Spring 引导 JPA 查询错误 - "No property '' found for type '' " 异常

Question

我目前正在学习使用 Spring Data JPA 的在线 Spring 引导课程。

我的项目包括 2 个实体：BDProject 和 BDUser，它们具有多对一关系。尝试从用户 ID 查找项目时，显示以下异常。

异常

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'BDProjectController': Unsatisfied dependency expressed through field 'bdProjectService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'BDProjectService': Unsatisfied dependency expressed through field 'bdProjectRepository'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'BDProjectRepository': Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Failed to create query for method public abstract java.util.List com.project.bdproject.BDProjectRepository.findByUserID(java.lang.String)! No property userID found for type BDProject!

我花了几个小时试图找出导致此异常的原因，但似乎没有任何解决办法。

我的代码：

实体

@Entity
public class BDUser {


@Id
private String userID;
private String bdUsername;
private String bdUserEmail;
private String bdUserPassword;

public BDUser(){
}

public BDUser(String userID, String bdUsername, String bdUserEmail, String bdUserPassword) {
    super();
    this.userID = userID;
    this.bdUsername = bdUsername;
    this.bdUserEmail = bdUserEmail;
    this.bdUserPassword = bdUserPassword;
}
// getters and setters...

@Entity
public class BDProject {

@Id
private String proID;
private String proName;
private String proCodeOwner;
private String proIDs;
@ManyToOne
private BDUser bdUser;

public BDProject() {
}

public BDProject(String proID, String proName, String proCodeOwner, String proIDs, String userID) {
    super();
    this.proID = proID;
    this.proName = proName;
    this.proCodeOwner = proCodeOwner;
    this.proIDs = proIDs;
    this.bdUser = new BDUser(userID, "", "", "");
}
// getters and setters...

控制器

@RestController
public class BDProjectController {

@Autowired
private BDProjectService bdProjectService;

@RequestMapping("/bdusers/{userID}/bdprojects")
public List<BDProject> getAllProjects(@PathVariable String proID){
    return bdProjectService.getAllProjects(proID);
}

@RequestMapping("/bdusers/{userID}/bdprojects/{proID}")
public BDProject getProject(@PathVariable String proID){
    return bdProjectService.getProject(proID);
}

@RequestMapping(method= RequestMethod.POST, value="/bdusers/{userID}/bdprojects")
public void addProject(@RequestBody BDProject bdProject, @PathVariable String userID){
    bdProject.setBdUser(new BDUser(userID, "", "", ""));
    bdProjectService.addProject(bdProject);
}

@RequestMapping(method= RequestMethod.PUT, value="/bdusers/{userID}/bdprojects/{proID}")
public void updateProject(@RequestBody BDProject bdProject, @PathVariable String userID, @PathVariable String proID){
    bdProject.setBdUser(new BDUser(userID, "", "", ""));
    bdProjectService.updateProject(bdProject);
}

@RequestMapping(method= RequestMethod.DELETE, value="/bdusers/{userID}/bdprojects/{proID}")
public void deleteProject(@PathVariable String proID){
    bdProjectService.deleteProject(proID);
}

}

服务

@Service
public class BDProjectService {

@Autowired
private BDProjectRepository bdProjectRepository;

public List<BDProject> getAllProjects(String userID){
    List<BDProject> bdProjects = new ArrayList<>();
    bdProjectRepository.findByUserID(userID).forEach(bdProjects::add);
    return bdProjects;
}

public BDProject getProject(String proID){

    return bdProjectRepository.findById(proID).orElse(null);
}

public void addProject(BDProject BDProject){

    bdProjectRepository.save(BDProject);
}

public void updateProject(BDProject BDProject){

    bdProjectRepository.save(BDProject);
}

public void deleteProject(String proID){

    bdProjectRepository.deleteById(proID);
}

}

存储库

public interface BDProjectRepository extends CrudRepository<BDProject, String>{

    public List<BDProject> findByUserID(String userID);

}

非常感谢任何和所有的帮助。谢谢！

Answer 1

您已经为 BDProject 实体创建了 BDProjectRepository 接口。请修改该存储库中的方法：

现在：public List<BDProject> findByUserID(String userID);

应该是：public List<BDProject> findByProID(String proID);

如果您想为特定用户获取 BDProject，您可以通过查询相关对象来检索它

public List<BDProject> findByBdUser_UserID(String proID);

Answer 2

当按引用对象中的字段查询时，您应该这样写 ChildObject_ChildID

public interface BDProjectRepository extends CrudRepository<BDProject, String>
{
    public List<BDProject> findByBdUser_UserID(String userID);
}

Answer 3

在 BDProject 中你有属性

private BDUser bdUser;

并且在您的存储库中：

public List<BDProject> findByUserID(String userID);

错误指出在 BDProject 中您没有属性 userID，这是正确的，因为您有 bdUser。

因此，请更改

findByUserID(String userID) to findByBdUserUserID(String userID)

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