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    1   /**
    2    *
    3    * Copyright 2003-2004 The Apache Software Foundation
    4    *
    5    *  Licensed under the Apache License, Version 2.0 (the "License");
    6    *  you may not use this file except in compliance with the License.
    7    *  You may obtain a copy of the License at
    8    *
    9    *     http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   *  Unless required by applicable law or agreed to in writing, software
    12   *  distributed under the License is distributed on an "AS IS" BASIS,
    13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   *  See the License for the specific language governing permissions and
    15   *  limitations under the License.
    16   */
    17
    18  //
    19  // This source code implements specifications defined by the Java
    20  // Community Process. In order to remain compliant with the specification
    21  // DO NOT add / change / or delete method signatures!
    22  //
    23
    24  package javax.servlet.jsp.tagext;
    25
    26  /**
    27   * Information on the scripting variables that are created/modified by
    28   * a tag (at run-time). This information is provided by TagExtraInfo
    29   * classes and it is used by the translation phase of JSP.
    30   *
    31   * <p>
    32   * Scripting variables generated by a custom action have an associated
    33   * scope of either AT_BEGIN, NESTED, or AT_END.
    34   *
    35   * <p>
    36   * The class name (VariableInfo.getClassName) in the returned objects
    37   * is used to determine the types of the scripting variables.
    38   * Note that because scripting variables are assigned their values
    39   * from scoped attributes which cannot be of primitive types,
    40   * &quot;boxed&quot; types such as <code>java.lang.Integer</code> must
    41   * be used instead of primitives.
    42   *
    43   * <p>
    44   * The class name may be a Fully Qualified Class Name, or a short
    45   * class name.
    46   *
    47   * <p>
    48   * If a Fully Qualified Class Name is provided, it should refer to a
    49   * class that should be in the CLASSPATH for the Web Application (see
    50   * Servlet 2.4 specification - essentially it is WEB-INF/lib and
    51   * WEB-INF/classes). Failure to be so will lead to a translation-time
    52   * error.
    53   *
    54   * <p>
    55   * If a short class name is given in the VariableInfo objects, then
    56   * the class name must be that of a public class in the context of the
    57   * import directives of the page where the custom action appears.
    58   * The class must also be in the CLASSPATH for the Web Application
    59   * (see Servlet 2.4 specification - essentially it is WEB-INF/lib and
    60   * WEB-INF/classes). Failure to be so will lead to a translation-time
    61   * error.
    62   *
    63   * <p><B>Usage Comments</B>
    64   * <p>
    65   * Frequently a fully qualified class name will refer to a class that
    66   * is known to the tag library and thus, delivered in the same JAR
    67   * file as the tag handlers. In most other remaining cases it will
    68   * refer to a class that is in the platform on which the JSP processor
    69   * is built (like J2EE). Using fully qualified class names in this
    70   * manner makes the usage relatively resistant to configuration
    71   * errors.
    72   *
    73   * <p>
    74   * A short name is usually generated by the tag library based on some
    75   * attributes passed through from the custom action user (the author),
    76   * and it is thus less robust: for instance a missing import directive
    77   * in the referring JSP page will lead to an invalid short name class
    78   * and a translation error.
    79   *
    80   * <p><B>Synchronization Protocol</B>
    81   *
    82   * <p>
    83   * The result of the invocation on getVariableInfo is an array of
    84   * VariableInfo objects.  Each such object describes a scripting
    85   * variable by providing its name, its type, whether the variable is
    86   * new or not, and what its scope is.  Scope is best described through
    87   * a picture:
    88   *
    89   * <p>
    90   * <IMG src="doc-files/VariableInfo-1.gif"
    91   *      alt="NESTED, AT_BEGIN and AT_END Variable Scopes"/>
    92   *
    93   *<p>
    94   * The JSP 2.0 specification defines the interpretation of 3 values:
    95   *
    96   * <ul>
    97   * <li> NESTED, if the scripting variable is available between
    98   * the start tag and the end tag of the action that defines it.
    99   * <li>
    100  * AT_BEGIN, if the scripting variable is available from the start tag
    101  * of the action that defines it until the end of the scope.
    102  * <li> AT_END, if the scripting variable is available after the end tag
    103  * of the action that defines it until the end of the scope.
    104  * </ul>
    105  *
    106  * The scope value for a variable implies what methods may affect its
    107  * value and thus where synchronization is needed as illustrated by
    108  * the table below.  <b>Note:</b> the synchronization of the variable(s)
    109  * will occur <em>after</em> the respective method has been called.
