Jakarta Expression Language 3.0 Implementation 3.0.4 · com.sun.el.ValueExpressionImpl

An Expression that can get or set a value.

In previous incarnations of this API, expressions could only be read. ValueExpression objects can now be used both to retrieve a value and to set a value. Expressions that can have a value set on them are referred to as l-value expressions. Those that cannot are referred to as r-value expressions. Not all r-value expressions can be used as l-value expressions (e.g. "${1+1}" or "${firstName} ${lastName}"). See the EL Specification for details. Expressions that cannot be used as l-values must always return true from isReadOnly().

The ExpressionFactory#createValueExpression method can be used to parse an expression string and return a concrete instance of ValueExpression that encapsulates the parsed expression. The FunctionMapper is used at parse time, not evaluation time, so one is not needed to evaluate an expression using this class. However, the ELContext is needed at evaluation time.

The getValue, setValue, isReadOnly and getType methods will evaluate the expression each time they are called. The ELResolver in the ELContext is used to resolve the top-level variables and to determine the behavior of the . and [] operators. For any of the four methods, the ELResolver#getValue method is used to resolve all properties up to but excluding the last one. This provides the base object. At the last resolution, the ValueExpression will call the corresponding ELResolver#getValue, ELResolver#setValue, ELResolver#isReadOnly or ELResolver#getType method, depending on which was called on the ValueExpression.

See the notes about comparison, serialization and immutability in the Expression javadocs.

Field Summary

Modifier and Type	Field and Description
private Class<?>	expectedType
private String	expr
private FunctionMapper	fnMapper
private transient Node	node
private VariableMapper	varMapper

Constructor Summary

Access	Constructor and Description
public	ValueExpressionImpl()
public	ValueExpressionImpl(String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType)

Method Summary

Modifier and Type	Method and Description
public boolean	equals(Object the `Object` to test for equality. obj) Implements abstract javax.el.Expression.equals. Determines whether the specified object is equal to this `Expression`.
public Class<?>	getExpectedType() Implements abstract javax.el.ValueExpression.getExpectedType. Returns the type the result of the expression will be coerced to after evaluation.
public String	Returns: the `expectedType` passed to the `ExpressionFactory.createValueExpression` method that created this `ValueExpression`. getExpressionString() Implements abstract javax.el.Expression.getExpressionString. Returns the type the result of the expression will be coerced to after evaluation.
private Node	Returns: The Node for the expression getNode()
public Class<?>	getType(ELContext The context of this evaluation. context) Implements abstract javax.el.ValueExpression.getType. Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as the `value` parameter in a future call to the `setValue` method.
public Object	getValue(ELContext The context of this evaluation. context) Implements abstract javax.el.ValueExpression.getValue. Evaluates the expression relative to the provided context, and returns the resulting value.
public ValueReference	getValueReference(ELContext the context of this evaluation context) Overrides javax.el.ValueExpression.getValueReference. Returns a `ValueReference` for this expression instance.
public int	hashCode() Implements abstract javax.el.Expression.hashCode. Returns the hash code for this `Expression`.
public boolean	isLiteralText() Implements abstract javax.el.Expression.isLiteralText. Returns whether this expression was created from only literal text.
public boolean	isReadOnly(ELContext The context of this evaluation. context) Implements abstract javax.el.ValueExpression.isReadOnly. Evaluates the expression relative to the provided context, and returns `true` if a call to `setValue` will always fail.
public void	readExternal(ObjectInput the stream to read data from in order to restore the object in) Implements java.io.Externalizable.readExternal. The object implements the readExternal method to restore its contents by calling the methods of DataInput for primitive types and readObject for objects, strings and arrays.
public void	setValue(ELContext The context of this evaluation. context, Object The new value to be set. value) Implements abstract javax.el.ValueExpression.setValue. Evaluates the expression relative to the provided context, and sets the result to the provided value.
public String	toString() Overrides java.lang.Object.toString. Returns a string representation of the object.
public void	writeExternal(ObjectOutput the stream to write the object to out) Implements java.io.Externalizable.writeExternal. The object implements the writeExternal method to save its contents by calling the methods of DataOutput for its primitive values or calling the writeObject method of ObjectOutput for objects, strings, and arrays.

