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Library to support implementing representations for
hyper-text driven REST web services.
/*
* Copyright 2012-2023 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.hateoas;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Objects;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.core.ResolvableType;
import org.springframework.core.ResolvableTypeProvider;
import org.springframework.lang.NonNull;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonProperty;
/**
* General helper to easily create a wrapper for a collection of entities.
*
* @author Oliver Gierke
* @author Greg Turnquist
*/
public class CollectionModel extends RepresentationModel>
implements Iterable, ResolvableTypeProvider {
private final Collection content;
private final @Nullable ResolvableType fallbackType;
private ResolvableType fullType;
/**
* Creates an empty {@link CollectionModel} instance.
*/
protected CollectionModel() {
this(Collections.emptyList());
}
protected CollectionModel(Iterable content) {
this(content, Links.NONE, null);
}
protected CollectionModel(Iterable content, Iterable links, @Nullable ResolvableType fallbackType) {
Assert.notNull(content, "Content must not be null!");
Assert.notNull(links, "Links must not be null!");
this.content = new ArrayList<>();
for (T element : content) {
this.content.add(element);
}
this.add(links);
this.fallbackType = fallbackType;
}
/**
* Creates a new empty collection model.
*
* @param
* @return
* @since 1.1
*/
public static CollectionModel empty() {
return of(Collections.emptyList());
}
/**
* Creates a new empty collection model with the given type defined as fallback type.
*
* @param
* @return
* @since 1.4
* @see #withFallbackType(Class, Class...)
*/
public static CollectionModel empty(Class elementType, Class... generics) {
return empty(ResolvableType.forClassWithGenerics(elementType, generics));
}
/**
* Creates a new empty collection model with the given type defined as fallback type.
*
* @param
* @return
* @since 1.4
* @see #withFallbackType(ParameterizedTypeReference)
*/
public static CollectionModel empty(ParameterizedTypeReference type) {
return empty(ResolvableType.forType(type.getType()));
}
/**
* Creates a new empty collection model with the given type defined as fallback type.
*
* @param
* @return
* @since 1.4
* @see #withFallbackType(ResolvableType)
*/
public static CollectionModel empty(ResolvableType elementType) {
return new CollectionModel<>(Collections.emptyList(), Collections.emptyList(), elementType);
}
/**
* Creates a new empty collection model with the given links.
*
* @param
* @param links must not be {@literal null}.
* @return
* @since 1.1
*/
public static CollectionModel empty(Link... links) {
return of(Collections.emptyList(), links);
}
/**
* Creates a new empty collection model with the given links.
*
* @param
* @param links must not be {@literal null}.
* @return
* @since 1.1
*/
public static CollectionModel empty(Iterable links) {
return of(Collections.emptyList(), links);
}
/**
* Creates a {@link CollectionModel} instance with the given content.
*
* @param content must not be {@literal null}.
* @return
* @since 1.1
* @see #withFallbackType(Class, Class...)
* @see #withFallbackType(ResolvableType)
*/
public static CollectionModel of(Iterable content) {
return of(content, Collections.emptyList());
}
/**
* Creates a {@link CollectionModel} instance with the given content and {@link Link}s (optional).
*
* @param content must not be {@literal null}.
* @param links the links to be added to the {@link CollectionModel}.
* @return
* @since 1.1
* @see #withFallbackType(Class, Class...)
* @see #withFallbackType(ResolvableType)
*/
public static CollectionModel of(Iterable content, Link... links) {
return of(content, Arrays.asList(links));
}
/**
* s Creates a {@link CollectionModel} instance with the given content and {@link Link}s.
*
* @param content must not be {@literal null}.
* @param links the links to be added to the {@link CollectionModel}.
* @return
* @since 1.1
* @see #withFallbackType(Class, Class...)
* @see #withFallbackType(ResolvableType)
*/
public static CollectionModel of(Iterable content, Iterable links) {
return new CollectionModel<>(content, links, null);
}
/**
* Creates a new {@link CollectionModel} instance by wrapping the given domain class instances into a
* {@link EntityModel}.
*
* @param content must not be {@literal null}.
* @return
*/
@SuppressWarnings("unchecked")
public static , S> CollectionModel wrap(Iterable content) {
Assert.notNull(content, "Content must not be null!");
ArrayList resources = new ArrayList<>();
for (S element : content) {
resources.add((T) EntityModel.of(element));
}
return CollectionModel.of(resources);
}
/**
* Returns the underlying elements.
*
* @return the content will never be {@literal null}.
*/
@JsonProperty("content")
public Collection getContent() {
return Collections.unmodifiableCollection(content);
}
/**
* Declares the given type as fallback element type in case the underlying collection is empty. This allows client
* components to still apply type matches at runtime.
*
* @param type must not be {@literal null}.
* @return will never be {@literal null}.
* @since 1.4
*/
public CollectionModel withFallbackType(Class type, Class... generics) {
Assert.notNull(type, "Fallback type must not be null!");
Assert.notNull(generics, "Generics must not be null!");
return withFallbackType(ResolvableType.forClassWithGenerics(type, generics));
}
/**
* Declares the given type as fallback element type in case the underlying collection is empty. This allows client
* components to still apply type matches at runtime.
*
* @param type must not be {@literal null}.
* @return will never be {@literal null}.
* @since 1.4
*/
public CollectionModel withFallbackType(ParameterizedTypeReference type) {
Assert.notNull(type, "Fallback type must not be null!");
return withFallbackType(ResolvableType.forType(type));
}
/**
* Declares the given type as fallback element type in case the underlying collection is empty. This allows client
* components to still apply type matches at runtime.
*
* @param type must not be {@literal null}.
* @return will never be {@literal null}.
* @since 1.4
*/
public CollectionModel withFallbackType(ResolvableType type) {
Assert.notNull(type, "Fallback type must not be null!");
return new CollectionModel<>(content, getLinks(), type);
}
/*
* (non-Javadoc)
* @see org.springframework.core.ResolvableTypeProvider#getResolvableType()
*/
@NonNull
@Override
@JsonIgnore
public ResolvableType getResolvableType() {
if (fullType == null) {
ResolvableType elementType = deriveElementType(this.content, fallbackType);
Class type = this.getClass();
this.fullType = elementType == null || type.getTypeParameters().length == 0 //
? ResolvableType.forClass(type) //
: ResolvableType.forClassWithGenerics(type, elementType);
}
return fullType;
}
/*
* (non-Javadoc)
* @see java.lang.Iterable#iterator()
*/
@Override
public Iterator iterator() {
return content.iterator();
}
/*
* (non-Javadoc)
* @see org.springframework.hateoas.RepresentationModel#toString()
*/
@Override
public String toString() {
return String.format("CollectionModel { content: %s, fallbackType: %s, %s }", //
getContent(), fallbackType, super.toString());
}
/*
* (non-Javadoc)
* @see org.springframework.hateoas.RepresentationModel#equals(java.lang.Object)
*/
@Override
public boolean equals(@Nullable Object obj) {
if (obj == this) {
return true;
}
if (obj == null || !obj.getClass().equals(getClass())) {
return false;
}
CollectionModel that = (CollectionModel) obj;
return Objects.equals(this.content, that.content)
&& Objects.equals(this.fallbackType, that.fallbackType)
&& super.equals(obj);
}
/*
* (non-Javadoc)
* @see org.springframework.hateoas.RepresentationModel#hashCode()
*/
@Override
public int hashCode() {
return super.hashCode() + Objects.hash(content, fallbackType);
}
/**
* Determines the most common element type from the given elements defaulting to the given fallback type.
*
* @param elements must not be {@literal null}.
* @param fallbackType can be {@literal null}.
* @return
*/
@Nullable
private static ResolvableType deriveElementType(Collection elements, @Nullable ResolvableType fallbackType) {
if (elements.isEmpty()) {
return fallbackType;
}
return elements.stream()
.filter(it -> it != null)
.> map(Object::getClass)
.reduce(ClassUtils::determineCommonAncestor)
.map(ResolvableType::forClass)
.orElse(fallbackType);
}
}