Java 在springboot中自动连接时找不到特定类型的bean
在开始之前,请假设Java 在springboot中自动连接时找不到特定类型的bean,java,spring,spring-boot,autowired,Java,Spring,Spring Boot,Autowired,在开始之前,请假设pom.xml是无错误的 话虽如此,让我们继续 我得到的错误如下: 应用程序无法启动 ***************************说明: com.sagarp.employee.EmployeeService中的字段empDao需要一个bean 键入找不到的“com.sagarp.employee.EmployeeDao” 现在,spring boot应用程序的类如下所示: package com.sagarp; import org.springframework
pom.xml
是无错误的
话虽如此,让我们继续
我得到的错误如下:
应用程序无法启动
***************************说明:
com.sagarp.employee.EmployeeService中的字段empDao需要一个bean
键入找不到的“com.sagarp.employee.EmployeeDao”
现在,spring boot应用程序的类如下所示:
package com.sagarp;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
@EnableEurekaClient //this is for eureka which not our concern right now.
@ComponentScan(basePackages = "com.sagarp.*") //Included all packages
public class EmployeeHibernateApplication {
public static void main(String[] args) {
SpringApplication.run(EmployeeHibernateApplication.class, args);
}
}
package com.sagarp.employee;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class EmployeeService {
@Autowired
private EmployeeDao empDao; // interface
public EmployeeDao getEmpDao() {
return empDao;
}
public void setEmpDao(EmployeeDao empDao) {
this.empDao = empDao;
}
//some methods
}
public interface EmployeeDao {
//Oh! so many methods to I have provided
}
EmployeeService
类别如下:
package com.sagarp;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
@EnableEurekaClient //this is for eureka which not our concern right now.
@ComponentScan(basePackages = "com.sagarp.*") //Included all packages
public class EmployeeHibernateApplication {
public static void main(String[] args) {
SpringApplication.run(EmployeeHibernateApplication.class, args);
}
}
package com.sagarp.employee;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class EmployeeService {
@Autowired
private EmployeeDao empDao; // interface
public EmployeeDao getEmpDao() {
return empDao;
}
public void setEmpDao(EmployeeDao empDao) {
this.empDao = empDao;
}
//some methods
}
public interface EmployeeDao {
//Oh! so many methods to I have provided
}
请注意,EmployeeDao
是一个接口
public class EmployeeDaoImpl implements EmployeeDao {
@Autowired
private SessionFactory sessionFactory;
//Oh!So many methods I had to implement
}
EmployeeDao
界面如下:
package com.sagarp;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
@EnableEurekaClient //this is for eureka which not our concern right now.
@ComponentScan(basePackages = "com.sagarp.*") //Included all packages
public class EmployeeHibernateApplication {
public static void main(String[] args) {
SpringApplication.run(EmployeeHibernateApplication.class, args);
}
}
package com.sagarp.employee;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class EmployeeService {
@Autowired
private EmployeeDao empDao; // interface
public EmployeeDao getEmpDao() {
return empDao;
}
public void setEmpDao(EmployeeDao empDao) {
this.empDao = empDao;
}
//some methods
}
public interface EmployeeDao {
//Oh! so many methods to I have provided
}
EmployeeDaoImpl
类,该类实现EmployeeDao
接口
public class EmployeeDaoImpl implements EmployeeDao {
@Autowired
private SessionFactory sessionFactory;
//Oh!So many methods I had to implement
}
我猜是由于员工服务
被标注为@Service
的原因,它是自动连接的。
我在components
中添加了所有包,这样它将扫描并实例化我可能拥有的所有依赖项
但事实并非如此,因此出现了问题
有人能帮我解决上面的错误吗。
如果需要更多详细信息,请告诉我。组件扫描搜索用Spring原型注释注释的类。为了使类符合自动连接的条件,它必须具有以下注释之一
解决方案是使用@Component、@Service或@Repository注释EmployeeDaoImpl。EmployeeDaoImpl
未注册为bean。有两种方法:XML或注释。由于您已经使用了注释,现在可以执行以下操作:
@Repository
public class EmployeeDaoImpl implements EmployeeDao {
@Autowired
private SessionFactory sessionFactory;
//...
}
注意,您已经将EmployeeService
注册为@Service
的bean。在此之后,应该在容器中识别bean并正确注入
为什么要使用DAO的@Repository
,而不是@Service
?如何决定?更多信息,请阅读本文
@Component
是任何Spring托管组件的通用原型
@Service
在服务层注释类
@Repository
注释持久层上的类,持久层将充当数据库存储库
还应注释EmployeeDaoImpl
@Repository
public class EmployeeDaoImpl implements EmployeeDao {
@Autowired
private SessionFactory sessionFactory;
//Oh!So many methods I had to implement
}
这应该可以解决问题。尝试用@Repository
注释EmployeeDaoImpl
类。感谢您的建议,它现在可以工作了,但这是sessionFactory的衍生问题。
@sagarpatro将一个答案标记为正确,并用其他人在评论中要求的内容提出另一个问题。sessionFactory的问题。请随意创建一个新问题。感谢您的建议,它现在可以工作了,但这是sessionFactory
的垃圾邮件问题。这是另一个与存储库问题无关的问题。为此,您必须提供EmployeeDaoImpl.java类的内容。感谢您的建议,它现在可以工作了,但它会引发sessionFactory的问题。