refactor(core): move StringUtil to text package, extend XSLT tran… (#2636)

* refactor(core): move `StringUtil` to `text` package, extend XSLT transformation support, and add tutorial examples

* refactor(tutorials): improve XML to JSON XSLT transformation readability and output consistency

* refactor(xslt): rename test class and improve error handling in XSLT transformations

* refactor(xslt): simplify `transformMsg` method and clean up test code

* refactor(xslt): fix case sensitivity in YAML file reference and remove unused test code

* refactor(xslt): update YAML file references, fix typo in test method, and clarify beautifier comment

* refactor(tutorials): change year type in XML to JSON transformation test to string for consistency

---------

Co-authored-by: Christian Gördes <118011644+christiangoerdes@users.noreply.github.com>

Author: predic8

core/src/main/java/com/predic8/membrane/core/interceptor/templating/AbstractTemplateInterceptor.java

@@ -31,7 +31,7 @@
 import static com.predic8.membrane.core.interceptor.Outcome.ABORT;
 import static com.predic8.membrane.core.interceptor.Outcome.*;
 import static com.predic8.membrane.core.resolver.ResolverMap.*;
-import static com.predic8.membrane.core.util.StringUtil.*;
+import static com.predic8.membrane.core.util.text.StringUtil.*;
 import static java.nio.charset.StandardCharsets.*;
 import static org.apache.commons.text.StringEscapeUtils.*;
 

core/src/main/java/com/predic8/membrane/core/interceptor/templating/TemplateInterceptor.java

@@ -31,7 +31,7 @@
 import static com.predic8.membrane.core.interceptor.Outcome.*;
 import static com.predic8.membrane.core.lang.ScriptingUtils.*;
 import static com.predic8.membrane.core.util.FileUtil.*;
-import static com.predic8.membrane.core.util.StringUtil.addLineNumbers;
+import static com.predic8.membrane.core.util.text.StringUtil.addLineNumbers;
 import static java.nio.charset.StandardCharsets.*;
 
 /**

core/src/main/java/com/predic8/membrane/core/interceptor/xml/Json2XmlInterceptor.java

@@ -24,7 +24,7 @@
 import static com.predic8.membrane.core.http.MimeType.*;
 import static com.predic8.membrane.core.interceptor.Interceptor.Flow.*;
 import static com.predic8.membrane.core.interceptor.Outcome.*;
-import static com.predic8.membrane.core.util.StringUtil.*;
+import static com.predic8.membrane.core.util.text.StringUtil.*;
 import static java.nio.charset.StandardCharsets.*;
 
 /**

core/src/main/java/com/predic8/membrane/core/interceptor/xslt/XSLTInterceptor.java

@@ -19,111 +19,127 @@
 import com.predic8.membrane.core.interceptor.*;
 import com.predic8.membrane.core.multipart.*;
 import com.predic8.membrane.core.util.*;
-import com.predic8.membrane.core.util.text.*;
+import org.jetbrains.annotations.*;
 import org.slf4j.*;
 
+import javax.xml.transform.*;
 import javax.xml.transform.stream.*;
 import java.util.*;
 
 import static com.predic8.membrane.core.exceptions.ProblemDetails.*;
+import static com.predic8.membrane.core.interceptor.Interceptor.Flow.*;
 import static com.predic8.membrane.core.interceptor.Outcome.*;
+import static com.predic8.membrane.core.interceptor.Outcome.ABORT;
+import static com.predic8.membrane.core.util.text.StringUtil.*;
+import static com.predic8.membrane.core.util.text.TextUtil.*;
 
 /**
  * @description <p>
- *              The transform feature applies an XSLT transformation to the content in the body of a message. After the
- *              transformation the body content is replaced with the result of the transformation.
- *              </p>
+ * The transform feature applies an XSLT transformation to the content in the body of a message. After the
+ * transformation the body content is replaced with the result of the transformation.
+ * </p>
  * @topic 2. Enterprise Integration Patterns
  */
-@MCElement(name="transform")
+@MCElement(name = "transform")
 public class XSLTInterceptor extends AbstractInterceptor {
 
