Example usage of guava's Equivalence, when in some cases, we just want to compare host (authority) parts of URLs

RemoteObject.java

package pl.lgawin.guavasandbox.equivalence;

import static com.google.common.base.MoreObjects.toStringHelper;
import static com.google.common.base.Objects.equal;

import com.google.common.base.Objects;
import com.google.common.net.MediaType;


public class RemoteObject {

    private final String url;
    private final MediaType mediaType;

    public RemoteObject(String url, MediaType mediaType) {
        this.url = url;
        this.mediaType = mediaType;
    }

    public String getUrl() {
        return url;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (!(o instanceof RemoteObject)) {
            return false;
        }

        RemoteObject that = (RemoteObject) o;
        return equal(this.url, that.url)
                && equal(this.mediaType, that.mediaType);
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(url, mediaType);
    }

    @Override
    public String toString() {
        return toStringHelper(this).add("url", url).add("mediaType", mediaType).toString();
    }
}

RemoteObjectTest.java

package pl.lgawin.guavasandbox.equivalence;

import static com.google.common.base.Objects.equal;
import static com.google.common.net.MediaType.HTML_UTF_8;
import static com.google.common.net.MediaType.JSON_UTF_8;
import static com.google.common.net.MediaType.XML_UTF_8;

import static org.assertj.core.api.Assertions.assertThat;

import com.google.common.base.Equivalence;
import com.google.common.base.Objects;

import org.junit.Before;
import org.junit.Test;

import java.net.URI;

public class RemoteObjectTest {

    private static final Equivalence<URI> URI_BY_AUTHORITY_EQUIVALENCE = new Equivalence<URI>() {

        @Override
        protected boolean doEquivalent(URI a, URI b) {
            return equal(a.getAuthority(), b.getAuthority());
        }

        @Override
        protected int doHash(URI url) {
            return Objects.hashCode(url.getAuthority());
        }
    };

    private Equivalence<RemoteObject> byAuthorityEquivalence;

    @Before
    public void setUp() throws Exception {
        byAuthorityEquivalence = new Equivalence<RemoteObject>() {

            @Override
            protected boolean doEquivalent(RemoteObject a, RemoteObject b) {
                return URI_BY_AUTHORITY_EQUIVALENCE.equivalent(URI.create(a.getUrl()), URI.create(b.getUrl()));
            }

            @Override
            protected int doHash(RemoteObject remoteObject) {
                return URI_BY_AUTHORITY_EQUIVALENCE.wrap(URI.create(remoteObject.getUrl())).hashCode();
            }
        };
    }

    @Test
    public void buildInEqualsReturnsTrueWhenObjectUrlsAndMediaTypesAreTheSame() throws Exception {
        RemoteObject object1 = new RemoteObject("http://example.com/resource1.html", HTML_UTF_8);
        RemoteObject object2 = new RemoteObject("http://example.com/resource1.html", HTML_UTF_8);

        assertThat(object1).isEqualTo(object2);
    }

    @Test
    public void buildInEqualsReturnsFalseWhenObjectUrlsAreDifferent() throws Exception {
        RemoteObject object1 = new RemoteObject("http://example.com/resource1.html", HTML_UTF_8);
        RemoteObject object2 = new RemoteObject("http://example.com/resource2.html", HTML_UTF_8);

        assertThat(object1).isNotEqualTo(object2);
    }

    @Test
    public void buildInEqualsReturnsFalseWhenObjectUrlsMediaTypesDifferent() throws Exception {
        RemoteObject object1 = new RemoteObject("http://example.com/resource1", XML_UTF_8);
        RemoteObject object2 = new RemoteObject("http://example.com/resource1", JSON_UTF_8);

        assertThat(object1).isNotEqualTo(object2);
    }

    @Test
    public void customEquivalenceComparingAuthoritiesOnlyReturnsTrueIfHostIsTheSame() throws Exception {
        RemoteObject object1 = new RemoteObject("http://example.com/resource1", XML_UTF_8);
        RemoteObject object2 = new RemoteObject("http://example.com/resource2", JSON_UTF_8);

        assertThat(byAuthorityEquivalence.wrap(object1))
                .isEqualTo(byAuthorityEquivalence.wrap(object2));
    }

    @Test
    public void customEquivalenceComparingAuthoritiesOnlyReturnsFalseForDifferentHosts() throws Exception {
        RemoteObject object1 = new RemoteObject("http://example.com/resource1", JSON_UTF_8);
        RemoteObject object2 = new RemoteObject("http://example2.com/resource1", JSON_UTF_8);

        assertThat(byAuthorityEquivalence.wrap(object1))
                .isNotEqualTo(byAuthorityEquivalence.wrap(object2));
    }
}