spring:eval tag initial commit

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/tags/EvalTag.java

@@ -0,0 +1,181 @@
+/*
+ * Copyright 2002-2009 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.tags;
+
+import java.io.IOException;
+
+import javax.servlet.jsp.JspException;
+import javax.servlet.jsp.PageContext;
+
+import org.springframework.beans.BeansException;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.expression.AccessException;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.Expression;
+import org.springframework.expression.ExpressionParser;
+import org.springframework.expression.PropertyAccessor;
+import org.springframework.expression.TypedValue;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
+import org.springframework.expression.spel.support.StandardTypeConverter;
+import org.springframework.web.util.ExpressionEvaluationUtils;
+import org.springframework.web.util.HtmlUtils;
+import org.springframework.web.util.JavaScriptUtils;
+import org.springframework.web.util.TagUtils;
+
+/**
+ * JSP tag for evaluating expressions with the Spring Expression Language (SpEL).
+ * Supports the standard JSP evaluation context consisting of implicit variables and scoped attributes.
+ * 
+ * @author Keith Donald
+ * @since 3.0.1
+ */
+public class EvalTag extends HtmlEscapingAwareTag {
+
+	private ExpressionParser expressionParser;
+	
+	private String expression;
+
+	private String var;
+
+	private int scope = PageContext.PAGE_SCOPE;
+
+	private boolean javaScriptEscape = false;
+
+	/**
+	 * Set the expression to evaluate.
+	 */
+	public void setExpression(String expression) {
+		this.expression = expression;
+	}
+
+	/**
+	 * Set the variable name to expose the evaluation result under.
+	 * Defaults to rendering the result to the current JspWriter
+	 */
+	public void setVar(String var) {
+		this.var = var;
+	}
+
+	/**
+	 * Set the scope to export the evaluation result to.
+	 * This attribute has no meaning unless var is also defined.
+	 */
+	public void setScope(String scope) {
+		this.scope = TagUtils.getScope(scope);
+	}
+
+	/**
+	 * Set JavaScript escaping for this tag, as boolean value.
+	 * Default is "false".
+	 */
+	public void setJavaScriptEscape(String javaScriptEscape) throws JspException {
+		this.javaScriptEscape =
+				ExpressionEvaluationUtils.evaluateBoolean("javaScriptEscape", javaScriptEscape, this.pageContext);
+	}
+
+	@Override
+	public int doStartTagInternal() throws JspException {
+		this.expressionParser = new SpelExpressionParser();
+		return EVAL_BODY_INCLUDE;
+	}
+
+	@Override
+	public int doEndTag() throws JspException {
+		Expression expression = this.expressionParser.parseExpression(this.expression);
+		EvaluationContext context = createEvaluationContext();
+		if (this.var == null) {
+			// print the url to the writer
+			try {
+				String result = expression.getValue(context, String.class);
+				result = isHtmlEscape() ? HtmlUtils.htmlEscape(result) : result;
+				result = this.javaScriptEscape ? JavaScriptUtils.javaScriptEscape(result) : result;
+				pageContext.getOut().print(result);
+			}
+			catch (IOException e) {
+				throw new JspException(e);
+			}
+		}
+		else {
+			// store the url as a variable
+			pageContext.setAttribute(var, expression.getValue(context), scope);
+		}
+		return EVAL_PAGE;
+	}
+	
+	private EvaluationContext createEvaluationContext() {
+		StandardEvaluationContext context = new StandardEvaluationContext();
+		context.addPropertyAccessor(new JspPropertyAccessor(this.pageContext));
+		ConversionService conversionService = getConversionService();
+		if (conversionService != null) {
+			context.setTypeConverter(new StandardTypeConverter());
+		}
+		return context;
+	}
+	
+	private ConversionService getConversionService() {
+		try {
+			// TODO replace this with a call to RequestContext that is not brittle
+			return getRequestContext().getWebApplicationContext().getBean("conversionService", ConversionService.class);
+		} catch (BeansException e) {
+			return null;
+		}
+	}
+	
+	private static class JspPropertyAccessor implements PropertyAccessor {
+
+		private PageContext pageContext;
+		
+		public JspPropertyAccessor(PageContext pageContext) {
+			this.pageContext = pageContext;
+		}
+		
+		public Class<?>[] getSpecificTargetClasses() {
+			return null;
+		}
+
+		public boolean canRead(EvaluationContext context, Object target,
+				String name) throws AccessException {
+			if (name.equals("pageContext")) {
+				return true;
+			}
+			// TODO support all other JSP implicit variables defined at http://java.sun.com/javaee/6/docs/api/javax/servlet/jsp/el/ImplicitObjectELResolver.html
+			return this.pageContext.findAttribute(name) != null;
+		}
+
+		public TypedValue read(EvaluationContext context, Object target,
+				String name) throws AccessException {
+			if (name.equals("pageContext")) {
+				return new TypedValue(this.pageContext);
+			}
+			// TODO support all other JSP implicit variables defined at http://java.sun.com/javaee/6/docs/api/javax/servlet/jsp/el/ImplicitObjectELResolver.html
+			return new TypedValue(this.pageContext.findAttribute(name));
+		}
+
+		public boolean canWrite(EvaluationContext context, Object target,
+				String name) throws AccessException {
+			return false;
+		}
+
+		public void write(EvaluationContext context, Object target,
+				String name, Object newValue) throws AccessException {
+			throw new UnsupportedOperationException();
+		}
+		
+	}
+
+}