SetTag


1   /*
2    * Copyright 2002,2004 The Apache Software Foundation.
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  package org.apache.commons.jelly.tags.core;
17  
18  import java.lang.reflect.InvocationTargetException  ;
19  import java.util.Map  ;
20  
21  import org.apache.commons.beanutils.BeanUtils;
22  import org.apache.commons.jelly.JellyTagException;
23  import org.apache.commons.jelly.TagSupport;
24  import org.apache.commons.jelly.XMLOutput;
25  import org.apache.commons.jelly.expression.Expression;
26  import org.apache.commons.logging.Log;
27  import org.apache.commons.logging.LogFactory;
28  
29  
30  /** A tag which sets a variable from the result of an expression
31    *
32    * @author <a HREF="mailto:jstrachan@apache.org">James Strachan</a>
33    * @version $Revision: 155420 $
34    */
35  public class SetTag extends TagSupport {
36  
37      /** The Log to which logging calls will be made. */
38      private static final Log log = LogFactory.getLog(SetTag.class);
39  
40      /** The variable name to export. */
41      private String   var;
42  
43      /** The variable scope to export */
44      private String   scope;
45  
46      /** The expression to evaluate. */
47      private Expression value;
48  
49      /** The default value */
50      private Expression defaultValue;
51  
52      /** The target object on which to set a property. */
53      private Object   target;
54  
55      /** The name of the property to set on the target object. */
56      private String   property;
57  
58      /** Should we XML encode the body of this tag as text? */
59      private boolean encode = true;
60  
61      public SetTag() {
62      }
63  
64      // Tag interface
65      //-------------------------------------------------------------------------
66      public void doTag(XMLOutput output) throws JellyTagException {
67          // perform validation up front to fail fast
68          if ( var != null ) {
69              if ( target != null || property != null ) {
70                  throw new JellyTagException( "The 'target' and 'property' attributes cannot be used in combination with the 'var' attribute" );
71              }
72          }
73          else {
74              if ( target == null ) {
75                  throw new JellyTagException( "Either a 'var' or a 'target' attribute must be defined for this tag" );
76              }
77              if ( property == null ) {
78                  throw new JellyTagException( "The 'target' attribute requires the 'property' attribute" );
79              }
80          }
81  
82          Object   answer = null;
83          if ( value != null ) {
84              answer = value.evaluate(context);
85              if (defaultValue != null && isEmpty(answer)) {
86                  answer = defaultValue.evaluate(context);
87              }
88          }
89          else {
90              answer = getBodyText(isEncode());
91          }
92  
93          if ( var != null ) {
94              if ( scope != null ) {
95                  context.setVariable(var, scope, answer);
96              }
97              else {
98                  context.setVariable(var, answer);
99              }
100         }
101         else {
102             setPropertyValue( target, property, answer );
103         }
104     }
105 
106     // Properties
107     //-------------------------------------------------------------------------
108     /** Sets the variable name to define for this expression
109      */
110     public void setVar(String   var) {
111         this.var = var;
112     }
113 
114     /**
115      * Sets the variable scope for this variable. For example setting this value to 'parent' will
116      * set this value in the parent scope. When Jelly is run from inside a Servlet environment
117      * then other scopes will be available such as 'request', 'session' or 'application'.
118      *
119      * Other applications may implement their own custom scopes.
120      */
121     public void setScope(String   scope) {
122         this.scope = scope;
123     }
124 
125     /** Sets the expression to evaluate. */
126     public void setValue(Expression value) {
127         this.value = value;
128     }
129 
130     /**
131      * Sets the default value to be used if the value exprsesion results
132      * in a null value or blank String
133      */
134     public void setDefaultValue(Expression defaultValue) {
135         this.defaultValue = defaultValue;
136     }
137 
138     /** Sets the target object on which to set a property. */
139     public void setTarget(Object   target) {
140         this.target = target;
141     }
142 
143     /** Sets the name of the property to set on the target object. */
144     public void setProperty(String   property) {
145         this.property = property;
146     }
147 
148     /**
149      * Returns whether the body of this tag will be XML encoded or not.
150      */
151     public boolean isEncode() {
152         return encode;
153     }
154 
155     /**
156      * Sets whether the body of the tag should be XML encoded as text (so that &lt; and &gt; are
157      * encoded as &amp;lt; and &amp;gt;) or leave the text as XML which is the default.
158      * This is only used if this tag is specified with no value so that the text body of this
159      * tag is used as the body.
160      */
161     public void setEncode(boolean encode) {
162         this.encode = encode;
163     }
164 
165 
166     // Implementation methods
167     //-------------------------------------------------------------------------
168     protected void setPropertyValue( Object   target, String   property, Object   value ) {
169         try {
170             if ( target instanceof Map   ) {
171                 Map   map = (Map  ) target;
172                 map.put( property, value );
173             }
174             else {
175                 BeanUtils.setProperty( target, property, value );
176             }
177         } catch (InvocationTargetException   e) {
178             log.error( "Failed to set the property: " + property + " on bean: " + target + " to value: " + value + " due to exception: " + e, e );
179         } catch (IllegalAccessException   e) {
180             log.error( "Failed to set the property: " + property + " on bean: " + target + " to value: " + value + " due to exception: " + e, e );
181         }
182     }
183 
184     /**
185      * @param value
186      * @return true if the given value is null or an empty String
187      */
188     protected boolean isEmpty(Object   value) {
189         if (value == null) {
190             return true;
191         }
192         if (value instanceof String  ) {
193             String   s = (String  ) value;
194             return s.length() == 0;
195         }
196         return false;
197     }
198 
199 }
200
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