Question

首先我求你原谅我的英语，如果我在标题或内容方面做错了，这是我第一次。我尝试第一次进行api休息，我尝试获取一些已经将mysql保存为json的数据。休息API。但是ı在控制台和邮递员中得到java.lang.NullPointerException：“错误”：“内部服务器错误”。我该如何解决？还是我做错了什么？

我已经尝试了很多事情，所以您可以看到更多东西。但是ı无法解决ı无法获取数据的问题。

我的对象

@Entity
@Data // It's  generate setters and  getters.
@Table(name="universities")//It says name of the table in database.
@JsonIgnoreProperties(value = {"createdAt", "updatedAt"}, allowGetters = 
true)
@EntityListeners(AuditingEntityListener.class)
public class UniversityDetailItem {

@Id
@Column(name = "api_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int api_id;

@Column(name = "id")
private int id;

@Column(name = "name")
private String name;

@Column(name = "city")
private String city;

@Column(name = "founded_at")
private int founded_at; //I declare as a integer because the variable consists of 4 integers.

@Column(name = "web_page")
private String web_page;

@Column(name = "type")
private String type;

}

我的DAO类

public class UniversityDAO {
@Autowired
UniversityRepository universityRepository;
@Query(value = "SELECT * FROM sampledatabase.universities", nativeQuery = true)
public Iterable<UniversityDetailItem> findAll(){
    return universityRepository.findAll();
}

}

我的控制器类

    @RestController
  public class UniversityController {
  @Autowired(required = false)
UniversityDAO universityDAO;
@GetMapping("/get")
public @ResponseBody Iterable<UniversityDetailItem> getAllUniversities(){
  return universityDAO.findAll();
}
@GetMapping("/universities") // try
public String ekmek(){
   return "Merhaba ekmek canavarı hamiidin"; 
  }}

入门应用程序

@SpringBootApplication
@EnableJpaAuditing
public class ProjectApplication {

public static void main(String[] args) {
    SpringApplication.run(ProjectApplication.class, args);
}

}

重新发布

 @Repository
public interface UniversityRepository extends 
JpaRepository<UniversityDetailItem,Long> {

 }

应用程序属性

## Spring DATASOURCE (DatSourceAutoConfiguration & DataSourceProperties)
spring.datasource.url= jdbc:mysql://localhost:3306/sampledatabase? 
useLegacyDatetimeCode=false&serverTimezone=UTC
spring.datasource.username = root
spring.datasource.password = ********

# Show or not log for each sql query
spring.jpa.show-sql = true
## Hibernate Properties
# The SQL dialect makes Hibernate generate better SQL for the chosen 
 database
spring.jpa.properties.hibernate.dialect = 
org.hibernate.dialect.MySQL5Dialect
# Naming strategy
#
spring.jpa.hibernate.naming-strategy = 
org.hibernate.cfg.ImprovedNamingStrategy
#Hibernate ddl auto (create,create-drop,validate,update)
spring.jpa.hibernate.ddl-auto=update

spring.mvc.view.prefix = /WEB-INF/views/
spring.mvc.view.suffix = .jsp
spring.mvc.static-path-pattern=/resources/**

mySQL表已创建

Columns:
id int(11) PK 
id_api int(11) 
name varchar(63) 
city varchar(15) 
founded_at int(11) 
web_page varchar(32) 
type varchar(6) 
created_at datetime 
updated_at datetime 
api_id int(11)

我怎么能解决ExceptionNULL问题Spring JAVA

0 个答案: