1+ /*
2+ * Copyright 2002-2009 the original author or authors.
3+ *
4+ * Licensed under the Apache License, Version 2.0 (the "License");
5+ * you may not use this file except in compliance with the License.
6+ * You may obtain a copy of the License at
7+ *
8+ * http://www.apache.org/licenses/LICENSE-2.0
9+ *
10+ * Unless required by applicable law or agreed to in writing, software
11+ * distributed under the License is distributed on an "AS IS" BASIS,
12+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13+ * See the License for the specific language governing permissions and
14+ * limitations under the License.
15+ */
16+
17+ package org .springframework .web .servlet .tags ;
18+
19+ import java .io .IOException ;
20+
21+ import javax .servlet .jsp .JspException ;
22+ import javax .servlet .jsp .PageContext ;
23+
24+ import org .springframework .beans .BeansException ;
25+ import org .springframework .core .convert .ConversionService ;
26+ import org .springframework .expression .AccessException ;
27+ import org .springframework .expression .EvaluationContext ;
28+ import org .springframework .expression .Expression ;
29+ import org .springframework .expression .ExpressionParser ;
30+ import org .springframework .expression .PropertyAccessor ;
31+ import org .springframework .expression .TypedValue ;
32+ import org .springframework .expression .spel .standard .SpelExpressionParser ;
33+ import org .springframework .expression .spel .support .StandardEvaluationContext ;
34+ import org .springframework .expression .spel .support .StandardTypeConverter ;
35+ import org .springframework .web .util .ExpressionEvaluationUtils ;
36+ import org .springframework .web .util .HtmlUtils ;
37+ import org .springframework .web .util .JavaScriptUtils ;
38+ import org .springframework .web .util .TagUtils ;
39+
40+ /**
41+ * JSP tag for evaluating expressions with the Spring Expression Language (SpEL).
42+ * Supports the standard JSP evaluation context consisting of implicit variables and scoped attributes.
43+ *
44+ * @author Keith Donald
45+ * @since 3.0.1
46+ */
47+ public class EvalTag extends HtmlEscapingAwareTag {
48+
49+ private ExpressionParser expressionParser ;
50+
51+ private String expression ;
52+
53+ private String var ;
54+
55+ private int scope = PageContext .PAGE_SCOPE ;
56+
57+ private boolean javaScriptEscape = false ;
58+
59+ /**
60+ * Set the expression to evaluate.
61+ */
62+ public void setExpression (String expression ) {
63+ this .expression = expression ;
64+ }
65+
66+ /**
67+ * Set the variable name to expose the evaluation result under.
68+ * Defaults to rendering the result to the current JspWriter
69+ */
70+ public void setVar (String var ) {
71+ this .var = var ;
72+ }
73+
74+ /**
75+ * Set the scope to export the evaluation result to.
76+ * This attribute has no meaning unless var is also defined.
77+ */
78+ public void setScope (String scope ) {
79+ this .scope = TagUtils .getScope (scope );
80+ }
81+
82+ /**
83+ * Set JavaScript escaping for this tag, as boolean value.
84+ * Default is "false".
85+ */
86+ public void setJavaScriptEscape (String javaScriptEscape ) throws JspException {
87+ this .javaScriptEscape =
88+ ExpressionEvaluationUtils .evaluateBoolean ("javaScriptEscape" , javaScriptEscape , this .pageContext );
89+ }
90+
91+ @ Override
92+ public int doStartTagInternal () throws JspException {
93+ this .expressionParser = new SpelExpressionParser ();
94+ return EVAL_BODY_INCLUDE ;
95+ }
96+
97+ @ Override
98+ public int doEndTag () throws JspException {
99+ Expression expression = this .expressionParser .parseExpression (this .expression );
100+ EvaluationContext context = createEvaluationContext ();
101+ if (this .var == null ) {
102+ // print the url to the writer
103+ try {
104+ String result = expression .getValue (context , String .class );
105+ result = isHtmlEscape () ? HtmlUtils .htmlEscape (result ) : result ;
106+ result = this .javaScriptEscape ? JavaScriptUtils .javaScriptEscape (result ) : result ;
107+ pageContext .getOut ().print (result );
108+ }
109+ catch (IOException e ) {
110+ throw new JspException (e );
111+ }
112+ }
113+ else {
114+ // store the url as a variable
115+ pageContext .setAttribute (var , expression .getValue (context ), scope );
116+ }
117+ return EVAL_PAGE ;
118+ }
119+
120+ private EvaluationContext createEvaluationContext () {
121+ StandardEvaluationContext context = new StandardEvaluationContext ();
122+ context .addPropertyAccessor (new JspPropertyAccessor (this .pageContext ));
123+ ConversionService conversionService = getConversionService ();
124+ if (conversionService != null ) {
125+ context .setTypeConverter (new StandardTypeConverter ());
126+ }
127+ return context ;
128+ }
129+
130+ private ConversionService getConversionService () {
131+ try {
132+ // TODO replace this with a call to RequestContext that is not brittle
133+ return getRequestContext ().getWebApplicationContext ().getBean ("conversionService" , ConversionService .class );
134+ } catch (BeansException e ) {
135+ return null ;
136+ }
137+ }
138+
139+ private static class JspPropertyAccessor implements PropertyAccessor {
140+
141+ private PageContext pageContext ;
142+
143+ public JspPropertyAccessor (PageContext pageContext ) {
144+ this .pageContext = pageContext ;
145+ }
146+
147+ public Class <?>[] getSpecificTargetClasses () {
148+ return null ;
149+ }
150+
151+ public boolean canRead (EvaluationContext context , Object target ,
152+ String name ) throws AccessException {
153+ if (name .equals ("pageContext" )) {
154+ return true ;
155+ }
156+ // TODO support all other JSP implicit variables defined at http://java.sun.com/javaee/6/docs/api/javax/servlet/jsp/el/ImplicitObjectELResolver.html
157+ return this .pageContext .findAttribute (name ) != null ;
158+ }
159+
160+ public TypedValue read (EvaluationContext context , Object target ,
161+ String name ) throws AccessException {
162+ if (name .equals ("pageContext" )) {
163+ return new TypedValue (this .pageContext );
164+ }
165+ // TODO support all other JSP implicit variables defined at http://java.sun.com/javaee/6/docs/api/javax/servlet/jsp/el/ImplicitObjectELResolver.html
166+ return new TypedValue (this .pageContext .findAttribute (name ));
167+ }
168+
169+ public boolean canWrite (EvaluationContext context , Object target ,
170+ String name ) throws AccessException {
171+ return false ;
172+ }
173+
174+ public void write (EvaluationContext context , Object target ,
175+ String name , Object newValue ) throws AccessException {
176+ throw new UnsupportedOperationException ();
177+ }
178+
179+ }
180+
181+ }
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