Package science.aist.jack.reflection

Class SafeFieldHandle<T,U>

java.lang.Object

science.aist.jack.reflection.SafeFieldHandle<T,U>

Type Parameters:

T - The Class, that contains the Field.

U - The type of the Fields value.

public class SafeFieldHandle<T,U>
extends Object

SafeFieldHandle

Allows typesafe access to Fields. The value is wrapped into Optional to allow functional error handling, if the Field is either of the wrong type, or not initialized.

This handle also checks initialisation of the Field by comparing the value with the datatype default value. The value is either derived from the datatype, or explicitly passed for application specific use cases.

Since:

2.3.0

Author:

Rainer Meindl

Constructor Summary

Constructors

Constructor	Description
SafeFieldHandle(Class<T> clazz, String name)	Creates a new instance of SafeFieldHandle, where the defaultValue is derived from the type, if possible.
SafeFieldHandle(Class<T> clazz, String name, U defaultValue)	Creates a new instance of SafeFieldHandle.
SafeFieldHandle(Field field)
SafeFieldHandle(Field field, U defaultValue)

Method Summary

Modifier and Type	Method	Description
Optional<U>	get(T object)	Accesses the unsafe Field and wraps it in an Optional of the type this class thinks it is.
protected U	getDefaultValue()	Returns the default value for the given type U.
protected Optional<U>	tryCast(Object fieldValue)	Tries to cast the fieldValue into the designated type U.

Methods inherited from class java.lang.Object

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

Constructor Detail

SafeFieldHandle

public SafeFieldHandle(Field field)

SafeFieldHandle

public SafeFieldHandle(Class<T> clazz,
                       String name)

Creates a new instance of SafeFieldHandle, where the defaultValue is derived from the type, if possible. Might fail, if no Field witht he provided name is found.

Parameters:

clazz - The Class, which should contain a Field with the provided name

name - The name of the Field, which should be declared in the clazz

SafeFieldHandle

public SafeFieldHandle(Field field,
                       U defaultValue)

SafeFieldHandle

public SafeFieldHandle(Class<T> clazz,
                       String name,
                       U defaultValue)

Creates a new instance of SafeFieldHandle. Might fail, if no Field with he provided name is found.

Parameters:

clazz - The Class, which should contain a Field with the provided name

name - The name of the Field, which should be declared in the clazz

defaultValue - Custom default value of the Field. If the Field holds this value, it is considered to be uninitialized

Method Detail

get

public Optional<U> get(T object)

Accesses the unsafe Field and wraps it in an Optional of the type this class thinks it is. If either the access, or the conversion of the value fails, as well as if the Fields value is equal to the defaultValue defined by this handle

Parameters:

object - The instance, whose fields needs to be accessed safely.

Returns:

Optional, either containing the typesafe value of the field or Optional.empty() s

tryCast

protected Optional<U> tryCast(Object fieldValue)

Tries to cast the fieldValue into the designated type U. If the cast fails, or the value is null, an empty Optional is returned.

Parameters:

fieldValue - an extracted value of the unsafeField, which should be casted into a type of U

Returns:

an Optional of U, either holding the mapped value of fieldValue, or empty, if the cast fails.

getDefaultValue

protected U getDefaultValue()

Returns the default value for the given type U.

Returns:

the default value for the given type U.