Top Description Fields Constructors Methods
jakarta.el

public Class ELProcessor

extends Object
Class Inheritance
Imports
java.lang.reflect.Array, .Method, .Modifier
Provides an API for using Jakarta Expression Language in a stand-alone environment.

This class provides a direct and simple interface for

This API is not a replacement for the APIs in Jakarta Expression Language 2.2. Containers that maintain Jakarta Expression Language environments can continue to do so, without using this API.

For Jakarta Expression Language users who want to manipulate Jakarta Expression Language environments, like adding custom ELResolvers, ELManager can be used.

Scope and Life Cycle

Since it maintains the state of the Jakarta Expression Language environments, ELProcessor is not thread safe. In the simplest case, an instance can be created and destroyed before and after evaluating Jakarta Expression Language expressions. A more general usage is to use an instance of ELProcessor for a session, so that the user can configure the Jakarta Expression Language evaluation environment for that session.

Automatic Bracketing of Expressions

A note about the Jakarta Expression Language expressions strings used in the class. The strings allowed in the methods ELProcessor#getValue, ELProcessor#setValue, and ELProcessor#setVariable are limited to non-composite expressions, i.e. expressions of the form ${...} or #{...} only. Also, it is not necessary (in fact not allowed) to bracket the expression strings with ${ or #{ and } in these methods: they will be automatically bracketed. This reduces the visual cluster, without any lost of functionalities (thanks to the addition of the concatenation operator).

Example

The following code snippet illustrates the use of ELProcessor to define a bean and evaluate its property. 
ELProcessor elp = new ELProcessor();
elp.defineBean("employee", new Employee("Charlie Brown"));
String name = elp.eval("employee.name");
Since
Jakarta Expression Language 3.0

Field Summary

Modifier and TypeField and Description
private ELManager
elManager

private ExpressionFactory
factory

Constructor Summary

AccessConstructor and Description
public
ELProcessor()

Method Summary

Modifier and TypeMethod and Description
private String
bracket(String expression)

public void
defineBean(String
The name of the bean
name, Object
The bean instance to be defined. If null, the name will be removed from the local bean repository.
bean)

Define a bean in a local bean repository, hiding other beans of the same name.

public void
defineFunction(String
The namespace for the function or "" for no namesapce.
prefix, String
The name of the function. If empty (""), the method name is used as the function name.
function, String
The full Java class name that implements the function.
className, String
The name (specified without parenthesis) or the signature (as in the Java Language Spec) of the static method that implements the function. If the name (e.g. "sum") is given, the first declared method in class that matches the name is selected. If the signature (e.g. "int sum(int, int)" ) is given, then the declared method with the signature is selected.
method)

Define a Jakarta Expression Language function in the local function mapper.

public void
defineFunction(String
The namespace for the function or "" for no namesapce.
prefix, String
The name of the function. If empty (""), the method name is used as the function name.
function, Method
The java.lang.reflect.Method instance of the method that implements the function.
method)

Define a Jakarta Expression Language function in the local function mapper.

public <T> T

Returns:

The result of the expression evaluation.
eval(String
The Jakarta Expression Language expression to be evaluated.
expression)

Evaluates an Jakarta Expression Language expression.

public ELManager

Returns:

The ELManager used for Jakarta Expression Language processing.
getELManager()

Return the ELManager used for Jakarta Expression Language processing.

public <T> T

Returns:

The result of the expression evaluation.
getValue(String
The Jakarta Expression Language expression to be evaluated.
expression, Class<T>
Specifies the type that the resultant evaluation will be coerced to.
expectedType)

Evaluates an Jakarta Expression Language expression, and coerces the result to the specified type.

public void
setValue(String
The target expression
expression, Object
The new value to set.
value)

Sets an expression with a new value.

public void
setVariable(String
The name of the variable.
var, String
The Jakarta Expression Language expression to be assigned to the variable.
expression)

Assign a Jakarta Expression Language expression to a Jakarta Expression Language variable.

private static Class<?>
toClass(String type, ClassLoader loader)

Return the Class object associated with the class or interface with the given name.

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Field Detail

elManagerback to summary
private ELManager elManager
factoryback to summary
private ExpressionFactory factory

Constructor Detail

ELProcessorback to summary
public ELProcessor()

Method Detail

bracketback to summary
private String bracket(String expression)
defineBeanback to summary
public void defineBean(String name, Object bean)

Define a bean in a local bean repository, hiding other beans of the same name.

Parameters
name:String

The name of the bean

bean:Object

The bean instance to be defined. If null, the name will be removed from the local bean repository.

defineFunctionback to summary
public void defineFunction(String prefix, String function, String className, String method) throws ClassNotFoundException, NoSuchMethodException

Define a Jakarta Expression Language function in the local function mapper.

Parameters
prefix:String

The namespace for the function or "" for no namesapce.

function:String

The name of the function. If empty (""), the method name is used as the function name.

className:String

The full Java class name that implements the function.

method:String

The name (specified without parenthesis) or the signature (as in the Java Language Spec) of the static method that implements the function. If the name (e.g. "sum") is given, the first declared method in class that matches the name is selected. If the signature (e.g. "int sum(int, int)" ) is given, then the declared method with the signature is selected.

Exceptions
ClassNotFoundException:
if the specified class does not exists.
NoSuchMethodException:
if the method (with or without the signature) is not a declared method of the class, or if the method signature is not valid, or if the method is not a static method.
NullPointerException:
if any of the arguments is null.
defineFunctionback to summary
public void defineFunction(String prefix, String function, Method method) throws NoSuchMethodException

Define a Jakarta Expression Language function in the local function mapper.

Parameters
prefix:String

The namespace for the function or "" for no namesapce.

function:String

The name of the function. If empty (""), the method name is used as the function name.

method:Method

The java.lang.reflect.Method instance of the method that implements the function.

Exceptions
NoSuchMethodException:
if the method is not a static method
NullPointerException:
if any of the arguments is null.
evalback to summary
public <T> T eval(String expression)

Evaluates an Jakarta Expression Language expression.

Parameters
expression:String

The Jakarta Expression Language expression to be evaluated.

Returns:T

The result of the expression evaluation.

getELManagerback to summary
public ELManager getELManager()

Return the ELManager used for Jakarta Expression Language processing.

Returns:ELManager

The ELManager used for Jakarta Expression Language processing.

getValueback to summary
public <T> T getValue(String expression, Class<T> expectedType)

Evaluates an Jakarta Expression Language expression, and coerces the result to the specified type.

Parameters
expression:String

The Jakarta Expression Language expression to be evaluated.

expectedType:Class<T>

Specifies the type that the resultant evaluation will be coerced to.

Returns:T

The result of the expression evaluation.

setValueback to summary
public void setValue(String expression, Object value)

Sets an expression with a new value. The target expression is evaluated, up to the last property resolution, and the resultant (base, property) pair is set to the provided value.

Parameters
expression:String

The target expression

value:Object

The new value to set.

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.
setVariableback to summary
public void setVariable(String var, String expression)

Assign a Jakarta Expression Language expression to a Jakarta Expression Language variable. The expression is parsed, but not evaluated, and the parsed expression is mapped to the Jakarta Expression Language variable in the local variable map. Any previously assigned expression to the same variable will be replaced. If the expression is null, the variable will be removed.

Parameters
var:String

The name of the variable.

expression:String

The Jakarta Expression Language expression to be assigned to the variable.

toClassback to summary
private static Class<?> toClass(String type, ClassLoader loader) throws ClassNotFoundException

Return the Class object associated with the class or interface with the given name.