The database now tries to detect if the classloader or virtual machine has almost shut down.

h2/src/main/org/h2/engine/Database.java

@@ -60,6 +60,7 @@ import org.h2.util.ClassUtils;
 import org.h2.util.FileUtils;
 import org.h2.util.IOUtils;
 import org.h2.util.IntHashMap;
+import org.h2.util.MemoryUtils;
 import org.h2.util.NetUtils;
 import org.h2.util.ObjectArray;
 import org.h2.util.SmallLRUCache;
@@ -1033,6 +1034,14 @@ public class Database implements DataHandler {
         if (closing) {
             return;
         }
+        if (MemoryUtils.isShutdown()) {
+            try {
+                traceSystem.getTrace(Trace.DATABASE).error("already shut down");
+            } catch (Exception e) {
+                // ignore
+            }
+            return;
+        }
         closing = true;
         stopServer();
         if (userSessions.size() > 0) {

h2/src/main/org/h2/engine/DatabaseCloser.java

@@ -8,6 +8,8 @@ package org.h2.engine;
 
 import java.lang.ref.WeakReference;
 
+import org.h2.message.Trace;
+
 /**
  * This class is responsible to close a database if the application did not
  * close a connection. A database closer object only exists if there is no user
@@ -16,6 +18,7 @@ import java.lang.ref.WeakReference;
 public class DatabaseCloser extends Thread {
 
     private final boolean shutdownHook;
+    private final Trace trace;
     private volatile WeakReference databaseRef;
     private int delayInMillis;
     private boolean stopImmediately;
@@ -24,6 +27,7 @@ public class DatabaseCloser extends Thread {
         this.databaseRef = new WeakReference(db);
         this.delayInMillis = delayInMillis;
         this.shutdownHook = shutdownHook;
+        trace = db.getTrace(Trace.DATABASE);
     }
 
     /**
@@ -72,7 +76,20 @@ public class DatabaseCloser extends Thread {
             }
         }
         if (database != null) {
+            try {
                 database.close(shutdownHook);
+            } catch (RuntimeException e) {
+                // this can happen when stopping a web application,
+                // if loading classes is no longer allowed
+                // it would throw an IllegalStateException
+                try {
+                    trace.error("Could not close the database", e);
+                    // if this was successful, we ignore the exception
+                    // otherwise not
+                } catch (RuntimeException e2) {
+                    throw e;
+                }
+            }
         }
     }
 

h2/src/main/org/h2/util/JdbcDriverUtils.java

@@ -75,4 +75,8 @@ public class JdbcDriverUtils {
         }
     }
     
+    static boolean isShutdown() {
+        return DRIVERS == null;
+    }
+
 }

h2/src/main/org/h2/util/MemoryUtils.java

@@ -80,4 +80,15 @@ public class MemoryUtils {
         reserveMemory = null;
     }
 
+    /**
+     * Check if the classloader or virtual machine is shut down. In this case
+     * static references are set to null, which can cause NullPointerExceptions
+     * and can be confusing because it looks like a bug in the application.
+     * 
+     * @return true if static references are set to null
+     */
+    public static boolean isShutdown() {
+        return StringCache.isShutdown() || JdbcDriverUtils.isShutdown() || Resources.isShutdown();
+    }    
+
 }

h2/src/main/org/h2/value/DataType.java

@@ -49,9 +49,9 @@ public class DataType {
      */
     public static final int TYPE_DATALINK = 70;
 
-    private static ObjectArray types = new ObjectArray();
-    private static HashMap typesByName = new HashMap();
-    private static DataType[] typesByValueType = new DataType[Value.TYPE_COUNT];
+    private static final ObjectArray TYPES = new ObjectArray();
+    private static final HashMap TYPES_BY_NAME = new HashMap();
+    private static final DataType[] TYPES_BY_VALUE_TYPE = new DataType[Value.TYPE_COUNT];
     
     /**
      * The value type of this data type.
@@ -318,8 +318,8 @@ public class DataType {
                 new String[]{"RESULT_SET"},
                 20
         );
-        for (int i = 0; i < typesByValueType.length; i++) {
-            DataType dt = typesByValueType[i];
+        for (int i = 0; i < TYPES_BY_VALUE_TYPE.length; i++) {
+            DataType dt = TYPES_BY_VALUE_TYPE[i];
             if (dt == null) {
                 throw Message.getInternalError("unmapped type " + i);
             }
@@ -350,17 +350,17 @@ public class DataType {
             dt.caseSensitive = dataType.caseSensitive;
             dt.hidden = i > 0;
             dt.memory = memory;
-            for (int j = 0; j < types.size(); j++) {
-                DataType t2 = (DataType) types.get(j);
+            for (int j = 0; j < TYPES.size(); j++) {
+                DataType t2 = (DataType) TYPES.get(j);
                 if (t2.sqlType == dt.sqlType) {
                     dt.sqlTypePos++;
                 }
             }
-            typesByName.put(dt.name, dt);
-            if (typesByValueType[type] == null) {
-                typesByValueType[type] = dt;
+            TYPES_BY_NAME.put(dt.name, dt);
+            if (TYPES_BY_VALUE_TYPE[type] == null) {
+                TYPES_BY_VALUE_TYPE[type] = dt;
             }
-            types.add(dt);
+            TYPES.add(dt);
         }
     }
 
