optimize mapper builder

Author: mawen12

src/main/java/org/apache/ibatis/builder/xml/XMLMapperBuilder.java

@@ -161,9 +161,9 @@ private void cacheRefElement(XNode context) {
   private void cacheElement(XNode context) {
     if (context != null) {
       String type = context.getStringAttribute("type", "PERPETUAL");
-      Class<? extends Cache> typeClass = typeAliasRegistry.resolveAlias(type);
+      Class<? extends Cache> typeClass = resolveAlias(type);
       String eviction = context.getStringAttribute("eviction", "LRU");
-      Class<? extends Cache> evictionClass = typeAliasRegistry.resolveAlias(eviction);
+      Class<? extends Cache> evictionClass = resolveAlias(eviction);
       Long flushInterval = context.getLongAttribute("flushInterval");
       Integer size = context.getIntAttribute("size");
       boolean readWrite = !context.getBooleanAttribute("readOnly", false);
@@ -239,7 +239,7 @@ private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> addi
         resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));
       }
     }
-    String id = resultMapNode.getStringAttribute("id", resultMapNode.getValueBasedIdentifier());
+    String id = resultMapNode.getStringAttribute("id", resultMapNode::getValueBasedIdentifier);
     String extend = resultMapNode.getStringAttribute("extends");
     Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
     ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator,
@@ -289,8 +289,7 @@ private Discriminator processDiscriminatorElement(XNode context, Class<?> result
     Map<String, String> discriminatorMap = new HashMap<>();
     for (XNode caseChild : context.getChildren()) {
       String value = caseChild.getStringAttribute("value");
-      String resultMap = caseChild.getStringAttribute("resultMap",
-          processNestedResultMappings(caseChild, resultMappings, resultType));
+      String resultMap = caseChild.getStringAttribute("resultMap", () -> processNestedResultMappings(caseChild, resultMappings, resultType));
       discriminatorMap.put(value, resultMap);
     }
     return builderAssistant.buildDiscriminator(resultType, column, javaTypeClass, jdbcTypeEnum, typeHandlerClass,