Exception:Field com.example.demo.cotroller.StudentController 中的 studentRepository 需要找不到类型 'com....Repository' 的 bean
Exception:Field studentRepository in com.example.demo.cotroller.StudentController required a bean of type 'com....Repository' that could not be found
我跟随 https://spring.io/guides/gs/accessing-data-mysql/#initial 和 MySQL 一起学习了 springboot。我遇到了如下错误。
2021-09-23 01:28:31.193 INFO 1196 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication using Java 1.8.0_144 on DESKTOP-PFH9867 with PID 1196 (C:\Users\Admin\IdeaProjects\demo\target\classes started by Admin in C:\Users\Admin\IdeaProjects\demo)
2021-09-23 01:28:31.196 INFO 1196 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to default profiles: default
2021-09-23 01:28:33.014 INFO 1196 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2021-09-23 01:28:33.027 INFO 1196 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2021-09-23 01:28:33.027 INFO 1196 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.52]
2021-09-23 01:28:33.145 INFO 1196 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2021-09-23 01:28:33.146 INFO 1196 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1875 ms
2021-09-23 01:28:33.218 WARN 1196 --- [ main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'studentController': Unsatisfied dependency expressed through field 'studentRepository'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.example.demo.repository.StudentRepository' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2021-09-23 01:28:33.221 INFO 1196 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat]
2021-09-23 01:28:33.242 INFO 1196 --- [ main] ConditionEvaluationReportLoggingListener :
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-09-23 01:28:33.269 ERROR 1196 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :
***************************
APPLICATION FAILED TO START
***************************
Description:
Field studentRepository in com.example.demo.cotroller.StudentController required a bean of type 'com.example.demo.repository.StudentRepository' that could not be found.
The injection point has the following annotations:
- @org.springframework.beans.factory.annotation.Autowired(required=true)
Action:
Consider defining a bean of type 'com.example.demo.repository.StudentRepository' in your configuration.
Process finished with exit code 1
很明显，主要问题是 @Autowired 在 Controller 中。因此，我搜索了很多方法来处理它。而且我不想添加新代码或新文件。正如网站在创建接口存储库时所说的那样，Spring automatically implements this repository interface in a bean that has the same name (with a change in the case — it is called userRepository). 因此，我不想添加新代码或文件。我认为问题出在我的 application.properties 或目录的相对位置。但它们根本不起作用。
而我的代码如下。
DemoApplication.java
package com.example.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
Student.java
package com.example.demo.entity;
import javax.persistence.Entity;
// https://spring.io/guides/gs/accessing-data-mysql/
@Entity // This tells Hibernate to make a table out of this class
public class Student {
// 2147483647
private Integer studentID;
private String name;
private String department;
private String major;
public Integer getStudentID() {
return studentID;
}
public void setStudentID(Integer studentID) {
this.studentID = studentID;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
public String getMajor() {
return major;
}
public void setMajor(String major) {
this.major = major;
}
}
StudentController.java
package com.example.demo.cotroller;
import com.example.demo.entity.Student;
import com.example.demo.repository.StudentRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
@Controller // This means that this class is a Controller
@RequestMapping(path="/api/v1/student") // This means URL's start with /demo (after Application path)
public class StudentController {
// This means to get the bean called studentRepository
// Which is auto-generated by Spring, we will use it to handle the data
@Autowired
private StudentRepository studentRepository;
@PostMapping(path="/add") // Map ONLY POST Requests
public @ResponseBody
String addNewUser (@RequestBody Student student) {
// @ResponseBody means the returned String is the response, not a view name
// @RequestParam means it is a parameter from the GET or POST request
studentRepository.save(student);
return "Saved";
}
}
StudentRepository.java
package com.example.demo.repository;
import com.example.demo.entity.Student;
import org.springframework.data.repository.CrudRepository;
// This will be AUTO IMPLEMENTED by Spring into a Bean called userRepository
// CRUD refers Create, Read, Update, Delete
public interface StudentRepository extends CrudRepository<Student, Integer> {
}
我的目录组织如下。
java
|--com.example.demo
|--controller
|--StudentController.java
|--entity
|--Student.java
|--repository
|--StudentRepository.java
DemoApplication.java
已解决！
终于找到真正的原因了！我太粗心了，无法按照教程进行操作。它说单击依赖项和 select Spring Web、Spring Data JPA 和 MySQL 驱动程序。但我没有点击 Spring Data JPA！
我在 IDEA 中通过 selecting Spring Web、Spring Data JPA 和 MySQL Driver 重新创建了项目，并复制了问题描述中描述的文件，那么问题就解决了。
是的，你是对的 spring 由他们执行存储库配置，但你必须通知 spring 你想在哪个 class 上执行或包含此功能。为此，您必须在存储库 class.
中添加 @Repository 注释
还有一件事供您参考。在任何语言中，结构都是任何编程语言的重要组成部分。要理解它，您始终必须遵循最佳实践。在这里，您直接在控制器中定义存储库 class，这是完全错误的。控制器仅用于控制即将到来的请求并将响应发送回给它们。所以，这种业务逻辑总是发生在你的服务 class 或 DAOImpl class 中。不要在其他 classes.
中定义数据库对象
此外，如果您与多个 类 一起工作，例如用户和部门，并且您只想执行任何操作，服务之间的通信不会共享存储库对象
我跟随 https://spring.io/guides/gs/accessing-data-mysql/#initial 和 MySQL 一起学习了 springboot。我遇到了如下错误。
2021-09-23 01:28:31.193 INFO 1196 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication using Java 1.8.0_144 on DESKTOP-PFH9867 with PID 1196 (C:\Users\Admin\IdeaProjects\demo\target\classes started by Admin in C:\Users\Admin\IdeaProjects\demo)
2021-09-23 01:28:31.196 INFO 1196 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to default profiles: default
2021-09-23 01:28:33.014 INFO 1196 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2021-09-23 01:28:33.027 INFO 1196 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2021-09-23 01:28:33.027 INFO 1196 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.52]
2021-09-23 01:28:33.145 INFO 1196 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2021-09-23 01:28:33.146 INFO 1196 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1875 ms
2021-09-23 01:28:33.218 WARN 1196 --- [ main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'studentController': Unsatisfied dependency expressed through field 'studentRepository'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.example.demo.repository.StudentRepository' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2021-09-23 01:28:33.221 INFO 1196 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat]
2021-09-23 01:28:33.242 INFO 1196 --- [ main] ConditionEvaluationReportLoggingListener :
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-09-23 01:28:33.269 ERROR 1196 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :
***************************
APPLICATION FAILED TO START
***************************
Description:
Field studentRepository in com.example.demo.cotroller.StudentController required a bean of type 'com.example.demo.repository.StudentRepository' that could not be found.
The injection point has the following annotations:
- @org.springframework.beans.factory.annotation.Autowired(required=true)
Action:
Consider defining a bean of type 'com.example.demo.repository.StudentRepository' in your configuration.
Process finished with exit code 1
很明显，主要问题是 @Autowired 在 Controller 中。因此，我搜索了很多方法来处理它。而且我不想添加新代码或新文件。正如网站在创建接口存储库时所说的那样，Spring automatically implements this repository interface in a bean that has the same name (with a change in the case — it is called userRepository). 因此，我不想添加新代码或文件。我认为问题出在我的 application.properties 或目录的相对位置。但它们根本不起作用。
而我的代码如下。
DemoApplication.java
package com.example.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
Student.java
package com.example.demo.entity;
import javax.persistence.Entity;
// https://spring.io/guides/gs/accessing-data-mysql/
@Entity // This tells Hibernate to make a table out of this class
public class Student {
// 2147483647
private Integer studentID;
private String name;
private String department;
private String major;
public Integer getStudentID() {
return studentID;
}
public void setStudentID(Integer studentID) {
this.studentID = studentID;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
public String getMajor() {
return major;
}
public void setMajor(String major) {
this.major = major;
}
}
StudentController.java
package com.example.demo.cotroller;
import com.example.demo.entity.Student;
import com.example.demo.repository.StudentRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
@Controller // This means that this class is a Controller
@RequestMapping(path="/api/v1/student") // This means URL's start with /demo (after Application path)
public class StudentController {
// This means to get the bean called studentRepository
// Which is auto-generated by Spring, we will use it to handle the data
@Autowired
private StudentRepository studentRepository;
@PostMapping(path="/add") // Map ONLY POST Requests
public @ResponseBody
String addNewUser (@RequestBody Student student) {
// @ResponseBody means the returned String is the response, not a view name
// @RequestParam means it is a parameter from the GET or POST request
studentRepository.save(student);
return "Saved";
}
}
StudentRepository.java
package com.example.demo.repository;
import com.example.demo.entity.Student;
import org.springframework.data.repository.CrudRepository;
// This will be AUTO IMPLEMENTED by Spring into a Bean called userRepository
// CRUD refers Create, Read, Update, Delete
public interface StudentRepository extends CrudRepository<Student, Integer> {
}
我的目录组织如下。
java
|--com.example.demo
|--controller
|--StudentController.java
|--entity
|--Student.java
|--repository
|--StudentRepository.java
DemoApplication.java
已解决！
终于找到真正的原因了！我太粗心了，无法按照教程进行操作。它说单击依赖项和 select Spring Web、Spring Data JPA 和 MySQL 驱动程序。但我没有点击 Spring Data JPA！
我在 IDEA 中通过 selecting Spring Web、Spring Data JPA 和 MySQL Driver 重新创建了项目，并复制了问题描述中描述的文件，那么问题就解决了。
是的，你是对的 spring 由他们执行存储库配置，但你必须通知 spring 你想在哪个 class 上执行或包含此功能。为此，您必须在存储库 class.
中添加 @Repository 注释还有一件事供您参考。在任何语言中，结构都是任何编程语言的重要组成部分。要理解它，您始终必须遵循最佳实践。在这里，您直接在控制器中定义存储库 class，这是完全错误的。控制器仅用于控制即将到来的请求并将响应发送回给它们。所以，这种业务逻辑总是发生在你的服务 class 或 DAOImpl class 中。不要在其他 classes.
中定义数据库对象此外，如果您与多个 类 一起工作，例如用户和部门，并且您只想执行任何操作，服务之间的通信不会共享存储库对象