw new IllegalStateException("Failed to render script template", ex);
+			throw new ServletException("Failed to render script template", new ScriptRenderException(ex.getMessage()));
 		}
 	}