More magic! We now automatically convert between java.sql.Timestamp,

java.sql.Date and java.util.Date and we support custom getters and setters to
do fancier aggregate conversion (multiple persistent fields into a single
runtime field and/or creation of partially initialized runtime objects from the
available persistent data).

src/java/com/samskivert/depot/util/RuntimeUtil.java

@@ -21,35 +21,68 @@
 package com.samskivert.depot.util;
 
 import java.lang.reflect.Field;
+import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
+import java.sql.Timestamp;
+import java.util.Date;
 import java.util.List;
+import java.util.Map;
 
 import com.google.common.base.Function;
 import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
 
 import com.samskivert.depot.PersistentRecord;
+import com.samskivert.util.Tuple;
 
 /**
- * Creates functions that map persistent records to runtime counterparts and vice versa.
+ * Creates functions that map persistent records to runtime counterparts and vice versa. A few bits
+ * of magic are provided to help in mapping from the persistent world to the runtime work. Namely:
+ *
+ * <p> {@link Timestamp} and {@link java.sql.Date} are automatically converted to and from {@link
+ * Date} if necessary.
+ *
+ * <p> You can define custom getter and setter methods in your persistent class like so:
+ * <pre>
+ * public class FooRecord extends PersistentRecord
+ * {
+ *     public long monkeyStamp;
+ *
+ *     public Date getMonkeyStamp ()
+ *     {
+ *         return new Date(monkeyStamp);
+ *     }
+ *
+ *     public void setMonkeyStamp (Date value)
+ *     {
+ *         monkeyStamp = value.getTime();
+ *     }
+ * }
+ * </pre>
+ *
+ * <p> The conversion methods must be named <code>get</code> and <code>set</code> followed by the
+ * name of your field with the first letter changed to a capital and their type signatures must
+ * exactly match those of the persistent and runtime types.
  */
 public class RuntimeUtil
 {
     /**
      * Creates a function that creates an instance of R and initializes all accessible (ie. public)
      * fields of R from fields of P with matching name. Fields of P that do not exist in R will be
-     * ignored. Note: the types of the fields must match exactly.
+     * ignored. See the class documentation for a list of field conversions that will be made
+     * automatically and the mechanism for performing other conversions.
      */
     public static <P extends PersistentRecord, R> Function<P, R> makeToRuntime (
         Class<P> pclass, final Class<R> rclass)
     {
         final Field[] rfields = getRuntimeFields(rclass);
-        final Field[] pfields = getPersistentFields(pclass, rfields);
+        final Getter[] getters = getPersistentGetters(pclass, rfields);
         return new Function<P, R>() {
             public R apply (P record) {
                 try {
                     R object = rclass.newInstance();
                     for (int ii = 0, ll = rfields.length; ii < ll; ii++) {
-                        rfields[ii].set(object, pfields[ii].get(record));
+                        rfields[ii].set(object, getters[ii].get(record));
                     }
                     return object;
                 } catch (Exception e) {
@@ -68,13 +101,13 @@ public class RuntimeUtil
         Class<R> rclass, final Class<P> pclass)
     {
         final Field[] rfields = getRuntimeFields(rclass);
-        final Field[] pfields = getPersistentFields(pclass, rfields);
+        final Setter[] setters = getPersistentSetters(pclass, rfields);
         return new Function<R, P>() {
             public P apply (R object) {
                 try {
                     P record = pclass.newInstance();
                     for (int ii = 0, ll = rfields.length; ii < ll; ii++) {
-                        pfields[ii].set(record, rfields[ii].get(object));
+                        setters[ii].set(record, rfields[ii].get(object));
                     }
                     return record;
                 } catch (Exception e) {
@@ -96,8 +129,104 @@ public class RuntimeUtil
         return fields.toArray(new Field[fields.size()]);
     }
 
-    protected static Field[] getPersistentFields (
-        Class<? extends PersistentRecord> pclass, Field[] rfields)
+    protected static Getter[] getPersistentGetters (Class<?> pclass, Field[] rfields)
+    {
+        Field[] pfields = getPersistentFields(pclass, rfields);
+        Getter[] getters = new Getter[rfields.length];
+        for (int ii = 0; ii < rfields.length; ii++) {
+            getters[ii] = makeGetter(pclass, pfields[ii], rfields[ii]);
+        }
+        return getters;
+    }
+
+    protected static Setter[] getPersistentSetters (Class<?> pclass, Field[] rfields)
+    {
+        Field[] pfields = getPersistentFields(pclass, rfields);
+        Setter[] setters = new Setter[rfields.length];
+        for (int ii = 0; ii < rfields.length; ii++) {
+            setters[ii] = makeSetter(pclass, pfields[ii], rfields[ii]);
+        }
+        return setters;
+    }
+
+    protected static Getter makeGetter (Class<?> pclass, final Field pfield, Field rfield)
+    {
+        // if there's a custom getter method for the field, use that foremost
+        try {
+            final Method method = pclass.getMethod(makeMethodName("get", pfield.getName()));
+            if (method.getReturnType().equals(rfield.getType())) {
+                return new Getter() {
+                    public Object get (Object object) throws Exception {
+                        return method.invoke(object);
+                    }
+                };
+            }
+        } catch (NoSuchMethodException nsme) {
+            // no problem, keep on truckin'
+        }
+
+        // if the fields match exactly, return a getter that just gets the field
+        if (rfield.getType().equals(pfield.getType())) {
+            return new Getter() {
+                public Object get (Object object) throws Exception {
+                    return pfield.get(object);
+                }
+            };
+        }
+
+        // if we can convert from the persistent type to the runtime type, do that
+        final Function<Object, Object> converter = getconv(pfield.getType(), rfield.getType());
+        if (converter != null) {
+            return new Getter() {
+                public Object get (Object object) throws Exception {
+                    return converter.apply(pfield.get(object));
+                }
+            };
+        }
+
+        // if we have exhausted all other approaches, we're SOL
+        throw new IllegalArgumentException("Cannot map " + pfield + " to " + rfield + ".");
+    }
+
+    protected static Setter makeSetter (Class<?> pclass, Field pfield, final Field rfield)
+    {
+        // check for a custom setter method for the field (with the correct argument type)
+        try {
+            final Method method = pclass.getMethod(
+                makeMethodName("set", pfield.getName()), rfield.getType());
+            return new Setter() {
+                public void set (Object object, Object value) throws Exception {
+                    method.invoke(object, value);
+                }
+            };
+        } catch (NoSuchMethodException nsme) {
+            // no problem, keep on truckin'
+        }
+
+        // if the fields match exactly, return a setter that just sets the field
+        if (rfield.getType().equals(pfield.getType())) {
+            return new Setter() {
+                public void set (Object object, Object value) throws Exception {
+                    rfield.set(object, value);
+                }
+            };
+        }
+
+        // if we can convert from the runtime type to the persistent type, do that
+        final Function<Object, Object> converter = getconv(rfield.getType(), pfield.getType());
+        if (converter != null) {
+            return new Setter() {
+                public void set (Object object, Object value) throws Exception {
+                    rfield.set(object, converter.apply(value));
+                }
+            };
+        }
+
+        // if we have exhausted all other approaches, we're SOL
+        throw new IllegalArgumentException("Cannot map " + rfield + " to " + pfield + ".");
+    }
+
+    protected static Field[] getPersistentFields (Class<?> pclass, Field[] rfields)
     {
         Field[] pfields = new Field[rfields.length];
         for (int ii = 0; ii < rfields.length; ii++) {
@@ -115,4 +244,58 @@ public class RuntimeUtil
         }
         return pfields;
     }
+
+    protected static String makeMethodName (String prefix, String fieldName)
+    {
+        return new StringBuilder().append(prefix).
+            append(Character.toUpperCase(fieldName.charAt(0))).
+            append(fieldName.substring(1)).toString();
+    }
+
+    protected static interface Getter
+    {
+        public Object get (Object object) throws Exception;
+    }
+
+    protected static interface Setter
+    {
+        public void set (Object object, Object value) throws Exception;
+    }
+
+    protected static Function<Object, Object> getconv (Class<?> fc, Class<?> tc)
+    {
+        return _converters.get(Tuple.newTuple(fc, tc));
+    }
+
+    protected static <F, T> void regconv (Class<F> fc, Class<T> tc, Function<F, T> conv)
+    {
+        @SuppressWarnings("unchecked") Function<Object, Object> value =
+            (Function<Object, Object>)conv;
+        _converters.put(Tuple.newTuple(fc, tc), value);
+    }
+
+    protected static Map<Object, Function<Object, Object>> _converters =
+        Maps.newHashMap();
+    static {
+        regconv(Timestamp.class, Date.class, new Function<Timestamp, Date>() {
+            public Date apply (Timestamp object) {
+                return (object == null) ? null : new Date(object.getTime());
+            }
+        });
+        regconv(Date.class, Timestamp.class, new Function<Date, Timestamp>() {
+            public Timestamp apply (Date object) {
+                return (object == null) ? null : new Timestamp(object.getTime());
+            }
+        });
+        regconv(java.sql.Date.class, Date.class, new Function<java.sql.Date, Date>() {
+            public Date apply (java.sql.Date object) {
+                return (object == null) ? null : new Date(object.getTime());
+            }
+        });
+        regconv(Date.class, java.sql.Date.class, new Function<Date, java.sql.Date>() {
+            public java.sql.Date apply (Date object) {
+                return (object == null) ? null : new java.sql.Date(object.getTime());
+            }
+        });
+    }
 }