Class ELSupport

java.lang.Object

org.apache.el.lang.ELSupport

public class ELSupport
extends Object

A helper class that implements the EL Specification.

Field Summary

Fields

Modifier and Type	Field	Description
protected static final boolean	COERCE_TO_ZERO

Method Summary

Modifier and Type	Method	Description
static Boolean	coerceToBoolean(ELContext ctx, Object obj, boolean primitive)	Convert an object to Boolean.
static Enum<?>	coerceToEnum(ELContext ctx, Object obj, Class type)	Coerces an object to an Enum value of the specified type.
static Number	coerceToNumber(ELContext ctx, Object obj, Class<?> type)	Coerces an object to a Number of the specified type.
protected static Number	coerceToNumber(Number number, Class<?> type)	Coerces a Number to the specified numeric type.
protected static Number	coerceToNumber(String val, Class<?> type)	Coerces a String to a Number of the specified type.
static String	coerceToString(ELContext ctx, Object obj)	Coerce an object to a string.
static <T> T	coerceToType(ELContext ctx, Object obj, Class<T> type)	Coerces an object to the specified target 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)	Checks if either operand is a BigDecimal.
static boolean	isBigIntegerOp(Object obj0, Object obj1)	Checks if either operand is a BigInteger.
static boolean	isDoubleOp(Object obj0, Object obj1)	Checks if either operand is a Double or Float.
static boolean	isLongOp(Object obj0, Object obj1)	Checks if either operand is a Long, Integer, Character, Short, or Byte.
static boolean	isStringFloat(String str)	Checks if a string represents a floating-point number by looking for 'E', 'e', or '.' characters.

Methods inherited from class Object

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

Field Details

COERCE_TO_ZERO

protected static final boolean COERCE_TO_ZERO

Method Details

compare

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

Coerces an object to an Enum value of the specified type.

If the object is null or an empty string, null is returned. If the object is already an instance of the target enum type, it is returned directly. Otherwise, the object must be a String matching one of the enum constant names.

Parameters:

ctx - the EL context

obj - the object to coerce

type - the target enum type

Returns:

the coerced enum value, or null if the object is null or empty

Throws:

ELException - if the object cannot be coerced to the target enum type

coerceToBoolean

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

Coerces a Number to the specified numeric type.

Parameters:

number - the number to coerce

type - the target numeric type

Returns:

the coerced number

Throws:

ELException - if the number cannot be coerced to the target type

coerceToNumber

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

Coerces an object to a Number of the specified type.

Supports coercion from String, Number, and Character types. If the object is null and the target type is not primitive, null is returned (unless COERCE_TO_ZERO is set).

Parameters:

ctx - the EL context

obj - the object to coerce

type - the target numeric type

Returns:

the coerced number, or null if the object is null and the target is not primitive

Throws:

ELException - if the object cannot be coerced to the target type

coerceToNumber

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

Coerces a String to a Number of the specified type.

Parameters:

val - the string value to parse

type - the target numeric type

Returns:

the coerced number

Throws:

ELException - if the string cannot be parsed as the target type

coerceToString

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

Coerces an object to the specified target type.

Supports coercion to String, Number, Character, Boolean, Enum, Instant, Date, arrays, and functional interfaces. Uses the ELResolver's convertToType method first if a context is provided.

Type Parameters:

T - the target type

Parameters:

ctx - the EL context

obj - the object to coerce

type - the target type

Returns:

the coerced object, or null if the object is null and the target is not primitive

Throws:

ELException - if the object cannot be coerced to the target type

isBigDecimalOp

public static boolean isBigDecimalOp(Object obj0,
 Object obj1)

Checks if either operand is a BigDecimal.

Parameters:

obj0 - the first operand

obj1 - the second operand

Returns:

true if either operand is a BigDecimal

isBigIntegerOp

public static boolean isBigIntegerOp(Object obj0,
 Object obj1)

Checks if either operand is a BigInteger.

Parameters:

obj0 - the first operand

obj1 - the second operand

Returns:

true if either operand is a BigInteger

isDoubleOp

public static boolean isDoubleOp(Object obj0,
 Object obj1)

Checks if either operand is a Double or Float.

Parameters:

obj0 - the first operand

obj1 - the second operand

Returns:

true if either operand is a Double or Float

isLongOp

public static boolean isLongOp(Object obj0,
 Object obj1)

Checks if either operand is a Long, Integer, Character, Short, or Byte.

Parameters:

obj0 - the first operand

obj1 - the second operand

Returns:

true if either operand is a Long-compatible type

isStringFloat

public static boolean isStringFloat(String str)

Checks if a string represents a floating-point number by looking for 'E', 'e', or '.' characters.

Parameters:

str - the string to check

Returns:

true if the string contains floating-point notation