CODEWITHSUNDEEP
javaspring
qaxi
qaxi

Reputation: 482

Java code design dilemma

I have a dilemma regarding the design of my code.

First of all, I am converting a VB to Java system. The VB program has a class module which is like a combination of POJO and access the database for its logic. I created a similar class in JAVA with getters and setters. My dilemma is that since I need to copy the structure of the VB codes (we are forced to), I also need to include the query services in my JAVA class. But in our framework, only service classes have access to the query services.

I am thinking of changing my JAVA class to an abstact class, and use Anonymous class instead.

Sample:

public abstract class MyClass {
     private int a;
     private int b;

     public String calculate1() {
          // do processing for variables a and b
          String sql = "" // build sql here
          List<Map<String, Object>> result = query(sql);
     }

     public String calculate2() {
          // do processing for variables a and b
          String anotherSql = "" // build anotherSql
          List<Map<String, Object>> result = query(anotherSql);
     }

     protected abstract List<Map<String, Object>> query(String sql);

     // getters and setters for a and b
}

public class MyService {
     @Autowired
     private QueryService myQueryService;

     public void execute() {
          MyClass myClass = new MyClass() {
             @Override
             protected List<Map<String, Object>> query(String sql) {
                 return myQueryService.executeQuery(sql);
             }
          };
     }
}

A few things to consider:

  1. My Service is a singleton-scope bean.
  2. I also like MyClass to be session based (1 instance per user).
  3. Since I wont be declaring the MyClass in my Spring context, it cannot use dependency injection and cannot use other services. I will be saving the instance in a session and will just be retrieving the instance of MyClass.

Also because of this dilemma, I am forced to use string queries and JDBC template. Originally, our framework uses DAO objects and Hibernate. If someone also can solve the code using DAO, that would be better. If I will be using DAO objects, I would have to use different DAO objects with their DAO service classes.

I am not entirely sure if this is a good design. I don't know also if this will work. I was not able to run this in my environment.

I would really appreciate it if someone can enlighten me.

Thanks!

Upvotes: 3

Views: 241

Answers (1)

Bohemian
Bohemian

Reputation: 425198

Since an instance of MyClass can't function without an instance of QueryService, how about you just pass an reference to the query service into the constructor of MyClass:

public abstract class MyClass {
    private final QueryService queryService;

    public MyClass (QueryService queryService) {
        this.queryService = queryService;
    }

    protected List<Map<String, Object>> query(String sql) {
        return queryService.executeQuery(sql);
    }
}

public class MyService {
     @Autowired
     private QueryService myQueryService;

     public void execute() {
          MyClass myClass = new MyClass(myQueryService);
     }
}

Making the queryService instance field final, and having such a constructor, clearly expresses this dependency in code.

Upvotes: 1

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