elresolver.html

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 object on the given <code>base</code> object.

 <p>If this resolver handles the given (base, property) pair, 
 the <code>propertyResolved</code> property of the 
 <code>ELContext</code> object must be set to <code>true</code>
 by the resolver, before returning. If this property is not 
 <code>true</code> after this method is called, the caller can
 safely assume no value has been set.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>context</CODE> - The context of this evaluation.<DD><CODE>base</CODE> - The base object whose property value is to be set,
     or <code>null</code> to set a top-level variable.<DD><CODE>property</CODE> - The property or variable to be set.<DD><CODE>value</CODE> - The value to set the property or variable to.
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.5/docs/api/java/lang/NullPointerException.html" title="class or interface in java.lang">NullPointerException</A></CODE> - if context is <code>null</code>
<DD><CODE><A HREF="../../javax/el/PropertyNotFoundException.html" title="class in javax.el">PropertyNotFoundException</A></CODE> - if the given (base, property) pair
     is handled by this <code>ELResolver</code> but the specified
     variable or property does not exist.
<DD><CODE><A HREF="../../javax/el/PropertyNotWritableException.html" title="class in javax.el">PropertyNotWritableException</A></CODE> - if the given (base, property)
     pair is handled by this <code>ELResolver</code> but the specified
     variable or property is not writable.
<DD><CODE><A HREF="../../javax/el/ELException.html" title="class in javax.el">ELException</A></CODE> - if an exception was thrown while attempting to
     set the property or variable. The thrown exception
     must be included as the cause property of this exception, if
     available.</DL>
</DD>
</DL>
<HR>

<A NAME="isReadOnly(javax.el.ELContext, java.lang.Object, java.lang.Object)"><!-- --></A><H3>
isReadOnly</H3>
<PRE>
public abstract boolean <B>isReadOnly</B>(<A HREF="../../javax/el/ELContext.html" title="class in javax.el">ELContext</A>&nbsp;context,
                                   <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A>&nbsp;base,
                                   <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A>&nbsp;property)</PRE>
<DL>
<DD>For a given <code>base</code> and <code>property</code>, attempts to
 determine whether a call to <A HREF="../../javax/el/ELResolver.html#setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)"><CODE>setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)</CODE></A> will always fail.

 <p>If this resolver handles the given (base, property) pair, 
 the <code>propertyResolved</code> property of the 
 <code>ELContext</code> object must be set to <code>true</code>
 by the resolver, before returning. If this property is not 
 <code>true</code> after this method is called, the caller should ignore 
 the return value.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>context</CODE> - The context of this evaluation.<DD><CODE>base</CODE> - The base object whose property value is to be analyzed,
     or <code>null</code> to analyze a top-level variable.<DD><CODE>property</CODE> - The property or variable to return the read-only status
     for.
<DT><B>Returns:</B><DD>If the <code>propertyResolved</code> property of 
     <code>ELContext</code> was set to <code>true</code>, then
     <code>true</code> if the property is read-only or
     <code>false</code> if not; otherwise undefined.
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.5/docs/api/java/lang/NullPointerException.html" title="class or interface in java.lang">NullPointerException</A></CODE> - if context is <code>null</code>
<DD><CODE><A HREF="../../javax/el/PropertyNotFoundException.html" title="class in javax.el">PropertyNotFoundException</A></CODE> - if the given (base, property) pair
     is handled by this <code>ELResolver</code> but the specified
     variable or property does not exist.
<DD><CODE><A HREF="../../javax/el/ELException.html" title="class in javax.el">ELException</A></CODE> - if an exception was thrown while performing
     the property or variable resolution. The thrown exception
     must be included as the cause property of this exception, if
     available.</DL>
</DD>
</DL>
<HR>

<A NAME="getFeatureDescriptors(javax.el.ELContext, java.lang.Object)"><!-- --></A><H3>
getFeatureDescriptors</H3>
<PRE>
public abstract <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/util/Iterator.html" title="class or interface in java.util">Iterator</A>&lt;<A HREF="http://java.sun.com/j2se/1.5/docs/api/java/beans/FeatureDescriptor.html" title="class or interface in java.beans">FeatureDescriptor</A>&gt; <B>getFeatureDescriptors</B>(<A HREF="../../javax/el/ELContext.html" title="class in javax.el">ELContext</A>&nbsp;context,
                                                                  <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A>&nbsp;base)</PRE>
<DL>
<DD>Returns information about the set of variables or properties that 
 can be resolved for the given <code>base</code> object. One use for
 this method is to assist tools in auto-completion.

