Spring Boot Dao和JpaRepositories在@Autowiring时抛出NullPointerException

7dl7o3gd  于 7个月前  发布在  Spring
关注(0)|答案(1)|浏览(72)

问题：

自动装配SingerDaoImpl和JpaRepositoryImpl Bean会导致null结果。不会抛出Exception，但不会返回Data。使用Thymeleaf视图显示数据

采用的技术：

Spring、JpaRepository、Hibernate、Thymeleaf、H2 Embedded DB（脚本位于resources/SQL文件夹中）、Spring MVC、javax. validation。
我使用localhost：8080/songers通过位于resources/templates/listSingers.html中的thymeleaf列出歌手。

我划掉的东西：

  • 没有使用new运算符声明@Component（或其专门化）Class
  • 所有@Autowired的bean都使用@Component、@Repository或@Service进行注解
  • 二传手已经就位，
  • @ browser已经指向了正确的bean
  • 嵌入式数据库使用位于resources/SQL/test.sql中的数据填充，并通过DBConfig.java类使用EmbeddedDatabaseBuilder.addScript（“SQL/test.sql”）方法添加
  • gradle.build文件版本中的所有依赖项均由gradle管理为最新版本

github页面链接：

https://github.com/NikitaDyagilev/LearningSprinbMVC
注意：我正在使用Amazon Corretto Java 11

DBConfig.java

package com.example.demo.Config;

@Configuration
@ComponentScan
@EnableJpaRepositories(basePackages = {"com.example.demo.JpaRepo"})
@PropertySource("classpath:application.properties")
public class DBconfig {

     @Value("${jdbc.driverClassName}")
     private String driverClassName;
     @Value("${jdbc.username}")
     private String username;
     @Value("${jdbc.password}")
     private String password;
     @Value("${jdbc.url}")
     private String url;

     private Logger logger = LoggerFactory.getLogger(DBconfig.class);

//   MySQL DataSource Connection
     @Bean
     public DataSource dataSourceR(){
          try{
               SimpleDriverDataSource db =
                       new SimpleDriverDataSource();
               Class<? extends Driver> driver =
                       (Class<? extends Driver>) Class.forName(driverClassName);
               db.setDriverClass(driver);
               db.setUsername(username);
               db.setPassword(password);
               db.setUrl(url);
               return db;
          } catch (Exception e){
               logger.error("Something Went wrong when trying to Create the MySQL DataSource bean");
               return null;
          }
     }

//   Embedded DataSource Connection
     @Bean
     public DataSource dataSourceE(){
          try{
               EmbeddedDatabaseBuilder db =
                       new EmbeddedDatabaseBuilder();
               db.setType(EmbeddedDatabaseType.H2);
               db.addScript("SQL/table.sql");
               db.addScript("SQL/test.sql");
               return db.build();
          } catch (Exception e ){
               logger.error("There was an error when trying to create Embeded DataSource: ", e);
               return null;
          }
     }

     @Bean
     public Properties hibernaProperties(){
          Properties prop = new Properties();
          prop.put("hibernate.dialect", "org.hibernate.dialect.H2Dialect");
//          prop.put("hibernate.dialect", "org.hibernate.dialect.MySQL8Dialect");
          prop.put("hibernate.hbm2ddl.auto", "create-drop");
          prop.put("hibernate.format_sql", true);
          prop.put("hibernate.show_sql", true);
          prop.put("hibernate.max_fetch_depth", 3);
          prop.put("hibernate.jdbc.batch_size", 10);
          prop.put("hibernate.jdbc.fetch_size", 50);
          return prop;
     }

     @Bean
     public PlatformTransactionManager transactionManager(){
          return new JpaTransactionManager(entityManagerFactory());
     }

     @Bean
     public JpaVendorAdapter jpaVendorAdapter(){
          return new HibernateJpaVendorAdapter();
     }

