feign.Request object now supported as exception constructor parameter

The ExceptionGenerator now

* also looks for constructor parameter of type feign.Request.
* creates the exception providing the feign.Request by calling response.request()

Author: sfellinger

README.md

@@ -85,7 +85,7 @@ Any exception can be used if they have a default constructor:
 class DefaultConstructorException extends Exception {}
 ```
 
-However, if you want to have parameters (such  as the body in the error response or headers), you have to annotate its 
+However, if you want to have parameters (such  as the feign.Request object or response body or response headers), you have to annotate its 
 constructor appropriately (the body annotation is optional, provided there aren't paramters which will clash)
 
 All the following examples are valid exceptions:
@@ -97,6 +97,20 @@ class JustBody extends Exception {
 
     }
 }
+class JustRequest extends Exception {
+
+    @FeignExceptionConstructor
+    public JustRequest(Request request) {
+
+    }
+}
+class RequestAndResponseBody extends Exception {
+
+    @FeignExceptionConstructor
+    public RequestAndResponseBody(Request request, String body) {
+
+    }
+}
 //Headers must be of type Map<String, Collection<String>>
 class BodyAndHeaders extends Exception {
 
@@ -105,6 +119,13 @@ class BodyAndHeaders extends Exception {
 
     }
 }
+class RequestAndResponseBodyAndHeaders extends Exception {
+
+    @FeignExceptionConstructor
+    public RequestAndResponseBodyAndHeaders(Request request, @ResponseBody String body, @ResponseHeaders Map<String, Collection<String>> headers) {
+
+    }
+}
 class JustHeaders extends Exception {
 
     @FeignExceptionConstructor

src/main/java/feign/error/ExceptionGenerator.java

@@ -46,15 +46,17 @@ class ExceptionGenerator {
   }
 
   private final Integer bodyIndex;
+  private final Integer requestIndex;
   private final Integer headerMapIndex;
   private final Integer numOfParams;
   private final Type bodyType;
   private final Class<? extends Exception> exceptionType;
   private final Decoder bodyDecoder;
 
-  ExceptionGenerator(Integer bodyIndex, Integer headerMapIndex, Integer numOfParams, Type bodyType,
+  ExceptionGenerator(Integer bodyIndex, Integer requestIndex, Integer headerMapIndex, Integer numOfParams, Type bodyType,
       Class<? extends Exception> exceptionType, Decoder bodyDecoder) {
     this.bodyIndex = bodyIndex;
+    this.requestIndex = requestIndex;
     this.headerMapIndex = headerMapIndex;
     this.numOfParams = numOfParams;
     this.bodyType = bodyType;
@@ -72,6 +74,10 @@ Exception createException(Response response) throws InvocationTargetException,
       paramClasses[bodyIndex] = Types.getRawType(bodyType);
       paramValues[bodyIndex] = resolveBody(response);
     }
+    if (requestIndex >= 0) {
+      paramClasses[requestIndex] = Request.class;
+      paramValues[requestIndex] = response.request();
+    }
     if (headerMapIndex >= 0) {
       paramValues[headerMapIndex] = response.headers();
       paramClasses[headerMapIndex] = Map.class;
@@ -120,6 +126,7 @@ public ExceptionGenerator build() {
       Annotation[][] parametersAnnotations = constructor.getParameterAnnotations();
 
       Integer bodyIndex = -1;
+      Integer requestIndex = -1;
       Integer headerMapIndex = -1;
       Integer numOfParams = parameterTypes.length;
       Type bodyType = null;
@@ -139,15 +146,22 @@ public ExceptionGenerator build() {
           }
         }
         if (!foundAnnotation) {
-          checkState(bodyIndex == -1,
-              "Cannot have two parameters either without annotations or with @ResponseBody annotation");
-          bodyIndex = i;
-          bodyType = parameterTypes[i];
+          if(parameterTypes[i].equals(Request.class)) {
+            checkState(requestIndex == -1,
+                    "Cannot have two parameters either without annotations or with object of type feign.Request");
+            requestIndex = i;
+          } else {
+            checkState(bodyIndex == -1,
+                    "Cannot have two parameters either without annotations or with @ResponseBody annotation");
+            bodyIndex = i;
+            bodyType = parameterTypes[i];
+          }
         }
       }
 
       ExceptionGenerator generator = new ExceptionGenerator(
           bodyIndex,
+          requestIndex,
           headerMapIndex,
           numOfParams,
           bodyType,