如何在Java中自动填充对象？

Question

i have a simple pojo

class animal{

private String name;

animal(String name){
 this.name = name;}

private Features features;

private int max_life;

//
*
* other properties and their getter's and setter's
*//
}

so now once i initialize the name of the POJO with any name i want the rest of the attributes to auto fill.

eg: animal("cat") should auto-fill other attributes such as max_life and features based on a cat.

is there any property's file or any way that will detect the initialization and auto fill them with pre-defined properties??

Answer 1

You have some options:

1 - Initializing in the constructor

class Animal {

   private String maxLife;

   public Animal (String name) {
      switch(name) {
         case "cat":
            maxLife = 10;
         case "dog":
            maxLife = 20;
         default:
           maxLife = 1;
      }
   }
}

2 - Using Inheritance:

abstract class Animal {
   String name;
   int maxLife;
}

class Cat extends Animal {
  public Cat() {
     maxLife = 10;
  }
}

class Dog extends Animal {
  public Dog() {
     maxLife = 20;
  }
}

3 - Using a factory (with classes of option 2):

class AnimalFactory {

   public static Animal create(String name) {
       switch(name) {
         case "cat":
            return new Cat();
         case "dog":
            return new Dog();
      }
   }

}

Also, in Java, the convention is to use CamelCase. For classes, it should be capitalized and for variables/fields should start with lowercase.

Answer 2

There is a library called Podam which helps in auto filling a Pojo. I provide below the link.

https://mtedone.github.io/podam/

To quote from the link, you have to use like this.

// Simplest scenario. Will delegate to Podam all decisions
PodamFactory factory = new PodamFactoryImpl();

// This will use constructor with minimum arguments and
// then setters to populate POJO
Pojo myPojo = factory.manufacturePojo(Pojo.class);

// This will use constructor with maximum arguments and
// then setters to populate POJO
Pojo myPojo2 = factory.manufacturePojoWithFullData(Pojo.class);

// If object instance is already available,
// Podam can fill it with random data
Pojo myPojo3 = MyFactory.getPojoInstance();
factory.populatePojo(myPojo3);

Answer 3

I can actually think of several ways to implement such thing. But what you're looking for is a factory .

The idea is: the factory receives the animal kind, and creates the instance based on the kind.

In general, the most basic (although terrible) example is:

public class AnimalFactory {
    public Animal create(String name) {
        if (name.equals(“cat”)) {
            return new Animal(...);
        }
    // other
    }
}

You may then create animals as such:

AnimalFactory factory = new AnimalFactory();
Animal kitty = factory.create(“cat”);

This can be done in multiple ways and improved in many aspects. Read more about the Factory design pattern .

Answer 4

您可以为此使用Factory Design Pattern ，也可以与Strategy Design Pattern结合使用。

Answer 5

class Animal{

private String name;

  Animal(String name)
  {
     this.name = name;
     switch(name){
        case "cat":
           this.features = new Features("cat");
           this.max_life = 16;
           break;
        case "dog":
           this.features = new Features("dog");
           this.max_life = 15;
           break;
        default:
           this.features = new Features("unknown");
           this.max_life = 0;
           break;
     }

  }

  private Features features;

  private int max_life;

//
*
* other properties and their getter's and setter's
*//
}

Answer 6

除了使用我建议的“ 抽象工厂模式”之外，您还可以考虑使用“ 原型模式” 。