uk.ac.ed.epcc.webapp.forms.transition

Interface TransitionFactory<K,T>

Type Parameters:

K - key type

T - target type

All Superinterfaces:

Contexed

All Known Subinterfaces:

AnonymousTransitionFactory<K,T>, DefaultingTransitionFactory<K,T>, IndexTransitionFactory<K,T>, IndexTransitionProvider<K,T>, LogTransitionProvider, NavigationProvider<K,T>, PathTransitionProvider<K,T>, ShowDisabledTransitions<K,T>, TitleTransitionProvider<K,T>, TransitionProvider<K,T>, ViewPathTransitionProvider<K,T>, ViewTransitionFactory<K,T>, ViewTransitionProvider<K,T>

All Known Implementing Classes:

AbstractIndexedTransitionProvider, AbstractPartTransitionProvider, AbstractPathTransitionProvider, AbstractTransitionFactory, AbstractTransitionProvider, AbstractViewIndexedTransitionProvider, AbstractViewPathTransitionProvider, AbstractViewTransitionFactory, AbstractViewTransitionProvider, AppUserTransitionProvider, CodeAuthTransitionProvider, DomTransitionProvider, DynamicFormTransitionProvider, EmailTransitionProvider, FormFactoryProviderTransitionProvider, LandingPageAppUserTransitionProvider, LogFactory.TransitionProvider, PartPathTransitionProvider, PersonalResponseTransitionProvider, PreferenceTransitionProvider, ResponseTransitionProvider, SimpleTransitionProvider, SimpleViewTransitionProvider, TableTransitionProvider

public interface TransitionFactory<K,T>
extends Contexed

A transition factory represents a set of bespoke operations (transitions) on a target type. Each transition is logically a method on the target type. The parameters of the method (if any) are represented by a form and the method returns an object (the return value of the FormAction). It is also possible to define target-less transitions which are equivalent to static methods.

This interface does not require the target and key types to implement any particular interface. All operations are methods on the transition factory. This is to allow greatest freedom of implementation.

The operations are identified using a key type. This is intended to be a lightweight type and may be as simple as a String or enum. Each key value must have a String representation as key values might be transferred as Strings. This String representation should be unique for the set of operations supported by any given target. The keys should be available as static constants as they will be needed to construct links and results that reference the transition. The same is not true of the transition classes. It is often convenient to make these inner classes of the TransitionFactory.

The separation into key and transition is not essential (they could be the same object or tightly bound together). Operations that act on the set of all possible operations usually use the key type so instantiating all possible transition classes can be avoided it also makes it easier for the same named transition to invoke a different operation depending on the state of the target or the roles of the operator.

This interface is a way of allowing a class that supports many different operations to describe the set of operations to the presentation logic.

Most methods in this interface take a target parameter. Implementations are therefore free to implement the associated logic in the TransitionProvider or in the target object depending on whichever is most appropriate. The key type is another possible location for the access control logic.

In a web-context this interface needs to be extended to provide mappings between the target object and string based identifiers that can be passed in form posts. e.g. TransitionProvider

See Also:

TransitionProvider, PathTransitionProvider, ViewTransitionFactory

Method Summary

Modifier and Type	Method and Description
<R> R	accept(TransitionFactoryVisitor<R,T,K> vis) Accept a TransitionFactoryVisitor.
boolean	allowTransition(AppContext c, T target, K key) Access control check.
default <X extends ContentBuilder> X	getSummaryContent(AppContext c, X cb, T target) Get target summary to be shown on transition page.
java.lang.String	getTargetName() What is the name for this type of transition.
Transition<T>	getTransition(T target, K key) Find a transition operator for this type by key.
java.util.Set<K>	getTransitions(T target) Get a list of all the transition keys supported by the target type to be presented to the user as a set of possible options in a view transition.
K	lookupTransition(T target, java.lang.String name) Lookup a transition key by String This has to be the same as the result of the toString method on the key as this is what is passed from transitions.jsp for a form transition.

Methods inherited from interface uk.ac.ed.epcc.webapp.Contexed

getContext

Method Detail

getTransitions

java.util.Set<K> getTransitions(T target)

Get a list of all the transition keys supported by the target type to be presented to the user as a set of possible options in a view transition. Options in this list that are not allowed by allowTransition(AppContext, Object, Object) will not be presented. Additional hidden operations may also be supported but these will never be presented to the user as options and can only generated as a ChainedTransitionResult. In most cases the transition set will be the same for all null/non-null targets though in principal dynamic transitions could be generated based on the state of the target e.g. a parameterised transition with the parameter encoded in the key.

Parameters:

target -

Returns:

Set of keys

getTransition

Transition<T> getTransition(T target,
                            K key)

Find a transition operator for this type by key. This method is permitted to return null for example if the current user is not permitted to perform the transition.

Parameters:

target - target (may be null)

key - key

Returns:

Transition or null

lookupTransition

K lookupTransition(T target,
                   java.lang.String name)

Lookup a transition key by String This has to be the same as the result of the toString method on the key as this is what is passed from transitions.jsp for a form transition.

Parameters:

target - (may be null)

name -

Returns:

Transition key

getTargetName

java.lang.String getTargetName()

What is the name for this type of transition. This value needs to resolve to the TransitionProvider in the TransitionServlet The value can also be used as the user presented text for the type of object in the title of the transition form page though this can be overridden by setting target-name.transition_title

Returns:

String

allowTransition

boolean allowTransition(AppContext c,
                        T target,
                        K key)

Access control check. Is this transition allowed for the current user/target

Parameters:

c - AppContext

target - target object

key - identifying key object for transition

Returns:

boolean is operation allowed

getSummaryContent

default <X extends ContentBuilder> X getSummaryContent(AppContext c,
                                                       X cb,
                                                       T target)

Get target summary to be shown on transition page. In html this content is embedded within a div.block element.

Parameters:

c - AppContext

cb - ContentBuilder

target -

Returns:

ContentBuilder

accept

<R> R accept(TransitionFactoryVisitor<R,T,K> vis)

Accept a TransitionFactoryVisitor. Any code that depends on the particular sub-interface of TransitionFactory should implement TransitionFactoryVisitor this ensures it will always handle all possible sub-classes.

Parameters:

vis -

Returns: