#2 Added gson support

Author: Evgeniy Sinev

pom.xml

@@ -98,11 +98,18 @@
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
-            <version>2.9.9</version>
+            <version>2.9.10.1</version>
             <optional>true</optional>
             <scope>provided</scope>
         </dependency>
 
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>2.8.6</version>
+            <scope>provided</scope>
+        </dependency>
+
         <dependency>
             <groupId>javax.servlet</groupId>
             <artifactId>javax.servlet-api</artifactId>

src/main/java/com/payneteasy/apiservlet/GsonApiServlet.java

@@ -0,0 +1,68 @@
+package com.payneteasy.apiservlet;
+
+import com.google.gson.Gson;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.util.UUID;
+
+public class GsonApiServlet<I, O> extends HttpServlet {
+
+    private static final Logger LOG = LoggerFactory.getLogger(GsonApiServlet.class);
+
+    private final IApiCall<I, O> apiCall;
+    private final Class<I>       requestClass;
+
+
+    private final Gson gson;
+
+    public GsonApiServlet(IApiCall<I, O> aApiCall, Class<I> aRequestClass, Gson aGson) {
+        apiCall = aApiCall;
+        gson = aGson;
+        requestClass = aRequestClass;
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest aRequest, HttpServletResponse aResponse) throws IOException {
+        String json    = toJsonString(aRequest.getReader());
+        I      request = gson.fromJson(json, requestClass);
+
+        LOG.debug("Got {} \n{}", aRequest.getRequestURI(), json);
+
+        processRequest(aRequest, aResponse, request);
+    }
+
+    @Override
+    protected void doGet(HttpServletRequest aRequest, HttpServletResponse aResponse) throws IOException {
+        processRequest(aRequest, aResponse, null);
+    }
+
+    private void processRequest(HttpServletRequest aRequest, HttpServletResponse aResponse, I request) throws IOException {
+        try {
+            O response = apiCall.exec(request);
+
+            aResponse.setContentType("application/json");
+            gson.toJson(response, aResponse.getWriter());
+        } catch (Exception e) {
+            String id = UUID.randomUUID().toString();
+            LOG.error("{}: Cannot process {}", aRequest.getRequestURI(), id, e);
+            aResponse.setHeader("UNIQUE-ERROR-ID", id);
+            aResponse.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+        }
+    }
+
+    private String toJsonString(BufferedReader aRequestReader) throws IOException {
+        StringBuilder sb = new StringBuilder();
+        String        line;
+        while ((line = aRequestReader.readLine()) != null) {
+            sb.append(line);
+            sb.append('\n');
+        }
+        return sb.toString();
+    }
+}