feat(objectionary#889): proceed with XMLDocument removal

src/main/java/org/eolang/jeo/Assembling.java

@@ -44,6 +44,11 @@ public final class Assembling implements Transformation {
      */
     private final Path from;
 
+    /**
+     * XMIR representation.
+     */
+    private final XmirRepresentation repr;
+
     /**
      * Constructor.
      * @param target Target folder.
@@ -52,6 +57,7 @@ public final class Assembling implements Transformation {
     Assembling(final Path target, final Path representation) {
         this.folder = target;
         this.from = representation;
+        this.repr = new XmirRepresentation(this.from);
     }
 
     @Override
@@ -61,15 +67,14 @@ public Path source() {
 
     @Override
     public Path target() {
-        final XmirRepresentation repr = new XmirRepresentation(this.from);
-        final String name = new PrefixedName(repr.name()).decode();
+        final String name = new PrefixedName(this.repr.name()).decode();
         final String[] subpath = name.split("\\.");
         subpath[subpath.length - 1] = String.format("%s.class", subpath[subpath.length - 1]);
         return Paths.get(this.folder.toString(), subpath);
     }
 
     @Override
     public byte[] transform() {
-        return new XmirRepresentation(this.from).toBytecode().bytes();
+        return this.repr.toBytecode().bytes();
     }
 }

src/main/java/org/eolang/jeo/representation/XmirRepresentation.java

@@ -27,12 +27,18 @@
 import com.jcabi.xml.XMLDocument;
 import java.io.FileNotFoundException;
 import java.nio.file.Path;
+import java.util.Optional;
+import javax.xml.xpath.XPath;
+import javax.xml.xpath.XPathConstants;
+import javax.xml.xpath.XPathExpressionException;
+import javax.xml.xpath.XPathFactory;
 import org.cactoos.scalar.Sticky;
 import org.cactoos.scalar.Synced;
 import org.cactoos.scalar.Unchecked;
 import org.eolang.jeo.representation.bytecode.Bytecode;
 import org.eolang.jeo.representation.xmir.XmlProgram;
 import org.eolang.parser.Schema;
+import org.w3c.dom.Node;
 
 /**
  * Intermediate representation of a class files from XMIR.
@@ -41,6 +47,11 @@
  */
 public final class XmirRepresentation {
 
+    /**
+     * XPath's factory.
+     */
+    private static final XPathFactory FACTORY = XPathFactory.newInstance();
+
     /**
      * XML.
      */
@@ -94,17 +105,36 @@ private XmirRepresentation(
 
     /**
      * Retrieves class name from XMIR.
+     * This method intentionally uses classes from `org.w3c.dom` instead of `com.jcabi.xml`
+     * by performance reasons.
      * @return Class name.
      */
     public String name() {
-        return new ClassName(
-            this.xml.value()
-                .xpath("/program/metas/meta/tail/text()")
-                .stream()
-                .findFirst()
-                .orElse(""),
-            this.xml.value().xpath("/program/@name").get(0)
-        ).full();
+        final Node node = this.xml.value().node();
+        final XPath xpath = XmirRepresentation.FACTORY.newXPath();
+        try {
+            return new ClassName(
+                Optional.ofNullable(
+                    ((Node) xpath.evaluate(
+                        "/program/metas/meta/tail/text()",
+                        node,
+                        XPathConstants.NODE
+                    )).getTextContent()
+                ).orElse(""),
+                String.valueOf(
+                    xpath.evaluate(
+                        "/program/@name",
+                        node,
+                        XPathConstants.STRING
+                    )
+                )
+            ).full();
+        } catch (final XPathExpressionException exception) {
+            throw new IllegalStateException(
+                String.format("Can't extract class name from the '%s' source", this.source),
+                exception
+            );
+        }
     }
 
     /**

src/main/java/org/eolang/jeo/representation/xmir/XmlProgram.java

@@ -89,7 +89,7 @@ public XmlProgram(final XML xml) {
      *
      * @param root Root node.
      */
-    private XmlProgram(final Node root) {
+    public XmlProgram(final Node root) {
         this.root = root;
     }