Optimised the XPath Handlebars helper's performance by caching parsed…

… XML documents and evaluated XPath expressions

src/main/java/com/github/tomakehurst/wiremock/extension/responsetemplating/HandlebarsOptimizedTemplate.java

@@ -17,6 +17,7 @@
 
 import java.io.IOException;
 
+import com.github.jknack.handlebars.Context;
 import com.github.jknack.handlebars.Handlebars;
 import com.github.jknack.handlebars.Template;
 import com.github.tomakehurst.wiremock.common.Exceptions;
@@ -56,8 +57,17 @@ private static Template uncheckedCompileTemplate(Handlebars handlebars, String t
 		}
 	}
 
-	public String apply(Object context) throws IOException {
+	public String apply(Object contextData) throws IOException {
+		final RenderCache renderCache = new RenderCache();
+		Context context = Context
+				.newBuilder(contextData)
+				.combine("renderCache", renderCache)
+				.build();
+
 		StringBuilder sb = new StringBuilder();
-		return sb.append(startContent).append(template.apply(context)).append(endContent).toString();
+		return sb.append(startContent)
+				 .append(template.apply(context))
+				 .append(endContent)
+				 .toString();
 	}
 }

src/main/java/com/github/tomakehurst/wiremock/extension/responsetemplating/RenderCache.java

@@ -0,0 +1,59 @@
+package com.github.tomakehurst.wiremock.extension.responsetemplating;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import static java.util.Arrays.asList;
+
+public class RenderCache {
+
+    private final Map<Key, Object> cache = new HashMap<>();
+
+    public void put(Key key, Object value) {
+        cache.put(key, value);
+    }
+
+    @SuppressWarnings("unchecked")
+    public <T> T get(Key key) {
+        return (T) cache.get(key);
+    }
+
+    public static class Key {
+        private final Class<?> forClass;
+        private final List<?> elements;
+
+        public static Key keyFor(Class<?> forClass, Object... elements) {
+            return new Key(forClass, asList(elements));
+        }
+
+        private Key(Class<?> forClass, List<?> elements) {
+            this.forClass = forClass;
+            this.elements = elements;
+        }
+
+        @Override
+        public String toString() {
+            final StringBuilder sb = new StringBuilder("Key{");
+            sb.append("forClass=").append(forClass);
+            sb.append(", elements=").append(elements);
+            sb.append('}');
+            return sb.toString();
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+            Key key = (Key) o;
+            return forClass.equals(key.forClass) &&
+                    elements.equals(key.elements);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(forClass, elements);
+        }
+    }
+}

src/main/java/com/github/tomakehurst/wiremock/extension/responsetemplating/helpers/HandlebarsXPathHelper.java

@@ -17,6 +17,7 @@
 
 import com.github.jknack.handlebars.Options;
 import com.github.tomakehurst.wiremock.common.Xml;
+import com.github.tomakehurst.wiremock.extension.responsetemplating.RenderCache;
 import org.w3c.dom.Document;
 import org.w3c.dom.Node;
 import org.xml.sax.InputSource;
@@ -73,16 +74,14 @@ public Object apply(final String inputXml, final Options options) throws IOExcep
         final String xPathInput = options.param(0);
 
         Document doc;
-        try (final StringReader reader = new StringReader(inputXml)) {
-            InputSource source = new InputSource(reader);
-            doc = localDocBuilder.get().parse(source);
+        try {
+            doc = getDocument(inputXml, options);
         } catch (SAXException se) {
             return handleError(inputXml + " is not valid XML");
         }
 
         try {
-            XPath xPath = localXPath.get();
-            Node node = (Node) xPath.evaluate(getXPathPrefix() + xPathInput, doc, NODE);
+            Node node = getNode(getXPathPrefix() + xPathInput, doc, options);
 
             if (node == null) {
                 return "";
@@ -94,6 +93,38 @@ public Object apply(final String inputXml, final Options options) throws IOExcep
         }
     }
 
+    private Node getNode(String xPathExpression, Document doc, Options options) throws XPathExpressionException {
+        RenderCache renderCache = getRenderCache(options);
+        RenderCache.Key cacheKey = RenderCache.Key.keyFor(Document.class, xPathExpression, doc);
+        Node node = renderCache.get(cacheKey);
+
+        if (node == null) {
+            XPath xPath = localXPath.get();
+            node = (Node) xPath.evaluate(xPathExpression, doc, NODE);
+            renderCache.put(cacheKey, node);
+        }
+
+        return node;
+    }
+
+    private Document getDocument(String xml, Options options) throws SAXException, IOException {
+        RenderCache renderCache = getRenderCache(options);
+        RenderCache.Key cacheKey = RenderCache.Key.keyFor(Document.class, xml);
+        Document document = renderCache.get(cacheKey);
+        if (document == null) {
+            try (final StringReader reader = new StringReader(xml)) {
+                InputSource source = new InputSource(reader);
+                document = localDocBuilder.get().parse(source);
+                renderCache.put(cacheKey, document);
+            }
+        }
+
+        return document;
+    }
+
+    private RenderCache getRenderCache(Options options) {
+        return options.get("renderCache", null);
+    }
 
     /**
      * No prefix by default. It allows to extend this class with a specified prefix. Just overwrite this method to do

src/test/java/com/github/tomakehurst/wiremock/extension/responsetemplating/helpers/HandlebarsHelperTestBase.java

@@ -15,49 +15,71 @@
  */
 package com.github.tomakehurst.wiremock.extension.responsetemplating.helpers;
 
