net.algart.contexts.SubContext Maven / Gradle / Ivy
Show all versions of algart Show documentation
/*
* The MIT License (MIT)
*
* Copyright (c) 2007-2024 Daniel Alievsky, AlgART Laboratory (http://algart.net)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package net.algart.contexts;
import java.util.HashSet;
import java.util.Arrays;
import java.util.Objects;
import net.algart.arrays.MemoryModel;
import net.algart.arrays.SimpleMemoryModel;
/**
* A tool allowing to build a new context, called "sub-context",
* that inherits behavior of an existing context with some changes or extensions.
*
* There are two basic ways to create a sub-context.
*
* The first way is inheriting this class with using the protected constructor
* {@link #SubContext(Context) SubContext(Context superContext)}.
* New subclass cannot override {@link #as(Class)} and {@link #is(Class)}
* methods, but may (and should) implement some additional specific context interfaces
* (for example, {@link ProgressUpdater}, {@link ArrayMemoryContext} or your custom contexts).
* The {@link #as(Class)} and {@link #is(Class)} method of the created sub-context
* will just call these methods of the super-context, excepting the case
* when the required contextClass is an interface implemented by your sub-context class.
* In the last case, {@link #as(Class)} method will return the reference to your sub-context instance
* and {@link #is(Class)} will return true.
* This technique is useful when you need to extend or override some
* functionality of the given context.
*
* The second way of creating sub-context is using the public constructor
* {@link #SubContext(Context, Class[]) SubContext(Context superContext, Class ...allowedClasses)},
* maybe, together with inheritance as in the first way.
* In this case, {@link #as(Class)} and {@link #is(Class)} will also pass the request
* to the super-context, as described above, if the required contextClass
* is implemented by your sub-context class (in particular, if you do not extend
* this class and just call the public constructor).
* However, the contextClass will be checked, is it in the classes list
* passed to the constructor. If contextClass is not in this list
* (and is not implemented by your sub-context), it is considered as unallowed,
* and the request is declined: {@link #as(Class)} throws an exception,
* and {@link #is(Class)} method returns false.
* This technique allows to restrict a set of passed contexts
* by only well-known, safe contexts.
*
* Another constructors may provide another behavior: please see comments to that constructors.
*
* @author Daniel Alievsky
*/
public class SubContext extends AbstractContext implements Context {
private final Context superContext;
private final HashSet> allowedClassesSet;
private final MemoryModel memoryModel;
/**
* Creates new context on the base of the passed super-context.
*
* @param superContext super-context.
*/
protected SubContext(Context superContext) {
super(false); // the constructor argument does not matter: we override both as and is methods
Objects.requireNonNull(superContext, "Null superContext argument");
this.superContext = superContext;
this.allowedClassesSet = null;
this.memoryModel = null;
}
/**
* Creates new context on the base of the passed super-context
* with the restricted set of allowed context classes.
*
* @param superContext super-context.
* @param allowedClasses the set of served specific contexts
* (in addition to interfaces implemented by this instance).
* @throws NullPointerException if superContext or one of allowedClasses is {@code null}.
* @throws IllegalArgumentException if one of allowedClasses is not a {@link Context}.
*/
public SubContext(Context superContext, Class ...allowedClasses) {
super(false); // the constructor argument does not matter: we override both as and is methods
Objects.requireNonNull(superContext, "Null superContext argument");
for (int k = 0; k < allowedClasses.length; k++) {
Class c = allowedClasses[k];
Objects.requireNonNull(c, "Null allowedClasses[" + k + "] argument");
if (!Context.class.isAssignableFrom(c)) {
throw new IllegalArgumentException("allowedClasses[" + k + "] does not inherit Context (" + c + ")");
}
}
this.superContext = superContext;
this.allowedClassesSet = new HashSet>(Arrays.asList(allowedClasses));
this.memoryModel = null;
}
/**
* Creates new context alike the {@link #SubContext(Context) base constructor}
* with the only difference that {@link #as(Class) as(ArrayMemoryContext.class)}
* method will return a {@link ArrayMemoryContext} describing the passed memory model.
* See comments to {@link #as(Class)} and {@link #is(Class)}
* method for more details.
*
* @param superContext super-context.
* @param memoryModel desired memory model.
* @throws NullPointerException if one of the arguments is {@code null}.
