struts-logic.html

struts api,学习使用struts必备的文档

       object, <code>ActionErrors</code> object, a String,
       or a String array is in request scope.  If
       such a bean is not found, nothing will be rendered.
    </p>
    <p>Since:  Struts 1.1</p>
<table class="tag-attributes">
<thead>
<tr>
<th class="attribute">Attribute Name</th>
<th>Description</th>
</tr>
</thead>
<tr class="evenRow">
<td align="center">name</td>
<td>
      <p>The parameter key to retrieve the message from request scope.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">property</td>
<td>
      <p>Name of the property for which messages should be
         retrieved.  If not specified, all messages (regardless
         of property) are retrieved.
      </p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">message</td>
<td>
      <p>By default the tag will retrieve the request scope bean it will
         iterate over from the <code>Globals.ERROR_KEY</code> constant string,
         but if this attribute is set to 'true' the request scope bean
         will be retrieved from the <code>Globals.MESSAGE_KEY</code>
         constant string.  Also if this is set to 'true', any value
         assigned to the name attribute will be ignored.
      </p>
      
            [RT Expr]
          </td>
</tr>
</table>
</div>
<p>
<a href="#top">Back to top</a>
</p>
<h3 id="notEmpty">
<strong>notEmpty</strong> - 
    Evaluate the nested body content of this tag if the requested variable is
    neither null, nor an empty string, nor an empty java.util.Collection
    (tested by the .isEmpty() method on the java.util.Collection interface).
    </h3>
<div class="indent">
    <p>This tag evaluates its nested body content only if the specified value
    is present (i.e. not <code>null</code>) and is not an empty string (i.e. a
    <code>java.lang.String</code> with a length of zero).</p>
    
    <p>
    <strong>JSTL</strong>:  The equivalent JSTL tag is &lt;c:if&gt; using the 
    <code>! empty</code> operator.  For example,
    <br />
    <code>
    	&lt;c:if test="${ ! empty sessionScope.myBean.myProperty}"&gt;
    	  do something
    	&lt;/c:if&gt;
    </code>
    </p>
    <table class="tag-attributes">
<thead>
<tr>
<th class="attribute">Attribute Name</th>
<th>Description</th>
</tr>
</thead>
<tr class="evenRow">
<td align="center">name</td>
<td>
      <p>The variable to be compared is the JSP bean specified by this
      attribute, if <code>property</code> is not specified, or the value
      of the specified property of this bean, if <code>property</code>
      is specified.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">property</td>
<td>
      <p>The variable to be compared is the property (of the bean specified
      by the <code>name</code> attribute) specified by this attribute.
      The property reference can be simple, nested, and/or indexed.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">scope</td>
<td>
      <p>The bean scope within which to search for the bean named by the
      <code>name</code> property, or "any scope" if not specified.</p>
      
            [RT Expr]
          </td>
</tr>
</table>
</div>
<p>
<a href="#top">Back to top</a>
</p>
<h3 id="notEqual">
<strong>notEqual</strong> - 
    Evaluate the nested body content of this tag if the requested
    variable is not equal to the specified value.
    </h3>
<div class="indent">
    <p>Compares the variable specified by one of the selector attributes
    against the specified constant value.  The nested body content of this
    tag is evaluated if the variable and value are <strong>not equal</strong>.
    </p>
    <table class="tag-attributes">
<thead>
<tr>
<th class="attribute">Attribute Name</th>
<th>Description</th>
</tr>
</thead>
<tr class="evenRow">
<td align="center">cookie</td>
<td>
      <p>The variable to be compared is the value of the cookie whose
      name is specified by this attribute.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">header</td>
<td>
      <p>The variable to be compared is the value of the header whose
      name is specified by this attribute.  The name match is performed
      in a case insensitive manner.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">name</td>
<td>
      <p>The variable to be compared is the JSP bean specified by this
      attribute, if <code>property</code> is not specified, or the value
      of the specified property of this bean, if <code>property</code>
      is specified.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">parameter</td>
<td>
      <p>The variable to be compared is the first, or only, value of the
      request parameter specified by this attribute.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">property</td>
<td>
      <p>The variable to be compared is the property (of the bean specified
      by the <code>name</code> attribute) specified by this attribute.
      The property reference can be simple, nested, and/or indexed.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">scope</td>
<td>
      <p>The bean scope within which to search for the bean named by the
      <code>name</code> property, or "any scope" if not specified.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">value</td>
<td>
      <p>The constant value to which the variable, specified by other
      attribute(s) of this tag, will be compared.</p>
      