@@ -412,7 +412,7 @@ public class DataType {
      * @return the list
      */
     public static ObjectArray getTypes() {
-        return types;
+        return TYPES;
     }
 
     /**
@@ -639,9 +639,9 @@ public class DataType {
      * @return the data type object
      */
     public static DataType getDataType(int type) {
-        DataType dt = typesByValueType[type];
+        DataType dt = TYPES_BY_VALUE_TYPE[type];
         if (dt == null) {
-            dt = typesByValueType[Value.NULL];
+            dt = TYPES_BY_VALUE_TYPE[Value.NULL];
         }
         return dt;
     }
@@ -857,7 +857,7 @@ public class DataType {
      * @return the data type object
      */
     public static DataType getTypeByName(String s) {
-        return (DataType) typesByName.get(s);
+        return (DataType) TYPES_BY_NAME.get(s);
     }
 
     /**

h2/src/main/org/h2/value/ValueInt.java

@@ -30,20 +30,17 @@ public class ValueInt extends Value {
      */
     public static final int DISPLAY_SIZE = 11; 
 
-    private static final int STATIC_SIZE = 100;
+    private static final int STATIC_SIZE = 128;
     // must be a power of 2
     private static final int DYNAMIC_SIZE = 256;
-    // TODO check performance of final static
-    private static ValueInt[] staticCache;
-    private static ValueInt[] dynamicCache;
+    private static final ValueInt[] STATIC_CACHE = new ValueInt[STATIC_SIZE];
+    private static final ValueInt[] DYNAMIC_CACHE = new ValueInt[DYNAMIC_SIZE];
 
     private final int value;
     
     static {
-        staticCache = new ValueInt[STATIC_SIZE];
-        dynamicCache = new ValueInt[DYNAMIC_SIZE];
         for (int i = 0; i < STATIC_SIZE; i++) {
-            staticCache[i] = new ValueInt(i);
+            STATIC_CACHE[i] = new ValueInt(i);
         }
     }
     
@@ -59,12 +56,12 @@ public class ValueInt extends Value {
      */
     public static ValueInt get(int i) {
         if (i >= 0 && i < STATIC_SIZE) {
-            return staticCache[i];
+            return STATIC_CACHE[i];
         }
-        ValueInt v = dynamicCache[i & DYNAMIC_SIZE - 1];
+        ValueInt v = DYNAMIC_CACHE[i & (DYNAMIC_SIZE - 1)];
         if (v == null || v.value != i) {
             v = new ValueInt(i);
-            dynamicCache[i & DYNAMIC_SIZE - 1] = v;
+            DYNAMIC_CACHE[i & (DYNAMIC_SIZE - 1)] = v;
         }
         return v;
     }

h2/src/main/org/h2/value/ValueLong.java

@@ -31,17 +31,17 @@ public class ValueLong extends Value {
      */    
     public static final int DISPLAY_SIZE = 20; 
     
-    private static final int STATIC_SIZE = 10;
-    private static ValueLong[] cache;
+    private static final int STATIC_SIZE = 100;
+    private static final ValueLong[] STATIC_CACHE;
     private static final BigInteger MIN = new BigInteger("" + Long.MIN_VALUE);
     private static final BigInteger MAX = new BigInteger("" + Long.MAX_VALUE);
     
     private final long value;
 
     static {
-        cache = new ValueLong[STATIC_SIZE];
+        STATIC_CACHE = new ValueLong[STATIC_SIZE];
         for (int i = 0; i < STATIC_SIZE; i++) {
-            cache[i] = new ValueLong(i);
+            STATIC_CACHE[i] = new ValueLong(i);
         }
     }
 
@@ -188,7 +188,7 @@ public class ValueLong extends Value {
      */
     public static ValueLong get(long i) {
         if (i >= 0 && i < STATIC_SIZE) {
-            return cache[(int) i];
+            return STATIC_CACHE[(int) i];
         }
         return (ValueLong) Value.cache(new ValueLong(i));
     }