Field Detail

expectedType	back to summary
private Class<?> expectedType

expr	back to summary
private String expr

fnMapper	back to summary
private FunctionMapper fnMapper

node	back to summary
private transient Node node

varMapper	back to summary
private VariableMapper varMapper

Constructor Detail

ValueExpressionImpl	back to summary
public ValueExpressionImpl()

ValueExpressionImpl	back to summary
public ValueExpressionImpl(String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType)

Method Detail

equals back to summary

equals	back to summary
public boolean equals(Object obj) Implements abstract javax.el.Expression.equals. Doc from javax.el.Expression.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. Annotations @Override

public boolean equals(Object obj)

Implements abstract javax.el.Expression.equals.

Doc from javax.el.Expression.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.

Annotations

@Override

getExpectedType back to summary

getExpectedType	back to summary
public Class<?> getExpectedType() Implements abstract javax.el.ValueExpression.getExpectedType. Doc from javax.el.ValueExpression.getExpectedType. Returns the type the result of the expression will be coerced to after evaluation. Returns:Class<?> the `expectedType` passed to the `ExpressionFactory.createValueExpression` method that created this `ValueExpression`. Annotations @Override

public Class<?> getExpectedType()

Implements abstract javax.el.ValueExpression.getExpectedType.

Doc from javax.el.ValueExpression.getExpectedType.

Returns the type the result of the expression will be coerced to after evaluation.

Returns:Class<?>

the expectedType passed to the ExpressionFactory.createValueExpression method that created this ValueExpression.

Annotations

@Override

getExpressionString back to summary

getExpressionString	back to summary
public String getExpressionString() Implements abstract javax.el.Expression.getExpressionString. Returns the type the result of the expression will be coerced to after evaluation. Returns:String the `expectedType` passed to the `ExpressionFactory.createValueExpression` method that created this `ValueExpression`. Annotations @Override See Also `javax.el.Expression#getExpressionString()`

public String getExpressionString()

Implements abstract javax.el.Expression.getExpressionString.

Returns the type the result of the expression will be coerced to after evaluation.

Returns:String

the expectedType passed to the ExpressionFactory.createValueExpression method that created this ValueExpression.

Annotations

@Override

getNode	back to summary
private Node getNode() throws ELException Returns:Node The Node for the expression

getType back to summary

getType	back to summary
public Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException Implements abstract javax.el.ValueExpression.getType. Doc from javax.el.ValueExpression.getType. Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as the `value` parameter in a future call to the `setValue` method. This is not always the same as `getValue().getClass()`. For example, in the case of an expression that references an array element, the `getType` method will return the element type of the array, which might be a superclass of the type of the actual element that is currently in the specified array element. Parameters context:ELContext The context of this evaluation. Returns:Class<?> the most general acceptable type; otherwise undefined. Annotations @Override Exceptions PropertyNotFoundException: if one of the property resolutions failed because a specified variable or property does not exist or is not readable. ELException: if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.

public Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException

Implements abstract javax.el.ValueExpression.getType.

Doc from javax.el.ValueExpression.getType.

Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as the value parameter in a future call to the setValue method.

This is not always the same as getValue().getClass(). For example, in the case of an expression that references an array element, the getType method will return the element type of the array, which might be a superclass of the type of the actual element that is currently in the specified array element.

Parameters

context:ELContext: The context of this evaluation.

Returns:Class<?>

the most general acceptable type; otherwise undefined.