     @Bean(name ="entityManagerFactory")
     public EntityManagerFactory entityManagerFactory(){
          LocalContainerEntityManagerFactoryBean emfb =
                  new LocalContainerEntityManagerFactoryBean();
          emfb.setDataSource(dataSourceE());
          emfb.setPackagesToScan("com.example.demo.Model");
          emfb.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
          emfb.setJpaProperties(hibernaProperties());
          emfb.setJpaVendorAdapter(jpaVendorAdapter());
          emfb.afterPropertiesSet();
          return emfb.getObject();
     }
}

字符串

控制器类

package com.example.demo.Controllers;

import java.util.List;

@Controller
public class TestController {

    private Logger logger = LoggerFactory.getLogger(TestController.class);

    private SingerDao dao;

    @GetMapping(value = "/hello")
    @ResponseBody
    public String sayHello(){
        return "Hello There";
    }

    @GetMapping(value ="/homepage")
    public String homepageListing(){
        return "homepage";
    }

    @GetMapping(value="/singers")
    public String listSingers(Model model){
        logger.info("Listing Singers:");
        List<Singer> singers = dao.findAll();
        String[] names = new String[singers.size()];
        for(int i = 0; i < names.length; i++){
            names[i] = singers.get(i).getFirstName();
        }
        model.addAttribute("singersNames", names);
        return "ListSingers";
    }

    @GetMapping(value="/getSinger{id}")
    public String getSingerById(Model model,@PathVariable Long id){
        model.addAttribute("singer", dao.findById(id).getFirstName());
        return "getSinger";
    }

    @Autowired
    public void setDao(SingerDao dao) {
        this.dao = dao;
    }
}

型

Jpa仓库

package com.example.demo.JpaRepo;

@Repository("jpaRepositoryImpl")
public class JpaRepositoryImpl implements JpaRepository {
    private EntityManagerFactory emf;

    @Override
    public List<Singer> findAll() {
        return emf.createEntityManager()
                .createQuery("select s from singer s")
                .getResultList();
    }

    @Override
    public Optional<Singer> findById(Long aLong) {
        return (Optional<Singer>) emf.createEntityManager().createQuery("select s from singer s where s.id = ?id").
                setParameter("id",aLong).getSingleResult();
    }

    @Autowired
    @Qualifier(value = "entityManagerFactory")
    public void setEmf(EntityManagerFactory emf) {
        this.emf = emf;
    }
}

型

DAO服务

package com.example.demo.DAO;

@Service("singerDaoImpl")
public class SingerDaoImpl implements SingerDao {

    private JpaRepository jpaRepo;

    @Override
    public List<Singer> findAll() {
        List<Singer> singers = new ArrayList<>();
        jpaRepo.findAll().forEach(item -> singers.add(item));
        System.out.println("# Of Singers: "+singers.size());
        return singers;
    }

    @Override
    public Singer findById(Long id) {
        return null;
    }

    @Autowired
    @Qualifier(value="jpaRepositoryImpl")
    public void setJpaRepo(JpaRepository jpaRepo) {
        this.jpaRepo = jpaRepo;
    }
}

型

型号

package com.example.demo.Model;

@Table(name="singer")
@Entity(name="singer")
public class Singer implements Serializable{

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

     @NotEmpty(message = "{validation.firstname.NotEmpty.message}")
     @Size(min=3,max=60,message="{validation.firstname.Size.message}")
     @Column(name="first_name")
     private String firstName;

     @NotEmpty(message = "{validation.lastname.NotEmpty.message}")
     @Size(min=3,max=60,message ="{validation.lastname.Size.message")
     @Column(name="last_name")
     private String lastName;

     @Temporal(TemporalType.DATE)
     @Column(name="birth_date")
     private Date birthDate;

