Question

我使用Spring和JpaRepository作为数据访问层。我的@Repository界面如下：

@Repository
interface EventRepository extends JpaRepository<Event, Long>, JpaSpecificationExecutor<Event> {
    .... some custom methods irrelevant to this post ....
}

这是我的简化模型类：

class Event {
    Long eventID;
    String name;
    Date time;
    Zone zone;
}


class Zone {
    Long zoneId;
    String zoneName;
    User user;
}


class User {
    Long userId;
    String username;
}

我使用JpaSpecificationExecutor来获取特定Event中time列表的数据库。我正在使用这种方法，它可以正常工作：

Page<T> findAll(Specification<T> spec, Pageable pageable);

但我想添加另一个条件来仅为特定User获取条目。

我尝试创建这样的新方法：

Page<Event> findAllByZone_User(User user, Specification<Event> spec, Pageable pageable);

但是当我调用它时，我会进入这一行Exception：

java.util.NoSuchElementException: null

甚至可以创建这样的方法吗？如果没有 - 我该怎么办？

Answer 1

我创建了一个像你这样的Spring boot project，这对我有用。你可以查看我的代码.....

<强> Event.java

    package com.example.model;

import java.util.Date;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Event {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long eventID;
    private String name;
    private Date time = new Date();

    @OneToOne(cascade = CascadeType.ALL)
    private Zone zone;

    public Long getEventID() {
        return eventID;
    }
    public void setEventID(Long eventID) {
        this.eventID = eventID;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Date getTime() {
        return time;
    }
    public void setTime(Date time) {
        this.time = time;
    }
    public Zone getZone() {
        return zone;
    }
    public void setZone(Zone zone) {
        this.zone = zone;
    }
}

<强> Zone.java

package com.example.model;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Zone {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long zoneId;
    private String zoneName;

    @OneToOne(cascade = CascadeType.ALL)
    private User user;

    public Long getZoneId() {
        return zoneId;
    }
    public void setZoneId(Long zoneId) {
        this.zoneId = zoneId;
    }
    public String getZoneName() {
        return zoneName;
    }
    public void setZoneName(String zoneName) {
        this.zoneName = zoneName;
    }
    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }
}

<强> User.java

package com.example.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long userId;
    private String username;

    public Long getUserId() {
        return userId;
    }
    public void setUserId(Long userId) {
        this.userId = userId;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
}

我的存储库是

<强> EventRepository.java

package com.example.model;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.repository.JpaRepository;

public interface EventRepository extends JpaRepository<Event, Long>, JpaSpecificationExecutor<Event>{

    Page<Event> findAllByZoneUser(User user, Pageable pageable);
}

<强> UserRepository.java

package com.example.model;

import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Long>{

}

我直接在我的控制器中调用存储库方法，如下所示

<强> UserController.java

package com.example.model;

import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @Autowired
    EventRepository eventRepository;
    @Autowired
    UserRepository userRepository;

    @RequestMapping(value = "/{userId}", method = RequestMethod.GET)
    public Map<String, Object> updateUserDO(@PathVariable Long userId) {
        Map<String, Object> map = new HashMap<>();
        User user = userRepository.findOne(userId);
        PageRequest pageRequest = new PageRequest(0, 10, Sort.Direction.ASC, "eventID");
        map.put("user", eventRepository.findAllByZoneUser(user, pageRequest));
        return map;
    }
}

Spring JpaSpecificationExecutor新查询方法NoSuchElementException

1 个答案: