Refactoring towards OO design.

src/main/java/com/softwaremill/java_fp_example/contest/barti271/FacebookImageVersionBarti271.java

@@ -0,0 +1,22 @@
+package com.softwaremill.java_fp_example.contest.barti271;
+
+import com.softwaremill.java_fp_example.contest.barti271.page.CachedPage;
+import com.softwaremill.java_fp_example.contest.barti271.page.Page;
+import com.softwaremill.java_fp_example.contest.barti271.page.SimplePage;
+import com.softwaremill.java_fp_example.contest.barti271.page.content.SimpleContent;
+import com.softwaremill.java_fp_example.contest.barti271.page.content.jspup.JsoupSource;
+
+public class FacebookImageVersionBarti271 {
+
+    private final Page page;
+
+    public FacebookImageVersionBarti271(String url) {
+        this.page = new CachedPage(new SimplePage(new SimpleContent(new JsoupSource(url))));
+    }
+
+    @Override
+    public String toString() {
+        return page.extractImageAddress();
+    }
+
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/LICENSE.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2017 barti271
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/CachedPage.java

@@ -0,0 +1,51 @@
+package com.softwaremill.java_fp_example.contest.barti271.page;
+
+import java.util.function.Supplier;
+
+/**
+ * Caches results produced by supplied page.
+ * This class is thread-safe.
+ */
+public class CachedPage implements Page {
+
+    private final Page page;
+    private Supplier<String> imageAddress = this::retrieveImageAddress;
+
+    public CachedPage(Page page) {
+        this.page = page;
+    }
+
+    @Override
+    public String extractImageAddress() {
+        return imageAddress.get();
+    }
+
+    private synchronized String retrieveImageAddress() {
+        return isInitialized() ? imageAddress.get() : initialize();
+    }
+
+    private boolean isInitialized() {
+        return imageAddress instanceof Holder;
+    }
+
+    private String initialize() {
+        imageAddress = new Holder(page.extractImageAddress());
+        return imageAddress.get();
+    }
+
+    private static class Holder implements Supplier<String> {
+
+        private final String url;
+
+        private Holder(String url) {
+            this.url = url;
+        }
+
+        @Override
+        public String get() {
+            return url;
+        }
+
+    }
+
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/Page.java

@@ -0,0 +1,7 @@
+package com.softwaremill.java_fp_example.contest.barti271.page;
+
+public interface Page {
+
+    String extractImageAddress();
+
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/SimplePage.java

@@ -0,0 +1,46 @@
+package com.softwaremill.java_fp_example.contest.barti271.page;
+
+import static com.softwaremill.java_fp_example.DefaultImage.DEFAULT_IMAGE;
+
+import com.softwaremill.java_fp_example.contest.barti271.page.content.Content;
+import com.softwaremill.java_fp_example.contest.barti271.page.content.Image;
+
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+public class SimplePage implements Page {
+
+    private final Content content;
+
+    public SimplePage(Content content) {
+        this.content = content;
+    }
+
+    /**
+     * @return URL of first og:image read from the supplied {@link Content} or
+     * {@link com.softwaremill.java_fp_example.DefaultImage#DEFAULT_IMAGE} URL when
+     * no images can be read.
+     */
+    @Override
+    public String extractImageAddress() {
+        try {
+            return tryExtractImageAddress();
+        } catch (RuntimeException e) {
+            log.error("Unable to extract og:image from url {}. Problem: {}",
+                e.getMessage(), e.getCause().getMessage());
+            return DEFAULT_IMAGE;
+        }
+    }
+
+    private String tryExtractImageAddress() {
+        return content.getOpenGraphImages()
+            .findFirst()
+            .map(Image::getUrl)
+            .orElseGet(this::defaultUrl);
+    }
+
+    private String defaultUrl() {
+        log.warn("No og:image found for blog post {}", content);
+        return DEFAULT_IMAGE;
+    }
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/content/Content.java

@@ -0,0 +1,8 @@
+package com.softwaremill.java_fp_example.contest.barti271.page.content;
+
+import java.util.stream.Stream;
+
+public interface Content {
+
+    Stream<Image> getOpenGraphImages();
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/content/Image.java

@@ -0,0 +1,7 @@
+package com.softwaremill.java_fp_example.contest.barti271.page.content;
+
+public interface Image {
+
+    String getUrl();
+
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/content/SimpleContent.java

@@ -0,0 +1,34 @@
+package com.softwaremill.java_fp_example.contest.barti271.page.content;
+
+import java.util.stream.Stream;
+
+import com.softwaremill.java_fp_example.contest.barti271.page.content.source.Source;
+
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+public class SimpleContent implements Content {
+
+    private static final String OG_IMAGE = "og:image";
+
+    private final Source source;
+
+    public SimpleContent(Source source) {
+        this.source = source;
+    }
+
+    /**
+     * @return stream of Open Graph {@link Image}s read from supplied {@link Source}
+     */
+    @Override
+    public Stream<Image> getOpenGraphImages() {
+        return source.getMetaElements()
+            .filter(m -> OG_IMAGE.equals(m.getProperty()))
+            .map(m -> m::getContent);
+    }
+
+    @Override
+    public String toString() {
+        return source.toString();
+    }
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/content/jspup/JsoupMetaElement.java