+import com.github.jknack.handlebars.Context;
 import com.github.jknack.handlebars.Helper;
 import com.github.jknack.handlebars.Options;
+import com.github.tomakehurst.wiremock.extension.responsetemplating.RenderCache;
 import org.hamcrest.Matcher;
 import org.junit.Assert;
+import org.junit.Before;
 
 import java.io.IOException;
 import java.util.ArrayList;
 
 import static org.hamcrest.Matchers.is;
-import static org.hamcrest.Matchers.startsWith;
 import static org.junit.Assert.assertThat;
 
 public abstract class HandlebarsHelperTestBase {
 
+    protected RenderCache renderCache;
+
+    @Before
+    public void initRenderCache() {
+        renderCache = new RenderCache();
+    }
+
     protected static final String FAIL_GRACEFULLY_MSG = "Handlebars helper should fail gracefully and show the issue directly in the response.";
 
-    protected static <T> void testHelperError(Helper<T> helper,
+    protected <T> void testHelperError(Helper<T> helper,
                                               T content,
                                               String pathExpression,
                                               Matcher<String> expectation) {
         try {
-            assertThat((String) helper.apply(content, createOptions(pathExpression)), expectation);
+            assertThat((String) renderHelperValue(helper, content, pathExpression), expectation);
         } catch (final IOException e) {
             Assert.fail(FAIL_GRACEFULLY_MSG);
         }
     }
 
-    protected static <T> void testHelper(Helper<T> helper,
+    @SuppressWarnings("unchecked")
+    protected <R, C> R renderHelperValue(Helper<C> helper, C content, String parameter) throws IOException {
+        return (R) helper.apply(content, createOptions(parameter));
+    }
+
+    protected <T> void testHelper(Helper<T> helper,
                                          T content,
                                          String optionParam,
                                          String expected) throws IOException {
         testHelper(helper, content, optionParam, is(expected));
     }
 
-    protected static <T> void testHelper(Helper<T> helper,
+    protected <T> void testHelper(Helper<T> helper,
                                          T content,
                                          String optionParam,
                                          Matcher<String> expected) throws IOException {
         assertThat(helper.apply(content, createOptions(optionParam)).toString(), expected);
     }
 
-    protected static Options createOptions(String optionParam) {
-        return new Options(null, null, null, null, null, null,
+    protected Options createOptions(String optionParam) {
+        return createOptions(optionParam, renderCache);
+    }
+
+    protected Options createOptions(String optionParam, RenderCache renderCache) {
+        Context context = Context.newBuilder(null)
+                .combine("renderCache", renderCache)
+                .build();
+
+        return new Options(null, null, null, context, null, null,
                            new Object[]{optionParam}, null, new ArrayList<String>(0));
     }
 }

src/test/java/com/github/tomakehurst/wiremock/extension/responsetemplating/helpers/HandlebarsXPathHelperTest.java

@@ -16,11 +16,16 @@
 package com.github.tomakehurst.wiremock.extension.responsetemplating.helpers;
 
 import com.github.tomakehurst.wiremock.extension.Parameters;
+import com.github.tomakehurst.wiremock.extension.responsetemplating.RenderCache;
 import com.github.tomakehurst.wiremock.extension.responsetemplating.ResponseTemplateTransformer;
 import com.github.tomakehurst.wiremock.http.ResponseDefinition;
 import com.github.tomakehurst.wiremock.testsupport.WireMatchers;
+import org.jmock.Expectations;
+import org.jmock.Mockery;
+import org.jmock.integration.junit4.JMock;
 import org.junit.Before;
 import org.junit.Test;
+import org.junit.runner.RunWith;
 
 import java.io.IOException;
 
@@ -30,6 +35,7 @@
 import static com.github.tomakehurst.wiremock.testsupport.WireMatchers.equalToXml;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.startsWith;
+import static org.jmock.Expectations.anything;
 import static org.junit.Assert.assertThat;
 
 public class HandlebarsXPathHelperTest extends HandlebarsHelperTestBase {
@@ -108,6 +114,31 @@ public void rendersABlankWhenTheInputXmlIsAbsent() {
         testHelperError(helper, null, "/test", is(""));
     }
 
+    @Test
+    public void returnsCorrectResultWhenSameExpressionUsedTwiceOnIdenticalDocuments() throws Exception {
+        String one = renderHelperValue(helper, "<test>one</test>", "/test/text()");
+        String two = renderHelperValue(helper, "<test>one</test>", "/test/text()");
+
+        assertThat(one, is("one"));
+        assertThat(two, is("one"));
+    }
+
+    @Test
+    public void returnsCorrectResultWhenSameExpressionUsedTwiceOnDifferentDocuments() throws Exception {
+        String one = renderHelperValue(helper, "<test>one</test>", "/test/text()");
+        String two = renderHelperValue(helper, "<test>two</test>", "/test/text()");
 
+        assertThat(one, is("one"));
+        assertThat(two, is("two"));
+    }
+
+    @Test
+    public void returnsCorrectResultWhenDifferentExpressionsUsedOnSameDocument() throws Exception {
+        String one = renderHelperValue(helper, "<test><one>1</one><two>2</two></test>", "/test/one/text()");
+        String two = renderHelperValue(helper, "<test><one>1</one><two>2</two></test>", "/test/two/text()");
+
+        assertThat(one, is("1"));
+        assertThat(two, is("2"));
+    }
 
 }