Improve log mediator to support string templating

modules/core/src/main/java/org/apache/synapse/config/xml/LogMediatorFactory.java

@@ -32,6 +32,7 @@
  *
  * <pre>
  * &lt;log [level="simple|headers|full|custom"]&gt;
+ *      &lt;message&gt;String template&lt;/message&gt;
  *      &lt;property&gt; *
  * &lt;/log&gt;
  * </pre>
@@ -52,6 +53,8 @@ public class LogMediatorFactory extends AbstractMediatorFactory  {
     private static final QName ATT_LEVEL = new QName("level");
     private static final QName ATT_SEPERATOR = new QName("separator");
     private static final QName ATT_CATEGORY = new QName("category");
+    protected static final QName ELEMENT_MESSAGE_Q
+            = new QName(XMLConfigConstants.SYNAPSE_NAMESPACE, "message");
 
     public QName getTagQName() {
         return LOG_Q;
@@ -64,7 +67,14 @@ public Mediator createSpecificMediator(OMElement elem, Properties properties) {
         // after successfully creating the mediator
         // set its common attributes such as tracing etc
         processAuditStatus(logMediator,elem);
-
+
+        boolean containMessageTemplate = false;
+        OMElement messageElement = elem.getFirstChildWithName(ELEMENT_MESSAGE_Q);
+        if (messageElement != null && messageElement.getText() != null) {
+            logMediator.setMessageTemplate(messageElement.getText());
+            containMessageTemplate = true;
+        }
+
         // Set the high level set of properties to be logged (i.e. log level)
         OMAttribute level = elem.getAttribute(ATT_LEVEL);
         if (level != null) {
@@ -81,6 +91,10 @@ public Mediator createSpecificMediator(OMElement elem, Properties properties) {
                 handleException("Invalid log level. Level has to be one of the following : "
                         + "simple, headers, full, custom");
             }
+        } else {
+            if (containMessageTemplate) {
+                logMediator.setLogLevel(LogMediator.MESSAGE_TEMPLATE);
+            }
         }
 
         // Set the log statement category (i.e. INFO, DEBUG, etc..)
@@ -112,7 +126,7 @@ public Mediator createSpecificMediator(OMElement elem, Properties properties) {
         }
 
         logMediator.addAllProperties(MediatorPropertyFactory.getMediatorProperties(elem));
-
+        logMediator.processTemplateAndSetContentAware();
         addAllCommentChildrenToList(elem, logMediator.getCommentsList());
 
         return logMediator;

modules/core/src/main/java/org/apache/synapse/config/xml/LogMediatorSerializer.java

@@ -20,12 +20,14 @@
 package org.apache.synapse.config.xml;
 
 import org.apache.axiom.om.OMElement;
+import org.apache.commons.lang3.StringUtils;
 import org.apache.synapse.Mediator;
 import org.apache.synapse.mediators.builtin.LogMediator;
 
 /**
  * <pre>
  * &lt;log [level="simple|headers|full|custom"] [separator="string"] [category="INFO|TRACE|DEBUG|WARN|ERROR|FATAL"]&gt;
+ *      &lt;message&gt;String template&lt;/message&gt;
  *      &lt;property&gt; *
  * &lt;/log&gt;
  * </pre>
@@ -42,7 +44,7 @@ public OMElement serializeSpecificMediator(Mediator m) {
         OMElement log = fac.createOMElement("log", synNS);
         saveTracingState(log,mediator);
 
-        if (mediator.getLogLevel() != LogMediator.SIMPLE) {
+        if (mediator.getLogLevel() != LogMediator.MESSAGE_TEMPLATE) {
             log.addAttribute(fac.createOMAttribute(
                 "level", nullNS,
                     mediator.getLogLevel() == LogMediator.HEADERS ? "headers" :
@@ -73,6 +75,12 @@ public OMElement serializeSpecificMediator(Mediator m) {
                     "separator", nullNS, mediator.getSeparator()));
         }
 
+        if (StringUtils.isNotBlank(mediator.getMessageTemplate())) {
+            OMElement onCompleteElem = fac.createOMElement("message", synNS);
+            onCompleteElem.setText(mediator.getMessageTemplate());
+            log.addChild(onCompleteElem);
+        }
+
         super.serializeProperties(log, mediator.getProperties());
 
         serializeComments(log, mediator.getCommentsList());

modules/core/src/main/java/org/apache/synapse/mediators/builtin/LogMediator.java

@@ -32,12 +32,13 @@
 import org.apache.synapse.core.axis2.Axis2MessageContext;
 import org.apache.synapse.mediators.AbstractMediator;
 import org.apache.synapse.mediators.MediatorProperty;
+import org.apache.synapse.util.InlineExpressionUtil;
+import org.jaxen.JaxenException;
 
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
-
 /**
  * Logs the specified message into the configured logger. The log levels specify
  * which attributes would be logged, and is configurable. Additionally custom
@@ -56,6 +57,9 @@ public class LogMediator extends AbstractMediator {
     /** all attributes of level 'simple' and the SOAP envelope and any properties */
     public static final int FULL    = 3;
 
+    /** The message template and the additional properties specified to the Log mediator */
+    public static final int MESSAGE_TEMPLATE = 4;
+
     public static final int CATEGORY_INFO = 0;
     public static final int CATEGORY_DEBUG = 1;
     public static final int CATEGORY_TRACE = 2;
@@ -74,6 +78,9 @@ public class LogMediator extends AbstractMediator {
     /** The holder for the custom properties */
     private final List<MediatorProperty> properties = new ArrayList<MediatorProperty>();
 
+    private String messageTemplate = "";
+    private boolean isContentAware = false;
+
     /**
      * Logs the current message according to the supplied semantics
      *
@@ -136,6 +143,7 @@ public boolean mediate(MessageContext synCtx) {
     private String getLogMessage(MessageContext synCtx) {
         switch (logLevel) {
             case CUSTOM:
+            case MESSAGE_TEMPLATE:
                 return getCustomLogMessage(synCtx);
             case SIMPLE:
                 return getSimpleLogMessage(synCtx);
@@ -150,12 +158,18 @@ private String getLogMessage(MessageContext synCtx) {
 
     private String getCustomLogMessage(MessageContext synCtx) {
         StringBuffer sb = new StringBuffer();
+        processMessageTemplate(sb, synCtx, messageTemplate);
         setCustomProperties(sb, synCtx);
         return trimLeadingSeparator(sb);
     }
 
     private String getSimpleLogMessage(MessageContext synCtx) {
         StringBuffer sb = new StringBuffer();
+        processMessageTemplate(sb, synCtx, messageTemplate);
+        // append separator if the message template is not empty
+        if (sb.length() > 0) {
+            sb.append(separator);
+        }
         if (synCtx.getTo() != null)
             sb.append("To: ").append(synCtx.getTo().getAddress());
         else
@@ -180,6 +194,7 @@ private String getSimpleLogMessage(MessageContext synCtx) {
 
     private String getHeadersLogMessage(MessageContext synCtx) {
         StringBuffer sb = new StringBuffer();
+        processMessageTemplate(sb, synCtx, messageTemplate);
         if (synCtx.getEnvelope() != null) {
             SOAPHeader header = synCtx.getEnvelope().getHeader();
             if (getCorrelationId(synCtx) != null)
@@ -288,6 +303,16 @@ public void setCategory(int category) {
         }
     }
 
+    public String getMessageTemplate() {
+
+        return messageTemplate;
+    }
+
+    public void setMessageTemplate(String messageTemplate) {
+
+        this.messageTemplate = messageTemplate.replace("\\n", "\n").replace("\\t", "\t");
+    }
+
     private String trimLeadingSeparator(StringBuffer sb) {
         String retStr = sb.toString();
         if (retStr.startsWith(separator)) {
@@ -297,16 +322,32 @@ private String trimLeadingSeparator(StringBuffer sb) {
         }
     }
 
+    private void processMessageTemplate(StringBuffer stringBuffer, MessageContext synCtx, String template) {
+        try {
+            stringBuffer.append(InlineExpressionUtil.processInLineSynapseExpressionTemplate(synCtx, template));
+        } catch (JaxenException e) {
+            handleException("Failed to process the message template : " + template, e, synCtx);
+        }
+    }
+
     @Override
     public boolean isContentAware() {
-        if (logLevel == CUSTOM) {
+
+        return isContentAware;
+    }
+
+    public void processTemplateAndSetContentAware() {
+
+        if (logLevel == MESSAGE_TEMPLATE || logLevel == CUSTOM) {
             for (MediatorProperty property : properties) {
                 if (property.getExpression() != null && property.getExpression().isContentAware()) {
-                    return true;
+                    isContentAware = true;
+                    return;
                 }
             }
-            return false;
+            isContentAware = InlineExpressionUtil.isInlineSynapseExpressionsContentAware(messageTemplate);
+        } else {
+            isContentAware = true;
         }
-        return true;
     }
 }

modules/core/src/main/java/org/apache/synapse/util/InlineExpressionUtil.java

@@ -19,7 +19,6 @@
 
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
-import com.google.gson.JsonNull;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParser;
 import com.google.gson.JsonPrimitive;
@@ -30,6 +29,8 @@
 import org.apache.synapse.MessageContext;
 import org.apache.synapse.SynapseException;
 import org.apache.synapse.config.xml.SynapsePath;
+import org.apache.synapse.util.xpath.SynapseExpression;
+import org.apache.synapse.util.xpath.SynapseExpressionUtils;
 import org.apache.synapse.util.xpath.SynapseJsonPath;
 import org.apache.synapse.util.xpath.SynapseXPath;
 import org.jaxen.JaxenException;
@@ -49,6 +50,9 @@ public final class InlineExpressionUtil {
     // Regex to identify expressions in inline text
     private static final Pattern EXPRESSION_PATTERN = Pattern.compile("(\\{[^\\s\",<>}\\]]+})");
 
+    // Regex to identify synapse expressions ${expression} in inline text
+    private static final Pattern SYNAPSE_EXPRESSION_PLACEHOLDER_PATTERN = Pattern.compile("\\$\\{(.+?)}");
+
     private InlineExpressionUtil() {
 
     }
@@ -197,4 +201,48 @@ private static boolean isValidXML(String stringToValidate) {
         }
         return false;
     }
+
+    /**
+     * Checks whether inline template contains content aware synapse expressions.
+     * Inline expressions will be denoted inside ${}
+     * e.g.: ${var.var1}, ${payload.element.id}
+     *
+     * @param inlineText Inline text string
+     * @return true if the string contains content aware inline synapse expressions, false otherwise
+     */
+    public static boolean isInlineSynapseExpressionsContentAware(String inlineText) {
+
+        Matcher matcher = SYNAPSE_EXPRESSION_PLACEHOLDER_PATTERN.matcher(inlineText);
+        while (matcher.find()) {
+            // Extract the expression inside ${...}
+            String expression = matcher.group(1);
+            if (SynapseExpressionUtils.isSynapseExpressionContentAware(expression)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Process the inline template and replace the synapse expressions with the resolved values
+     *
+     * @param synCtx   Message Context
+     * @param template Inline template
+     * @return Processed inline template
+     */
+    public static String processInLineSynapseExpressionTemplate(MessageContext synCtx, String template)
+            throws JaxenException {
+
+        Matcher matcher = SYNAPSE_EXPRESSION_PLACEHOLDER_PATTERN.matcher(template);
+        StringBuffer result = new StringBuffer();
+        while (matcher.find()) {
+            // Extract the expression inside ${...}
+            String placeholder = matcher.group(1);
+            SynapseExpression expression = new SynapseExpression(placeholder);
+            String replacement = expression.stringValueOf(synCtx);
+            matcher.appendReplacement(result, Matcher.quoteReplacement(replacement));
+        }
+        matcher.appendTail(result);
+        return result.toString();
+    }
 }

