Class Coercions

java.lang.Object

org.apache.commons.el.Coercions

public class Coercions
extends Object

This class contains the logic for coercing data types before operators are applied to them.

The following is the list of rules applied for various type conversions.

Applying arithmetic operator
  Binary operator - A {+,-,*} B
    if A and B are null
      return 0
    if A or B is BigDecimal, coerce both to BigDecimal and then:
      if operator is +, return A.add(B)
      if operator is -, return A.subtract(B)
      if operator is *, return A.multiply(B)
    if A or B is Float, Double, or String containing ".", "e", or "E"
      if A or B is BigInteger, coerce both A and B to BigDecimal and apply operator
      coerce both A and B to Double and apply operator
    if A or B is BigInteger, coerce both to BigInteger and then:
      if operator is +, return A.add(B)
      if operator is -, return A.subtract(B)
      if operator is *, return A.multiply(B)
    otherwise
      coerce both A and B to Long
      apply operator
    if operator results in exception (such as divide by 0), error

  Binary operator - A {/,div} B
    if A and B are null
      return 0
    if A or B is a BigDecimal or BigInteger, coerce both to BigDecimal and
     return A.divide(B, BigDecimal.ROUND_HALF_UP)
    otherwise
      coerce both A and B to Double
      apply operator
    if operator results in exception (such as divide by 0), error

  Binary operator - A {%,mod} B
    if A and B are null
      return 0
    if A or B is BigDecimal, Float, Double, or String containing ".", "e" or "E"
      coerce both to Double
      apply operator
    if A or B is BigInteger, coerce both to BigInteger and return
     A.remainder(B)
    otherwise
      coerce both A and B to Long
      apply operator
    if operator results in exception (such as divide by 0), error

  Unary minus operator - -A
    if A is null
      return 0
    if A is BigInteger or BigDecimal, return A.negate()
    if A is String
      if A contains ".", "e", or "E"
        coerce to Double, apply operator
      otherwise
        coerce to a Long and apply operator
    if A is Byte,Short,Integer,Long,Float,Double
      retain type, apply operator
    if operator results in exception, error
    otherwise
      error

Applying "empty" operator - empty A
  if A is null
    return true
  if A is zero-length String
    return true
  if A is zero-length array
    return true
  if A is List and ((List) A).isEmpty()
    return true
  if A is Map and ((Map) A).isEmpty()
    return true
  if A is Collection an ((Collection) A).isEmpty()
    return true
  otherwise
    return false

Applying logical operators
  Binary operator - A {and,or} B
    coerce both A and B to Boolean, apply operator
  NOTE - operator stops as soon as expression can be determined, i.e.,
    A and B and C and D - if B is false, then only A and B is evaluated
  Unary not operator - not A
    coerce A to Boolean, apply operator

Applying relational operator
  A {invalid input: '<',>,invalid input: '<'=,>=,lt,gt,lte,gte} B
    if A==B
      if operator is >= or invalid input: '<'=
        return true
      otherwise
        return false
    if A or B is null
      return false
    if A or B is BigDecimal, coerce both A and B to BigDecimal and use the
     return value of A.compareTo(B)
    if A or B is Float or Double
      coerce both A and B to Double
      apply operator
    if A or B is BigInteger, coerce both A and B to BigInteger and use the
     return value of A.compareTo(B)
    if A or B is Byte,Short,Character,Integer,Long
      coerce both A and B to Long
      apply operator
    if A or B is String
      coerce both A and B to String, compare lexically
    if A is Comparable
      if A.compareTo (B) throws exception
        error
      otherwise
        use result of A.compareTo(B)
    if B is Comparable
      if B.compareTo (A) throws exception
        error
      otherwise
        use result of B.compareTo(A)
    otherwise
      error

Applying equality operator
  A {==,!=} B
    if A==B
      apply operator
    if A or B is null
      return false for ==, true for !=
    if A or B is BigDecimal, coerce both A and B to BigDecimal and then:
      if operator is == or eq, return A.equals(B)
      if operator is != or ne, return !A.equals(B)
    if A or B is Float or Double
      coerce both A and B to Double
      apply operator
    if A or B is BigInteger, coerce both A and B to BigInteger and then:
      if operator is == or eq, return A.equals(B)
      if operator is != or ne, return !A.equals(B)
    if A or B is Byte,Short,Character,Integer,Long
      coerce both A and B to Long
      apply operator
    if A or B is Boolean
      coerce both A and B to Boolean
      apply operator
    if A or B is String
      coerce both A and B to String, compare lexically
    otherwise
      if an error occurs while calling A.equals(B)
        error
      apply operator to result of A.equals(B)

coercions

  coerce A to String
    A is String
      return A
    A is null
      return ""
    A.toString throws exception
      error
    otherwise
      return A.toString

