feat(#213): improve code quality and remove the 213 puzzle

src/main/java/com/jcabi/xml/SaxonDocument.java

@@ -43,7 +43,14 @@
 import net.sf.saxon.s9api.XdmNode;
 import org.w3c.dom.Node;
 
-public class SaxonDocument implements XML {
+/**
+ * Saxon XML document.
+ *
+ * <p>Objects of this class are immutable, but NOT thread-safe.
+ *
+ * @since 0.28
+ */
+public final class SaxonDocument implements XML {
 
     /**
      * Saxon processor.
@@ -53,7 +60,7 @@ public class SaxonDocument implements XML {
     /**
      * Saxon document builder.
      */
-    private static final DocumentBuilder DOCUMENT_BUILDER = SaxonDocument.SAXON.newDocumentBuilder();
+    private static final DocumentBuilder DOC_BUILDER = SaxonDocument.SAXON.newDocumentBuilder();
 
     /**
      * Saxon XPath compiler.
@@ -69,7 +76,7 @@ public class SaxonDocument implements XML {
     /**
      * Saxon XML document node.
      */
-    private final XdmNode node;
+    private final XdmNode xdm;
 
     /**
      * Public constructor from XML as string text.
@@ -81,17 +88,17 @@ public SaxonDocument(final String text) {
 
     /**
      * Public constructor from Saxon XML document node.
-     * @param node Saxon XML document node.
+     * @param xml Saxon XML document node.
      */
-    public SaxonDocument(final XdmNode node) {
-        this.node = node;
+    public SaxonDocument(final XdmNode xml) {
+        this.xdm = xml;
     }
 
     @Override
     public List<String> xpath(final String query) {
         try {
             final XPathSelector selector = SaxonDocument.XPATH_COMPILER.compile(query).load();
-            selector.setContextItem(this.node);
+            selector.setContextItem(this.xdm);
             return selector.evaluate()
                 .stream()
                 .map(XdmItem::getStringValue)
@@ -139,7 +146,7 @@ public Node node() {
      */
     private static XdmNode node(final String text) {
         try {
-            return SaxonDocument.DOCUMENT_BUILDER
+            return SaxonDocument.DOC_BUILDER
                 .build(new StreamSource(new StringReader(text)));
         } catch (final SaxonApiException exception) {
             throw new IllegalArgumentException(

src/test/java/com/jcabi/xml/SaxonDocumentTest.java

@@ -1,10 +1,43 @@
+/*
+ * Copyright (c) 2012-2022, jcabi.com
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met: 1) Redistributions of source code must retain the above
+ * copyright notice, this list of conditions and the following
+ * disclaimer. 2) Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following
+ * disclaimer in the documentation and/or other materials provided
+ * with the distribution. 3) Neither the name of the jcabi.com nor
+ * the names of its contributors may be used to endorse or promote
+ * products derived from this software without specific prior written
+ * permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
+ * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
 package com.jcabi.xml;
 
 import org.hamcrest.MatcherAssert;
 import org.hamcrest.Matchers;
 import org.junit.jupiter.api.Test;
 
-class SaxonDocumentTest {
+/**
+ * Test case for {@link SaxonDocument}.
+ * @since 0.28
+ */
+final class SaxonDocumentTest {
 
     @Test
     void findsXpathWithFunctionThatReturnsSeveralItems() {
@@ -16,4 +49,4 @@ void findsXpathWithFunctionThatReturnsSeveralItems() {
             Matchers.hasItems("a|1", "b|2")
         );
     }
-}
+}

src/test/java/com/jcabi/xml/XMLDocumentTest.java

@@ -56,12 +56,6 @@
  *
  * @since 0.1
  * @checkstyle AbbreviationAsWordInNameCheck (20 lines)
- * @todo #221:30min Implement XPath 2.0 evaluations.
- *  We have to implement XPath 2.0 evaluations in order to support more complex XPath queries.
- *  For example, the following query is not supported:
- *  - "//o[@base and @ver]/concat(@base,'|',@ver)"
- *  When we implement XPath 2.0 evaluations, we should remove the @Disabled annotation from
- *  findsXpathWithFunctionThatReturnsSeveralItems test.
  */
 @SuppressWarnings({"PMD.TooManyMethods", "PMD.DoNotUseThreads"})
 final class XMLDocumentTest {
@@ -414,16 +408,4 @@ void appliesXpathToClonedNode() {
             Matchers.equalTo("433")
         );
     }
-
-    @Test
-    @Disabled
-    void findsXpathWithFunctionThatReturnsSeveralItems() {
-        MatcherAssert.assertThat(
-            "XMLDocument can handle XPath 2.0 feature - XPath evaluation of concat method, but it can't",
-            new XMLDocument(
-                "<o><o base='a' ver='1'/><o base='b' ver='2'/></o>"
-            ).xpath("//o[@base and @ver]/concat(@base,'|',@ver)"),
-            Matchers.hasItems("a|1", "b|2")
-        );
-    }
 }