Added a precondition check to ensure that a parameter being added to a ParamMap is compatible with its spec.

Added comments in RequestBody and ResponseBody to indicate that their Gson type adapters must be used.

wsdef/src/main/java/com/google/gson/webservice/definition/ParamMap.java

@@ -41,7 +41,7 @@ class ParamMap {
     }
 
     public Builder<T> put(String paramName, Object content, Type typeOfContent) {
-      spec.checkIfCompatible(paramName, typeOfContent);
+      Preconditions.checkArgument(spec.checkIfCompatible(paramName, typeOfContent));
       contents.put(paramName, content);
       return this;
     }

wsdef/src/main/java/com/google/gson/webservice/definition/RequestBody.java

@@ -23,6 +23,8 @@ import java.util.Map;
  * in the output stream of the request (for example, with 
  * {@link java.net.HttpURLConnection#getOutputStream()}) , and is read by the 
  * {@link javax.servlet.http.HttpServletRequest#getInputStream()}.
+ * This class omits the default constructor for use by Gson. Instead the user must use
+ * {@link com.google.gson.webservice.typeadapters.RequestBodyGsonConverter}
  * 
  * @author inder
  */

wsdef/src/main/java/com/google/gson/webservice/definition/ResponseBody.java

@@ -20,7 +20,9 @@ import java.util.Map;
 
 /**
  * body of the response. This is written out as JSON to be sent out to the client. 
- * 
+ * This class omits the default constructor for use by Gson. Instead the user must use
+ * {@link com.google.gson.webservice.typeadapters.ResponseBodyGsonConverter}
+ *
  * @author inder
  */
 public final class ResponseBody extends ContentBody {
@@ -46,7 +48,6 @@ public final class ResponseBody extends ContentBody {
     }    
   }
 
-
   private ResponseBody(ResponseBodySpec spec, Map<String, Object> contents) {
     super(spec, contents);
   }