如何在Spring实体中输出像totalAmount这样的方法的返回值

Question

是否可以输出一个实体totalAmount的返回值ShoppingCart，它不是类中的值，而是一个方法？例如，我有一个带有项目列表的类Shoppingcart。以及一种方法totalAmount。现在，当我使用URL http://localhost:8082/carts/1向API发出请求时，我希望得到如下响应：

{ 
"creationDate": "2016-12-07T09:45:38.000+0000",
  "items": [
    {
      "itemName": "Nintendo 2DS",
      "description": "Konsole from Nintendo",
      "price": 300.5,
      "quantity": 3
    },
    {
      "itemName": "Nintendo Classic",
      "description": "Classic nintendo Console from the 80th...",
      "price": 75,
      "quantity": 2
    }
  ],
  "totalAmount": "1051,50",
  "_links": {
    "self": {
      "href": "http://localhost:8082/carts/2"
    },
    "cart": {
      "href": "http://localhost:8082/carts/2"
    },
    "checkout": {
      "href": "http://localhost:8083/order"
    }
  }
}

当前，API请求的响应如下：

{
  "creationDate": "2016-12-07T09:45:38.000+0000",
  "items": [
    {
      "itemName": "Nintendo 2DS",
      "description": "Konsole from Nintendo",
      "price": 300.5,
      "quantity": 3
    },
    {
      "itemName": "Nintendo Classic",
      "description": "Classic nintendo Console from the 80th...",
      "price": 75,
      "quantity": 2
    }
  ],
  "_links": {
    "self": {
      "href": "http://localhost:8082/carts/2"
    },
    "cart": {
      "href": "http://localhost:8082/carts/2"
    },
    "checkout": {
      "href": "http://localhost:8083/order"
    }
  }
}

有什么注释能做这件事还是别的什么吗。我试图将其添加到(org.springframework.hateoas.ResourceProcessor)中，但只有添加额外链接的可能性。还是我需要添加一个类值totalAmount？

Answer 1

是的，您可以通过用Jackson @JsonProperty注释注释您的方法来实现这一点。

代码样本

@JsonProperty("totalAmount")
public double computeTotalAmount()
{
    // compute totalAmout and return it
}

Answer 2

为了回答下一个可能的问题，你在阅读完这篇文章后会得到一个答案。如何计算totalAmount。在这里的片段

public Class Cart{
   // some Class values

   @JsonProperty("totalAmount")
   public BigDecimal total(){

        return items.stream()
                .map(Item::total)
                .reduce(BigDecimal.ZERO, BigDecimal::add);
    }
}

public class Item{
     // some Item values

     @JsonProperty("totalAmount")
     public BigDecimal total(){
         return price.multiply(new BigDecimal(this.quantity));
     }
}

输出类似于此的内容：

{
  "creationDate": "2016-12-07T09:45:38.000+0000",
  "items": [
    {
      "itemName": "Nintendo 2DS",
      "description": "Konsole from Nintendo",
      "price": 300.5,
      "quantity": 3,
      "totalAmount": 901.5
    },
    {
      "itemName": "Nintendo Classic",
      "description": "Classic nintendo Console from the 80th...",
      "price": 75,
      "quantity": 2,
      "totalAmount": 150
    }
  ],
  "totalAmount": 1051.5,
  "_links": {
    "self": {
      "href": "http://localhost:8082/carts/2"
    },
    "cart": {
      "href": "http://localhost:8082/carts/2"
    },
    "checkout": {
      "href": "http://localhost:8083/order"
    }
  }
}

希望它能帮助你:)