From 4038be5e42b54bd096c6b6c3fc20c4e40898f98a Mon Sep 17 00:00:00 2001
From: Julian Vassev <jvassev@vmware.com>
Date: Thu, 2 Nov 2017 19:14:37 +0200
Subject: [PATCH] Replace switch with reflection in generated code

This patch expands on the suggestion in
https://github.com/ben-manes/caffeine/issues/110#issuecomment-238676087

Instead of the proposed numeric code the name of factory is used as the
classname to instantiate using reflection.
This reduces the class size with 21K bringing the jar size to 786K.
---
 .../cache/LocalCacheSelectorCode.java         | 25 +++++++++++--------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java b/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java
index 2318cc9a4a..15a3e37049 100644
--- a/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java
+++ b/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java
@@ -15,6 +15,7 @@
  */
 package com.github.benmanes.caffeine.cache;
 
+import java.lang.reflect.Constructor;
 import java.util.Set;
 
 import com.squareup.javapoet.CodeBlock;
@@ -88,16 +89,18 @@ private LocalCacheSelectorCode expires() {
     return this;
   }
 
-  private LocalCacheSelectorCode selector(Set<String> classNames) {
-    CodeBlock.Builder switchBuilder = CodeBlock.builder();
-    switchBuilder.beginControlFlow("switch (sb.toString())");
-    for (String className : classNames) {
-      switchBuilder.addStatement(
-          "case $S: return new $N<>(builder, cacheLoader, async)", className, className);
-    }
-    switchBuilder.addStatement("default: throw new $T(sb.toString())", IllegalStateException.class);
-    switchBuilder.endControlFlow();
-    block.add(switchBuilder.build());
+  private LocalCacheSelectorCode selector() {
+    CodeBlock.Builder reflectBuilder = CodeBlock.builder();
+    reflectBuilder.add("try {\n"
+            + "  Class<?> cls = LocalCacheFactory.class.getClassLoader()\n"
+            + "    .loadClass(\"com.github.benmanes.caffeine.cache.LocalCacheFactory$$\" + sb.toString());\n"
+            + "  $T<?> ctor = cls.getDeclaredConstructor(Caffeine.class, CacheLoader.class, boolean.class);\n"
+            + "  return (BoundedLocalCache<K, V>) ctor.newInstance(builder, cacheLoader, async);\n"
+            + "} catch (ReflectiveOperationException e) {\n"
+            + "  throw new IllegalStateException(sb.toString());\n"
+            + "}\n"
+            + "\n", Constructor.class);
+    block.add(reflectBuilder.build());
     return this;
   }
 
@@ -113,7 +116,7 @@ public static CodeBlock get(Set<String> classNames) {
         .stats()
         .maximum()
         .expires()
-        .selector(classNames)
+        .selector()
         .build();
   }
 }