public abstract class MethodExpression extends Expression
ExpressionFactory.createMethodExpression(ELContext, String, Class, Class[])
method can be used to parse an expression string and
return a concrete instance of MethodExpression 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 getMethodInfo(ELContext)
and invoke(ELContext, Object[])
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 two
methods, the ELResolver.getValue(ELContext, Object, Object)
method is used to resolve all properties up to but excluding the last one. This provides the base object on which the method
appears. If the base object is null, a PropertyNotFoundException must be thrown. At the last resolution, the final property is then coerced to a String, which provides the name of the method to be
found. A method matching the name and expected parameters provided at parse time is found and it is either queried or invoked (depending on the method called on this MethodExpression). See the
notes about comparison, serialization and immutability in the Expression
javadocs.ELResolver
,
Expression
,
ExpressionFactory
,
Serialized FormConstructor and Description |
---|
MethodExpression() |
Modifier and Type | Method and Description |
---|---|
abstract MethodInfo |
getMethodInfo(ELContext context)
Evaluates the expression relative to the provided context, and returns information about the actual referenced method.
|
abstract Object |
invoke(ELContext context,
Object[] params)
If a String literal is specified as the expression, returns the String literal coerced to the expected return type of the method signature.
|
boolean |
isParmetersProvided()
Return whether this MethodExpression was created with parameters.
|
equals, getExpressionString, hashCode, isLiteralText
public abstract MethodInfo getMethodInfo(ELContext context)
context
- The context of this evaluation.NullPointerException
- if context is nullPropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.MethodNotFoundException
- if no suitable method can be found.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 abstract Object invoke(ELContext context, Object[] params)
context
- The context of this evaluation.params
- The parameters to pass to the method, or null if no parameters.NullPointerException
- if context is nullPropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.MethodNotFoundException
- if no suitable method can be found.ELException
- if a String literal is specified and expectedReturnType of the MethodExpression is void or if the coercion of the String literal to the expectedReturnType yields an error (see Section
"1.16 Type Conversion").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. If the
exception thrown is an InvocationTargetException, extract its cause and pass it to the ELException constructor.public boolean isParmetersProvided()
This method must return true
if and only if parameters are specified in the EL, using the expr-a.expr-b(...) syntax.
true
if the MethodExpression was created with parameters, false
otherwise.Copyright © 2015 Alfresco. All rights reserved.