Package com.sun.el

Class ValueExpressionImpl

  • All Implemented Interfaces:
    java.io.Externalizable, java.io.Serializable
    public final class ValueExpressionImpl
extends javax.el.ValueExpression
implements java.io.Externalizable
    An Expression that can get or set a value.

    In previous incarnations of this API, expressions could only be read. ValueExpression objects can now be used both to retrieve a value and to set a value. Expressions that can have a value set on them are referred to as l-value expressions. Those that cannot are referred to as r-value expressions. Not all r-value expressions can be used as l-value expressions (e.g. "${1+1}" or "${firstName} ${lastName}"). See the EL Specification for details. Expressions that cannot be used as l-values must always return true from isReadOnly().

    The ExpressionFactory.createValueExpression(javax.el.ELContext, java.lang.String, java.lang.Class<?>) method can be used to parse an expression string and return a concrete instance of ValueExpression that encapsulates the parsed expression. The FunctionMapper is used at parse time, not evaluation time, so one is not needed to evaluate an expression using this class. However, the ELContext is needed at evaluation time.

    The getValue(javax.el.ELContext), setValue(javax.el.ELContext, java.lang.Object), isReadOnly(javax.el.ELContext) and getType(javax.el.ELContext) methods will evaluate the expression each time they are called. The ELResolver in the ELContext is used to resolve the top-level variables and to determine the behavior of the . and [] operators. For any of the four methods, the ELResolver.getValue(javax.el.ELContext, java.lang.Object, java.lang.Object) method is used to resolve all properties up to but excluding the last one. This provides the base object. At the last resolution, the ValueExpression will call the corresponding ELResolver.getValue(javax.el.ELContext, java.lang.Object, java.lang.Object), ELResolver.setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object), ELResolver.isReadOnly(javax.el.ELContext, java.lang.Object, java.lang.Object) or ELResolver.getType(javax.el.ELContext, java.lang.Object, java.lang.Object) method, depending on which was called on the ValueExpression.

    See the notes about comparison, serialization and immutability in the Expression javadocs.

    Version:
    $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: dochez $
    Author:
    Jacob Hookom [jacob@hookom.net]
    See Also:
    ELResolver, Expression, ExpressionFactory, ValueExpression, Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      ValueExpressionImpl()  
      ValueExpressionImpl​(java.lang.String expr, Node node, javax.el.FunctionMapper fnMapper, javax.el.VariableMapper varMapper, java.lang.Class expectedType)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean equals​(java.lang.Object obj)  
      java.lang.Class getExpectedType()  
      java.lang.String getExpressionString()
      Returns the type the result of the expression will be coerced to after evaluation.
      java.lang.Class getType​(javax.el.ELContext context)  
      java.lang.Object getValue​(javax.el.ELContext context)  
      javax.el.ValueReference getValueReference​(javax.el.ELContext context)  
      int hashCode()  
      boolean isLiteralText()  
      boolean isReadOnly​(javax.el.ELContext context)  
      void readExternal​(java.io.ObjectInput in)  
      void setValue​(javax.el.ELContext context, java.lang.Object value)  
      java.lang.String toString()  
      void writeExternal​(java.io.ObjectOutput out)  

      • Methods inherited from class java.lang.Object

        clone, finalize, getClass, notify, notifyAll, wait, wait, wait

    • Constructor Detail

      • ValueExpressionImpl

        public ValueExpressionImpl()

      • ValueExpressionImpl

        public ValueExpressionImpl​(java.lang.String expr,
                           Node node,
                           javax.el.FunctionMapper fnMapper,
                           javax.el.VariableMapper varMapper,
                           java.lang.Class expectedType)

    • Method Detail

      • equals

        public boolean equals​(java.lang.Object obj)
        Specified by:
        equals in class javax.el.Expression

      • getExpectedType

        public java.lang.Class getExpectedType()
        Specified by:
        getExpectedType in class javax.el.ValueExpression

      • getExpressionString

        public java.lang.String getExpressionString()
        Returns the type the result of the expression will be coerced to after evaluation.
        Specified by:
        getExpressionString in class javax.el.Expression
        Returns:
        the expectedType passed to the ExpressionFactory.createValueExpression method that created this ValueExpression.
        See Also:
        Expression.getExpressionString()

      • getType

        public java.lang.Class getType​(javax.el.ELContext context)
                        throws javax.el.PropertyNotFoundException,
                               javax.el.ELException
        Specified by:
        getType in class javax.el.ValueExpression
        Throws:
        javax.el.PropertyNotFoundException
        javax.el.ELException

      • getValueReference

        public javax.el.ValueReference getValueReference​(javax.el.ELContext context)
                                          throws javax.el.PropertyNotFoundException,
                                                 javax.el.ELException
        Overrides:
        getValueReference in class javax.el.ValueExpression
        Throws:
        javax.el.PropertyNotFoundException
        javax.el.ELException

      • getValue

        public java.lang.Object getValue​(javax.el.ELContext context)
                          throws javax.el.PropertyNotFoundException,
                                 javax.el.ELException
        Specified by:
        getValue in class javax.el.ValueExpression
        Throws:
        javax.el.PropertyNotFoundException
        javax.el.ELException

      • hashCode

        public int hashCode()
        Specified by:
        hashCode in class javax.el.Expression

      • isLiteralText

        public boolean isLiteralText()
        Specified by:
        isLiteralText in class javax.el.Expression

      • isReadOnly

        public boolean isReadOnly​(javax.el.ELContext context)
                   throws javax.el.PropertyNotFoundException,
                          javax.el.ELException
        Specified by:
        isReadOnly in class javax.el.ValueExpression
        Throws:
        javax.el.PropertyNotFoundException
        javax.el.ELException

      • readExternal

        public void readExternal​(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException
        Specified by:
        readExternal in interface java.io.Externalizable
        Throws:
        java.io.IOException
        java.lang.ClassNotFoundException

      • setValue

        public void setValue​(javax.el.ELContext context,
                     java.lang.Object value)
              throws javax.el.PropertyNotFoundException,
                     javax.el.PropertyNotWritableException,
                     javax.el.ELException
        Specified by:
        setValue in class javax.el.ValueExpression
        Throws:
        javax.el.PropertyNotFoundException
        javax.el.PropertyNotWritableException
        javax.el.ELException

      • writeExternal

        public void writeExternal​(java.io.ObjectOutput out)
                   throws java.io.IOException
        Specified by:
        writeExternal in interface java.io.Externalizable
        Throws:
        java.io.IOException

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object