Question

我有一个REST端点，我可以调用它请求一些数据，但是它在JSON响应中返回了3次相同的对象，而不是仅返回不同的结果。

这是我得到的答复：

[
    {
        "id": "5555 ",
        "label": "MAIN USER (5555)  "
    },
    {
        "id": "5555 ",
        "label": "MAIN USER (5555)  "
    },
   {
        "id": "5555 ",
        "label": "MAIN USER (5555)  "
    }
]

这是用于生成JSON响应的控制器：

@RestController
public class AutoCompleteController {
    private AutoCompleteService autoCompleteService;
    private EntityManager em;

    public AutoCompleteController(AutoCompleteService autoCompleteService, EntityManager em) {
        this.autoCompleteService = autoCompleteService;
        this.em = em;
    }

    @RequestMapping(value = "jobs", method = RequestMethod.GET)
    public @ResponseBody
    List<AutoComplete> getSalary(@RequestParam(value = "autocomplete") String autocompleteValue) {
      return autoCompleteService.retrieveSalary(autocompleteValue);
   }
}

依次，控制器调用AutoCompleteService：

@Service
public class AutoCompleteService {
    private AutoCompleteRepository autocompleteRepository;

    public AutoCompleteService(AutoCompleteRepository autRepo) {
        this.autocompleteRepository = autRepo;
    }

    public List<AutoComplete> retrieveSalary(String jobClassCd) {
        List<AutoComplete>  salaries = autocompleteRepository.findAllByJobClassCdIsContaining(jobClassCd);
        if (salaries.size() <= 0) {
            throw new AutoCompleteNotFoundException(jobClassCd);
        }
        return salaries;
    }
}

Answer 1

只需确保您的方法autoCompleteService.retrieveSalary仅返回1个结果，然后根据您的过滤器检查数据库是否存在内容相同的多行。如果您始终希望得到1个结果，则使您返回一个Object，而不是List <>。

Answer 2

假设您的请求是在Java代码中对来自自动完成服务的信息进行重复数据删除，那么可以选择将信息转换为Set，然后返回到列表。假设正确设置哈希码和等于条件，这将仅返回一个唯一的结果。

import java.util.*;

class AutoComplete {
    // Not using getter / setters just for convenience here
    public String id;
    public String label;

    public AutoComplete(String id, String label) {
        this.id = id;
        this.label = label;
    }

    @Override
    public boolean equals(Object other) {
        if (other instanceof AutoComplete) {
            AutoComplete o = (AutoComplete) other;
            return o.id.equals(this.id) && o.label.equals(this.label);
        }
        return false;
    }

    @Override
    public int hashCode() {
        return (this.id + "-" + this.label).hashCode();
    }

    public String toString() {
        return this.id + " -- " + this.label;
    }
}

class Main {
    public static void main(String[] args) {
        ArrayList<AutoComplete> initialList = new ArrayList<AutoComplete>();
        initialList.add(new AutoComplete("555", "MAIN"));
        initialList.add(new AutoComplete("555", "MAIN"));
        initialList.add(new AutoComplete("555", "MAIN"));

        System.out.println(initialList);

        HashSet<AutoComplete> deduped = new HashSet<AutoComplete>(initialList);

        List<AutoComplete> dedupedList = new ArrayList<AutoComplete>(deduped);

        System.out.println(dedupedList);
    }
}

Json在Java中返回3个对象而不是一个？

2 个答案: