Update and ClassLoaderHelper#classLoader to load class using the class loader of that class and fallback to context class loader and system class loader. See #56

Address comments and make classLoader fallback to contextClassLoader

Author: zoewangg

.changes/next-release/bugfix-AWSSDKforJavav2-508ab51.json

@@ -0,0 +1,5 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "type": "bugfix", 
+    "description": "Use the class loader that loaded the SDK to load the HTTP implementations. See [#56](https://github.com/aws/aws-sdk-java-v2/issues/56)"
+}

core/sdk-core/src/main/java/software/amazon/awssdk/core/interceptor/ClasspathInterceptorChainFactory.java

@@ -136,7 +136,7 @@ private ExecutionInterceptor createExecutionInterceptor(String interceptorClassN
     }
 
     private ClassLoader classLoader() {
-        return Validate.notNull(ClassLoaderHelper.classLoader(),
-                                "Failed to load the classloader for the current thread or the system.");
+        return Validate.notNull(ClassLoaderHelper.classLoader(getClass()),
+                                "Failed to load the classloader of this class or the system.");
     }
 }

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/http/loader/SdkServiceLoader.java

@@ -18,16 +18,17 @@
 import java.util.Iterator;
 import java.util.ServiceLoader;
 import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.core.internal.util.ClassLoaderHelper;
 
 /**
- * Thin layer over {@link ServiceLoader} to allow mocking in tests.
+ * Thin layer over {@link ServiceLoader}.
  */
 @SdkInternalApi
 class SdkServiceLoader {
 
     public static final SdkServiceLoader INSTANCE = new SdkServiceLoader();
 
     <T> Iterator<T> loadServices(Class<T> clzz) {
-        return ServiceLoader.load(clzz).iterator();
+        return ServiceLoader.load(clzz, ClassLoaderHelper.classLoader(SdkServiceLoader.class)).iterator();
     }
 }

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/util/ClassLoaderHelper.java

@@ -24,23 +24,25 @@ private ClassLoaderHelper() {
     }
 
     private static Class<?> loadClassViaClasses(String fqcn, Class<?>[] classes) {
-        if (classes != null) {
-            for (Class<?> c : classes) {
-                ClassLoader loader = c.getClassLoader();
-                if (loader != null) {
-                    try {
-                        return loader.loadClass(fqcn);
-                    } catch (ClassNotFoundException e) {
-                        // move on to try the next class loader
-                    }
+        if (classes == null) {
+            return null;
+        }
+
+        for (Class<?> clzz: classes) {
+            ClassLoader loader = clzz.getClassLoader();
+            if (loader != null) {
+                try {
+                    return loader.loadClass(fqcn);
+                } catch (ClassNotFoundException e) {
+                    // move on to try the next class loader
                 }
             }
         }
         return null;
     }
 
     private static Class<?> loadClassViaContext(String fqcn) {
-        ClassLoader loader = classLoader();
+        ClassLoader loader = contextClassLoader();
         try {
             return loader == null ? null : loader.loadClass(fqcn);
         } catch (ClassNotFoundException e) {
@@ -114,11 +116,32 @@ public static Class<?> loadClass(String fqcn, boolean classesFirst,
      * Attempt to get the current thread's class loader and fallback to the system classloader if null
      * @return a {@link ClassLoader} or null if none found
      */
-    public static ClassLoader classLoader() {
+    private static ClassLoader contextClassLoader() {
         ClassLoader threadClassLoader = Thread.currentThread().getContextClassLoader();
         if (threadClassLoader != null) {
             return threadClassLoader;
         }
         return ClassLoader.getSystemClassLoader();
     }
+
+    /**
+     * Attempt to get class loader that loads the classes and fallback to the thread context classloader if null.
+     *
+     * @param classes the classes
+     * @return a {@link ClassLoader} or null if none found
+     */
+    public static ClassLoader classLoader(Class<?>... classes) {
+        if (classes != null) {
+            for (Class clzz : classes) {
+                ClassLoader classLoader = clzz.getClassLoader();
+
+                if (classLoader != null) {
+                    return classLoader;
+                }
+            }
+        }
+
+        return contextClassLoader();
+    }
+
 }

core/sdk-core/src/main/java/software/amazon/awssdk/core/internal/util/Mimetype.java

@@ -71,7 +71,7 @@ public final class Mimetype {
 
     private static final String MIME_TYPE_PATH = "software/amazon/awssdk/core/util/mime.types";
 
-    private static final ClassLoader CLASS_LOADER = ClassLoaderHelper.classLoader();
+    private static final ClassLoader CLASS_LOADER = ClassLoaderHelper.classLoader(Mimetype.class);
 
     private static volatile Mimetype mimetype;
 

services/sts/src/main/java/software/amazon/awssdk/services/sts/auth/StsAssumeRoleWithSamlCredentialsProvider.java

@@ -100,7 +100,7 @@ public Builder refreshRequest(AssumeRoleWithSamlRequest assumeRoleWithSamlReques
         }
 
         /**
-         * Similar to {@link #refreshRequest(AssumeRoleRequest)}, but takes a {@link Supplier} to supply the request to
+         * Similar to {@link #refreshRequest(AssumeRoleWithSamlRequest)}, but takes a {@link Supplier} to supply the request to
          * STS.
          *
          * @param assumeRoleWithSamlRequestSupplier A supplier