Enable adding type handlers and aliases with annotations (for MyBatis core && MyBatis-Spring). See http://code.google.com/p/mybatis/issues/detail?id=314

Author: emacarron

src/main/java/org/apache/ibatis/type/Alias.java

@@ -0,0 +1,12 @@
+package org.apache.ibatis.type;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+public @interface Alias {
+	public String value();
+}

src/main/java/org/apache/ibatis/type/MappedJdbcTypes.java

@@ -0,0 +1,12 @@
+package org.apache.ibatis.type;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+public @interface MappedJdbcTypes {
+	public JdbcType[] value();
+}

src/main/java/org/apache/ibatis/type/TypeAliasRegistry.java

@@ -1,11 +1,18 @@
 package org.apache.ibatis.type;
 
-import org.apache.ibatis.io.ResolverUtil;
-import org.apache.ibatis.io.Resources;
-
 import java.math.BigDecimal;
-import java.util.*;
 import java.sql.ResultSet;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.ibatis.io.ResolverUtil;
+import org.apache.ibatis.io.Resources;
 
 public class TypeAliasRegistry {
 
@@ -96,13 +103,19 @@ public void registerAliases(String packageName, Class superType){
     Set<Class<? extends Class>> typeSet = resolverUtil.getClasses();
     for(Class type : typeSet){
       //Ignore inner classes
-      if (!type.isAnonymousClass())
-        registerAlias(type.getSimpleName(), type);
+      if (!type.isAnonymousClass()) {
+        registerAlias(type);
+      }
     }
   }
 
   public void registerAlias(Class type) {
-    registerAlias(type.getSimpleName(), type.getName());
+    String alias = type.getSimpleName();
+    Alias aliasAnnotation = (Alias) type.getAnnotation(Alias.class);
+    if (aliasAnnotation != null) {
+      alias = aliasAnnotation.value();
+    } 
+    registerAlias(alias, type);
   }
 
   public void registerAlias(String alias, Class value) {

src/main/java/org/apache/ibatis/type/TypeHandlerRegistry.java

@@ -144,9 +144,30 @@ public void register(JdbcType jdbcType, TypeHandler handler) {
   }
 
   public void register(Class<?> type, TypeHandler handler) {
-    register(type, null, handler);
+    MappedJdbcTypes mappedJdbcTypes = (MappedJdbcTypes) handler.getClass().getAnnotation(MappedJdbcTypes.class);
+    if (mappedJdbcTypes != null) {
+      for (JdbcType handledJdbcType : mappedJdbcTypes.value()) {
+        register(type, handledJdbcType, handler);
+      }
+    } else {
+      register(type, null, handler);
+    }
   }
 
+  public void register(TypeHandler handler) {
+    boolean mappedTypeFound = false;
+    MappedTypes mappedTypes = (MappedTypes) handler.getClass().getAnnotation(MappedTypes.class);
+    if (mappedTypes != null) {
+      for (Class<?> handledType : mappedTypes.value()) {
+          register(handledType, handler);
+          mappedTypeFound = true;
+      }
+    }
+    if (!mappedTypeFound) {
+      throw new RuntimeException("Unable to get mapped types, check @MappedTypes annotation for type handler " + handler);
+    }
+  }
+  
   public void register(Class<?> type, JdbcType jdbcType, TypeHandler handler) {
     Map<JdbcType, TypeHandler> map = TYPE_HANDLER_MAP.get(type);
     if (map == null) {
@@ -164,21 +185,13 @@ public void register(String packageName) {
     resolverUtil.find(new ResolverUtil.IsA(TypeHandler.class), packageName);
     Set<Class<? extends Class<?>>> handlerSet = resolverUtil.getClasses();
 
-    TypeHandler handler;
     for (Class<?> type : handlerSet) {
-      @SuppressWarnings({"unchecked"})
-      Annotation annotation = type.getAnnotation(MappedTypes.class);
       try {
-        handler = (TypeHandler) type.getConstructor().newInstance();
+        TypeHandler handler = (TypeHandler) type.getConstructor().newInstance();
+        register(handler);
       } catch (Exception e) {
         throw new RuntimeException("Unable to find a usable constructor for " + type, e);
       }
-      if (null != annotation) {
-        MappedTypes mappedType = (MappedTypes) annotation;
-        for (Class<?> handledType : mappedType.value()) {
-          register(handledType, handler);
-        }
-      }
     }
   }