public class ELProcessor extends Object
Provides an API for using EL in a stand-alone environment.
This class provides a direct and simple interface for
ValueExpression
to a EL variable.This API is not a replacement for the APIs in EL 2.2. Containers that maintains EL environments can continue to do so, without using this API.
For EL users who want to manipulate EL environments, like adding custom
ELResolver
s, ELManager
can be used.
Since it maintains the state of the EL environments,
ELProcessor
is not thread safe. In the simplest case,
an instance can be created and destroyed before and after evaluating
EL expressions. A more general usage is to use an instance of
ELProcessor
for a session, so that the user can configure the
EL evaluation environment for that session.
A note about the EL expressions strings used in the class. The strings
allowed in the methods getValue(java.lang.String, java.lang.Class<?>)
,
setValue(java.lang.String, java.lang.Object)
, and setVariable(java.lang.String, java.lang.String)
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).
ELProcessor elp = new ELProcessor(); elp.defineBean("employee", new Employee("Charlie Brown")); String name = elp.eval("employee.name");
Constructor and Description |
---|
ELProcessor() |
Modifier and Type | Method and Description |
---|---|
void |
defineBean(String name,
Object bean)
Define a bean in a local bean repository, hiding other beans of the
same name.
|
void |
defineFunction(String prefix,
String function,
Method method)
Define an EL function in the local function mapper.
|
void |
defineFunction(String prefix,
String function,
String className,
String method)
Define an EL function in the local function mapper.
|
Object |
eval(String expression)
Evaluates an EL expression.
|
ELManager |
getELManager()
Return the ELManager used for EL processing.
|
Object |
getValue(String expression,
Class<?> expectedType)
Evaluates an EL expression, and coerces the result to the specified type.
|
void |
setValue(String expression,
Object value)
Sets an expression with a new value.
|
void |
setVariable(String var,
String expression)
Assign an EL expression to an EL variable.
|
public ELManager getELManager()
public Object eval(String expression)
expression
- The EL expression to be evaluated.public Object getValue(String expression, Class<?> expectedType)
expression
- The EL expression to be evaluated.expectedType
- Specifies the type that the resultant evaluation
will be coerced to.public void setValue(String expression, Object value)
expression
- The target expressionvalue
- The new value to set.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.public void setVariable(String var, String expression)
null
, the variable will be removed.var
- The name of the variable.expression
- The EL expression to be assigned to the variable.public void defineFunction(String prefix, String function, String className, String method) throws ClassNotFoundException, NoSuchMethodException
prefix
- The namespace for the function or "" for no namesapce.function
- The name of the function.
If empty (""), the method name is used as the function name.className
- The full Java class name that implements the function.method
- 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.NullPointerException
- if any of the arguments is null.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.public void defineFunction(String prefix, String function, Method method) throws NoSuchMethodException
prefix
- The namespace for the function or "" for no namesapce.function
- The name of the function.
If empty (""), the method name is used as the function name.method
- The java.lang.reflect.Method
instance of
the method that implements the function.NullPointerException
- if any of the arguments is null.NoSuchMethodException
- if the method is not a static methodCopyright © 1996-2017, Oracle and/or its affiliates. All Rights Reserved. Use is subject to license terms.