Spring CrudRepository方法findAll（）返回一个空列表

Question

So, my problem is in the title - crudrepository method findAll() returns a null list. 所以，我的问题在于标题 - crudrepository方法findAll()返回一个空列表。 I've overriden Crud's method because it returned an iterable instead of a list. 我已经覆盖了Crud的方法，因为它返回了一个iterable而不是一个列表。

I've tried using the JpaRepository instead of CrudRepository (I didn't override the findAll() method then), but got the same result. 我已经尝试使用JpaRepository而不是CrudRepository （我没有覆盖findAll()方法），但得到了相同的结果。

My code: 我的代码：

Event.java Event.java

@Data
@Entity
@NoArgsConstructor
public class Event{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@Column(nullable=false)
private String name;

@Column(nullable=false)
private LocalDateTime time;

@ManyToOne
@JoinColumn
private City city;

}

City.java City.java

@Data
@Entity
@NoArgsConstructor
public class City {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@Column(nullable=false)
private Long code;

@Column(nullable=false)
private String name;

    @OneToMany(mappedBy = "city", cascade = CascadeType.ALL)
    private Set<Event> events;
}

CityRepository.java CityRepository.java

@Repository
public interface CityRepository extends CrudRepository<City, Long> {

@Override
List<City> findAll();
}

EventsController.java EventsController.java

@Controller
@RequestMapping
public class EventsController {

@Autowired
static CityRepository cityRepository;

public static List<Event> eventList = new ArrayList<>();

@RequestMapping
public String eventEntry(Model model) {

    model.addAttribute("event", new Event());
    model.addAttribute("cities", cityRepository.findAll());

    return "eventEntry";
}
}

eventEntry.html eventEntry.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
  xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Event entry</title>
</head>
<body>

    <h3>New event</h3>

    <form method="POST" th:object="${event}">

        <div class="form-group">
            <label for="city">City: </label>
            <select th:field="*{city}">
                <option value="" >Choose a city</option>
                <option th:each="city : ${cities}" th:value="${city}" th:text="${city}"></option>
            </select>
            <span class="validation-error" th:if="${#fields.hasErrors('city')}" th:errors="*{city}">City Error</span>
        </div>

        <div class="form-group">
            <label for="name">Name: </label>
            <input type="text" th:field="*{name}" />
            <span class="validation-error" th:if="${#fields.hasErrors('name')}" th:errors="*{name}">Name Error</span>
        </div>

        <div class="form-group">
            <label for="time">Time: </label>
            <input type="datetime-local" th:field="*{time}" />
            <span class="validation-error" th:if="${#fields.hasErrors('time')}" th:errors="*{time}">Time Error</span>
        </div>

        <div class="form-group">
            <input type="submit" th:value="Save">
        </div>

    </form>
</body>

I am using an embedded H2 database with a data.sql file used to fill data into the database (I don't have the schema.sql file since tables are created using annotations). 我使用嵌入式H2数据库和data.sql文件，用于将数据填充到数据库中（我没有schema.sql文件，因为表是使用注释创建的）。 When viewing the H2 database console and using the SELECT * FROM CITY I'm getting the list of the cities. 查看H2数据库控制台并使用SELECT * FROM CITY我将获取城市列表。

I am getting a NullPointerException on this line from the EventController class: model.addAttribute("cities", cityRepository.findAll()); 我从EventController类获取此行的NullPointerException ： model.addAttribute("cities", cityRepository.findAll()); Can someone explain why? 有人可以解释原因吗？

Answer 1

删除了存储库前面的static声明，现在工作正常

Spring CrudRepository方法findAll（）返回一个空列表

问题描述

1 个解决方案

解决方案1
0 已采纳 2019-05-28 08:12:34

Spring CrudRepository方法findAll（）返回一个空列表

问题描述

1 个解决方案

解决方案1 0 已采纳 2019-05-28 08:12:34

解决方案1
0 已采纳 2019-05-28 08:12:34