org.springframework.data.web.PagedResourcesAssembler Maven / Gradle / Ivy
/*
* Copyright 2013-2023 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.data.web;
import static org.springframework.web.util.UriComponentsBuilder.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import org.springframework.core.MethodParameter;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.hateoas.EntityModel;
import org.springframework.hateoas.IanaLinkRelations;
import org.springframework.hateoas.Link;
import org.springframework.hateoas.LinkRelation;
import org.springframework.hateoas.PagedModel;
import org.springframework.hateoas.PagedModel.PageMetadata;
import org.springframework.hateoas.RepresentationModel;
import org.springframework.hateoas.UriTemplate;
import org.springframework.hateoas.server.RepresentationModelAssembler;
import org.springframework.hateoas.server.core.EmbeddedWrapper;
import org.springframework.hateoas.server.core.EmbeddedWrappers;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;
/**
* {@link RepresentationModelAssembler} to easily convert {@link Page} instances into {@link PagedModel}.
*
* @since 1.6
* @author Oliver Gierke
* @author Nick Williams
* @author Marcel Overdijk
*/
public class PagedResourcesAssembler implements RepresentationModelAssembler, PagedModel>> {
private final HateoasPageableHandlerMethodArgumentResolver pageableResolver;
private final Optional baseUri;
private final EmbeddedWrappers wrappers = new EmbeddedWrappers(false);
private boolean forceFirstAndLastRels = false;
private @Nullable MethodParameter parameter;
/**
* Creates a new {@link PagedResourcesAssembler} using the given {@link PageableHandlerMethodArgumentResolver} and
* base URI. If the former is {@literal null}, a default one will be created. If the latter is {@literal null}, calls
* to {@link #toModel(Page)} will use the current request's URI to build the relevant previous and next links.
*
* @param resolver can be {@literal null}.
* @param baseUri can be {@literal null}.
*/
public PagedResourcesAssembler(@Nullable HateoasPageableHandlerMethodArgumentResolver resolver,
@Nullable UriComponents baseUri) {
this(resolver, Optional.ofNullable(baseUri), null);
}
private PagedResourcesAssembler(@Nullable HateoasPageableHandlerMethodArgumentResolver resolver,
Optional baseUri, @Nullable MethodParameter parameter) {
this.pageableResolver = resolver == null ? new HateoasPageableHandlerMethodArgumentResolver() : resolver;
this.baseUri = baseUri;
this.parameter = parameter;
}
/**
* Configures whether to always add {@code first} and {@code last} links to the {@link PagedModel} created. Defaults
* to {@literal false} which means that {@code first} and {@code last} links only appear in conjunction with
* {@code prev} and {@code next} links.
*
* @param forceFirstAndLastRels whether to always add {@code first} and {@code last} links to the {@link PagedModel}
* created.
* @since 1.11
*/
public void setForceFirstAndLastRels(boolean forceFirstAndLastRels) {
this.forceFirstAndLastRels = forceFirstAndLastRels;
}
/**
* Creates a new {@link PagedResourcesAssembler} with the given reference {@link MethodParameter}.
*
* @param parameter can be {@literal null}.
* @return will never be {@literal null}.
* @since 3.1
*/
public PagedResourcesAssembler withParameter(@Nullable MethodParameter parameter) {
return new PagedResourcesAssembler<>(pageableResolver, baseUri, parameter);
}
@Override
public PagedModel> toModel(Page entity) {
return toModel(entity, EntityModel::of);
}
/**
* Creates a new {@link PagedModel} by converting the given {@link Page} into a {@link PageMetadata} instance and
* wrapping the contained elements into {@link PagedModel} instances. Will add pagination links based on the given the
* self link.
*
* @param page must not be {@literal null}.
* @param selfLink must not be {@literal null}.
* @return
*/
public PagedModel> toModel(Page page, Link selfLink) {
return toModel(page, EntityModel::of, selfLink);
}
/**
* Creates a new {@link PagedModel} by converting the given {@link Page} into a {@link PageMetadata} instance and
* using the given {@link PagedModel} to turn elements of the {@link Page} into resources.
*
* @param page must not be {@literal null}.
* @param assembler must not be {@literal null}.
* @return
*/
public > PagedModel toModel(Page page,
RepresentationModelAssembler assembler) {
return createModel(page, assembler, Optional.empty());
}
/**
* Creates a new {@link PagedModel} by converting the given {@link Page} into a {@link PageMetadata} instance and
* using the given {@link PagedModel} to turn elements of the {@link Page} into resources. Will add pagination links
* based on the given the self link.
*
* @param page must not be {@literal null}.
* @param assembler must not be {@literal null}.
* @param link must not be {@literal null}.
* @return
*/
public > PagedModel toModel(Page page,
RepresentationModelAssembler assembler, Link link) {
Assert.notNull(link, "Link must not be null");
return createModel(page, assembler, Optional.of(link));
}
/**
* Creates a {@link PagedModel} with an empt collection {@link EmbeddedWrapper} for the given domain type.
*
* @param page must not be {@literal null}, content must be empty.
* @param type must not be {@literal null}.
* @return
* @since 2.0
*/
public PagedModel toEmptyModel(Page page, Class type) {
return toEmptyModel(page, type, Optional.empty());
}
/**
* Creates a {@link PagedModel} with an empt collection {@link EmbeddedWrapper} for the given domain type.
