JavaEE Web API 8.0.1 · javax.el.MethodExpression

An Expression that refers to a method on an object.

The javax.el.ExpressionFactory#createMethodExpression 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 and invoke 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 javax.el.ELResolver#getValue 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.

Constructor Summary

Access	Constructor and Description
public	MethodExpression()

Method Summary

Modifier and Type	Method and Description
public abstract MethodInfo	Returns: an instance of `MethodInfo` containing information about the method the expression evaluated to. getMethodInfo(ELContext The context of this evaluation context) Evaluates the expression relative to the provided context, and returns information about the actual referenced method.
public abstract Object	Returns: the result of the method invocation (`null` if the method has a `void` return type). invoke(ELContext The context of this evaluation. context, Object[] The parameters to pass to the method, or `null` if no parameters. params) If a String literal is specified as the expression, returns the String literal coerced to the expected return type of the method signature.
public boolean	Returns: `true` if the MethodExpression was created with parameters, `false` otherwise. isParametersProvided() Return whether this MethodExpression was created with parameters.
public boolean	isParmetersProvided() Deprecated Use isParametersProvided instead.

Inherited from javax.el.Expression:: equals getExpressionString hashCode isLiteralText

Constructor Detail

MethodExpression	back to summary
public MethodExpression()

Method Detail

getMethodInfo back to summary

getMethodInfo	back to summary
public abstract MethodInfo getMethodInfo(ELContext context) Evaluates the expression relative to the provided context, and returns information about the actual referenced method. Parameters context:ELContext The context of this evaluation Returns:MethodInfo an instance of `MethodInfo` containing information about the method the expression evaluated to. Exceptions NullPointerException: if context is `null` PropertyNotFoundException: 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 MethodInfo getMethodInfo(ELContext context)

Evaluates the expression relative to the provided context, and returns information about the actual referenced method.

Parameters

context:ELContext: The context of this evaluation

Returns:MethodInfo

an instance of MethodInfo containing information about the method the expression evaluated to.

Exceptions

NullPointerException:: if context is null
PropertyNotFoundException:: 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.

invoke back to summary

invoke	back to summary
public 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. An `ELException` is thrown if `expectedReturnType` is void or if the coercion of the String literal to the `expectedReturnType` yields an error (see Section "1.18 Type Conversion" of the EL specification). If not a String literal, evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation. Any parameters passed to this method is ignored if isLiteralText() or isParmetersProvided() is true. Parameters context:ELContext The context of this evaluation. params:Object[] The parameters to pass to the method, or `null` if no parameters. Returns:Object the result of the method invocation (`null` if the method has a `void` return type). Exceptions NullPointerException: if context is `null` PropertyNotFoundException: 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 "1.18 Type Conversion"). 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 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. An ELException is thrown if expectedReturnType is void or if the coercion of the String literal to the expectedReturnType yields an error (see Section "1.18 Type Conversion" of the EL specification). If not a String literal, evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation. Any parameters passed to this method is ignored if isLiteralText() or isParmetersProvided() is true.

Parameters

context:ELContext: The context of this evaluation.
params:Object[]: The parameters to pass to the method, or null if no parameters.

Returns:Object

the result of the method invocation (null if the method has a void return type).

Exceptions

NullPointerException:

if context is null

PropertyNotFoundException:

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 "1.18 Type Conversion").
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.

isParametersProvided back to summary

isParametersProvided	back to summary
public boolean isParametersProvided() Return whether this MethodExpression was created with parameters. This method must return `true` if and only if parameters are specified in the EL, using the expr-a.expr-b(...) syntax. Returns:boolean `true` if the MethodExpression was created with parameters, `false` otherwise. Since EL 2.2

public boolean isParametersProvided()

Return whether this MethodExpression was created with parameters.

This method must return true if and only if parameters are specified in the EL, using the expr-a.expr-b(...) syntax.

Returns:boolean: true if the MethodExpression was created with parameters, false otherwise.
Since: EL 2.2

isParmetersProvided	back to summary
public boolean isParmetersProvided() Deprecated Use isParametersProvided instead. Annotations @Deprecated

isParmetersProvided

back to summary

public boolean isParmetersProvided()

Deprecated

Use isParametersProvided instead.

Annotations

@Deprecated

public abstract Class MethodExpression

Constructor Summary

Method Summary

Constructor Detail

Method Detail