support Feign.builder() w/ SAX decoder

README.md

@@ -94,6 +94,15 @@ GitHub github = Feign.create(GitHub.class, "https://api.github.com", new GsonMod
 ### Sax
 [SaxDecoder](https://github.com/Netflix/feign/tree/master/sax) allows you to decode XML in a way that is compatible with normal JVM and also Android environments.
 
+Here's an example of how to configure Sax response parsing:
+```java
+api = Feign.builder()
+           .decoder(SAXDecoder.builder()
+                              .registerContentHandler(UserIdHandler.class)
+                              .build())
+           .target(Api.class, "https://apihost");
+```
+
 ### JAX-RS
 [JAXRSModule](https://github.com/Netflix/feign/tree/master/jaxrs) overrides annotation processing to instead use standard ones supplied by the JAX-RS specification.  This is currently targeted at the 1.1 spec.
 

sax/README.md

@@ -6,19 +6,9 @@ This module adds support for decoding xml via SAX.
 Add this to your object graph like so:
 
 ```java
-IAM iam = Feign.create(IAM.class, "https://iam.amazonaws.com", new DecodeWithSax());
-
---snip--
-@Module(addsTo = Feign.Defaults.class)
-static class DecodeWithSax {
-  @Provides Decoder saxDecoder(Provider<UserIdHandler> userIdHandler) {
-    return SAXDecoder.builder() //
-        .addContentHandler(userIdHandler) //
-        .build();
-  }
-
-  @Provides Encoder defaultEncoder() {
-    return new Encoder.Default();
-  }
-}
+api = Feign.builder()
+           .decoder(SAXDecoder.builder()
+                              .registerContentHandler(UserIdHandler.class)
+                              .build())
+           .target(Api.class, "https://apihost");
 ```

sax/src/main/java/feign/sax/SAXDecoder.java

@@ -16,8 +16,8 @@
 package feign.sax;
 
 import feign.Response;
-import feign.codec.Decoder;
 import feign.codec.DecodeException;
+import feign.codec.Decoder;
 import org.xml.sax.ContentHandler;
 import org.xml.sax.InputSource;
 import org.xml.sax.SAXException;
@@ -27,6 +27,7 @@ import org.xml.sax.helpers.XMLReaderFactory;
 import javax.inject.Provider;
 import java.io.IOException;
 import java.io.Reader;
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Type;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -37,17 +38,28 @@ import static feign.Util.ensureClosed;
 import static feign.Util.resolveLastTypeParameter;
 
 /**
- * Decodes responses using SAX. Configure using the {@link SAXDecoder.Builder
- * builder}.
+ * Decodes responses using SAX, which is supported both in normal JVM environments, as well Android.
+ * <br>
+ * <h4>Basic example with with Feign.Builder</h4>
+ * <br>
+ * <pre>
+ * api = Feign.builder()
+ *            .decoder(SAXDecoder.builder()
+ *                               .registerContentHandler(ContentHandlerForFoo.class)
+ *                               .registerContentHandler(ContentHandlerForBar.class)
+ *                               .build())
+ *            .target(MyApi.class, "http://api");
+ * </pre>
  * <p/>
- * 
+ * <h4>Advanced example with Dagger</h4>
+ * <br>
  * <pre>
  * &#064;Provides
  * Decoder saxDecoder(Provider&lt;ContentHandlerForFoo&gt; foo, //
  *         Provider&lt;ContentHandlerForBar&gt; bar) {
  *     return SAXDecoder.builder() //
- *             .addContentHandler(foo) //
- *             .addContentHandler(bar) //
+ *             .registerContentHandler(Foo.class, foo) //
+ *             .registerContentHandler(Bar.class, bar) //
  *             .build();
  * }
  * </pre>
@@ -63,10 +75,48 @@ public class SAXDecoder implements Decoder {
     private final Map<Type, Provider<? extends ContentHandlerWithResult<?>>> handlerProviders =
         new LinkedHashMap<Type, Provider<? extends ContentHandlerWithResult<?>>>();
 
