public final class MethodExpressionImpl extends javax.el.MethodExpression implements Externalizable
Expression
that refers to a method on an object.
The
ExpressionFactory.createMethodExpression(javax.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(javax.el.ELContext)
and invoke(javax.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(javax.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.
- Version:
- $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: tcfujii $
- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
ELResolver
,
Expression
,
ExpressionFactory
,
MethodExpression
,
Serialized Form
-
-
Constructor Summary
Constructors
Constructor and Description
MethodExpressionImpl()
MethodExpressionImpl(String expr,
Node node,
javax.el.FunctionMapper fnMapper,
javax.el.VariableMapper varMapper,
Class expectedType,
Class[] paramTypes)
-
Method Summary
All Methods Instance Methods Concrete Methods
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.
javax.el.MethodInfo
getMethodInfo(javax.el.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(javax.el.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()
void
readExternal(ObjectInput in)
void
writeExternal(ObjectOutput out)
-
-
Method Detail
-
equals
public boolean equals(Object obj)
Determines whether the specified object is equal to this
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.
- Specified by:
equals
in class javax.el.Expression
- Parameters:
obj
- the Object
to test for equality.
- Returns:
true
if obj
equals this
Expression
; false
otherwise.
- See Also:
Hashtable
,
Object.equals(java.lang.Object)
-
getExpressionString
public String getExpressionString()
Returns the original String used to create this 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
.
- Specified by:
getExpressionString
in class javax.el.Expression
- Returns:
- The original expression String.
- See Also:
Expression.getExpressionString()
-
getMethodInfo
public javax.el.MethodInfo getMethodInfo(javax.el.ELContext context)
throws javax.el.ELException
Evaluates the expression relative to the provided context, and returns
information about the actual referenced method.
- Specified by:
getMethodInfo
in class javax.el.MethodExpression
- Parameters:
context
- The context of this evaluation
- Returns:
- an instance of
MethodInfo
containing information
about the method the expression evaluated to.
- Throws:
NullPointerException
- if context is null
or the base object is
null
on the last resolution.
javax.el.PropertyNotFoundException
- if one of the property resolutions failed because a specified
variable or property does not exist or is not readable.
javax.el.MethodNotFoundException
- if no suitable method can be found.
javax.el.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.
- See Also:
MethodExpression.getMethodInfo(javax.el.ELContext)
-
hashCode
public int hashCode()
Returns the hash code for this 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.
- Specified by:
hashCode
in class javax.el.Expression
- Returns:
- The hash code for this
Expression
.
- See Also:
equals(java.lang.Object)
,
Hashtable
,
Object.hashCode()
-
invoke
public Object invoke(javax.el.ELContext context,
Object[] params)
throws javax.el.ELException
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.
- Specified by:
invoke
in class javax.el.MethodExpression
- Parameters:
context
- The context of this evaluation.
params
- The parameters to pass to the method, or null
if no parameters.
- Returns:
- the result of the method invocation (
null
if the
method has a void
return type).
- Throws:
NullPointerException
- if context is null
or the base object is
null
on the last resolution.
javax.el.PropertyNotFoundException
- if one of the property resolutions failed because a specified
variable or property does not exist or is not readable.
javax.el.MethodNotFoundException
- if no suitable method can be found.
javax.el.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.
- See Also:
MethodExpression.invoke(javax.el.ELContext,
java.lang.Object[])
-
readExternal
public void readExternal(ObjectInput in)
throws IOException,
ClassNotFoundException
- Specified by:
readExternal
in interface Externalizable
- Throws:
IOException
ClassNotFoundException
-
writeExternal
public void writeExternal(ObjectOutput out)
throws IOException
- Specified by:
writeExternal
in interface Externalizable
- Throws:
IOException
-
isLiteralText
public boolean isLiteralText()
- Specified by:
isLiteralText
in class javax.el.Expression
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