# Class FunctionMapperImpl

java.lang.Object
jakarta.el.FunctionMapper
org.apache.el.lang.FunctionMapperImpl

All Implemented Interfaces:
  `Externalizable, Serializable`

public class FunctionMapperImpl extends FunctionMapper implements Externalizable
Thread-safe implementation of FunctionMapper that supports externalization.

See Also:
  - Serialized Form

## Nested Class Summary

Nested Classes
Modifier and Type
Class
Description
`static class`
`FunctionMapperImpl.Function`
Represents a mapped EL function with serialization support.

## Field Summary

Fields
Modifier and Type
Field
Description
`protected ConcurrentMap<String, FunctionMapperImpl.Function>`
`functions`
Map of function keys to their Function instances.

## Constructor Summary

Constructors
Constructor
Description
`FunctionMapperImpl()`
Creates a new empty function mapper.

## Method Summary

Modifier and Type
Method
Description
`void`
`mapFunction(String prefix, String localName, Method m)`
Map a method to a function name.
`void`
`readExternal(ObjectInput in)`
`Method`
`resolveFunction(String prefix, String localName)`
Resolves a function reference to its corresponding static `Method`.
`void`
`writeExternal(ObjectOutput out)`

### Methods inherited from class Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Field Details

### functions

protected ConcurrentMap<String, FunctionMapperImpl.Function> functions
Map of function keys to their Function instances.

## Constructor Details

### FunctionMapperImpl

public FunctionMapperImpl()
Creates a new empty function mapper.

## Method Details

### resolveFunction

public Method resolveFunction(String prefix, String localName)
Description copied from class: `jakarta.el.FunctionMapper`
Resolves a function reference to its corresponding static `Method`.

Specified by:
  `resolveFunction` in class `FunctionMapper`
Parameters:
  `prefix` - the namespace prefix of the function
  `localName` - the local name of the function
Returns:
  the `Method` object for the resolved function, or `null` if not found

### mapFunction

public void mapFunction(String prefix, String localName, Method m)
Description copied from class: `jakarta.el.FunctionMapper`
Map a method to a function name.

Overrides:
  `mapFunction` in class `FunctionMapper`
Parameters:
  `prefix` - Function prefix
  `localName` - Function name
  `m` - Method

### writeExternal

public void writeExternal(ObjectOutput out) throws IOException

Specified by:
  `writeExternal` in interface `Externalizable`
Throws:
  `IOException`

### readExternal

public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException

Specified by:
  `readExternal` in interface `Externalizable`
Throws:
  `IOException`
  `ClassNotFoundException`