-	private static final Logger log = LoggerFactory.getLogger(XSLTInterceptor.class.getName());
+    private static final Logger log = LoggerFactory.getLogger(XSLTInterceptor.class.getName());
 
-	private String xslt;
-	private volatile XSLTTransformer xsltTransformer;
-	private final XOPReconstitutor xopr = new XOPReconstitutor();
+    private String xslt;
+    private volatile XSLTTransformer xsltTransformer;
+    private final XOPReconstitutor xopr = new XOPReconstitutor();
 
-	public XSLTInterceptor() {
-		name = "xslt transformer";
-	}
+    public XSLTInterceptor() {
+        name = "xslt transformer";
+    }
 
-	@Override
-	public Outcome handleRequest(Exchange exc) {
-        try {
-            transformMsg(exc.getRequest(), xslt, exc.getStringProperties());
-        } catch (Exception e) {
-			user(router.getConfiguration().isProduction(),getDisplayName())
-					.detail("Error transforming request!")
-					.exception(e)
-					.buildAndSetResponse(exc);
-			return ABORT;
-        }
-        return CONTINUE;
-	}
+    @Override
+    public Outcome handleRequest(Exchange exc) {
+        return handleInternal(exc, REQUEST);
+    }
+
+    @Override
+    public Outcome handleResponse(Exchange exc) {
+        return handleInternal(exc, RESPONSE);
+    }
+
+    private Outcome handleInternal(Exchange exc, Flow flow) {
+        var msg = exc.getMessage(flow);
 
-	@Override
-	public Outcome handleResponse(Exchange exc) {
         try {
-            transformMsg(exc.getResponse(), xslt, exc.getStringProperties());
+            transformMsg(msg, exc.getStringProperties());
+        } catch (TransformerException e) {
+            log.debug("", e);
+            if (e.getMessage() != null && e.getMessage().contains("not allowed in prolog")) {
+                user(router.getConfiguration().isProduction(), getDisplayName())
+                        .title("Content not allowed in prolog of XML input.")
+                        .detail("Check for extra characters before the XML declaration <?xml ... ?>")
+                        .internal("offendingInput", truncateAfter(msg.getBodyAsStringDecoded() + "...", 50))
+                        .buildAndSetResponse(exc);
+                return ABORT;
+            }
+            return createErrorResponse(exc,e,flow);
         } catch (Exception e) {
-			log.error("Error transforming response!", e);
-			user(router.getConfiguration().isProduction(),getDisplayName())
-					.detail("Error transforming response!")
-					.exception(e)
-					.buildAndSetResponse(exc);
-			return ABORT;
+            log.info("", e);
+            return createErrorResponse(exc,e,flow);
         }
         return CONTINUE;
-	}
-
-	private void transformMsg(Message msg, String ss, Map<String, String> parameter) throws Exception {
-		if (msg.isBodyEmpty())
-			return;
-		msg.setBodyContent(xsltTransformer.transform(
-				new StreamSource(xopr.reconstituteIfNecessary(msg)), parameter));
-	}
-
-	@Override
-	public void init() {
-		super.init();
+    }
+
+    private @NotNull Outcome createErrorResponse(Exchange exc, Exception e, Flow flow) {
+        user(router.getConfiguration().isProduction(), getDisplayName())
+                .detail("Error transforming message!")
+                .exception(e)
+                .internal("flow", flow.toString())
+                .buildAndSetResponse(exc);
+        return ABORT;
+    }
+
+    private void transformMsg(Message msg, Map<String, String> parameter) throws Exception {
+        if (msg.isBodyEmpty())
+            return;
+        msg.setBodyContent(xsltTransformer.transform(
+                new StreamSource(xopr.reconstituteIfNecessary(msg)), parameter));
+    }
+
+    @Override
+    public void init() {
+        super.init();
         try {
             xsltTransformer = new XSLTTransformer(xslt, router, getConcurrency());
         } catch (Exception e) {
-			log.debug("",e);
+			      log.debug("",e);
             throw new ConfigurationException("Could not create XSLT transformer",e);
+
         }
     }
 