  coerce A to Number type N
    A is null or ""
      return 0
    A is Character
      convert to short, apply following rules
    A is Boolean
      error
    A is Number type N
      return A
    A is Number, coerce quietly to type N using the following algorithm
        If N is BigInteger
            If A is BigDecimal, return A.toBigInteger()
            Otherwise, return BigInteger.valueOf(A.longValue())
       if N is BigDecimal
            If A is a BigInteger, return new BigDecimal(A)
            Otherwise, return new BigDecimal(A.doubleValue())
       If N is Byte, return new Byte(A.byteValue())
       If N is Short, return new Short(A.shortValue())
       If N is Integer, return new Integer(A.integerValue())
       If N is Long, return new Long(A.longValue())
       If N is Float, return new Float(A.floatValue())
       If N is Double, return new Double(A.doubleValue())
       otherwise ERROR
    A is String
      If N is BigDecimal then:
           If new BigDecimal(A) throws an exception then ERROR
           Otherwise, return new BigDecimal(A)
      If N is BigInteger then:
           If new BigInteger(A) throws an exception, then ERROR
           Otherwise, return new BigInteger(A)
      new N.valueOf(A) throws exception
        error
      return N.valueOf(A)
    otherwise
      error

  coerce A to Character should be
    A is null or ""
      return (char) 0
    A is Character
      return A
    A is Boolean
      error
    A is Number with less precision than short
      coerce quietly - return (char) A
    A is Number with greater precision than short
      coerce quietly - return (char) A
    A is String
      return A.charAt (0)
    otherwise
      error

  coerce A to Boolean
    A is null or ""
      return false
    A is Boolean
      return A
    A is String
      Boolean.valueOf(A) throws exception
        error
      return Boolean.valueOf(A)
    otherwise
      error

  coerce A to any other type T
    A is null
      return null
    A is assignable to T
      coerce quietly
    A is String
      T has no PropertyEditor
        if A is "", return null
        otherwise error
      T's PropertyEditor throws exception
        if A is "", return null
        otherwise error
      otherwise
        apply T's PropertyEditor
    otherwise
      error

Version:

$Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: luehe $

Author:

Nathan Abramson - Art Technology Group

Field Summary

Fields

Modifier and Type	Field	Description
private static final Number	ZERO

Constructor Summary

Constructors

Constructor	Description
Coercions()

Method Summary

Modifier and Type	Method	Description
static Object	applyArithmeticOperator(Object pLeft, Object pRight, ArithmeticOperator pOperator, Logger pLogger)	Performs all of the necessary type conversions, then calls on the appropriate operator.
static Object	applyEqualityOperator(Object pLeft, Object pRight, EqualityOperator pOperator, Logger pLogger)	Performs all of the necessary type conversions, then calls on the appropriate operator.
static Object	applyRelationalOperator(Object pLeft, Object pRight, RelationalOperator pOperator, Logger pLogger)	Performs all of the necessary type conversions, then calls on the appropriate operator.
static Object	coerce(Object pValue, Class pClass, Logger pLogger)	Coerces the given value to the specified class.
static Boolean	coerceToBoolean(Object pValue, Logger pLogger)	Coerces a value to a Boolean
static Character	coerceToCharacter(Object pValue, Logger pLogger)	Coerces a value to a Character
static Integer	coerceToInteger(Object pValue, Logger pLogger)	Coerces a value to an Integer, returning null if the coercion isn't possible.
static Object	coerceToObject(Object pValue, Class pClass, Logger pLogger)	Coerces a value to the specified Class that is not covered by any of the above cases
(package private) static Number	coerceToPrimitiveNumber(double pValue, Class pClass)	Coerces a double to the given primitive number class
(package private) static Number	coerceToPrimitiveNumber(long pValue, Class pClass)	Coerces a long to the given primitive number class
(package private) static Number	coerceToPrimitiveNumber(Number pValue, Class pClass)	Coerces a Number to the given primitive number class
static Number	coerceToPrimitiveNumber(Object pValue, Class pClass, Logger pLogger)	Coerces a value to the given primitive number class
(package private) static Number	coerceToPrimitiveNumber(String pValue, Class pClass)	Coerces a String to the given primitive number class
static String	coerceToString(Object pValue, Logger pLogger)	Coerces the specified value to a String
static boolean	isBigDecimal(Object pObject)	Returns true if the given object is BigDecimal.
static boolean	isBigInteger(Object pObject)	Returns true if the given object is BigInteger.
static boolean	isFloatingPointString(Object pObject)	Returns true if the given string might contain a floating point number - i.e., it contains ".", "e", or "E"
static boolean	isFloatingPointType(Class pClass)	Returns true if the given class is of a floating point type
static boolean	isFloatingPointType(Object pObject)	Returns true if the given Object is of a floating point type
static boolean	isIntegerType(Class pClass)	Returns true if the given class is of an integer type
static boolean	isIntegerType(Object pObject)	Returns true if the given Object is of an integer type
(package private) static boolean	isNumberClass(Class pClass)	Returns true if the given class is Byte, Short, Integer, Long, Float, Double, BigInteger, or BigDecimal

Methods inherited from class Object

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

Field Details

ZERO

private static final Number ZERO

Constructor Details

Coercions

public Coercions()

Method Details

coerce

public static Object coerce(Object pValue,
 Class pClass,
 Logger pLogger)
                     throws javax.servlet.jsp.el.ELException

Coerces the given value to the specified class.