    110  *
    111  * <blockquote>
    112  * <table cellpadding="2" cellspacing="2" border="0" width="55%"
    113  *        bgcolor="#999999" summary="Variable Synchronization Points">
    114  * <tbody>
    115  *   <tr align="center">
    116  *     <td valign="top" colspan="6" bgcolor="#999999"><u><b>Variable Synchronization
    117  *     Points</b></u><br>
    118  *     </td>
    119  *   </tr>
    120  *   <tr>
    121  *     <th valign="top" bgcolor="#c0c0c0">&nbsp;</th>
    122  *     <th valign="top" bgcolor="#c0c0c0" align="center">doStartTag()</th>
    123  *     <th valign="top" bgcolor="#c0c0c0" align="center">doInitBody()</th>
    124  *     <th valign="top" bgcolor="#c0c0c0" align="center">doAfterBody()</th>
    125  *     <th valign="top" bgcolor="#c0c0c0" align="center">doEndTag()</th>
    126  *     <th valign="top" bgcolor="#c0c0c0" align="center">doTag()</th>
    127  *   </tr>
    128  *   <tr>
    129  *     <td valign="top" bgcolor="#c0c0c0"><b>Tag<br>
    130  *     </b></td>
    131  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, NESTED<br>
    132  *     </td>
    133  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    134  *     </td>
    135  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    136  *     </td>
    137  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, AT_END<br>
    138  *     </td>
    139  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    140  *     </td>
    141  *   </tr>
    142  *   <tr>
    143  *     <td valign="top" bgcolor="#c0c0c0"><b>IterationTag<br>
    144  *     </b></td>
    145  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, NESTED<br>
    146  *     </td>
    147  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    148  *     </td>
    149  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, NESTED<br>
    150  *     </td>
    151  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, AT_END<br>
    152  *     </td>
    153  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    154  *     </td>
    155  *   </tr>
    156  *   <tr>
    157  *     <td valign="top" bgcolor="#c0c0c0"><b>BodyTag<br>
    158  *     </b></td>
    159  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, NESTED<sup>1</sup><br>
    160  *     </td>
    161  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, NESTED<sup>1</sup><br>
    162  *     </td>
    163  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, NESTED<br>
    164  *     </td>
    165  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, AT_END<br>
    166  *     </td>
    167  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    168  *     </td>
    169  *   </tr>
    170  *   <tr>
    171  *     <td valign="top" bgcolor="#c0c0c0"><b>SimpleTag<br>
    172  *     </b></td>
    173  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    174  *     </td>
    175  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    176  *     </td>
    177  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    178  *     </td>
    179  *     <td valign="top" align="center" bgcolor="#ffffff"><br>
    180  *     </td>
    181  *     <td valign="top" align="center" bgcolor="#ffffff">AT_BEGIN, AT_END<br>
    182  *     </td>
    183  *   </tr>
    184  * </tbody>
    185  * </table>
    186  * <sup>1</sup> Called after <code>doStartTag()</code> if
    187  * <code>EVAL_BODY_INCLUDE</code> is returned, or after
    188  * <code>doInitBody()</code> otherwise.
    189  * </blockquote>
    190  *
    191  * <p><B>Variable Information in the TLD</B>
    192  * <p>
    193  * Scripting variable information can also be encoded directly for most cases
    194  * into the Tag Library Descriptor using the &lt;variable&gt; subelement of the
    195  * &lt;tag&gt; element.  See the JSP specification.
    196  */
    197
    198 public class VariableInfo {
    199
    200     /**
    201      * Scope information that scripting variable is visible only within the
    202      * start/end tags.
    203      */
    204     public static final int NESTED = 0;
    205
    206     /**
    207      * Scope information that scripting variable is visible after start tag.
    208      */
    209     public static final int AT_BEGIN = 1;
    210
    211     /**
    212      * Scope information that scripting variable is visible after end tag.
    213      */
    214     public static final int AT_END = 2;
    215
    216
    217     /**
    218      * Constructor
    219      * These objects can be created (at translation time) by the TagExtraInfo
    220      * instances.
    221      *
    222      * @param varName The name of the scripting variable
    223      * @param className The type of this variable
    224      * @param declare If true, it is a new variable (in some languages this will
    225      *     require a declaration)
    226      * @param scope Indication on the lexical scope of the variable
    227      */
    228
    229     public VariableInfo(String varName,
    230 			String className,
    231 			boolean declare,
    232 			int scope) {
    233 	this.varName = varName;
    234 	this.className = className;
    235 	this.declare = declare;
    236 	this.scope = scope;
    237     }
    238
    239     // Accessor methods
    240
    241     /**
    242      * Returns the name of the scripting variable.
    243      *
    244      * @return the name of the scripting variable
    245      */
    246     public String getVarName() {
    247         return varName;
    248     }
    249
    250     /**
    251      * Returns the type of this variable.
    252      *
    253      * @return the type of this variable
    254      */
    255     public String getClassName() {
    256         return className;
    257     }
    258
    259     /**
    260      * Returns whether this is a new variable.
    261      * If so, in some languages this will require a declaration.
    262      *
    263      * @return whether this is a new variable.
    264      */
    265     public boolean getDeclare() {
    266         return declare;
    267     }
    268
    269     /**
    270      * Returns the lexical scope of the variable.
    271      *
    272      * @return the lexical scope of the variable, either AT_BEGIN, AT_END,
    273      *    or NESTED.
    274      * @see #AT_BEGIN
    275      * @see #AT_END
    276      * @see #NESTED
    277      */
    278     public int getScope() {
    279         return scope;
    280     }
    281
    282
    283     // == private data
    284     private String varName;
    285     private String className;
    286     private boolean declare;
    287     private int scope;
    288 }
    289