public final class MethodExpressionImpl extends MethodExpression implements Externalizable
Expression
that refers to a method on an object.
The ExpressionFactory.createMethodExpression(jakarta.el.ELContext, java.lang.String, java.lang.Class<?>, java.lang.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(jakarta.el.ELContext)
and invoke(jakarta.el.ELContext, java.lang.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(jakarta.el.ELContext, java.lang.Object, java.lang.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
NullPointerException
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
,
MethodExpression
,
Serialized FormConstructor and Description |
---|
MethodExpressionImpl() |
MethodExpressionImpl(String expr,
Node node,
FunctionMapper fnMapper,
VariableMapper varMapper,
Class<?> expectedType,
Class<?>[] paramTypes) |
Modifier and Type | Method and Description |
---|---|
boolean |
equals(Object obj)
Determines whether the specified object is equal to this
Expression . |
String |
getExpressionString()
Returns the original String used to create this
Expression , unmodified. |
MethodInfo |
getMethodInfo(ELContext context)
Evaluates the expression relative to the provided context, and returns information about the actual referenced
method.
|
int |
hashCode()
Returns the hash code for this
Expression . |
Object |
invoke(ELContext context,
Object[] params)
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.
|
boolean |
isLiteralText()
Returns whether this expression was created from only literal text.
|
boolean |
isParametersProvided()
Return whether this MethodExpression was created with parameters.
|
void |
readExternal(ObjectInput in) |
void |
writeExternal(ObjectOutput out) |
isParmetersProvided
public MethodExpressionImpl()
public MethodExpressionImpl(String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType, Class<?>[] paramTypes)
expr
- the expressionnode
- the nodefnMapper
- the function mappervarMapper
- the variable mapperexpectedType
- expected return type of methodparamTypes
- the method parameterspublic boolean equals(Object obj)
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.
equals
in class Expression
obj
- the Object
to test for equality.true
if obj
equals this Expression
; false
otherwise.Hashtable
,
Object.equals(java.lang.Object)
public String getExpressionString()
Expression
, unmodified.
This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed).
This method does not provide sufficient information to re-create an expression. Two different expressions can have
exactly the same expression string but different function mappings. Serialization should be used to save and restore
the state of an Expression
.
getExpressionString
in class Expression
Expression.getExpressionString()
public MethodInfo getMethodInfo(ELContext context) throws PropertyNotFoundException, MethodNotFoundException, ELException
getMethodInfo
in class MethodExpression
context
- The context of this evaluationMethodInfo
containing information about the method the expression evaluated to.NullPointerException
- if context is null
or the base object is null
on the last
resolution.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.MethodExpression.getMethodInfo(ELContext)
public int hashCode()
Expression
.
See the note in the equals(java.lang.Object)
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.
hashCode
in class Expression
Expression
.equals(java.lang.Object)
,
Hashtable
,
Object.hashCode()
public Object invoke(ELContext context, Object[] params) throws PropertyNotFoundException, MethodNotFoundException, ELException
invoke
in class MethodExpression
context
- The context of this evaluation.params
- The parameters to pass to the method, or null
if no parameters.null
if the method has a void
return type).NullPointerException
- if context is null
or the base object is null
on the last
resolution.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. If the exception thrown is an
InvocationTargetException
, extract its cause
and pass it to the ELException
constructor.MethodExpression.invoke(ELContext, java.lang.Object[])
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
readExternal
in interface Externalizable
IOException
ClassNotFoundException
public void writeExternal(ObjectOutput out) throws IOException
writeExternal
in interface Externalizable
IOException
public boolean isLiteralText()
Expression
This method must return true
if and only if the expression string this expression was created from
contained no unescaped Jakarta Expression Language delimeters (${...}
or #{...}
).
isLiteralText
in class Expression
true
if this expression was created from only literal text; false
otherwise.public boolean isParametersProvided()
MethodExpression
This method must return true
if and only if parameters are specified in the EL, using the
expr-a.expr-b(...) syntax.
isParametersProvided
in class MethodExpression
true
if the MethodExpression was created with parameters, false
otherwise.Copyright © 2023. All rights reserved.