 <p>If the <code>base</code> parameter is <code>null</code>, the 
 resolver must enumerate the list of top-level variables it can 
 resolve.</p>

 <p>The <code>Iterator</code> returned must contain zero or more 
 instances of <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/beans/FeatureDescriptor.html" title="class or interface in java.beans"><CODE>FeatureDescriptor</CODE></A>, in no guaranteed 
 order. In the case of primitive types such as <code>int</code>, the 
 value <code>null</code> must be returned. This is to prevent the 
 useless iteration through all possible primitive values. A 
 return value of <code>null</code> indicates that this resolver does 
 not handle the given <code>base</code> object or that the results 
 are too complex to represent with this method and the 
 <A HREF="../../javax/el/ELResolver.html#getCommonPropertyType(javax.el.ELContext, java.lang.Object)"><CODE>getCommonPropertyType(javax.el.ELContext, java.lang.Object)</CODE></A> method should be used instead.</p>

 <p>Each <code>FeatureDescriptor</code> will contain information about
 a single variable or property. In addition to the standard
 properties, the <code>FeatureDescriptor</code> must have two
 named attributes (as set by the <code>setValue</code> method):
 <ul>
   <li><A HREF="../../javax/el/ELResolver.html#TYPE"><CODE>TYPE</CODE></A> - The value of this named attribute must be 
       an instance of <code>java.lang.Class</code> and specify the 
       runtime type of the variable or property.</li>
   <li><A HREF="../../javax/el/ELResolver.html#RESOLVABLE_AT_DESIGN_TIME"><CODE>RESOLVABLE_AT_DESIGN_TIME</CODE></A> - The value of this 
       named attribute must be an instance of 
       <code>java.lang.Boolean</code> and indicates whether it is safe 
       to attempt to resolve this property at design-time. For 
       instance, it may be unsafe to attempt a resolution at design 
       time if the <code>ELResolver</code> needs access to a resource 
       that is only available at runtime and no acceptable simulated 
       value can be provided.</li>
 </ul></p>

 <p>The caller should be aware that the <code>Iterator</code> 
 returned might iterate through a very large or even infinitely large 
 set of properties. Care should be taken by the caller to not get 
 stuck in an infinite loop.</p>

 <p>This is a "best-effort" list.  Not all <code>ELResolver</code>s
 will return completely accurate results, but all must be callable
 at both design-time and runtime (i.e. whether or not
 <code>Beans.isDesignTime()</code> returns <code>true</code>),
 without causing errors.</p>

 <p>The <code>propertyResolved</code> property of the 
 <code>ELContext</code> is not relevant to this method.
 The results of all <code>ELResolver</code>s are concatenated
 in the case of composite resolvers.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>context</CODE> - The context of this evaluation.<DD><CODE>base</CODE> - The base object whose set of valid properties is to
     be enumerated, or <code>null</code> to enumerate the set of
     top-level variables that this resolver can evaluate.
<DT><B>Returns:</B><DD>An <code>Iterator</code> containing zero or more (possibly
     infinitely more) <code>FeatureDescriptor</code> objects, or 
     <code>null</code> if this resolver does not handle the given 
     <code>base</code> object or that the results are too complex to 
     represent with this method<DT><B>See Also:</B><DD><A HREF="http://java.sun.com/j2se/1.5/docs/api/java/beans/FeatureDescriptor.html" title="class or interface in java.beans"><CODE>FeatureDescriptor</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="getCommonPropertyType(javax.el.ELContext, java.lang.Object)"><!-- --></A><H3>
getCommonPropertyType</H3>
<PRE>
public abstract <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/lang/Class.html" title="class or interface in java.lang">Class</A>&lt;?&gt; <B>getCommonPropertyType</B>(<A HREF="../../javax/el/ELContext.html" title="class in javax.el">ELContext</A>&nbsp;context,
                                               <A HREF="http://java.sun.com/j2se/1.5/docs/api/java/lang/Object.html" title="class or interface in java.lang">Object</A>&nbsp;base)</PRE>
<DL>
<DD>Returns the most general type that this resolver accepts for the
 <code>property</code> argument, given a <code>base</code> object.
 One use for this method is to assist tools in auto-completion.

 <p>This assists tools in auto-completion and also provides a 
 way to express that the resolver accepts a primitive value, 
 such as an integer index into an array. For example, the 
 <A HREF="../../javax/el/ArrayELResolver.html" title="class in javax.el"><CODE>ArrayELResolver</CODE></A> will accept any <code>int</code> as a 
 <code>property</code>, so the return value would be 
 <code>Integer.class</code>.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>context</CODE> - The context of this evaluation.<DD><CODE>base</CODE> - The base object to return the most general property
     type for, or <code>null</code> to enumerate the set of
     top-level variables that this resolver can evaluate.
<DT><B>Returns:</B><DD><code>null</code> if this <code>ELResolver</code> does not
     know how to handle the given <code>base</code> object; otherwise
     <code>Object.class</code> if any type of <code>property</code>
     is accepted; otherwise the most general <code>property</code>
     type accepted for the given <code>base</code>.</DL>
</DD>
</DL>
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