Annotations

@Override

Exceptions

PropertyNotFoundException:: if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
ELException:: if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.

getValue back to summary

getValue	back to summary
public Object getValue(ELContext context) throws PropertyNotFoundException, ELException Implements abstract javax.el.ValueExpression.getValue. Doc from javax.el.ValueExpression.getValue. Evaluates the expression relative to the provided context, and returns the resulting value. The resulting value is automatically coerced to the type returned by `getExpectedType()`, which was provided to the `ExpressionFactory` when this expression was created. Parameters context:ELContext The context of this evaluation. Returns:Object The result of the expression evaluation. Annotations @Override Exceptions PropertyNotFoundException: if one of the property resolutions failed because a specified variable or property does not exist or is not readable. ELException: if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.

public Object getValue(ELContext context) throws PropertyNotFoundException, ELException

Implements abstract javax.el.ValueExpression.getValue.

Doc from javax.el.ValueExpression.getValue.

Evaluates the expression relative to the provided context, and returns the resulting value.

The resulting value is automatically coerced to the type returned by getExpectedType(), which was provided to the ExpressionFactory when this expression was created.

Parameters

context:ELContext: The context of this evaluation.

Returns:Object

The result of the expression evaluation.

Annotations

@Override

Exceptions

PropertyNotFoundException:: if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
ELException:: if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.

getValueReference back to summary

getValueReference	back to summary
public ValueReference getValueReference(ELContext context) throws PropertyNotFoundException, ELException Overrides javax.el.ValueExpression.getValueReference. Doc from javax.el.ValueExpression.getValueReference. Returns a `ValueReference` for this expression instance. Parameters context:ELContext the context of this evaluation Returns:ValueReference the `ValueReference` for this `ValueExpression`, or `null` if this `ValueExpression` is not a reference to a base (null or non-null) and a property. If the base is null, and the property is a EL variable, return the `ValueReference` for the `ValueExpression` associated with this EL variable. Annotations @Override

public ValueReference getValueReference(ELContext context) throws PropertyNotFoundException, ELException

Overrides javax.el.ValueExpression.getValueReference.

Doc from javax.el.ValueExpression.getValueReference.

Returns a ValueReference for this expression instance.

Parameters

context:ELContext: the context of this evaluation

Returns:ValueReference

the ValueReference for this ValueExpression, or null if this ValueExpression is not a reference to a base (null or non-null) and a property. If the base is null, and the property is a EL variable, return the ValueReference for the ValueExpression associated with this EL variable.

Annotations

@Override

hashCode back to summary

hashCode	back to summary
public int hashCode() Implements abstract javax.el.Expression.hashCode. Doc from javax.el.Expression.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`. Annotations @Override

public int hashCode()

Implements abstract javax.el.Expression.hashCode.

Doc from javax.el.Expression.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.

Annotations

@Override

isLiteralText back to summary

isLiteralText	back to summary
public boolean isLiteralText() Implements abstract javax.el.Expression.isLiteralText. Doc from javax.el.Expression.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. Annotations @Override

public boolean isLiteralText()

Implements abstract javax.el.Expression.isLiteralText.

Doc from javax.el.Expression.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.

Annotations

@Override

isReadOnly back to summary

isReadOnly	back to summary
public boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException Implements abstract javax.el.ValueExpression.isReadOnly. Doc from javax.el.ValueExpression.isReadOnly. Evaluates the expression relative to the provided context, and returns `true` if a call to `setValue` will always fail. Parameters context:ELContext The context of this evaluation. Returns:boolean `true` if the expression is read-only or `false` if not. Annotations @Override Exceptions PropertyNotFoundException: if one of the property resolutions failed because a specified variable or property does not exist or is not readable. ELException: if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available. * @throws NullPointerException if context is `null`

public boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException

Implements abstract javax.el.ValueExpression.isReadOnly.

Doc from javax.el.ValueExpression.isReadOnly.

Evaluates the expression relative to the provided context, and returns true if a call to setValue will always fail.

