Module com.sun.el
Package com.sun.el

Class ValueExpressionImpl

  • All Implemented Interfaces:
    Externalizable, Serializable
    public final class ValueExpressionImpl
extends jakarta.el.ValueExpression
implements 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(jakarta.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(jakarta.el.ELContext), setValue(jakarta.el.ELContext, java.lang.Object), isReadOnly(jakarta.el.ELContext) and getType(jakarta.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(jakarta.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(jakarta.el.ELContext, java.lang.Object, java.lang.Object), ELResolver.setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object), ELResolver.isReadOnly(jakarta.el.ELContext, java.lang.Object, java.lang.Object) or ELResolver.getType(jakarta.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 Detail

      • ValueExpressionImpl

        public ValueExpressionImpl()

      • ValueExpressionImpl

        public ValueExpressionImpl​(String expr,
                           Node node,
                           jakarta.el.FunctionMapper fnMapper,
                           jakarta.el.VariableMapper varMapper,
                           Class<?> expectedType)

    • Method Detail

      • equals

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

      • getExpectedType

        public Class<?> getExpectedType()
        Specified by:
        getExpectedType in class jakarta.el.ValueExpression

      • getExpressionString

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

      • getType

        public Class<?> getType​(jakarta.el.ELContext context)
                 throws jakarta.el.PropertyNotFoundException,
                        jakarta.el.ELException
        Specified by:
        getType in class jakarta.el.ValueExpression
        Throws:
        jakarta.el.PropertyNotFoundException
        jakarta.el.ELException

      • getValueReference

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

      • getValue

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

      • hashCode

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

      • isLiteralText

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

      • isReadOnly

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

      • setValue

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