*/
public SubContext(Context superContext, MemoryModel memoryModel) {
super(false); // the constructor argument does not matter: we override both as and is methods
Objects.requireNonNull(superContext, "Null superContext argument");
Objects.requireNonNull(memoryModel, "Null memoryModel argument");
this.superContext = superContext;
this.allowedClassesSet = null;
this.memoryModel = memoryModel;
}
/**
* This implementation returns the reference to this instance, if
* contextClass.isAssignableFrom(thisInstance.getClass()),
* or calls superContext.{@link #as(Class) as}(contextClass)
* in other case.
*
* If this instance was created by the constructor with the specified set of allowed classes
* ({@link #SubContext(Context, Class[])}),
* and the condition contextClass.isAssignableFrom(thisInstance.getClass()) is not fulfilled,
* then context class is checked before passing to the superContext.{@link #as(Class) as} method.
* Namely, if this class is not in the list of allowed contexts, passed to the constructor,
* this method throws {@link UnsupportedContextException}.
*
*
If this instance was created by the constructor with the specified memory model
* ({@link #SubContext(Context, MemoryModel)}), and if contextClass==ArrayMemoryContext.class, but
* !contextClass.isAssignableFrom(thisInstance.getClass()),
* then this method does not call superContext, but creates new implementation
* of {@link ArrayMemoryContext} with {@link ArrayMemoryContext#getMemoryModel() getMemoryModel()},
* {@link ArrayMemoryContext#getMemoryModel(Class) getMemoryModel(Class)} and
* {@link ArrayMemoryContext#getMemoryModel(String) getMemoryModel(String)} methods,
* returning the memory model specified in the constructor.
* The second {@link ArrayMemoryContext#getMemoryModel(Class) getMemoryModel(Class)} method
* will return {@link SimpleMemoryModel#getInstance()}, if the required element type
* is not supported by the memory model specified in the constructor.
*
* @param contextClass the class of returned object (or superclass, or implemented interface).
* @return this instance.
* @throws NullPointerException if contextClass is {@code null}.
* @throws IllegalArgumentException if contextClass does not extends or implements
* {@link Context} interface.
* @throws UnsupportedContextException if this instance does not implement or extend the required type.
*/
public final T as(Class contextClass) {
Objects.requireNonNull(contextClass, "Null contextClass argument");
if (!Context.class.isAssignableFrom(contextClass)) {
throw new IllegalArgumentException("The contextClass argument is not a context class ("
+ contextClass.getName() + ")");
}
if (contextClass.isAssignableFrom(getClass())) {
return contextClass.cast(this);
} else {
if (allowedClassesSet != null && !allowedClassesSet.contains(contextClass)) {
throw new UnsupportedContextException("Unallowed context class: " + contextClass.getName());
}
if (contextClass == ArrayMemoryContext.class && this.memoryModel != null) {
return contextClass.cast(new MemorySubContext());
}
return superContext.as(contextClass);
}
}
/**
* This implementation returns true if contextClass is not {@code null}
* and contextClass.isAssignableFrom(thisInstance.getClass()).
* In another case, if this instance was created by the constructor with the specified set of allowed classes
* ({@link #SubContext(Context, Class[])}) and if the passed context class is not
* in the list of allowed contexts, passed to the constructor,
* this implementation returns false.
*
* If this instance was created by the constructor with the specified memory model
* ({@link #SubContext(Context, MemoryModel)}),
* and if contextClass==ArrayMemoryContext.class,
* this implementation returns true.
*
*
In all other cases, this implementation returns
* superContext.{@link #is is}(contextClass).
*
* @param contextClass the class or interface of a sub-context.
* @return true if this context class can be processed by {@link #as(Class)} method.
*/
public final boolean is(Class contextClass) {
if (contextClass == null || !Context.class.isAssignableFrom(contextClass)) {
return false;
}
if (contextClass.isAssignableFrom(getClass())) {
return true;
}
if (allowedClassesSet != null && !allowedClassesSet.contains(contextClass)) {
return false;
}
if (contextClass == ArrayMemoryContext.class && this.memoryModel != null) {
return true;
}
return superContext.is(contextClass);
}
private class MemorySubContext extends AbstractContext implements ArrayMemoryContext {
private MemorySubContext() {
super(false);
}
public MemoryModel getMemoryModel() {
return memoryModel;
}
public MemoryModel getMemoryModel(Class elementType) {
return memoryModel.isElementTypeSupported(elementType) ? memoryModel : SimpleMemoryModel.getInstance();
}
public MemoryModel getMemoryModel(String settings) {
Objects.requireNonNull(settings, "Null settings argument");
return memoryModel;
}
}
}