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

     @Basic(fetch=FetchType.LAZY)
     @Lob
     @Column(name="photo")
     private byte photo;

     public Long getId() {
          return id;
     }

     public void setId(Long id) {
          this.id = id;
     }

     public String getFirstName() {
          return firstName;
     }

     public void setFirstName(String firstName) {
          this.firstName = firstName;
     }

     public String getLastName() {
          return lastName;
     }

     public void setLastName(String lastName) {
          this.lastName = lastName;
     }

     public Date getDate() {
          return birthDate;
     }

     public void setDate(Date date) {
          this.birthDate = date;
     }

     public String getDescription() {
          return description;
     }

     public void setDescription(String description) {
          this.description = description;
     }

     public byte getPhoto() {
          return photo;
     }

     public void setPhoto(byte photo) {
          this.photo = photo;
     }

     @Transient
     public String getBirthDateString(){
          String birthDateString = "";
          if(birthDate != null){
               SimpleDateFormat sdf = new SimpleDateFormat("yyy-MM-dd");
                    birthDateString = sdf.format(birthDate);
          }
          return birthDateString;
     }

     @Override
     public String toString() {
          return "Singer{" +
                  "id=" + id +
                  ", firstName='" + firstName + '\'' +
                  ", lastName='" + lastName + '\'' +
                  ", birthDate=" + birthDate +
                  ", description='" + description + '\'' +
                  ", photo=" + photo +
                  '}';
     }
}

