org.zkoss.zel.impl.lang

Class ELSupport

java.lang.Object

org.zkoss.zel.impl.lang.ELSupport

Direct Known Subclasses:

SimpleNode

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_NULL_TO_NULL EL 2.2 by spec.
protected static boolean	COERCE_TO_ZERO

Constructor Summary

Constructors

Constructor and Description
ELSupport()

Method Summary

Methods

Modifier and Type	Method and Description
static Boolean	coerceToBoolean(Object obj, boolean primitive) Convert an object to Boolean.
static Date	coerceToDateTime(Object obj, Class type) Coerce an object to an instance of java.util.Date
static Enum<?>	coerceToEnum(Object obj, Class type)
protected static Number	coerceToNumber(Number number, Class<?> type)
static Number	coerceToNumber(Object obj, Class<?> type)
protected static Number	coerceToNumber(String val, Class<?> type)
static String	coerceToString(Object obj) Coerce an object to a string.
static Object	coerceToType(Object obj, Class<?> type)
protected static Object	coerceToTypeForSetValue(Object obj, Class<?> type)
static int	compare(Object obj0, Object obj1) Compare two objects, after coercing to the same type if appropriate.
static boolean	equals(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	isDateTimeType(Class<?> type)
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_NULL_TO_NULL

protected static final boolean COERCE_NULL_TO_NULL

EL 2.2 by spec. should coerce "null" value to 0 number, 0 character, "" String, false boolean. This spec. makes it impossible to store null state into java lang object when doing setValue() and can set unexpected coerced value into java lang object. So we provide a system property "org.zkoss.zel.impl.parser.COERCE_NULL_TO_NULL" to switch this behavior when doing setValue(). By default we will set org.zkoss.zel.impl.parser.COERCE_NULL_TO_NULL to true to allow set null value though this is not compliant to the EL 2.2 spec. Shall you need to make ZEL to follow EL 2.2 spec. when doing setValue, please set "org.zkoss.zel.impl.parser.COERCE_NULL_TO_NULL" system property to false. Ref. https://services.brics.dk/java/courseadmin/SWP2011/documents/getDocument/expression_language-2_2-mrel-spec.pdf?d=41976

COERCE_TO_ZERO

protected static final boolean COERCE_TO_ZERO

Constructor Detail

ELSupport

public ELSupport()

Method Detail

compare

public static final int compare(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(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:

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(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:

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(Object obj,
                   Class type)

coerceToBoolean

public static final Boolean coerceToBoolean(Object obj,
                      boolean primitive)
                                     throws ELException

Convert an object to Boolean. Null and empty string are false.

Parameters:

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(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(Object obj)

Coerce an object to a string.

Parameters:

obj - the object to convert

Returns:

the String value of the object

coerceToTypeForSetValue

protected static final Object coerceToTypeForSetValue(Object obj,
                             Class<?> type)
                                               throws ELException

Throws:

ELException

coerceToType

public static final Object coerceToType(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)

isDateTimeType

public static final boolean isDateTimeType(Class<?> type)

coerceToDateTime

public static final Date coerceToDateTime(Object obj,
                    Class type)
                                   throws ELException

Coerce an object to an instance of java.util.Date

Parameters:

obj - the object to be converted; must be an instance of java.util.Date or a number which represents the millisecond since "the epoch" base time, namely January 1, 1970, 00:00:00 GMT.

type - the class type which shall be a kind of java.util.Date; e.g. java.sql.Date, java.sql.Time, java.sql.Timestamp

Returns:

the instance as requested by the specified type

Throws:

ELException