            [Required]
          
            [RT Expr]
          </td>
</tr>
</table>
</div>
<p>
<a href="#top">Back to top</a>
</p>
<h3 id="notMatch">
<strong>notMatch</strong> - 
    Evaluate the nested body content of this tag if the specified value
    is not an appropriate substring of the requested variable.
    </h3>
<div class="indent">
    <p>Matches the variable specified by one of the selector attributes
    (as a String) against the specified constant value.  If the value is
    not a substring (appropriately limited by the <code>location</code>
    attribute), the nested body content of this tag is evaluated.</p>
    <table class="tag-attributes">
<thead>
<tr>
<th class="attribute">Attribute Name</th>
<th>Description</th>
</tr>
</thead>
<tr class="evenRow">
<td align="center">cookie</td>
<td>
      <p>The variable to be matched is the value of the cookie whose
      name is specified by this attribute.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">header</td>
<td>
      <p>The variable to be matched is the value of the header whose
      name is specified by this attribute.  The name match is performed
      in a case insensitive manner.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">location</td>
<td>
      <p>If not specified, a match between the variable and the value may
      occur at any position within the variable string.  If specified, the
      match must occur at the specified location (either <code>start</code>
      or <code>end</code>) of the variable string.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">name</td>
<td>
      <p>The variable to be matched is the JSP bean specified by this
      attribute, if <code>property</code> is not specified, or the value
      of the specified property of this bean, if <code>property</code>
      is specified.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">parameter</td>
<td>
      <p>The variable to be matched is the first, or only, value of the
      request parameter specified by this attribute.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">property</td>
<td>
      <p>The variable to be matched is the property (of the bean specified
      by the <code>name</code> attribute) specified by this attribute.
      The property reference can be simple, nested, and/or indexed.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">scope</td>
<td>
      <p>The bean scope within which to search for the bean named by the
      <code>name</code> property, or "any scope" if not specified.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">value</td>
<td>
      <p>The constant value which is checked for existence as a substring
      of the specified variable.</p>
      
            [Required]
          
            [RT Expr]
          </td>
</tr>
</table>
</div>
<p>
<a href="#top">Back to top</a>
</p>
<h3 id="notPresent">
<strong>notPresent</strong> - 
    Generate the nested body content of this tag if the specified
    value is not present in this request.
    </h3>
<div class="indent">
    <p>Depending on which attribute is specified, this tag checks the
    current request, and evaluates the nested body content of this tag
    only if the specified value <strong>is not</strong> present.  Only one
    of the attributes may be used in one occurrence of this tag, unless
    you use the <code>property</code> attribute, in which case the
    <code>name</code> attribute is also required.</p>
    <table class="tag-attributes">
<thead>
<tr>
<th class="attribute">Attribute Name</th>
<th>Description</th>
</tr>
</thead>
<tr class="evenRow">
<td align="center">cookie</td>
<td>
      <p>Checks for the existence of a cookie with the specified name.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">header</td>
<td>
      <p>Checks for the existence of an HTTP header with the specified
      name.  The name match is performed in a case insensitive manner.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">name</td>
<td>
      <p>Checks for the existence of a JSP bean, in any scope, with the
      specified name.  If <code>property</code> is also specified, checks
      for a non-null property value for the specified property.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">parameter</td>
<td>
      <p>Checks for the existence of at least one occurrence of the
      specified request parameter on this request, even if the parameter
      value is a zero-length string.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">property</td>
<td>
      <p>Checks for the existence of a non-null property value, returned
      by a property getter method on the JSP bean (in any scope) that is
      specified by the <code>name</code> attribute.  Property references
      can be simple, nested, and/or indexed.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">role</td>
<td>
      <p>Checks whether the currently authenticated user (if any) has been
      associated with the specified security role.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="evenRow">
<td align="center">scope</td>
<td>
      <p>The bean scope within which to search for the bean named by the
      <code>name</code> property, or "any scope" if not specified.</p>
      
            [RT Expr]
          </td>
</tr>
<tr class="oddRow">
<td align="center">user</td>
<td>
      <p>Checks whether the currently authenticated user principal has the
      specified name.</p>
      
            [RT Expr]