Merge pull request #288 from z529192557/master

修改类加载时间，将类加载时机提前到init阶段，同时恢复addTransformer时机

Author: dongchenxu

sandbox-core/src/main/java/com/alibaba/jvm/sandbox/core/JvmSandbox.java

@@ -9,12 +9,24 @@
 import com.alibaba.jvm.sandbox.core.util.SpyUtils;
 
 import java.lang.instrument.Instrumentation;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * 沙箱
  */
 public class JvmSandbox {
 
+    /**
+     * 需要提前加载的sandbox工具类
+     */
+    private final static List<String> earlyLoadSandboxClassNameList = new ArrayList<String>();
+
+    static {
+        earlyLoadSandboxClassNameList.add("com.alibaba.jvm.sandbox.core.util.SandboxClassUtils");
+        earlyLoadSandboxClassNameList.add("com.alibaba.jvm.sandbox.core.util.matcher.structure.ClassStructureImplByAsm");
+    }
+
     private final CoreConfigure cfg;
     private final CoreModuleManager coreModuleManager;
 
@@ -33,9 +45,22 @@ public JvmSandbox(final CoreConfigure cfg,
     }
 
     private void init() {
+        doEarlyLoadSandboxClass();
         SpyUtils.init(cfg.getNamespace());
     }
 
+    /**
+     * 提前加载某些必要的类
+     */
+    private void doEarlyLoadSandboxClass() {
+        for(String className : earlyLoadSandboxClassNameList){
+            try {
+                Class.forName(className);
+            } catch (ClassNotFoundException e) {
+                //加载sandbox内部的类，不可能加载不到
+            }
+        }
+    }
 
     /**
      * 获取模块管理器

sandbox-core/src/main/java/com/alibaba/jvm/sandbox/core/manager/impl/DefaultModuleEventWatcher.java

@@ -83,14 +83,9 @@ private void finishProgress(final Progress progress, final int cCnt, final int m
      * 形变观察所影响的类
      */
     private void reTransformClasses(
-        SandboxClassFileTransformer transformer,
         final int watchId,
         final List<Class<?>> waitingReTransformClasses,
         final Progress progress) {
-        // 在真正做retransform 前的一刻，做addTransformer，避免java.lang.ClassCircularityError
-        if(null != transformer){
-            inst.addTransformer(transformer, true);
-        }
         // 需要形变总数
         final int total = waitingReTransformClasses.size();
 
@@ -184,6 +179,9 @@ private int watch(final Matcher matcher,
         // 注册到CoreModule中
         coreModule.getSandboxClassFileTransformers().add(sandClassFileTransformer);
 
+        //这里addTransformer后，接下来引起的类加载都会经过sandClassFileTransformer
+        inst.addTransformer(sandClassFileTransformer, true);
+
         // 查找需要渲染的类集合
         final List<Class<?>> waitingReTransformClasses = classDataSource.findForReTransform(matcher);
         logger.info("watch={} in module={} found {} classes for watch(ing).",
@@ -199,7 +197,7 @@ private int watch(final Matcher matcher,
         try {
 
             // 应用JVM
-            reTransformClasses(sandClassFileTransformer,watchId, waitingReTransformClasses, progress);
+            reTransformClasses(watchId,waitingReTransformClasses, progress);
 
             // 计数
             cCnt += sandClassFileTransformer.getAffectStatistic().cCnt();
@@ -266,7 +264,7 @@ public void delete(final int watcherId,
         beginProgress(progress, waitingReTransformClasses.size());
         try {
             // 应用JVM
-            reTransformClasses(null, watcherId, waitingReTransformClasses, progress);
+            reTransformClasses(watcherId, waitingReTransformClasses, progress);
         } finally {
             finishProgress(progress, cCnt, mCnt);
         }