com.example.User.UserService 中构造函数的参数 0 需要找不到类型为 \'com.example.User.UserRepository\' 的 bean答案

【问题标题】：Parameter 0 of constructor in com.example.User.UserService required a bean of type 'com.example.User.UserRepository' that could not be foundcom.example.User.UserService 中构造函数的参数 0 需要找不到类型为 \'com.example.User.UserRepository\' 的 bean
【发布时间】：2022-08-11 03:28:51
【问题描述】：

我不确定为什么会收到此错误，但我怀疑它来自 TestApplication.java。我尝试了各种方法，例如Question1，但无法弄清楚出了什么问题。

我引用了这个video 来构建这个应用程序。

错误

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in com.example.User.UserService required a bean 
of type \'com.example.User.UserRepository\' that could not be found.


Action:

Consider defining a bean of type \'com.example.User.UserRepository\' in your 
configuration.

测试应用程序.java

package com.example.test;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

import com.example.User.UserController;

@SpringBootApplication
@ComponentScan(basePackageClasses = {UserController.class})
public class TestApplication {

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

用户.java

package com.example.User;

import java.time.LocalDate;

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

@Entity
@Table(name = \"USER\")
public class User {
    @Id
    @SequenceGenerator(
        name = \"user_sequence\",
        sequenceName = \"user_sequence\",
        allocationSize = 1
    )
    @GeneratedValue(
        strategy = GenerationType.SEQUENCE,
        generator = \"user_sequence\"
    )
    private Long id;
    private String PDGA_id;
    private String first_name;
    private String last_name;
    private String email;
    private boolean email_verified;
    private String phone_number;
    private String password;
    private LocalDate created_date;
    private LocalDate modified_date;

    public User(){
    }

    public User(Long id, 
                String PDGA_id, 
                String first_name, 
                String last_name, 
                String email, 
                boolean email_verified, 
                String phone_number, 
                String password, 
                LocalDate created_date, 
                LocalDate modified_date)
    {
        this.id = id;
        this.PDGA_id = PDGA_id;
        this.first_name = first_name;
        this.last_name = last_name;
        this.email = email;
        this.email_verified = email_verified;
        this.phone_number = phone_number;
        this.password = password;
        this.created_date = created_date;
        this.modified_date = modified_date;
    }

    public User(String PDGA_id, 
                String first_name, 
                String last_name, 
                String email, 
                boolean email_verified, 
                String phone_number, 
                String password, 
                LocalDate created_date, 
                LocalDate modified_date)
    {
        this.PDGA_id = PDGA_id;
        this.first_name = first_name;
        this.last_name = last_name;
        this.email = email;
        this.email_verified = email_verified;
        this.phone_number = phone_number;
        this.password = password;
        this.created_date = created_date;
        this.modified_date = modified_date;
    }

    // Getter-Setter
    public Long getId() {
        return this.id;
    }

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

    public String getPDGA_id() {
        return this.PDGA_id;
    }

    public void setPDGA_id(String PDGA_id) {
        this.PDGA_id = PDGA_id;
    }

    public String getFirst_name() {
        return this.first_name;
    }

    public void setFirst_name(String first_name) {
        this.first_name = first_name;
    }

    public String getLast_name() {
        return this.last_name;
    }

    public void setLast_name(String last_name) {
        this.last_name = last_name;
    }

    public String getEmail() {
        return this.email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public boolean isEmail_verified() {
        return this.email_verified;
    }

    public void setEmail_verified(boolean email_verified) {
        this.email_verified = email_verified;
    }

    public String getPhone_number() {
        return this.phone_number;
    }

    public void setPhone_number(String phone_number) {
        this.phone_number = phone_number;
    }

    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public LocalDate getCreated_date() {
        return this.created_date;
    }

    public void setCreated_date(LocalDate created_date) {
        this.created_date = created_date;
    }

    public LocalDate getModified_date() {
        return this.modified_date;
    }

    public void setModified_date(LocalDate modified_date) {
        this.modified_date = modified_date;
    }

    @Override
    public String toString(){
        return \"User{\" +
                \"id =\" + id +
                \", PDGA_id\" + PDGA_id + \'\\\'\' +
                \", first_name\" + first_name + \'\\\'\' + 
                \", last_name\" + last_name + \'\\\'\' + 
                \", email\" + email + \'\\\'\' + 
                \", email_verified\" + email_verified +
                \", phone_number\" + phone_number + \'\\\'\' + 
                \", password\" + password + \'\\\'\' + 
                \", created_date\" + created_date +
                \", modified_date\" + modified_date +
                \"}\";
    }
}

用户控制器.java

package com.example.User;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping(path = \"api/v1/user\")
public class UserController {
    
    private final UserService userService;

    @Autowired
    public UserController(UserService userService){
        this.userService = userService;
    }

    @GetMapping()
    public List<User> getUsers(){
        return userService.getUsers();
    }
}

用户存储库.java

package com.example.User;

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

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
}

用户服务.java

package com.example.User;

import org.springframework.stereotype.Service;
import org.springframework.beans.factory.annotation.Autowired;

@Service
public class UserService {

    private final UserRepository userRepository;

    @Autowired
    public UserService(UserRepository userRepository){
        this.userRepository = userRepository;
    }

    public List<User> getUsers(){
        return userRepository.findAll();
    }
}

应用程序属性

spring.datasource.url=jdbc:mariadb://localhost:3306/LiensDiGoLinks
spring.datasource.username=root
spring.datasource.password=Password123!
spring.datasource.driver-class-name=org.mariadb.jdbc.Driver

spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.properties.hibernate.format_sql=true

嗨，从 TestApplication.class 中删除此注释 @ComponentScan(basePackageClasses = {UserController.class})。由于这个 spring 无法扫描和创建 bean。

标签： java spring spring-boot hibernate spring-data-jpa

【解决方案1】：

只需删除 UserService 类的构造函数并声明 UserRepository 如下：

@AutoWired
UserRepository userRepository;

我希望这会有所帮助。

【讨论】：