Class Coercions
- java.lang.Object
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- org.apache.taglibs.standard.lang.jstl.Coercions
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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 Float, Double, or String containing ".", "e", or "E" coerce both A and B to Double apply operator 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 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 Float, Double, or String containing ".", "e" or "E" coerce both to Double apply operator 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 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 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 {<,>,<=,>=,lt,gt,lte,gte} B if A==B if operator is >= or <= return true otherwise return false if A or B is null return false if A or B is Float or Double coerce both A and B to Double apply operator 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 Float or Double coerce both A and B to Double apply operator 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 primitive 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 with less precision than N coerce quietly A is Number with greater precision than N coerce quietly A is String 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: kchung $
- Author:
- Nathan Abramson - Art Technology Group
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Constructor Summary
Constructors Constructor Description Coercions()
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Method Summary
All Methods Static Methods Concrete Methods 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 Booleanstatic Character
coerceToCharacter(Object pValue, Logger pLogger)
Coerces a value to a Characterstatic 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 casesstatic Number
coerceToPrimitiveNumber(Object pValue, Class pClass, Logger pLogger)
Coerces a value to the given primitive number classstatic String
coerceToString(Object pValue, Logger pLogger)
Coerces the specified value to a Stringstatic 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 typestatic boolean
isFloatingPointType(Object pObject)
Returns true if the given Object is of a floating point typestatic boolean
isIntegerType(Class pClass)
Returns true if the given class is of an integer typestatic boolean
isIntegerType(Object pObject)
Returns true if the given Object is of an integer type
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Method Detail
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coerce
public static Object coerce(Object pValue, Class pClass, Logger pLogger) throws ELException
Coerces the given value to the specified class.- Throws:
ELException
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coerceToString
public static String coerceToString(Object pValue, Logger pLogger) throws ELException
Coerces the specified value to a String- Throws:
ELException
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coerceToPrimitiveNumber
public static Number coerceToPrimitiveNumber(Object pValue, Class pClass, Logger pLogger) throws ELException
Coerces a value to the given primitive number class- Throws:
ELException
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coerceToInteger
public static Integer coerceToInteger(Object pValue, Logger pLogger) throws ELException
Coerces a value to an Integer, returning null if the coercion isn't possible.- Throws:
ELException
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coerceToCharacter
public static Character coerceToCharacter(Object pValue, Logger pLogger) throws ELException
Coerces a value to a Character- Throws:
ELException
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coerceToBoolean
public static Boolean coerceToBoolean(Object pValue, Logger pLogger) throws ELException
Coerces a value to a Boolean- Throws:
ELException
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coerceToObject
public static Object coerceToObject(Object pValue, Class pClass, Logger pLogger) throws ELException
Coerces a value to the specified Class that is not covered by any of the above cases- Throws:
ELException
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applyArithmeticOperator
public static Object applyArithmeticOperator(Object pLeft, Object pRight, ArithmeticOperator pOperator, Logger pLogger) throws ELException
Performs all of the necessary type conversions, then calls on the appropriate operator.- Throws:
ELException
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applyRelationalOperator
public static Object applyRelationalOperator(Object pLeft, Object pRight, RelationalOperator pOperator, Logger pLogger) throws ELException
Performs all of the necessary type conversions, then calls on the appropriate operator.- Throws:
ELException
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applyEqualityOperator
public static Object applyEqualityOperator(Object pLeft, Object pRight, EqualityOperator pOperator, Logger pLogger) throws ELException
Performs all of the necessary type conversions, then calls on the appropriate operator.- Throws:
ELException
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isFloatingPointType
public static boolean isFloatingPointType(Object pObject)
Returns true if the given Object is of a floating point type
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isFloatingPointType
public static boolean isFloatingPointType(Class pClass)
Returns true if the given class is of a floating point type
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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"
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isIntegerType
public static boolean isIntegerType(Object pObject)
Returns true if the given Object is of an integer type
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isIntegerType
public static boolean isIntegerType(Class pClass)
Returns true if the given class is of an integer type
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