Throws:

javax.servlet.jsp.el.ELException

isNumberClass

static boolean isNumberClass(Class pClass)

Returns true if the given class is Byte, Short, Integer, Long, Float, Double, BigInteger, or BigDecimal

coerceToString

public static String coerceToString(Object pValue,
 Logger pLogger)
                             throws javax.servlet.jsp.el.ELException

Coerces the specified value to a String

Throws:

javax.servlet.jsp.el.ELException

coerceToPrimitiveNumber

public static Number coerceToPrimitiveNumber(Object pValue,
 Class pClass,
 Logger pLogger)
                                      throws javax.servlet.jsp.el.ELException

Coerces a value to the given primitive number class

Throws:

javax.servlet.jsp.el.ELException

coerceToInteger

public static Integer coerceToInteger(Object pValue,
 Logger pLogger)
                               throws javax.servlet.jsp.el.ELException

Coerces a value to an Integer, returning null if the coercion isn't possible.

Throws:

javax.servlet.jsp.el.ELException

coerceToPrimitiveNumber

static Number coerceToPrimitiveNumber(long pValue,
 Class pClass)
                               throws javax.servlet.jsp.el.ELException

Coerces a long to the given primitive number class

Throws:

javax.servlet.jsp.el.ELException

coerceToPrimitiveNumber

static Number coerceToPrimitiveNumber(double pValue,
 Class pClass)
                               throws javax.servlet.jsp.el.ELException

Coerces a double to the given primitive number class

Throws:

javax.servlet.jsp.el.ELException

coerceToPrimitiveNumber

static Number coerceToPrimitiveNumber(Number pValue,
 Class pClass)
                               throws javax.servlet.jsp.el.ELException

Coerces a Number to the given primitive number class

Throws:

javax.servlet.jsp.el.ELException

coerceToPrimitiveNumber

static Number coerceToPrimitiveNumber(String pValue,
 Class pClass)
                               throws javax.servlet.jsp.el.ELException

Coerces a String to the given primitive number class

Throws:

javax.servlet.jsp.el.ELException

coerceToCharacter

public static Character coerceToCharacter(Object pValue,
 Logger pLogger)
                                   throws javax.servlet.jsp.el.ELException

Coerces a value to a Character

Throws:

javax.servlet.jsp.el.ELException

coerceToBoolean

public static Boolean coerceToBoolean(Object pValue,
 Logger pLogger)
                               throws javax.servlet.jsp.el.ELException

Coerces a value to a Boolean

Throws:

javax.servlet.jsp.el.ELException

coerceToObject

public static Object coerceToObject(Object pValue,
 Class pClass,
 Logger pLogger)
                             throws javax.servlet.jsp.el.ELException

Coerces a value to the specified Class that is not covered by any of the above cases

Throws:

javax.servlet.jsp.el.ELException

applyArithmeticOperator

public static Object applyArithmeticOperator(Object pLeft,
 Object pRight,
 ArithmeticOperator pOperator,
 Logger pLogger)
                                      throws javax.servlet.jsp.el.ELException

Performs all of the necessary type conversions, then calls on the appropriate operator.

Throws:

javax.servlet.jsp.el.ELException

applyRelationalOperator

public static Object applyRelationalOperator(Object pLeft,
 Object pRight,
 RelationalOperator pOperator,
 Logger pLogger)
                                      throws javax.servlet.jsp.el.ELException

Performs all of the necessary type conversions, then calls on the appropriate operator.

Throws:

javax.servlet.jsp.el.ELException

applyEqualityOperator

public static Object applyEqualityOperator(Object pLeft,
 Object pRight,
 EqualityOperator pOperator,
 Logger pLogger)
                                    throws javax.servlet.jsp.el.ELException

Performs all of the necessary type conversions, then calls on the appropriate operator.

Throws:

javax.servlet.jsp.el.ELException

isFloatingPointType

public static boolean isFloatingPointType(Object pObject)

Returns true if the given Object is of a floating point type

isFloatingPointType

public static boolean isFloatingPointType(Class pClass)

Returns true if the given class is of a floating point type

isFloatingPointString

public static boolean isFloatingPointString(Object pObject)

Returns true if the given string might contain a floating point number - i.e., it contains ".", "e", or "E"

isIntegerType

public static boolean isIntegerType(Object pObject)

Returns true if the given Object is of an integer type

isIntegerType

public static boolean isIntegerType(Class pClass)

Returns true if the given class is of an integer type

isBigInteger

public static boolean isBigInteger(Object pObject)

Returns true if the given object is BigInteger.

Parameters:

pObject - - Object to evaluate

Returns:

- true if the given object is BigInteger

isBigDecimal

public static boolean isBigDecimal(Object pObject)

Returns true if the given object is BigDecimal.

Parameters:

pObject - - Object to evaluate

Returns:

- true if the given object is BigDecimal