Parameters

context:ELContext: The context of this evaluation.

Returns:boolean

true if the expression is read-only or false if not.

Annotations

@Override

Exceptions

PropertyNotFoundException:: if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
ELException:: if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available. * @throws NullPointerException if context is null

readExternal	back to summary
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException Implements java.io.Externalizable.readExternal. Doc from java.io.Externalizable.readExternal. The object implements the readExternal method to restore its contents by calling the methods of DataInput for primitive types and readObject for objects, strings and arrays. The readExternal method must read the values in the same sequence and with the same types as were written by writeExternal. Parameters in:ObjectInput the stream to read data from in order to restore the object Annotations @Override Exceptions IOException: if I/O errors occur ClassNotFoundException: If the class for an object being restored cannot be found.

readExternal

back to summary

public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException

Implements java.io.Externalizable.readExternal.

Doc from java.io.Externalizable.readExternal.

The object implements the readExternal method to restore its contents by calling the methods of DataInput for primitive types and readObject for objects, strings and arrays. The readExternal method must read the values in the same sequence and with the same types as were written by writeExternal.

Parameters

in:ObjectInput: the stream to read data from in order to restore the object

Annotations

@Override

Exceptions

IOException:: if I/O errors occur
ClassNotFoundException:: If the class for an object being restored cannot be found.

setValue	back to summary
public void setValue(ELContext context, Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException Implements abstract javax.el.ValueExpression.setValue. Doc from javax.el.ValueExpression.setValue. Evaluates the expression relative to the provided context, and sets the result to the provided value. Parameters context:ELContext The context of this evaluation. value:Object The new value to be set. Annotations @Override Exceptions PropertyNotFoundException: if one of the property resolutions failed because a specified variable or property does not exist or is not readable. PropertyNotWritableException: if the final variable or property resolution failed because the specified variable or property is not writable. ELException: if an exception was thrown while attempting to set the property or variable. The thrown exception must be included as the cause property of this exception, if available.

setValue

back to summary

public void setValue(ELContext context, Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException

Implements abstract javax.el.ValueExpression.setValue.

Doc from javax.el.ValueExpression.setValue.

Evaluates the expression relative to the provided context, and sets the result to the provided value.

Parameters

context:ELContext: The context of this evaluation.
value:Object: The new value to be set.

Annotations

@Override

Exceptions

PropertyNotFoundException:: if one of the property resolutions failed because a specified variable or property does not exist or is not readable.
PropertyNotWritableException:: if the final variable or property resolution failed because the specified variable or property is not writable.
ELException:: if an exception was thrown while attempting to set the property or variable. The thrown exception must be included as the cause property of this exception, if available.

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Doc from java.lang.Object.toString. Returns a string representation of the object. Returns:String a string representation of the object. Annotations @Override

toString

back to summary

public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object.

Returns:String

a string representation of the object.

Annotations

@Override

writeExternal	back to summary
public void writeExternal(ObjectOutput out) throws IOException Implements java.io.Externalizable.writeExternal. Doc from java.io.Externalizable.writeExternal. The object implements the writeExternal method to save its contents by calling the methods of DataOutput for its primitive values or calling the writeObject method of ObjectOutput for objects, strings, and arrays. Parameters out:ObjectOutput the stream to write the object to Annotations @Override Exceptions IOException: Includes any I/O exceptions that may occur

writeExternal

back to summary

public void writeExternal(ObjectOutput out) throws IOException

Implements java.io.Externalizable.writeExternal.

Doc from java.io.Externalizable.writeExternal.

The object implements the writeExternal method to save its contents by calling the methods of DataOutput for its primitive values or calling the writeObject method of ObjectOutput for objects, strings, and arrays.

Parameters

out:ObjectOutput: the stream to write the object to

Annotations

@Override

Exceptions

IOException:: Includes any I/O exceptions that may occur

public final Class ValueExpressionImpl

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail