Improve log mediator to support string templating

Author: SanojPunchihewa

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 +67,13 @@ public Mediator createSpecificMediator(OMElement elem, Properties properties) {
         // after successfully creating the mediator
         // set its common attributes such as tracing etc
         processAuditStatus(logMediator,elem);
-        
+
+        OMElement messageElement = elem.getFirstChildWithName(ELEMENT_MESSAGE_Q);
+        if (messageElement != null && messageElement.getText() != null) {
+            logMediator.setMessageTemplate(messageElement.getText());
+            logMediator.setLogLevel(LogMediator.MESSAGE_TEMPLATE);
+        }
+
         // Set the high level set of properties to be logged (i.e. log level)
         OMAttribute level = elem.getAttribute(ATT_LEVEL);
         if (level != null) {

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 (StringUtils.isBlank(mediator.getMessageTemplate()) && mediator.getLogLevel() != LogMediator.SIMPLE) {
             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

@@ -29,14 +29,17 @@
 import org.apache.synapse.SynapseLog;
 import org.apache.synapse.commons.json.JsonUtil;
 import org.apache.synapse.commons.CorrelationConstants;
+import org.apache.synapse.config.xml.SynapsePath;
 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 java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
-
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * Logs the specified message into the configured logger. The log levels specify
@@ -56,6 +59,9 @@ 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 +80,8 @@ public class LogMediator extends AbstractMediator {
     /** The holder for the custom properties */
     private final List<MediatorProperty> properties = new ArrayList<MediatorProperty>();
 
+    private String messageTemplate;
+
     /**
      * Logs the current message according to the supplied semantics
      *
@@ -143,6 +151,8 @@ private String getLogMessage(MessageContext synCtx) {
                 return getHeadersLogMessage(synCtx);
             case FULL:
                 return getFullLogMessage(synCtx);
+            case MESSAGE_TEMPLATE:
+                return processMessageTemplate(synCtx, messageTemplate);
             default:
                 return "Invalid log level specified";
         }
@@ -288,6 +298,16 @@ public void setCategory(int category) {
         }
     }
 
+    public String getMessageTemplate() {
+
+        return messageTemplate;
+    }
+
+    public void setMessageTemplate(String messageTemplate) {
+
+        this.messageTemplate = messageTemplate;
+    }
+
     private String trimLeadingSeparator(StringBuffer sb) {
         String retStr = sb.toString();
         if (retStr.startsWith(separator)) {
@@ -297,8 +317,16 @@ private String trimLeadingSeparator(StringBuffer sb) {
         }
     }
 
+    private String processMessageTemplate(MessageContext synCtx, String template) {
+        StringBuffer result = new StringBuffer();
+        result.append(InlineExpressionUtil.processInLineTemplate(synCtx, template));
+        setCustomProperties(result, synCtx);
+        return result.toString();
+    }
+
     @Override
     public boolean isContentAware() {
+        // TODO Use the new simplified expression model to check if the log mediator is content aware
         if (logLevel == CUSTOM) {
             for (MediatorProperty property : properties) {
                 if (property.getExpression() != null && property.getExpression().isContentAware()) {

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

@@ -49,6 +49,9 @@ 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 EXPRESSION_PLACEHOLDER_PATTERN = Pattern.compile("#\\[(.+?)\\]");
+
     private InlineExpressionUtil() {
 
     }
@@ -197,4 +200,37 @@ private static boolean isValidXML(String stringToValidate) {
         }
         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 processInLineTemplate(MessageContext synCtx, String template) {
+
+        Matcher matcher = EXPRESSION_PLACEHOLDER_PATTERN.matcher(template);
+        StringBuffer result = new StringBuffer();
+        while (matcher.find()) {
+            // Extract the expression inside #[...]
+            String placeholder = matcher.group(1);
+            // Dummy resolver for expressions to test the Log mediator
+            // TODO update the #getDynamicValue method with synapse expressions and replace this
+            String replacement = ExpressionResolver.resolve(placeholder, synCtx);
+            matcher.appendReplacement(result, Matcher.quoteReplacement(replacement));
+        }
+        matcher.appendTail(result);
+        return result.toString();
+    }
+
+    static class ExpressionResolver {
+        public static String resolve(String expression, MessageContext synCtx) {
+            String variableName = expression.substring(5);
+            if (synCtx.getVariable(variableName) != null) {
+                return synCtx.getVariable(variableName).toString();
+            }
+            return expression;
+        }
+    }
 }

modules/core/src/test/java/org/apache/synapse/config/xml/LogMediatorSerializationTest.java

@@ -51,6 +51,12 @@ public LogMediatorSerializationTest() {
         logMediatorSerializer = new LogMediatorSerializer();
     }
 
+    public void testLogMediatorSerializationWithTemplate() throws Exception {
+
+        assertTrue(serialization(getXmlOfLogMediatorWithTemplate(), logMediatorFactory, logMediatorSerializer));
+        assertTrue(serialization(getXmlOfLogMediatorWithTemplateAndProps(), logMediatorFactory, logMediatorSerializer));
+    }
+
     public void testLogMediatorSerializationSenarioOne() throws Exception {
 
         //    assertTrue(serialization(getXmlOfMediatorScenarioOne(SIMPLE), logMediatorFactory, logMediatorSerializer));
@@ -130,6 +136,17 @@ private String getXmlOfMediatorScenarioOne(String level) {
 
     }
 
+    private String getXmlOfLogMediatorWithTemplate() {
+        return "<log xmlns=\"http://ws.apache.org/ns/synapse\">" +
+                "<message>Processing message with ID: 123</message></log>";
+    }
+
+    private String getXmlOfLogMediatorWithTemplateAndProps() {
+        return "<log xmlns=\"http://ws.apache.org/ns/synapse\">" +
+                "<message>Processing message with ID: 123</message>" +
+                "<property name=\"Text\" value=\"Sending quote request\"/></log>";
+    }
+
     private String getXmlOfMediatorScenarioOneA(String level) {
         return "<log level=\"" +
                 level + "\"><property name=\"Text\" value=\"Sending quote request\"/></log>";