org.apache.el.lang

Class ELSupport

java.lang.Object

org.apache.el.lang.ELSupport

public class ELSupport
extends Object

A helper class that implements the EL Specification

Author:

Jacob Hookom [jacob@hookom.net]

Field Summary

Fields

Modifier and Type	Field and Description
protected static boolean	COERCE_TO_ZERO

Constructor Summary

Constructors

Constructor and Description
ELSupport()

Method Summary

Modifier and Type	Method and Description
static Boolean	coerceToBoolean(ELContext ctx, Object obj, boolean primitive) Convert an object to Boolean.
static Enum<?>	coerceToEnum(ELContext ctx, Object obj, Class type)
static Number	coerceToNumber(ELContext ctx, Object obj, Class<?> type)
protected static Number	coerceToNumber(Number number, Class<?> type)
protected static Number	coerceToNumber(String val, Class<?> type)
static String	coerceToString(ELContext ctx, Object obj) Coerce an object to a string.
static Object	coerceToType(ELContext ctx, Object obj, Class<?> type)
static int	compare(ELContext ctx, Object obj0, Object obj1) Compare two objects, after coercing to the same type if appropriate.
static boolean	equals(ELContext ctx, Object obj0, Object obj1) Compare two objects for equality, after coercing to the same type if appropriate.
static boolean	isBigDecimalOp(Object obj0, Object obj1)
static boolean	isBigIntegerOp(Object obj0, Object obj1)
static boolean	isDoubleOp(Object obj0, Object obj1)
static boolean	isLongOp(Object obj0, Object obj1)
static boolean	isStringFloat(String str)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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

coerceToEnum

public static final Enum<?> coerceToEnum(ELContext ctx,
                                         Object obj,
                                         Class type)

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

coerceToNumber

protected static final Number coerceToNumber(Number number,
                                             Class<?> type)
                                      throws ELException

Throws:

ELException

coerceToNumber

public static final Number coerceToNumber(ELContext ctx,
                                          Object obj,
                                          Class<?> type)
                                   throws ELException

Throws:

ELException

coerceToNumber

protected static final Number coerceToNumber(String val,
                                             Class<?> type)
                                      throws ELException

Throws:

ELException

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

coerceToType

public static final Object coerceToType(ELContext ctx,
                                        Object obj,
                                        Class<?> type)
                                 throws ELException

Throws:

ELException

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)