如何將@RestController中的請求體轉換為抽象值列表？

Question

假設我們有以下類：

public abstract class Investment {

   private String investmentType;

   // getters & setters
}

public class Equity extends Investment {
}

public class Bond extends Investment {
}

public class InvestmentFactory {

    public static Investment getTypeFromString(String investmentType) {
        Investment investment = null;
        if ("Bond".equals(investmentType)) {
            investment = new Bond();
        } else if ("Equity".equals(investmentType)) {
            investment = new Equity();
        } else {
            // throw exception
        }
        return investment;
    }
}

以下@RestController ：

@RestController
public class InvestmentsRestController {

    private InvestmentRepository investmentRepository;

    @Autowired
    public InvestmentsRestController(InvestmentRepository investmentRepository) {
        this.investmentRepository = investmentRepository;
    }

    @RequestMapping(RequestMethod.POST)
    public List<Investment> update(@RequestBody List<Investment> investments) {
       return investmentRepository.update(investments);
    }

}

以及請求體中的以下json：

[
  {"investmentType":"Bond"},
  {"investmentType":"Equity"}
]

如何在不使用Jackson的抽象類Investment的@JsonSubTypes情況下將json綁定或轉換為List<Investment>的請求主體，而是使用InvestmentFactory ？

Answer 1

@JsonDeserialize效果很好，但是如果你有更多的字段而不僅僅是類型，那么你必須手動設置它們。 如果你要回到傑克遜，你可以使用：

Investment.class

    @JsonTypeInfo(
            use = JsonTypeInfo.Id.NAME,
            include = JsonTypeInfo.As.PROPERTY,
            property = "investmentType")
    @JsonTypeIdResolver(InvestmentResolver.class)
    public abstract class Investment {
    } 

InvestmentResolver.class

public class InvestmentResolver extends TypeIdResolverBase {

    @Override
    public JavaType typeFromId(DatabindContext context, String id) throws IOException {
        Investment investment = InvestmentFactory.getTypeFromString(type);
        return context.constructType(investment.getClass());
    }

這樣做的好處是，如果你開始向投資添加字段，你就不必在Desrializer中添加它們（至少，在我的情況下這發生在我身上），但傑克遜會為你照顧它。 所以明天你可以得到測試用例：

'[{"investmentType":"Bond","investmentName":"ABC"},{"investmentType":"Equity","investmentName":"APPL"}]'

你應該好好去！

Answer 2

如果你可以使用@JsonDeserialize ：

@JsonDeserialize(using = InvestmentDeserializer.class)
public abstract class Investment {
}



public class InvestmentDeserializer extends JsonDeserializer<Investment> {
    @Override
    public Investment deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        ObjectMapper objectMapper = (ObjectMapper) p.getCodec();
        TreeNode node = objectMapper.readTree(p);

        TreeNode investmentNode = node.get("investmentType");
        String type = objectMapper.readValue(investmentNode.traverse(objectMapper), String.class);
        return InvestmentFactory.getTypeFromString(type);
    }
}

示例控制器：

@RestController
public class MyController {
    @RequestMapping("/")
    public List<Class<?>> update(@RequestBody List<Investment> investments) {
        return investments.stream().map(Object::getClass).collect(Collectors.toList());
    }
}

測試：

$ curl localhost:8080 -H "Content-Type: application/json" -d '[{"investmentType":"Bond"},{"investmentType":"Equity"}]'

輸出：

["com.example.demo.Bond","com.example.demo.Equity"]