Class ValueExpression

    • Constructor Detail

      • ValueExpression

        public ValueExpression()
    • Method Detail

      • getExpectedType

        public abstract java.lang.Class<?> getExpectedType()
        Returns the type the result of the expression will be coerced to after evaluation.
        Returns:
        the expectedType passed to the ExpressionFactory.createValueExpression method that created this ValueExpression.
      • getType

        public abstract java.lang.Class<?> getType​(ELContext context)
        Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as the value parameter in a future call to the setValue(ELContext, Object) method. This is not always the same as getValue().getClass(). For example, in the case of an expression that references an array element, the getType method will return the element type of the array, which might be a superclass of the type of the actual element that is currently in the specified array element.
        Parameters:
        context - The context of this evaluation.
        Returns:
        the most general acceptable type; otherwise undefined.
        Throws:
        java.lang.NullPointerException - if context is null.
        PropertyNotFoundException - if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
        ELException - if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.
      • getValue

        public abstract java.lang.Object getValue​(ELContext context)
        Evaluates the expression relative to the provided context, and returns the resulting value. The resulting value is automatically coerced to the type returned by getExpectedType(), which was provided to the ExpressionFactory when this expression was created.
        Parameters:
        context - The context of this evaluation.
        Returns:
        The result of the expression evaluation.
        Throws:
        java.lang.NullPointerException - if context is null.
        PropertyNotFoundException - if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
        ELException - if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.
      • isReadOnly

        public abstract boolean isReadOnly​(ELContext context)
        Evaluates the expression relative to the provided context, and returns true if a call to setValue(ELContext, Object) will always fail.
        Parameters:
        context - The context of this evaluation.
        Returns:
        true if the expression is read-only or false if not.
        Throws:
        java.lang.NullPointerException - if context is null.
        PropertyNotFoundException - if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
        ELException - if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.
      • setValue

        public abstract void setValue​(ELContext context,
                                      java.lang.Object value)
        Evaluates the expression relative to the provided context, and sets the result to the provided value.
        Parameters:
        context - The context of this evaluation.
        value - The new value to be set.
        Throws:
        java.lang.NullPointerException - if context is null.
        PropertyNotFoundException - if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
        PropertyNotWritableException - if the final variable or property resolution failed because the specified variable or property is not writable.
        ELException - 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.
      • getValueReference

        public ValueReference getValueReference​(ELContext context)
        Returns a ValueReference for this expression instance.
        Parameters:
        context - the context of this evaluation
        Returns:
        the ValueReference for this ValueExpression, or null if this ValueExpression is not a reference to a base (null or non-null) and a property. If the base is null, and the property is a EL variable, return the ValueReference for the ValueExpression associated with this EL variable.
        Since:
        2.2