#1146 cache XSL factories

Author: yegor256

src/main/java/org/takes/rs/RsWithHeader.java

@@ -26,6 +26,7 @@
 import java.util.regex.Pattern;
 import lombok.EqualsAndHashCode;
 import lombok.ToString;
+import org.cactoos.Scalar;
 import org.cactoos.iterable.IterableOf;
 import org.cactoos.iterable.Joined;
 import org.takes.Response;
@@ -99,9 +100,18 @@ public RsWithHeader(final Response res, final CharSequence name,
      * @param header Header to add
      */
     public RsWithHeader(final Response res, final CharSequence header) {
+        this(res, () -> header);
+    }
+
+    /**
+     * Ctor.
+     * @param res Original response
+     * @param header Header to add
+     */
+    public RsWithHeader(final Response res, final Scalar<CharSequence> header) {
         super(
             new ResponseOf(
-                () -> RsWithHeader.extend(res.head(), header.toString()),
+                () -> RsWithHeader.extend(res.head(), header.value().toString()),
                 res::body
             )
         );

src/main/java/org/takes/rs/RsXslt.java

@@ -27,6 +27,8 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URI;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import javax.xml.transform.Source;
 import javax.xml.transform.Transformer;
 import javax.xml.transform.TransformerConfigurationException;
@@ -84,6 +86,12 @@
 @EqualsAndHashCode(callSuper = true)
 public final class RsXslt extends RsWrap {
 
+    /**
+     * Cached factory.
+     */
+    private static final Map<URIResolver, TransformerFactory> FACTORIES =
+        new ConcurrentHashMap<>(0);
+
     /**
      * Ctor.
      * @param rsp Original response
@@ -99,13 +107,35 @@ public RsXslt(final Response rsp) {
      */
     public RsXslt(final Response rsp, final URIResolver resolver) {
         super(
-            new ResponseOf(
-                rsp::head,
-                () -> RsXslt.transform(rsp.body(), resolver)
+            new RsWithHeader(
+                new ResponseOf(
+                    rsp::head,
+                    () -> RsXslt.transform(rsp.body(), resolver)
+                ),
+                () -> String.format(
+                    "X-Takes-RsXslt-TransformerFactory: %s",
+                    RsXslt.factory(resolver).getClass().getCanonicalName()
+                )
             )
         );
     }
 
+    /**
+     * Get factory for the given resolver.
+     * @param resolver Resolver
+     * @return Factory
+     */
+    private static TransformerFactory factory(final URIResolver resolver) {
+        return RsXslt.FACTORIES.computeIfAbsent(
+            resolver,
+            res -> {
+                final TransformerFactory fct = TransformerFactory.newInstance();
+                fct.setURIResolver(res);
+                return fct;
+            }
+        );
+    }
+
     /**
      * Build body.
      * @param origin Original body
@@ -115,12 +145,17 @@ public RsXslt(final Response rsp, final URIResolver resolver) {
      */
     private static InputStream transform(final InputStream origin,
         final URIResolver resolver) throws IOException {
+        final TransformerFactory fct = RsXslt.factory(resolver);
         try {
-            final TransformerFactory factory = TransformerFactory.newInstance();
-            factory.setURIResolver(resolver);
-            return RsXslt.transform(factory, origin);
+            return RsXslt.transform(fct, origin);
         } catch (final TransformerException ex) {
-            throw new IOException(ex);
+            throw new IOException(
+                String.format(
+                    "Can't transform via %s",
+                    fct.getClass().getName()
+                ),
+                ex
+            );
         }
     }