modules/core/src/main/java/org/apache/synapse/util/xpath/SynapseExpression.java

@@ -74,33 +74,7 @@ public SynapseExpression(String synapseExpression) throws JaxenException {
             }
             throw new JaxenException(errorMessage.toString());
         }
-
-        // TODO : Need to improve the content aware detection logic
-        if (synapseExpression.equals("payload") || synapseExpression.equals("$")
-                || synapseExpression.contains("payload.") || synapseExpression.contains("$.")) {
-            isContentAware = true;
-        } else if (synapseExpression.contains("xpath(")) {
-            // TODO change the regex to support xpath + variable syntax
-            Pattern pattern = Pattern.compile("xpath\\(['\"](.*?)['\"]\\s*(,\\s*['\"](.*?)['\"])?\\)?");
-            Matcher matcher = pattern.matcher(synapseExpression);
-            // Find all matches
-            while (matcher.find()) {
-                if (matcher.group(2) != null) {
-                    // evaluating xpath on a variable so not content aware
-                    continue;
-                }
-                String xpath = matcher.group(1);
-                try {
-                    SynapseXPath synapseXPath = new SynapseXPath(xpath);
-                    if (synapseXPath.isContentAware()) {
-                        isContentAware = true;
-                        break;
-                    }
-                } catch (JaxenException e) {
-                    // Ignore the exception and continue
-                }
-            }
-        }
+        isContentAware = SynapseExpressionUtils.isSynapseExpressionContentAware(synapseExpression);
     }
 
     @Override

modules/core/src/main/java/org/apache/synapse/util/xpath/SynapseExpressionUtils.java

@@ -0,0 +1,66 @@
+/*
+ *  Copyright (c) 2024, WSO2 LLC. (http://www.wso2.org) All Rights Reserved.
+ *
+ *  WSO2 LLC. licenses this file to you under the Apache License,
+ *  Version 2.0 (the "License"); you may not use this file except
+ *  in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied. See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+
+package org.apache.synapse.util.xpath;
+
+import org.jaxen.JaxenException;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Utility class for Synapse Expressions
+ */
+public class SynapseExpressionUtils {
+
+    /**
+     * Checks whether the synapse expression is content aware
+     *
+     * @param synapseExpression synapse expression string
+     * @return true if the synapse expression is content aware, false otherwise
+     */
+    public static boolean isSynapseExpressionContentAware(String synapseExpression) {
+
+        // TODO : Need to improve the content aware detection logic
+        if (synapseExpression.equals("payload") || synapseExpression.equals("$")
+                || synapseExpression.contains("payload.") || synapseExpression.contains("$.")) {
+            return true;
+        } else if (synapseExpression.contains("xpath(")) {
+            // TODO change the regex to support xpath + variable syntax
+            Pattern pattern = Pattern.compile("xpath\\(['\"](.*?)['\"]\\s*(,\\s*['\"](.*?)['\"])?\\)?");
+            Matcher matcher = pattern.matcher(synapseExpression);
+            // Find all matches
+            while (matcher.find()) {
+                if (matcher.group(2) != null) {
+                    // evaluating xpath on a variable so not content aware
+                    continue;
+                }
+                String xpath = matcher.group(1);
+                try {
+                    SynapseXPath synapseXPath = new SynapseXPath(xpath);
+                    if (synapseXPath.isContentAware()) {
+                        return true;
+                    }
+                } catch (JaxenException e) {
+                    // Ignore the exception and continue
+                }
+            }
+        }
+        return false;
+    }
+}