Techie Shah

Hibernate is an Object Relation mapping framework for Java language. It has more benefits over JDBC. Since I am using it since 2010, I have found that one of the biggest benefits of Hibernate is that code written using Hibernate is almost database independent and can be a key feature if one wants to shift the code base from one database to another. Using Hibernate, one has to be careful with the following two a) A singleton SessionFactory instance should be maintained throughout the application (if using a single database)  It can be easily done using either a static code block OR implementing the Singleton pattern. b) Single Session instance should be maintained per Thread This is a tricky part but luckily we have the ThreadLocal  to our rescue.  This class provides thread-local variables. Below is the code to maintain a single Session instance per Thread private static final ThreadLocal<Session> session = new ThreadLocal<Session>();    public static S

Recently when working on a rest client using the Spring's RestTemplate, I needed to log the request and response as I had no clue what was wrong with my code. Spring provides the option to write your own Interceptors. For this specific requirement, Spring provides the  ClientHttpRequestInterceptor interface. I had to override its intercept method and implement my logic there. Below is the snapshot of my code public class MyInterceptor implements ClientHttpRequestInterceptor  {       @Override     public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] body, ClientHttpRequestExecution execution)                 throws IOException {              printRequest(httpRequest, body);             ClientHttpResponse response = execution.execute(httpRequest, body);             printResponse(response);             return response;     }     private void printRequest(HttpRequest httpRequest, byte[] body) throws IOException {                          System.out.print

Recently when working on restful webservices, I came across a situation where I have to receive variant  JSON  in my Request and have to return the variant JSON in response. In previous projects, I was using the specific Java Objects in my request and response.  In the current project, I had no idea how to handle the generic JSON instead of specific Java objects (jackson lib that automatically marshal/unmarshal JSON/Java Objects).  I came across the jackson's JsonNode class. Using JsonNode, I can accept any kind of Json in my request and similarly can return generic Json in my response.

I have written a Rest client using the Spring's RestTemplate with the following code  try {               response = restTemplate.exchange( url,HttpMethod.POST, entity , JsonNode.class);  }catch (HttpStatusCodeException codeException) {         String responseBody = codeException.getResponseBodyAsString();            ......................  } catch(Exception ex) {                   ex.printStackTrace();            ObjectMapper mapper = new ObjectMapper();           JsonNode node = mapper.readTree(" { \"error\" : \"" + ex.getMessage() + "\" }" );            response = new ResponseEntity<>(node, HttpStatus.INTERNAL_SERVER_ERROR );  } In the above code, I am not able to read the response body. This is the issue with the RestTemplate default error handler. In order to fix this issue, I have the following two options a) Write my own Error Handler that implements ResponseErrorHandler b) Write my own Error Handler tha