Java tutorial
/* * Copyright 2012 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 * * http://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 javax.xml.bind.annotation.XmlAttribute; import javax.xml.bind.annotation.XmlRootElement; import org.springframework.util.Assert; import com.fasterxml.jackson.annotation.JsonIgnore; import com.fasterxml.jackson.annotation.JsonProperty; /** * DTO to implement binding response representations of pageable collections. * * @author Oliver Gierke */ @XmlRootElement(name = "pagedEntities") public class PagedResources<T> extends Resources<T> { public static PagedResources<?> NO_PAGE = new PagedResources<Object>(); private PageMetadata metadata; /** * Default constructor to allow instantiation by reflection. */ protected PagedResources() { this(new ArrayList<T>(), null); } /** * Creates a new {@link PagedResources} from the given content, {@link PageMetadata} and {@link Link}s (optional). * * @param content must not be {@literal null}. * @param metadata * @param links */ public PagedResources(Collection<T> content, PageMetadata metadata, Link... links) { this(content, metadata, Arrays.asList(links)); } /** * Creates a new {@link PagedResources} from the given content {@link PageMetadata} and {@link Link}s. * * @param content must not be {@literal null}. * @param metadata * @param links */ public PagedResources(Collection<T> content, PageMetadata metadata, Iterable<Link> links) { super(content, links); this.metadata = metadata; } /** * Returns the pagination metadata. * * @return the metadata */ @JsonProperty("page") public PageMetadata getMetadata() { return metadata; } /** * Factory method to easily create a {@link PagedResources} instance from a set of entities and pagination metadata. * * @param content must not be {@literal null}. * @param metadata * @return */ @SuppressWarnings("unchecked") public static <T extends Resource<S>, S> PagedResources<T> wrap(Iterable<S> content, PageMetadata metadata) { Assert.notNull(content); ArrayList<T> resources = new ArrayList<T>(); for (S element : content) { resources.add((T) new Resource<S>(element)); } return new PagedResources<T>(resources, metadata); } /** * Returns the Link pointing to the next page (if set). * * @see #addPaginationLinks(Link) * @return */ @JsonIgnore public Link getNextLink() { return getLink(Link.REL_NEXT); } /** * Returns the Link pointing to the previous page (if set). * * @see #addPaginationLinks(Link) * @return */ @JsonIgnore public Link getPreviousLink() { return getLink(Link.REL_PREVIOUS); } /* * (non-Javadoc) * @see org.springframework.hateoas.ResourceSupport#toString() */ @Override public String toString() { return String.format("PagedResource { content: %s, metadata: %s, links: %s }", getContent(), metadata, getLinks()); } /* * (non-Javadoc) * @see org.springframework.hateoas.Resources#equals(java.lang.Object) */ @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj == null || !getClass().equals(obj.getClass())) { return false; } PagedResources<?> that = (PagedResources<?>) obj; boolean metadataEquals = this.metadata == null ? that.metadata == null : this.metadata.equals(that.metadata); return metadataEquals ? super.equals(obj) : false; } /* * (non-Javadoc) * @see org.springframework.hateoas.Resources#hashCode() */ @Override public int hashCode() { int result = super.hashCode(); result += this.metadata == null ? 0 : 31 * this.metadata.hashCode(); return result; } /** * Value object for pagination metadata. * * @author Oliver Gierke */ public static class PageMetadata { @XmlAttribute @JsonProperty private long size; @XmlAttribute @JsonProperty private long totalElements; @XmlAttribute @JsonProperty private long totalPages; @XmlAttribute @JsonProperty private long number; protected PageMetadata() { } /** * Creates a new {@link PageMetadata} from the given size, number, total elements and total pages. * * @param size * @param number zero-indexed, must be less than totalPages * @param totalElements * @param totalPages */ public PageMetadata(long size, long number, long totalElements, long totalPages) { Assert.isTrue(size > -1, "Size must not be negative!"); Assert.isTrue(number > -1, "Number must not be negative!"); Assert.isTrue(totalElements > -1, "Total elements must not be negative!"); Assert.isTrue(totalPages > -1, "Total pages must not be negative!"); this.size = size; this.number = number; this.totalElements = totalElements; this.totalPages = totalPages; } /** * Creates a new {@link PageMetadata} from the given size, numer and total elements. * * @param size the size of the page * @param number the number of the page * @param totalElements the total number of elements available */ public PageMetadata(long size, long number, long totalElements) { this(size, number, totalElements, size == 0 ? 0 : totalElements / size); } /** * Returns the requested size of the page. * * @return the size a positive long. */ public long getSize() { return size; } /** * Returns the total number of elements available. * * @return the totalElements a positive long. */ public long getTotalElements() { return totalElements; } /** * Returns how many pages are available in total. * * @return the totalPages a positive long. */ public long getTotalPages() { return totalPages; } /** * Returns the number of the current page. * * @return the number a positive long. */ public long getNumber() { return number; } /* * (non-Javadoc) * @see java.lang.Object#toString() */ @Override public String toString() { return String.format("Metadata { number: %d, total pages: %d, total elements: %d, size: %d }", number, totalPages, totalElements, size); } /* * (non-Javadoc) * @see java.lang.Object#equals(java.lang.Object) */ @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj == null || !obj.getClass().equals(getClass())) { return false; } PageMetadata that = (PageMetadata) obj; return this.number == that.number && this.size == that.size && this.totalElements == that.totalElements && this.totalPages == that.totalPages; } /* * (non-Javadoc) * @see java.lang.Object#hashCode() */ @Override public int hashCode() { int result = 17; result += 31 * (int) (this.number ^ this.number >>> 32); result += 31 * (int) (this.size ^ this.size >>> 32); result += 31 * (int) (this.totalElements ^ this.totalElements >>> 32); result += 31 * (int) (this.totalPages ^ this.totalPages >>> 32); return result; } } }