MethodExpressionImpl (Apache Tomcat 7.0.67 API Documentation)

java.lang.Object
- javax.el.Expression
- - javax.el.MethodExpression
  - - org.apache.el.MethodExpressionImpl

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable
```
public final class MethodExpressionImpl
extends MethodExpression
implements java.io.Externalizable
```
An 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.
Author: Jacob Hookom [jacob@hookom.net] See Also: ELResolver, Expression, ExpressionFactory, MethodExpression, Serialized Form










Constructor Summary

Constructors 

Constructor and Description


MethodExpressionImpl() 


MethodExpressionImpl(java.lang.String expr,
                    Node node,
                    FunctionMapper fnMapper,
                    VariableMapper varMapper,
                    java.lang.Class<?> expectedType,
                    java.lang.Class<?>[] paramTypes) 









Method Summary

Methods 

Modifier and Type
Method and Description


boolean
equals(java.lang.Object obj)
Determines whether the specified object is equal to this
 Expression.



java.lang.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.



java.lang.Object
invoke(ELContext context,
      java.lang.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() 


boolean
isParmetersProvided() 


void
readExternal(java.io.ObjectInput in) 


void
writeExternal(java.io.ObjectOutput out) 






Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait














Constructor Detail





MethodExpressionImpl
public MethodExpressionImpl()







MethodExpressionImpl
public MethodExpressionImpl(java.lang.String expr,
                    Node node,
                    FunctionMapper fnMapper,
                    VariableMapper varMapper,
                    java.lang.Class<?> expectedType,
                    java.lang.Class<?>[] paramTypes)
Parameters:
expr - 
node - 
fnMapper - 
expectedType - 
paramTypes - 









Method Detail





equals
public boolean equals(java.lang.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
 FunctionMappers mapped fn1:foo and
 fn2:foo to the same method.
 

Specified by:
equals in class 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 java.lang.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 Expression
Returns:
The original expression String.
See Also:
Expression.getExpressionString()







getMethodInfo
public MethodInfo getMethodInfo(ELContext context)
                         throws PropertyNotFoundException,
                                MethodNotFoundException,
                                ELException
Evaluates the expression relative to the provided context, and returns
 information about the actual referenced method.

Specified by:
getMethodInfo in class MethodExpression
Parameters:
context - The context of this evaluation
Returns:
an instance of MethodInfo containing information
         about the method the expression evaluated to.
Throws:
java.lang.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.
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 Expression
Returns:
The hash code for this Expression.
See Also:
equals(java.lang.Object), 
Hashtable, 
Object.hashCode()







invoke
public java.lang.Object invoke(ELContext context,
                      java.lang.Object[] params)
                        throws PropertyNotFoundException,
                               MethodNotFoundException,
                               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 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:
java.lang.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.
See Also:
MethodExpression.invoke(javax.el.ELContext,
      java.lang.Object[])







readExternal
public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException

Specified by:
readExternal in interface java.io.Externalizable
Throws:
java.io.IOException
java.lang.ClassNotFoundException







writeExternal
public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

Specified by:
writeExternal in interface java.io.Externalizable
Throws:
java.io.IOException







isLiteralText
public boolean isLiteralText()

Specified by:
isLiteralText in class Expression








isParmetersProvided
public boolean isParmetersProvided()

Overrides:
isParmetersProvided in class MethodExpression
Since:
  EL 2.2
 Note: The spelling mistake is deliberate.
 isParmetersProvided()  - Specification definition
 isParametersProvided() - Corrected spelling

Modifier and Type	Method and Description
`boolean`	`equals(java.lang.Object obj)` Determines whether the specified object is equal to this `Expression`.
`java.lang.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`.
`java.lang.Object`	`invoke(ELContext context, java.lang.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()`
`boolean`	`isParmetersProvided()`
`void`	`readExternal(java.io.ObjectInput in)`
`void`	`writeExternal(java.io.ObjectOutput out)`

Class MethodExpressionImpl

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

MethodExpressionImpl

MethodExpressionImpl

Method Detail

equals

getExpressionString

getMethodInfo

hashCode

invoke

readExternal

writeExternal

isLiteralText

isParmetersProvided