Class ELSupport


  • public class ELSupport
    extends Object
    A helper class that implements the EL Specification
    Author:
    Jacob Hookom [jacob@hookom.net]
    • Field Detail

      • COERCE_TO_ZERO

        protected static final boolean COERCE_TO_ZERO
    • Constructor Detail

      • ELSupport

        public ELSupport()
    • Method Detail

      • compare

        public static final int compare​(ELContext ctx,
                                        Object obj0,
                                        Object obj1)
                                 throws ELException
        Compare two objects, after coercing to the same type if appropriate. If the objects are identical, or they are equal according to equals(ELContext, Object, Object) then return 0. If either object is a BigDecimal, then coerce both to BigDecimal first. Similarly for Double(Float), BigInteger, and Long(Integer, Char, Short, Byte). Otherwise, check that the first object is an instance of Comparable, and compare against the second object. If that is null, return 1, otherwise return the result of comparing against the second object. Similarly, if the second object is Comparable, if the first is null, return -1, else return the result of comparing against the first object. A null object is considered as:
        • ZERO when compared with Numbers
        • the empty string for String compares
        • Otherwise null is considered to be lower than anything else.
        Parameters:
        ctx - the context in which this comparison is taking place
        obj0 - first object
        obj1 - second object
        Returns:
        -1, 0, or 1 if this object is less than, equal to, or greater than val.
        Throws:
        ELException - if neither object is Comparable
        ClassCastException - if the objects are not mutually comparable
      • equals

        public static final boolean equals​(ELContext ctx,
                                           Object obj0,
                                           Object obj1)
                                    throws ELException
        Compare two objects for equality, after coercing to the same type if appropriate. If the objects are identical (including both null) return true. If either object is null, return false. If either object is Boolean, coerce both to Boolean and check equality. Similarly for Enum, String, BigDecimal, Double(Float), Long(Integer, Short, Byte, Character) Otherwise default to using Object.equals().
        Parameters:
        ctx - the context in which this equality test is taking place
        obj0 - the first object
        obj1 - the second object
        Returns:
        true if the objects are equal
        Throws:
        ELException - if one of the coercion fails
      • coerceToBoolean

        public static final Boolean coerceToBoolean​(ELContext ctx,
                                                    Object obj,
                                                    boolean primitive)
                                             throws ELException
        Convert an object to Boolean. Null and empty string are false.
        Parameters:
        ctx - the context in which this conversion is taking place
        obj - the object to convert
        primitive - is the target a primitive in which case coercion to null is not permitted
        Returns:
        the Boolean value of the object
        Throws:
        ELException - if object is not Boolean or String
      • coerceToString

        public static final String coerceToString​(ELContext ctx,
                                                  Object obj)
        Coerce an object to a string.
        Parameters:
        ctx - the context in which this conversion is taking place
        obj - the object to convert
        Returns:
        the String value of the object
      • isBigDecimalOp

        public static final boolean isBigDecimalOp​(Object obj0,
                                                   Object obj1)
      • isBigIntegerOp

        public static final boolean isBigIntegerOp​(Object obj0,
                                                   Object obj1)
      • isDoubleOp

        public static final boolean isDoubleOp​(Object obj0,
                                               Object obj1)
      • isLongOp

        public static final boolean isLongOp​(Object obj0,
                                             Object obj1)
      • isStringFloat

        public static final boolean isStringFloat​(String str)