Smell Detail

Data Class

纯数据类

Dispensables

The class only contains fields and accessor methods and has no other functionality.

Define

Introduction

A Data Class contains only data and simple accessor methods, with no behavior. Such classes often indicate that behavior has been placed in the wrong location.

Key Identifiers

  • The class contains only fields and getter/setter methods
  • No business logic or behavioral methods
  • Related behavior is scattered across other classes
  • Violates the object-oriented principle of encapsulation

Refactoring Suggestions

  1. Move Method: Move related behavior into the data class
  2. Encapsulate Field: Reduce unnecessary setter methods
  3. Add Behavior: Add meaningful domain methods to the data class

Explanation

The Customer class is merely a data container; related business behavior should be moved into the Customer class so that data and behavior stay together.

Code Example
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class Customer {
    private String name;
    private String email;
    private String address;
    private double creditLimit;
    
    // Only getters and setters, no other behavior
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }
    
    public String getAddress() { return address; }
    public void setAddress(String address) { this.address = address; }
    
    public double getCreditLimit() { return creditLimit; }
    public void setCreditLimit(double creditLimit) { this.creditLimit = creditLimit; }
}


// Behavior is placed in other classes
class CustomerService {
    public boolean canPurchase(Customer customer, double amount) {
        return customer.getCreditLimit() >= amount;
    }
    
    public void updateCreditLimit(Customer customer, double newLimit) {
        customer.setCreditLimit(newLimit);
    }
}