当我运行应用程序时，我得到参数 0 构造函数错误，我该如何解决这个问题？答案

【问题标题】：When i run the application i get parameter 0 constructor error , How can I fix this?当我运行应用程序时，我得到参数 0 构造函数错误，我该如何解决这个问题？
【发布时间】：2021-05-09 21:37:41
【问题描述】：

当我运行我的主类时，我得到了这个错误：

Java HotSpot(TM) 64-Bit Server VM warning: Options -Xverify:none and -noverify were deprecated in JDK 13 and will likely be removed in a future release.I don't understand why it still gives an error . 


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.4.5)

2021-05-10 00:26:58.833  INFO 2704 --- [           main] k.io.northwind.NorthwindApplication      : Starting NorthwindApplication using Java 16.0.1 on VEYSEL with PID 2704 (C:\javaKamp\northwind\target\classes started by veyse in C:\javaKamp\northwind)
2021-05-10 00:26:58.835  INFO 2704 --- [           main] k.io.northwind.NorthwindApplication      : No active profile set, falling back to default profiles: default
2021-05-10 00:26:59.348  INFO 2704 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2021-05-10 00:26:59.354  INFO 2704 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2021-05-10 00:26:59.355  INFO 2704 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.45]
2021-05-10 00:26:59.396  INFO 2704 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2021-05-10 00:26:59.396  INFO 2704 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 528 ms
2021-05-10 00:26:59.420  WARN 2704 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'productsController' defined in file [C:\javaKamp\northwind\target\classes\kodlama\io\northwind\api\controllers\ProductsController.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'productManager' defined in file [C:\javaKamp\northwind\target\classes\kodlama\io\northwind\business\concretes\ProductManager.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'kodlama.io.northwind.dataAccess.abstracts.ProductDao' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
2021-05-10 00:26:59.422  INFO 2704 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2021-05-10 00:26:59.429  INFO 2704 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-05-10 00:26:59.437 ERROR 2704 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

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

Description:

Parameter 0 of constructor in kodlama.io.northwind.business.concretes.ProductManager required a bean of type 'kodlama.io.northwind.dataAccess.abstracts.ProductDao' that could not be found.


Action:

Consider defining a bean of type 'kodlama.io.northwind.dataAccess.abstracts.ProductDao' in your configuration.


Process finished with exit code 1

ProductDao 接口：

package kodlama.io.northwind.dataAccess.abstracts;

import kodlama.io.northwind.entities.concretes.Product;
import org.springframework.data.jpa.repository.JpaRepository;

public interface ProductDao extends JpaRepository<Product,Integer> { //interface interface'i extend eder. Product Türünde ve PK int olacak.
}

ProductManager 类：

package kodlama.io.northwind.business.concretes;

import kodlama.io.northwind.business.abstracts.ProductService;
import kodlama.io.northwind.dataAccess.abstracts.ProductDao;
import kodlama.io.northwind.entities.concretes.Product;


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

import java.util.List;

@Service//springe  bu class service görevi görecek dedik.
public class ProductManager implements ProductService {

    private ProductDao productDao;


    @Autowired //spring arkaplanda paroductDao sınıfı newleyip üretir.
    public ProductManager(ProductDao productDao) {
        super();
        this.productDao = productDao;
    }

    @Override
    public List<Product> getAll() {
        return this.productDao.findAll();  //tüm verileri getir.
    }
}

Pom xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>northwind</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>2.5.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.2.14.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>RELEASE</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-test</artifactId>
            <version>2.4.5</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.7.1</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <version>2.4.5</version>
        </dependency>

    </dependencies>

    <properties>
        <maven.compiler.source>16</maven.compiler.source>
        <maven.compiler.target>16</maven.compiler.target>
    </properties>

</project>

主类

package kodlamaio.northwind;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@SpringBootApplication
@EnableJpaRepositories
public class NorthwindApplication {

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

}

我不明白为什么它仍然给出错误。我不明白为什么它仍然给出错误。我不明白为什么它仍然给出错误。我不明白为什么它仍然给出错误。我不明白为什么它仍然给出错误。

【问题讨论】：

标签： java spring spring-boot hibernate

【解决方案1】：

使用@Repository 注释您的存储库接口。像这样。

@Repository
public interface ProductDao extends JpaRepository<Product,Integer> { //interface interface'i extend eder. Product Türünde ve PK int olacak.
}

【讨论】：

你能分享你的 Main 类和 pom.xml 文件（如果是 maven）或 build.gradle（如果是 gradle）
应该没用，因为现在不需要添加 Repository 注释
我添加到问题@vishal

【解决方案2】：

你已经通过构造函数注入了依赖，你已经创建了一个扩展 JpaRepository 的接口 ProductDao，所以它应该可以工作。

您唯一没有提到的是将 @EnableJpaRepositories 注释放在您的 Configuration 类上。所以也许这是唯一缺少的东西。

尝试将 @EnableJpaRepositories 注释放在 NorthwindApplication 或您拥有的任何其他配置上。

【讨论】：

【解决方案3】：

在你的依赖中使用它。

  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

【讨论】：