Fix issue with @Mixins under Java 6

Resolves #78

agent-parent/agent/src/main/java/org/glowroot/agent/weaving/WeavingClassFileTransformer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -98,7 +98,9 @@ private static boolean ignoreClass(String className) {
             // sun/reflect/GeneratedMethodAccessor..
             return true;
         }
-        if (className.startsWith("com/sun/proxy/$Proxy")) {
+        // proxies under JDK 6 start with $Proxy
+        // proxies under JDK 7+ start with com/sun/proxy/$Proxy
+        if (className.startsWith("com/sun/proxy/$Proxy") || className.startsWith("$Proxy")) {
             // optimization, especially for jdbc plugin to avoid weaving proxy wrappers when dealing
             // with connection pools
             return true;

agent-parent/integration-tests/src/main/java/org/glowroot/agent/tests/plugin/MixinAspect.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.glowroot.agent.tests.plugin;
+
+import javax.annotation.Nullable;
+
+import org.glowroot.agent.plugin.api.weaving.Mixin;
+import org.glowroot.agent.plugin.api.weaving.MixinInit;
+
+public class MixinAspect {
+
+    @Mixin("java.lang.Runnable")
+    public static class RunnableMixinImpl implements RunnableMixin {
+
+        private @Nullable String string;
+
+        @MixinInit
+        private void initHasString() {
+            string = "a string";
+        }
+
+        @Override
+        public @Nullable String getString() {
+            return string;
+        }
+
+        @Override
+        public void setString(@Nullable String string) {
+            this.string = string;
+        }
+    }
+
+    public interface RunnableMixin {
+        @Nullable
+        String getString();
+        void setString(@Nullable String string);
+    }
+}

agent-parent/integration-tests/src/test/java/org/glowroot/agent/tests/javaagent/MixinProxyIT.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.glowroot.agent.tests.javaagent;
+
+import java.lang.reflect.Proxy;
+
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import org.glowroot.agent.it.harness.AppUnderTest;
+import org.glowroot.agent.it.harness.Container;
+import org.glowroot.agent.it.harness.impl.JavaagentContainer;
+
+public class MixinProxyIT {
+
+    private static Container container;
+
+    @BeforeClass
+    public static void setUp() throws Exception {
+        // this test only works under javaagent because Proxy classes don't get loaded normally
+        // through class loader and so IsolatedWeavingClassLoader cannot weave them
+        container = JavaagentContainer.create();
+    }
+
+    @AfterClass
+    public static void tearDown() throws Exception {
+        container.close();
+    }
+
+    @After
+    public void afterEachTest() throws Exception {
+        container.checkAndReset();
+    }
+
+    @Test
+    public void testCausedBy() throws Exception {
+        // given
+        // when
+        container.executeNoExpectedTrace(MixinProxyApp.class);
+        // then
+        // don't generate ClassFormatError
+    }
+
+    public static class MixinProxyApp implements AppUnderTest {
+        @Override
+        public void executeApp() throws Exception {
+            Proxy.getProxyClass(MixinProxyApp.class.getClassLoader(),
+                    MyRunnable.class.getInterfaces());
+        }
+    }
+
+    public static class MyRunnable implements Runnable {
+        @Override
+        public void run() {}
+    }
+}

agent-parent/integration-tests/src/test/resources/META-INF/glowroot.plugin.json

@@ -142,6 +142,7 @@
     "org.glowroot.agent.tests.plugin.LogCauseAspect",
     "org.glowroot.agent.tests.plugin.PauseAspect",
     "org.glowroot.agent.tests.plugin.MockDriverAspect",
-    "org.glowroot.agent.tests.plugin.TraceGeneratorAspect"
+    "org.glowroot.agent.tests.plugin.TraceGeneratorAspect",
+    "org.glowroot.agent.tests.plugin.MixinAspect"
   ]
 }