[Story #196234] [XPath] Export method for cache entries

src/main/java/org/apache/commons/jxpath/ri/JXPathContextReferenceImpl.java

@@ -120,7 +120,7 @@ protected boolean removeEldestEntry(java.util.Map.Entry eldest) {
             if (CACHE_STATISTICS) {
                 MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
                 try {
-                    jXPathStatisticsMBeanImpl = new JXPathStatisticsMBeanImpl();
+                    jXPathStatisticsMBeanImpl = new JXPathStatisticsMBeanImpl(compiled);
                     mbs.registerMBean(jXPathStatisticsMBeanImpl, ObjectName.getInstance("org.apache.commons.commons-jxpath:Type=JXPathStatisticsMBean"));
                 } catch (JMException e) {
                     // best effort only

src/main/java/org/apache/commons/jxpath/ri/jmx/JXPathStatisticsMBean.java

@@ -16,4 +16,6 @@ public interface JXPathStatisticsMBean {
     long getParseCount();
 
     long getAverageParseTimeInMillis();
+
+    void exportCacheKeys();
 }

src/main/java/org/apache/commons/jxpath/ri/jmx/JXPathStatisticsMBeanImpl.java

@@ -2,10 +2,16 @@
 
 import javax.management.NotCompliantMBeanException;
 import javax.management.StandardMBean;
+
+import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
+import org.apache.commons.jxpath.ri.compiler.Expression;
+import org.apache.commons.jxpath.util.CacheExportUtil;
+
+
 public class JXPathStatisticsMBeanImpl extends StandardMBean implements JXPathStatisticsMBean {
 
     private static final AtomicInteger cacheSize = new AtomicInteger();
@@ -14,9 +20,11 @@ public class JXPathStatisticsMBeanImpl extends StandardMBean implements JXPathSt
     private static final AtomicLong limitExceeded = new AtomicLong();
     private static final AtomicLong parseTime = new AtomicLong();
     private static final AtomicLong parseCount = new AtomicLong();
+    private final Map<String, Expression> cache;
 
-    public JXPathStatisticsMBeanImpl() throws NotCompliantMBeanException {
+    public JXPathStatisticsMBeanImpl(Map<String, Expression> cache) throws NotCompliantMBeanException {
         super(JXPathStatisticsMBean.class);
+        this.cache = cache;
     }
 
     @Override
@@ -90,4 +98,9 @@ public void incrementLimitExceeded()
         limitExceeded.incrementAndGet();
     }
 
+    @Override
+    public void exportCacheKeys() {
+        CacheExportUtil.exportCacheKeys(cache);
+    }
+
 }

src/main/java/org/apache/commons/jxpath/util/CacheExportUtil.java

@@ -0,0 +1,53 @@
+package org.apache.commons.jxpath.util;
+
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.logging.Logger;
+
+import org.apache.commons.jxpath.ri.compiler.Expression;
+
+
+/**
+ * Utility class for exporting cache contents to a file.
+ *
+ */
+public class CacheExportUtil
+{
+    private static final Logger LOGGER = Logger.getLogger(CacheExportUtil.class.getName());
+
+    private static final String FILE_NAME = "xpath-cache-keys.";
+    private static final String TEMP_DIR = System.getProperty("bisas.temp", ".");
+
+
+    private CacheExportUtil()
+    {
+        // utility class
+    }
+
+
+    public static void exportCacheKeys(Map<String, Expression> cache)
+    {
+        if (cache == null) {
+            return;
+        }
+
+        File file = new File(TEMP_DIR, FILE_NAME + System.currentTimeMillis());
+
+        try (PrintWriter out = new PrintWriter(new FileWriter(file))) {
+            List<String> keysSnapshot = new CopyOnWriteArrayList<>(cache.keySet());
+            keysSnapshot.forEach(out::println);
+            out.println("Size: " + keysSnapshot.size());
+            LOGGER.info("Exported cache keys to " + file.getAbsolutePath());
+        }
+        catch (IOException ex) {
+            throw new RuntimeException("Failed to export cache keys", ex);
+        }
+    }
+
+}