型

  • 编辑：* 我添加了logging.level.org.springframework = debug

下面是控制台的相关部分

2020-05-26 11:26:13.500  INFO 14664 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2935 ms
2020-05-26 11:26:13.508 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'requestContextFilter'
2020-05-26 11:26:13.513 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'formContentFilter'
2020-05-26 11:26:13.513 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration'
2020-05-26 11:26:13.519 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'characterEncodingFilter'
2020-05-26 11:26:13.531 DEBUG 14664 --- [           main] o.s.b.w.s.ServletContextInitializerBeans : Mapping filters: characterEncodingFilter urls=[/*] order=-2147483648, formContentFilter urls=[/*] order=-9900, requestContextFilter urls=[/*] order=-105
2020-05-26 11:26:13.532 DEBUG 14664 --- [           main] o.s.b.w.s.ServletContextInitializerBeans : Mapping servlets: dispatcherServlet urls=[/]
2020-05-26 11:26:13.565 DEBUG 14664 --- [           main] o.s.b.w.s.f.OrderedRequestContextFilter  : Filter 'requestContextFilter' configured for use
2020-05-26 11:26:13.565 DEBUG 14664 --- [           main] s.b.w.s.f.OrderedCharacterEncodingFilter : Filter 'characterEncodingFilter' configured for use
2020-05-26 11:26:13.566 DEBUG 14664 --- [           main] o.s.b.w.s.f.OrderedFormContentFilter     : Filter 'formContentFilter' configured for use
2020-05-26 11:26:13.585 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'demoApplication'
2020-05-26 11:26:13.586 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'DBconfig'
2020-05-26 11:26:13.591 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.driverClassName' in PropertySource 'applicationConfig: [classpath:/application.properties]' with value of type String
2020-05-26 11:26:13.591 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.driverClassName' in PropertySource 'environmentProperties' with value of type String
2020-05-26 11:26:13.593 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.username' in PropertySource 'configurationProperties' with value of type String
2020-05-26 11:26:13.593 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.username' in PropertySource 'environmentProperties' with value of type String
2020-05-26 11:26:13.595 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.password' in PropertySource 'configurationProperties' with value of type String
2020-05-26 11:26:13.595 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.password' in PropertySource 'environmentProperties' with value of type String
2020-05-26 11:26:13.595 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.url' in PropertySource 'configurationProperties' with value of type String
2020-05-26 11:26:13.595 DEBUG 14664 --- [           main] o.s.c.e.PropertySourcesPropertyResolver  : Found key 'jdbc.url' in PropertySource 'environmentProperties' with value of type String
2020-05-26 11:26:13.599 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'testController'
2020-05-26 11:26:13.607 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'singerDaoImpl'
2020-05-26 11:26:13.614 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'jpaRepositoryImpl'
2020-05-26 11:26:13.621 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'entityManagerFactory'
2020-05-26 11:26:13.673 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'dataSourceE'
2020-05-26 11:26:13.702  INFO 14664 --- [           main] o.s.j.d.e.EmbeddedDatabaseFactory        : Starting embedded database: url='jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=false', username='sa'
2020-05-26 11:26:13.712 DEBUG 14664 --- [           main] o.s.jdbc.datasource.DataSourceUtils      : Fetching JDBC Connection from DataSource
2020-05-26 11:26:13.713 DEBUG 14664 --- [           main] o.s.j.datasource.SimpleDriverDataSource  : Creating new JDBC Driver Connection to [jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=false]
2020-05-26 11:26:13.971 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : Executing SQL script from class path resource [SQL/table.sql]
2020-05-26 11:26:14.002 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 0 returned as update count for SQL: CREATE TABLE SINGER ( ID INT NOT NULL AUTO_INCREMENT, FIRST_NAME VARCHAR(60), LAST_NAME VARCHAR(40), BIRTH_DATE DATE, DESCRIPTION VARCHAR(2000) NULL, PHOTO BLOB NULL, VERSION INT NOT NULL DEFAULT 0, UNIQUE UQ_SINGER_1 (FIRST_NAME, LAST_NAME), PRIMARY KEY (ID) )
2020-05-26 11:26:14.002 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : Executed SQL script from class path resource [SQL/table.sql] in 30 ms.
2020-05-26 11:26:14.002 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : Executing SQL script from class path resource [SQL/test.sql]
2020-05-26 11:26:14.014 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('John', 'Mayer', '1977-10-16')
2020-05-26 11:26:14.014 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Eric', 'Clampton', '1954-03-20')
2020-05-26 11:26:14.017 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('John', 'Butler', '1975-04-01')
2020-05-26 11:26:14.017 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('B.B' , 'King', '1925-09-16')
2020-05-26 11:26:14.019 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Jimi', 'Hendrix', '1942-11-27')
2020-05-26 11:26:14.021 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Eddie', 'Van Halen','1955-01-26')
2020-05-26 11:26:14.022 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Saul Slash', 'Hudson', '1965-07-23')
2020-05-26 11:26:14.023 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Stevie', 'Ray Vaughan','1954-10-03')
2020-05-26 11:26:14.023 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('David', 'Gilmour','1946-03-06')
2020-05-26 11:26:14.026 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Kirk','Hammett','1992-11-18')
2020-05-26 11:26:14.027 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Angus','Young','1955-03-31')
2020-05-26 11:26:14.028 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Dimebad','Darrell','1966-08-20')
2020-05-26 11:26:14.029 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : 1 returned as update count for SQL: INSERT INTO SINGER (FIRST_NAME, LAST_NAME, BIRTH_DATE) VALUES ('Carlos','Santana','1947-07-20')
2020-05-26 11:26:14.030 DEBUG 14664 --- [           main] o.s.jdbc.datasource.init.ScriptUtils     : Executed SQL script from class path resource [SQL/test.sql] in 28 ms.
2020-05-26 11:26:14.039 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker'
2020-05-26 11:26:14.043 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'spring.datasource-org.springframework.boot.autoconfigure.jdbc.DataSourceProperties'
2020-05-26 11:26:14.064 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Autowiring by type from bean name 'org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker' via constructor to bean named 'spring.datasource-org.springframework.boot.autoconfigure.jdbc.DataSourceProperties'
2020-05-26 11:26:14.065 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Autowiring by type from bean name 'org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker' via constructor to bean named 'org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@456d6c1e'
2020-05-26 11:26:14.227 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'hibernaProperties'
2020-05-26 11:26:14.230 DEBUG 14664 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Creating shared instance of singleton bean 'jpaVendorAdapter'
2020-05-26 11:26:14.245 DEBUG 14664 --- [           main] j.LocalContainerEntityManagerFactoryBean : Building JPA container EntityManagerFactory for persistence unit 'default'
2020-05-26 11:26:14.294  INFO 14664 --- [           main] o.hibernate.jpa.internal.util.LogHelper  : HHH000204: Processing PersistenceUnitInfo [name: default]
2020-05-26 11:26:14.412  INFO 14664 --- [           main] org.hibernate.Version                    : HHH000412: Hibernate ORM core version 5.4.15.Final
2020-05-26 11:26:14.685  INFO 14664 --- [           main] o.hibernate.annotations.common.Version   : HCANN000001: Hibernate Commons Annotations {5.1.0.Final}
2020-05-26 11:26:14.906 DEBUG 14664 --- [           main] o.s.j.datasource.SimpleDriverDataSource  : Creating new JDBC Driver Connection to [jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=false]
2020-05-26 11:26:14.940  INFO 14664 --- [           main] org.hibernate.dialect.Dialect            : HHH000400: Using dialect: org.hibernate.dialect.H2Dialect
Hibernate:

