org.springframework.hateoas.client.Hop Maven / Gradle / Ivy

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/*
 * Copyright 2015-2022 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.client;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;

import org.springframework.http.HttpHeaders;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Container for customizations to a single traverson "hop"
 *
 * @author Greg Turnquist
 * @author Oliver Gierke
 * @author Manish Misra
 * @since 0.18
 */
public final class Hop {

	/**
	 * Name of this hop.
	 */
	private final String rel;

	/**
	 * Collection of URI Template parameters.
	 */
	private final Map parameters;

	/**
	 * Extra {@link HttpHeaders} to apply to this hop.
	 */
	private final HttpHeaders headers;

	private Hop(String rel, Map parameters, HttpHeaders headers) {

		this.rel = rel;
		this.parameters = parameters;
		this.headers = headers;
	}

	/**
	 * Creates a new {@link Hop} for the given relation name.
	 *
	 * @param rel must not be {@literal null} or empty.
	 * @return
	 */
	public static Hop rel(String rel) {

		Assert.hasText(rel, "Relation must not be null or empty!");

		return new Hop(rel, Collections.emptyMap(), HttpHeaders.EMPTY);
	}

	/**
	 * Add one parameter to the map of parameters.
	 *
	 * @param name must not be {@literal null} or empty.
	 * @param value can be {@literal null}.
	 * @return
	 */
	public Hop withParameter(String name, Object value) {

		Assert.hasText(name, "Name must not be null or empty!");

		HashMap parameters = new HashMap<>(this.parameters);
		parameters.put(name, value);

		return new Hop(this.rel, parameters, this.headers);
	}

	/**
	 * Create a new {@link Hop} by copying all the attributes and replacing the {@literal parameters}.
	 *
	 * @param parameters
	 * @return
	 */
	public Hop withParameters(Map parameters) {
		return this.parameters == parameters ? this : new Hop(this.rel, parameters, this.headers);
	}

	/**
	 * Create a new {@link Hop} by copying all the attributes and replacing the {@literal headers}.
	 *
	 * @param headers
	 * @return
	 */
	public Hop withHeaders(HttpHeaders headers) {
		return this.headers == headers ? this : new Hop(this.rel, this.parameters, headers);
	}

	/**
	 * Add one header to the HttpHeaders collection.
	 *
	 * @param headerName must not be {@literal null} or empty.
	 * @param headerValue can be {@literal null}.
	 * @return
	 */
	public Hop header(String headerName, String headerValue) {

		Assert.hasText(headerName, "headerName must not be null or empty!");

		if (this.headers == HttpHeaders.EMPTY) {

			HttpHeaders newHeaders = new HttpHeaders();
			newHeaders.add(headerName, headerValue);

			return new Hop(this.rel, this.parameters, newHeaders);
		}

		this.headers.add(headerName, headerValue);
		return this;
	}

	/**
	 * Returns whether the {@link Hop} has parameters declared.
	 *
	 * @return
	 */
	boolean hasParameters() {
		return !this.parameters.isEmpty();
	}

	/**
	 * Create a new {@link Map} starting with the supplied template parameters. Then add the ones for this hop. This
	 * allows a local hop to override global parameters.
	 *
	 * @param globalParameters must not be {@literal null}.
	 * @return a merged map of URI Template parameters, will never be {@literal null}.
	 */
	Map getMergedParameters(Map globalParameters) {

		Assert.notNull(globalParameters, "Global parameters must not be null!");

		Map mergedParameters = new HashMap<>();

		mergedParameters.putAll(globalParameters);
		mergedParameters.putAll(this.parameters);

		return mergedParameters;
	}

	String getRel() {
		return this.rel;
	}

	Map getParameters() {
		return this.parameters;
	}

	HttpHeaders getHeaders() {
		return this.headers;
	}

	@Override
	public boolean equals(@Nullable Object o) {

		if (this == o) {
			return true;
		}
		if (o == null || getClass() != o.getClass()) {
			return false;
		}
		Hop hop = (Hop) o;
		return Objects.equals(this.rel, hop.rel) && Objects.equals(this.parameters, hop.parameters)
				&& Objects.equals(this.headers, hop.headers);
	}

	@Override
	public int hashCode() {
		return Objects.hash(this.rel, this.parameters, this.headers);
	}

	@Override
	public String toString() {
		return "Hop(rel=" + this.rel + ", parameters=" + this.parameters + ", headers=" + this.headers + ")";
	}
}