*
* @param page must not be {@literal null}, content must be empty.
* @param type must not be {@literal null}.
* @param link must not be {@literal null}.
* @return
* @since 1.11
*/
public PagedModel toEmptyModel(Page page, Class type, Link link) {
return toEmptyModel(page, type, Optional.of(link));
}
private PagedModel toEmptyModel(Page page, Class type, Optional link) {
Assert.notNull(page, "Page must not be null");
Assert.isTrue(!page.hasContent(), "Page must not have any content");
Assert.notNull(type, "Type must not be null");
Assert.notNull(link, "Link must not be null");
PageMetadata metadata = asPageMetadata(page);
EmbeddedWrapper wrapper = wrappers.emptyCollectionOf(type);
List embedded = Collections.singletonList(wrapper);
return addPaginationLinks(PagedModel.of(embedded, metadata), page, link);
}
/**
* Creates the {@link PagedModel} to be equipped with pagination links downstream.
*
* @param resources the original page's elements mapped into {@link RepresentationModel} instances.
* @param metadata the calculated {@link PageMetadata}, must not be {@literal null}.
* @param page the original page handed to the assembler, must not be {@literal null}.
* @return must not be {@literal null}.
*/
protected , S> PagedModel createPagedModel(List resources,
PageMetadata metadata, Page page) {
Assert.notNull(resources, "Content resources must not be null");
Assert.notNull(metadata, "PageMetadata must not be null");
Assert.notNull(page, "Page must not be null");
return PagedModel.of(resources, metadata);
}
private > PagedModel createModel(Page page,
RepresentationModelAssembler assembler, Optional link) {
Assert.notNull(page, "Page must not be null");
Assert.notNull(assembler, "ResourceAssembler must not be null");
List resources = new ArrayList<>(page.getNumberOfElements());
for (S element : page) {
resources.add(assembler.toModel(element));
}
PagedModel resource = createPagedModel(resources, asPageMetadata(page), page);
return addPaginationLinks(resource, page, link);
}
private PagedModel addPaginationLinks(PagedModel resources, Page page, Optional link) {
UriTemplate base = getUriTemplate(link);
boolean isNavigable = page.hasPrevious() || page.hasNext();
if (isNavigable || forceFirstAndLastRels) {
resources.add(createLink(base, PageRequest.of(0, page.getSize(), page.getSort()), IanaLinkRelations.FIRST));
}
if (page.hasPrevious()) {
resources.add(createLink(base, page.previousPageable(), IanaLinkRelations.PREV));
}
Link selfLink = link.map(Link::withSelfRel)//
.orElseGet(() -> createLink(base, page.getPageable(), IanaLinkRelations.SELF));
resources.add(selfLink);
if (page.hasNext()) {
resources.add(createLink(base, page.nextPageable(), IanaLinkRelations.NEXT));
}
if (isNavigable || forceFirstAndLastRels) {
int lastIndex = page.getTotalPages() == 0 ? 0 : page.getTotalPages() - 1;
resources
.add(createLink(base, PageRequest.of(lastIndex, page.getSize(), page.getSort()), IanaLinkRelations.LAST));
}
return resources;
}
/**
* Returns a default URI string either from the one configured on assembler creatino or by looking it up from the
* current request.
*
* @return
*/
private UriTemplate getUriTemplate(Optional baseLink) {
return UriTemplate.of(baseLink.map(Link::getHref).orElseGet(this::baseUriOrCurrentRequest));
}
/**
* Creates a {@link Link} with the given {@link LinkRelation} that will be based on the given {@link UriTemplate} but
* enriched with the values of the given {@link Pageable} (if not {@literal null}).
*
* @param base must not be {@literal null}.
* @param pageable can be {@literal null}
* @param relation must not be {@literal null}.
* @return
*/
private Link createLink(UriTemplate base, Pageable pageable, LinkRelation relation) {
UriComponentsBuilder builder = fromUri(base.expand());
pageableResolver.enhance(builder, parameter, pageable);
return Link.of(UriTemplate.of(builder.build().toString()), relation);
}
/**
* Return the {@link MethodParameter} to be used to potentially qualify the paging and sorting request parameters to.
* Default implementations returns {@literal null}, which means the parameters will not be qualified.
*
* @return
* @since 1.7
* @deprecated since 3.1, rather set up the instance with {@link #withParameter(MethodParameter)}.
*/
@Nullable
@Deprecated(since = "3.1", forRemoval = true)
protected MethodParameter getMethodParameter() {
return null;
}
/**
* Creates a new {@link PageMetadata} instance from the given {@link Page}.
*
* @param page must not be {@literal null}.
* @return
*/
private PageMetadata asPageMetadata(Page page) {
Assert.notNull(page, "Page must not be null");
int number = pageableResolver.isOneIndexedParameters() ? page.getNumber() + 1 : page.getNumber();
return new PageMetadata(page.getSize(), number, page.getTotalElements(), page.getTotalPages());
}
private String baseUriOrCurrentRequest() {
return baseUri.map(Object::toString).orElseGet(PagedResourcesAssembler::currentRequest);
}
private static String currentRequest() {
return ServletUriComponentsBuilder.fromCurrentRequest().build().toString();
}
}
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