型

**SQL查询 *

drop table if exists singer CASCADE 
2020-05-26 11:26:16.139 DEBUG 14664 --- [           main] o.s.j.datasource.SimpleDriverDataSource  : Creating new JDBC Driver Connection to [jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=false]
Hibernate: 

    create table singer (
       id bigint generated by default as identity,
        birth_date date,
        description varchar(255),
        first_name varchar(255),
        last_name varchar(255),
        photo blob,
        primary key (id)
    )

型
我找到了一个表达方式

javax.validation.NoProviderFoundException: Unable to create a Configuration, because no Bean Validation provider could be found. Add a provider like Hibernate Validator (RI) to your classpath.
    at javax.validation.Validation$GenericBootstrapImpl.configure(Validation.java:291) ~[validation-api-2.0.1.Final.jar:na]
    at org.springframework.validation.beanvalidation.LocalValidatorFactoryBean.afterPropertiesSet(LocalValidatorFactoryBean.java:257) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.validation.beanvalidation.OptionalValidatorFactoryBean.afterPropertiesSet(OptionalValidatorFactoryBean.java:40) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.boot.autoconfigure.validation.ValidatorAdapter.afterPropertiesSet(ValidatorAdapter.java:83) ~[spring-boot-autoconfigure-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1855) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1792) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:595) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1306) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:539) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:895) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at com.example.demo.DemoApplication.main(DemoApplication.java:13) ~[main/:na]

型

spring-boot

1条答案

按热度按时间
3pvhb19x

3pvhb19x1#

你几乎就在那里了。事实上，你的数据库 * 是 * 空的。为什么？因为你的DBConfig类. prop.put("hibernate.hbm2ddl.auto", "create-drop");中的这一行（链接到该属性的文档）。你可以安全地删除它或将该属性设置为一个对你有意义的值。
您还需要设置照片属性（以及它的getter和setter）转换为Byte（这种类型也称为Wrapper Class）而不是byte，因为字节是一个不能设置为null的原始值。然而，在您的DB脚本中，您允许photo为null，因此，如果您不更改此代码，当你试图把DB列Map到Java对象时，它会导致一个异常。一旦你完成了这两件事，歌手的列表就会显示在浏览器中。
现在，一些最后的提示，因为你对编程有点陌生：
我已经检查了你的repo，你正在做很多你不需要做的工作和配置，因为你使用的是Sping Boot 和Sping Boot Data Jpa，而不仅仅是Spring。我建议你先开始全面使用Sping Boot ，然后学习Spring以及如何根据你的需求定制它，如果您需要单独使用Spring来满足您的需求，请使用Use this link作为网关来了解有关Sping Boot 和Sping Boot Data Jpa的更多信息。

赞(0）分享  回复(0）举报  7个月前
我来回答

相关问题

    查看更多
    微信公众号

    热门标签

    更多
    JavaquerypythonNode开发语言requestUtil数据库Table后端算法LoggerMessageElementParser

    最新问答

    更多
    • 蜀ICP备13028337号-1 大数据知识库 https://www.saoniuhuo.com © All rights reserved
    • 本站内容来源互联网,如果侵犯您的权益请联系我们删除, 联系方式：448109455@qq.com