-	private static int getConcurrency() {
-		return Runtime.getRuntime().availableProcessors() * 2;
-	}
-
-	public String getXslt() {
-		return xslt;
-	}
-
-	/**
-	 * @description Location of the XSLT stylesheet that will be applied to request and response.
-	 * @example strip.xslt
-	 */
-	@MCAttribute
-	public void setXslt(String xslt) {
-		this.xslt = xslt;
-		this.xsltTransformer = null;
-	}
-
-	@Override
-	public String getShortDescription() {
-		return "Applies an XSLT transformation.";
-	}
-
-	@Override
-	public String getLongDescription() {
-        return TextUtil.removeFinalChar(getShortDescription()) +
-               " using the stylesheet at " +
-               TextUtil.linkURL(xslt) +
-               " .";
-	}
+    private static int getConcurrency() {
+        return Runtime.getRuntime().availableProcessors() * 2;
+    }
+
+    public String getXslt() {
+        return xslt;
+    }
+
+    /**
+     * @description Location of the XSLT stylesheet that will be applied to request and response.
+     * @example strip.xslt
+     */
+    @MCAttribute
+    public void setXslt(String xslt) {
+        this.xslt = xslt;
+        this.xsltTransformer = null;
+    }
+
+    @Override
+    public String getShortDescription() {
+        return "Applies an XSLT transformation.";
+    }
+
+    @Override
+    public String getLongDescription() {
+        return "%s using the stylesheet at %s .".formatted(removeFinalChar(getShortDescription()), linkURL(xslt));
+    }
 
 }

core/src/main/java/com/predic8/membrane/core/lang/jsonpath/JsonpathExchangeExpression.java

@@ -28,7 +28,7 @@
 import java.io.*;
 import java.util.*;
 
-import static com.predic8.membrane.core.util.StringUtil.*;
+import static com.predic8.membrane.core.util.text.StringUtil.*;
 import static java.lang.Boolean.*;
 import static java.nio.charset.StandardCharsets.*;
 

core/src/main/java/com/predic8/membrane/core/openapi/serviceproxy/APIProxy.java

@@ -38,7 +38,7 @@
 
 import static com.predic8.membrane.core.lang.ExchangeExpression.Language.SPEL;
 import static com.predic8.membrane.core.lang.ExchangeExpression.expression;
-import static com.predic8.membrane.core.util.StringUtil.maskNonPrintableCharacters;
+import static com.predic8.membrane.core.util.text.StringUtil.maskNonPrintableCharacters;
 
 /**
  * @description The api proxy extends the serviceProxy with API related functions like OpenAPI support and path parameters.

core/src/main/java/com/predic8/membrane/core/transport/http/HttpServerHandler.java

@@ -35,8 +35,8 @@
 import static com.predic8.membrane.core.transport.http.ByteStreamLogging.wrapConnectionOutputStream;
 import static com.predic8.membrane.core.transport.http.HttpServerHandler.RequestProcessingResult.*;
 import static com.predic8.membrane.core.transport.http.HttpServerThreadFactory.DEFAULT_THREAD_NAME;
-import static com.predic8.membrane.core.util.StringUtil.maskNonPrintableCharacters;
-import static com.predic8.membrane.core.util.StringUtil.truncateAfter;
+import static com.predic8.membrane.core.util.text.StringUtil.maskNonPrintableCharacters;
+import static com.predic8.membrane.core.util.text.StringUtil.truncateAfter;
 import static java.lang.Thread.currentThread;
 
 public class HttpServerHandler extends AbstractHttpHandler implements Runnable, TwoWayStreaming {

core/src/main/java/com/predic8/membrane/core/util/text/StringUtil.java

@@ -12,7 +12,7 @@
    See the License for the specific language governing permissions and
    limitations under the License. */
 
-package com.predic8.membrane.core.util;
+package com.predic8.membrane.core.util.text;
 
 import java.util.*;