Report bad-request for invalid YAML

Added classes and modified code to report bad-request when a servlet
attempts to read invalid YAML.

Change-Id: Iacddee92a448fb69d5c778a3c3f3f2b5528983f7
Issue-ID: POLICY-2085
Signed-off-by: Jim Hahn <jrh3@att.com>

4 files changed, 78 insertions, 6 deletions

diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/JsonExceptionMapper.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/JsonExceptionMapper.java
index 9ee72f03..55b3a0d5 100644
--- a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/JsonExceptionMapper.java
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/JsonExceptionMapper.java
@@ -42,7 +42,7 @@ public class JsonExceptionMapper implements ExceptionMapper<JsonSyntaxException>
     @Override
     public Response toResponse(JsonSyntaxException exception) {
         logger.warn("invalid JSON request", exception);
-        return Response.status(Response.Status.BAD_REQUEST).entity(new SimpleResponse("Invalid JSON request")).build();
+        return Response.status(Response.Status.BAD_REQUEST).entity(new SimpleResponse("Invalid request")).build();
     }
 
     @Getter
diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/RestServer.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/RestServer.java
index decf95f9..43e39d33 100644
--- a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/RestServer.java
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/RestServer.java
@@ -100,7 +100,7 @@ public class RestServer extends ServiceManagerContainer {
                         String.valueOf(restServerParameters.isAaf()));
         props.setProperty(svcpfx + PolicyEndPointProperties.PROPERTY_HTTP_SERIALIZATION_PROVIDER,
                         String.join(",", GsonMessageBodyHandler.class.getName(), YamlMessageBodyHandler.class.getName(),
-                                        JsonExceptionMapper.class.getName()));
+                                        JsonExceptionMapper.class.getName(), YamlExceptionMapper.class.getName()));
         return props;
     }
 
diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/YamlExceptionMapper.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/YamlExceptionMapper.java
new file mode 100644
index 00000000..ac96cab0
--- /dev/null
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/YamlExceptionMapper.java
@@ -0,0 +1,55 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.http.server;
+
+import javax.ws.rs.Produces;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.ExceptionMapper;
+import javax.ws.rs.ext.Provider;
+import lombok.Getter;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.yaml.snakeyaml.error.YAMLException;
+
+/**
+ * Catches JSON exceptions when decoding a REST request and converts them from an HTTP 500
+ * error code to an HTTP 400 error code.
+ */
+@Provider
+@Produces("application/yaml")
+public class YamlExceptionMapper implements ExceptionMapper<YAMLException> {
+    private static Logger logger = LoggerFactory.getLogger(YamlExceptionMapper.class);
+
+    @Override
+    public Response toResponse(YAMLException exception) {
+        logger.warn("invalid YAML request", exception);
+        return Response.status(Response.Status.BAD_REQUEST).entity(new SimpleResponse("Invalid request")).build();
+    }
+
+    @Getter
+    private static class SimpleResponse {
+        private String errorDetails;
+
+        public SimpleResponse(String errorDetails) {
+            this.errorDetails = errorDetails;
+        }
+    }
+}
diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/YamlMessageBodyHandler.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/YamlMessageBodyHandler.java
index ab09c1a6..36418e4a 100644
--- a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/YamlMessageBodyHandler.java
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/http/server/YamlMessageBodyHandler.java
@@ -20,11 +20,13 @@
 
 package org.onap.policy.common.endpoints.http.server;
 
+import com.google.gson.JsonSyntaxException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
+import java.io.Reader;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Type;
 import java.nio.charset.StandardCharsets;
@@ -39,6 +41,7 @@ import org.onap.policy.common.utils.coder.CoderException;
 import org.onap.policy.common.utils.coder.StandardYamlCoder;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.yaml.snakeyaml.error.YAMLException;
 
 /**
  * Provider that serializes and de-serializes JSON via gson.
@@ -72,7 +75,7 @@ public class YamlMessageBodyHandler implements MessageBodyReader<Object>, Messag
                     MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException {
 
         try (OutputStreamWriter writer = new OutputStreamWriter(entityStream, StandardCharsets.UTF_8)) {
-            new StandardYamlCoder().encode(writer, object);
+            new MyYamlCoder().encode(writer, object);
 
         } catch (CoderException e) {
             throw new IOException(e);
@@ -101,10 +104,24 @@ public class YamlMessageBodyHandler implements MessageBodyReader<Object>, Messag
 
         try (InputStreamReader streamReader = new InputStreamReader(entityStream, StandardCharsets.UTF_8)) {
             Class<?> clazz = (Class<?>) genericType;
-            return new StandardYamlCoder().decode(streamReader, clazz);
+            return new MyYamlCoder().decode(streamReader, clazz);
+        }
+    }
 
-        } catch (CoderException e) {
-            throw new IOException(e);
+    /**
+     * Yaml coder that yields YAMLException on input so that the http servlet can identify
+     * it and generate a bad-request status code. Only the {@link #decode(Reader, Class)}
+     * method must be overridden.
+     */
+    private static class MyYamlCoder extends StandardYamlCoder {
+        @Override
+        public <T> T decode(Reader source, Class<T> clazz) {
+            try {
+                return fromJson(source, clazz);
+
+            } catch (JsonSyntaxException e) {
+                throw new YAMLException(e);
+            }
         }
     }
 }