How can i reduce amount of boilerplate code in vert.x

Question

I've read several tutorials on vertx.io but I can't still understand how I can minimise repeated code.

For example, i need to implement RESTful service which gets data from DB. I've prepared 2 bean classes for tables (Customer, Administrator) and implemented services classes:

AdministratorService.java:

public void getAll(RoutingContext routingContext) {
    jdbc.getConnection(ar -> {
      SQLConnection connection = ar.result();
      connection.query(Queries.SELECT_ALL_ADMINS, result -> {
        List<Administrator> admins = result.result().getRows().stream().map(Administrator::new).collect(Collectors.toList());
        routingContext.response()
          .putHeader("content-type", "application/json; charset=utf-8")
          .end(Json.encodePrettily(admins));
        connection.close();
      });
    });
  }

  public void getOneById(RoutingContext routingContext) {
    final String id = routingContext.request().getParam("id");
    if (id == null) {
      routingContext.response().setStatusCode(400).end();
    } else {
      jdbc.getConnection(ar -> {
        // Read the request's content and create an instance of Administrator.
        SQLConnection connection = ar.result();
        select(id, connection, Queries.SELECT_ONE_ADMIN_BY_ID, result -> {
          if (result.succeeded()) {
            routingContext.response()
              .setStatusCode(200)
              .putHeader("content-type", "application/json; charset=utf-8")
              .end(Json.encodePrettily(result.result()));
          } else {
            routingContext.response()
              .setStatusCode(404).end();
          }
          connection.close();
        });
      });
    }
  }

CustomerService.java:

public void getAll(RoutingContext routingContext) {
    jdbc.getConnection(ar -> {
      SQLConnection connection = ar.result();
      connection.query(Queries.SELECT_ALL_CUSTOMERS, result -> {
        List<Customer> customers = result.result().getRows().stream().map(Customer::new).collect(Collectors.toList());
        routingContext.response()
          .putHeader("content-type", "application/json; charset=utf-8")
          .end(Json.encodePrettily(customers));
        connection.close();
      });
    });
  }


  public void getOneById(RoutingContext routingContext) {
    final String id = routingContext.request().getParam("id");
    if (id == null) {
      routingContext.response().setStatusCode(400).end();
    } else {
      jdbc.getConnection(ar -> {
        // Read the request's content and create an instance of Administrator.
        SQLConnection connection = ar.result();
        select(id, connection, Queries.SELECT_ONE_CUSTOMER_BY_ID, result -> {
          if (result.succeeded()) {
            routingContext.response()
              .setStatusCode(200)
              .putHeader("content-type", "application/json; charset=utf-8")
              .end(Json.encodePrettily(result.result()));
          } else {
            routingContext.response()
              .setStatusCode(404).end();
          }
          connection.close();
        });
      });
    }
  }

Not hard to see that part

.routingContext.response()
.putHeader("content-type", "application/json; charset=utf-8")

is repeated in each method. And in general speaking all difference between these classes is sql requests and bean classes.

Could you share your example or show how to change my methods?

Answer 1

VertX is not a framework, which makes easy for some developers to design their own structure, but for some it becomes nightmare. What you are looking for is a pre designed framework, which is ready with router, controllers, DB connections. Apparently that's not what vertx is, its more like a library, extend it the way you want.

I see in your code that for every Service function you are getting SQL connection. If you have worked on other frameworks like Spring, the connection is already available using DI. You need to implement DI, some MVC design and then your boilerplate code will be removed.

I have done something similar, but for MongoDB.

VertX with MongoDB