@@ -0,0 +1,26 @@
+package com.softwaremill.java_fp_example.contest.barti271.page.content.jspup;
+
+import org.jsoup.nodes.Element;
+
+import com.softwaremill.java_fp_example.contest.barti271.page.content.source.MetaElement;
+
+
+class JsoupMetaElement implements MetaElement {
+
+    private final Element element;
+
+    JsoupMetaElement(Element element) {
+        this.element = element;
+    }
+
+    @Override
+    public String getContent() {
+        return element.attr("content");
+    }
+
+    @Override
+    public String getProperty() {
+        return element.attr("property");
+    }
+
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/content/jspup/JsoupSource.java

@@ -0,0 +1,51 @@
+package com.softwaremill.java_fp_example.contest.barti271.page.content.jspup;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.stream.Stream;
+
+import org.jsoup.Jsoup;
+import org.jsoup.nodes.Element;
+
+import com.softwaremill.java_fp_example.contest.barti271.page.content.source.MetaElement;
+import com.softwaremill.java_fp_example.contest.barti271.page.content.source.Source;
+
+
+/**
+ * {@link Jsoup} based implementation of {@link Source}.
+ */
+public class JsoupSource implements Source {
+
+    private static final int TIMEOUT_TEN_SECONDS = 10_000;
+
+    private final String url;
+
+    public JsoupSource(String url) {
+        this.url = url;
+    }
+
+    @Override
+    public Stream<MetaElement> getMetaElements() {
+        Element head = parseHead();
+        return head == null
+            ? Stream.empty()
+            : head.getElementsByTag("meta").stream().map(JsoupMetaElement::new);
+    }
+
+    private Element parseHead() {
+        try {
+            return tryParseHead();
+        } catch (IOException e) {
+            throw new IllegalStateException(url, e);
+        }
+    }
+
+    private Element tryParseHead() throws IOException {
+        return Jsoup.parse(new URL(url), TIMEOUT_TEN_SECONDS).head();
+    }
+
+    @Override
+    public String toString() {
+        return url;
+    }
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/content/source/MetaElement.java

@@ -0,0 +1,9 @@
+package com.softwaremill.java_fp_example.contest.barti271.page.content.source;
+
+public interface MetaElement {
+
+    String getProperty();
+
+    String getContent();
+
+}

src/main/java/com/softwaremill/java_fp_example/contest/barti271/page/content/source/Source.java

@@ -0,0 +1,9 @@
+package com.softwaremill.java_fp_example.contest.barti271.page.content.source;
+
+import java.util.stream.Stream;
+
+public interface Source {
+
+    Stream<MetaElement> getMetaElements();
+
+}

src/test/groovy/com/softwaremill/java_fp_example/FacebookImageSpec.groovy

@@ -5,7 +5,6 @@ import spock.lang.Unroll
 
 import static com.softwaremill.java_fp_example.DefaultImage.DEFAULT_IMAGE
 
-
 class FacebookImageSpec extends Specification {
 
     @Unroll
@@ -62,7 +61,7 @@ class FacebookImageSpec extends Specification {
     @Unroll
     def "should test Better Javaslang version with address #postAddress"() {
         when:
-        FacebookImageVersion2Javaslang facebookImage = new FacebookImageVersion2Javaslang(postAddress)
+        FacebookImageVersion3BetterJavaslang facebookImage = new FacebookImageVersion3BetterJavaslang(postAddress)
 
         then:
         facebookImage.getUrl() == expectedImageUrl
@@ -74,5 +73,5 @@ class FacebookImageSpec extends Specification {
         "https://twitter.com/softwaremill"                         || DEFAULT_IMAGE
         "http://i-do-not-exist.pl"                                 || DEFAULT_IMAGE
     }
-    
+
 }

src/test/groovy/com/softwaremill/java_fp_example/contest/barti271/FacebookImageSpec.groovy

@@ -0,0 +1,25 @@
+package com.softwaremill.java_fp_example.contest.barti271
+
+import spock.lang.Specification
+import spock.lang.Unroll
+
+import static com.softwaremill.java_fp_example.DefaultImage.DEFAULT_IMAGE
+
+class FacebookImageSpec extends Specification {
+
+    @Unroll
+    def "should test Barti271 version with address #postAddress"() {
+        when:
+        FacebookImageVersionBarti271 facebookImage = new FacebookImageVersionBarti271(postAddress)
+
+        then:
+        facebookImage.toString() == expectedImageUrl
+
+        where:
+        postAddress                                                || expectedImageUrl
+        "https://softwaremill.com/the-wrong-abstraction-recap/"    || "https://softwaremill.com/images/uploads/2017/02/street-shoe-chewing-gum.0526d557.jpg"
+        "https://softwaremill.com/using-kafka-as-a-message-queue/" || "https://softwaremill.com/images/uploads/2017/02/kmq.93f842cf.png"
+        "https://twitter.com/softwaremill"                         || DEFAULT_IMAGE
+        "http://i-do-not-exist.pl"                                 || DEFAULT_IMAGE
+    }
+}

src/test/groovy/com/softwaremill/java_fp_example/contest/barti271/LICENSE.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2017 barti271
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.