View Javadoc

    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 }