-    public Builder addContentHandler(Provider<? extends ContentHandlerWithResult<?>> handler) {
-      Type type = resolveLastTypeParameter(checkNotNull(handler, "handler").getClass(), Provider.class);
-      type = resolveLastTypeParameter(type, ContentHandlerWithResult.class);
-      this.handlerProviders.put(type, handler);
+    /**
+     * Will call {@link Constructor#newInstance(Object...)} on {@code handlerClass} for each content stream.
+     * <p/>
+     * <h3>Note</h3>
+     * <br/>
+     * While this is costly vs {@code new}, it may not affect real performance due to the high cost of reading streams.
+     *
+     * @throws IllegalArgumentException if there's no no-arg constructor on {@code handlerClass}.
+     */
+    public <T extends ContentHandlerWithResult<?>> Builder registerContentHandler(Class<T> handlerClass) {
+      Type type = resolveLastTypeParameter(checkNotNull(handlerClass, "handlerClass"), ContentHandlerWithResult.class);
+      return registerContentHandler(type, new NewInstanceProvider(handlerClass));
+    }
+
+    private static class NewInstanceProvider<T extends ContentHandlerWithResult<?>> implements Provider<T> {
+      private final Constructor<T> ctor;
+
+      private NewInstanceProvider(Class<T> clazz) {
+        try {
+          this.ctor = clazz.getDeclaredConstructor();
+          // allow private or package protected ctors
+          ctor.setAccessible(true);
+        } catch (NoSuchMethodException e) {
+          throw new IllegalArgumentException("ensure " + clazz + " has a no-args constructor", e);
+        }
+      }
+
+      @Override public T get() {
+        try {
+          return ctor.newInstance();
+        } catch (Exception e) {
+          throw new IllegalArgumentException("exception attempting to instantiate " + ctor, e);
+        }
+      }
+    }
+
+    /**
+     * Will call {@link Provider#get()} on {@code handler} for each content stream.
+     * The {@code handler} is expected to have a generic parameter of {@code type}.
+     */
+    public Builder registerContentHandler(Type type, Provider<? extends ContentHandlerWithResult<?>> handler) {
+      this.handlerProviders.put(checkNotNull(type, "type"), checkNotNull(handler, "handler"));
       return this;
     }
 
@@ -75,11 +125,12 @@ public class SAXDecoder implements Decoder {
     }
   }
 
-  /* Implementations are not intended to be shared across requests. */
+  /**
+   * Implementations are not intended to be shared across requests.
+   */
   public interface ContentHandlerWithResult<T> extends ContentHandler {
-    /*
-     * expected to be set following a call to {@link
-     * XMLReader#parse(InputSource)}
+    /**
+     * expected to be set following a call to {@link XMLReader#parse(InputSource)}
      */
     T result();
   }

sax/src/test/java/feign/sax/SAXDecoderTest.java

@@ -17,9 +17,8 @@ package feign.sax;
 
 import dagger.ObjectGraph;
 import dagger.Provides;
-import feign.codec.Decoder;
-import feign.codec.DecodeException;
 import feign.Response;
+import feign.codec.Decoder;
 import org.testng.annotations.BeforeClass;
 import org.testng.annotations.Test;
 import org.xml.sax.helpers.DefaultHandler;
@@ -39,11 +38,10 @@ public class SAXDecoderTest {
 
   @dagger.Module(injects = SAXDecoderTest.class)
   static class Module {
-    @Provides Decoder saxDecoder(Provider<NetworkStatusHandler> networkStatus, //
-                                 Provider<NetworkStatusStringHandler> networkStatusAsString) {
+    @Provides Decoder saxDecoder(Provider<NetworkStatusHandler> networkStatus) {
       return SAXDecoder.builder() //
-          .addContentHandler(networkStatus) //
-          .addContentHandler(networkStatusAsString) //
+          .registerContentHandler(NetworkStatus.class, networkStatus) //
+          .registerContentHandler(NetworkStatusStringHandler.class) //
           .build();
     }
   }

sax/src/test/java/feign/sax/examples/IAMExample.java

@@ -15,21 +15,14 @@
  */
 package feign.sax.examples;
 
-import dagger.Module;
-import dagger.Provides;
 import feign.Feign;
 import feign.Request;
 import feign.RequestLine;
 import feign.RequestTemplate;
 import feign.Target;
-import feign.codec.Decoder;
-import feign.codec.Encoder;
 import feign.sax.SAXDecoder;
 import org.xml.sax.helpers.DefaultHandler;
 
-import javax.inject.Inject;
-import javax.inject.Provider;
-
 public class IAMExample {
 
   interface IAM {
@@ -37,7 +30,9 @@ public class IAMExample {
   }
 
   public static void main(String... args) {
-    IAM iam = Feign.create(new IAMTarget(args[0], args[1]), new DecodeWithSax());
+    IAM iam = Feign.builder()//
+        .decoder(SAXDecoder.builder().registerContentHandler(UserIdHandler.class).build())//
+        .target(new IAMTarget(args[0], args[1]));
     System.out.println(iam.userId());
   }
 
@@ -65,23 +60,7 @@ public class IAMExample {
     }
   }
 
-  @Module(addsTo = Feign.Defaults.class)
-  static class DecodeWithSax {
-    @Provides Decoder saxDecoder(Provider<UserIdHandler> userIdHandler) {
-      return SAXDecoder.builder() //
-          .addContentHandler(userIdHandler) //
-          .build();
-    }
-
-    @Provides Encoder defaultEncoder() {
-      return new Encoder.Default();
-    }
-  }
-
-  static class UserIdHandler extends DefaultHandler implements
-      SAXDecoder.ContentHandlerWithResult<Long> {
-    @Inject UserIdHandler() {
-    }
+  static class UserIdHandler extends DefaultHandler implements SAXDecoder.ContentHandlerWithResult<Long> {
 
     private StringBuilder currentText = new StringBuilder();