JavaEE Web API 8.0.1 · javax.el.Expression

Base class for the expression subclasses ValueExpression and MethodExpression, implementing characteristics common to both.

All expressions must implement the equals() and hashCode() methods so that two expressions can be compared for equality. They are redefined abstract in this class to force their implementation in subclasses.

All expressions must also be Serializable so that they can be saved and restored.

Expressions are also designed to be immutable so that only one instance needs to be created for any given expression String / FunctionMapper. This allows a container to pre-create expressions and not have to re-parse them each time they are evaluated.

Constructor Summary

Access	Constructor and Description
public	Expression()

Method Summary

Modifier and Type	Method and Description
public abstract boolean	Returns: `true` if `obj` equals this `Expression`; `false` otherwise. equals(Object the `Object` to test for equality. obj) Overrides java.lang.Object.equals. Determines whether the specified object is equal to this `Expression`.
public abstract String	Returns: The original expression String. getExpressionString() Returns the original String used to create this `Expression`, unmodified.
public abstract int	Returns: The hash code for this `Expression`. hashCode() Overrides java.lang.Object.hashCode. Returns the hash code for this `Expression`.
public abstract boolean	Returns: `true` if this expression was created from only literal text; `false` otherwise. isLiteralText() Returns whether this expression was created from only literal text.

Inherited from java.lang.Object:: clone finalize getClass notify notifyAll toString wait wait wait

Constructor Detail

Expression	back to summary
public Expression()

Method Detail

equals back to summary

equals	back to summary
public abstract boolean equals(Object obj) Overrides java.lang.Object.equals. Determines whether the specified object is equal to this `Expression`. The result is `true` if and only if the argument is not `null`, is an `Expression` object that is the of the same type (`ValueExpression` or `MethodExpression`), and has an identical parsed representation. Note that two expressions can be equal if their expression Strings are different. For example, `${fn1:foo()}` and `${fn2:foo()}` are equal if their corresponding `FunctionMapper`s mapped `fn1:foo` and `fn2:foo` to the same method. Parameters obj:Object the `Object` to test for equality. Returns:boolean `true` if `obj` equals this `Expression`; `false` otherwise. See Also `java.util.Hashtable`, `java.lang.Object#equals(java.lang.Object)`

public abstract boolean equals(Object obj)

Overrides java.lang.Object.equals.

Determines whether the specified object is equal to this Expression.

The result is true if and only if the argument is not null, is an Expression object that is the of the same type (ValueExpression or MethodExpression), and has an identical parsed representation.

Note that two expressions can be equal if their expression Strings are different. For example, ${fn1:foo()} and ${fn2:foo()} are equal if their corresponding FunctionMappers mapped fn1:foo and fn2:foo to the same method.

Parameters

obj:Object: the Object to test for equality.

Returns:boolean

true if obj equals this Expression; false otherwise.

getExpressionString back to summary

getExpressionString	back to summary
public abstract String getExpressionString() Returns the original String used to create this `Expression`, unmodified. This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed). This method does not provide sufficient information to re-create an expression. Two different expressions can have exactly the same expression string but different function mappings. Serialization should be used to save and restore the state of an `Expression`. Returns:String The original expression String.

public abstract String getExpressionString()

Returns the original String used to create this Expression, unmodified.

This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed).

This method does not provide sufficient information to re-create an expression. Two different expressions can have exactly the same expression string but different function mappings. Serialization should be used to save and restore the state of an Expression.

Returns:String: The original expression String.

hashCode back to summary

hashCode	back to summary
public abstract int hashCode() Overrides java.lang.Object.hashCode. Returns the hash code for this `Expression`. See the note in the `equals` method on how two expressions can be equal if their expression Strings are different. Recall that if two objects are equal according to the `equals(Object)` method, then calling the `hashCode` method on each of the two objects must produce the same integer result. Implementations must take special note and implement `hashCode` correctly. Returns:int The hash code for this `Expression`. See Also `equals`, `java.util.Hashtable`, `java.lang.Object#hashCode()`

public abstract int hashCode()

Overrides java.lang.Object.hashCode.

Returns the hash code for this Expression.

See the note in the equals method on how two expressions can be equal if their expression Strings are different. Recall that if two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result. Implementations must take special note and implement hashCode correctly.

Returns:int: The hash code for this Expression.
See Also: equals, java.util.Hashtable, java.lang.Object#hashCode()

isLiteralText back to summary

isLiteralText	back to summary
public abstract boolean isLiteralText() Returns whether this expression was created from only literal text. This method must return `true` if and only if the expression string this expression was created from contained no unescaped EL delimeters (`${...}` or `#{...}`). Returns:boolean `true` if this expression was created from only literal text; `false` otherwise.

public abstract boolean isLiteralText()

Returns whether this expression was created from only literal text.

This method must return true if and only if the expression string this expression was created from contained no unescaped EL delimeters (${...} or #{...}).

Returns:boolean: true if this expression was created from only literal text; false otherwise.

public abstract Class Expression

Constructor Summary

Method Summary

Constructor Detail

Method Detail