java - 使用 Spring、JPA 和 Hibernate 的通用 DAO 设置
问题描述
我正在尝试制作一个通用代码,以在任何实体上实现一些最常见的操作。我使用 Spring Initializr 使用 Gradle、Spring Boot 2.1.0 SNAPSHOT、JPA 和 Hibernate 生成产品的基础。我使用 MySQL Workbench 创建了模式和表,并使用它为我的项目生成实体。所以谈到实际问题,我尝试创建一个通用 DAO,其中一些常见的操作,如 findbyid、编辑、删除、创建、更新、getall 将被实现,然后将其扩展到其他 DAO 类以提高可重用性并完成工作快点。所以这是我到目前为止的代码:
用户控制器.java:
@RestController
public class UserController {
@Autowired
UserService userService;
@RequestMapping(value = "/getUser", method = RequestMethod.GET)
@ResponseBody
public UserEntity getUser() throws Exception {
userService.getUser();
}
}
用户服务.java:
public interface UserService {
UsersEntity getUser();
}
用户服务Impl.java:
@Service
public class UserServiceImpl implements UserService {
@Autowired
UserDAO userDAO;
@Transactional
public UsersEntity getUser() {
return userDAO.find(Long.valueOf("123"));
}
}
用户DAO.java:
public interface UserDAO extends GenericRepositoryInterface<UsersEntity> {
}
用户DAOImpl.java:
@Repository
public abstract class UserDAOImpl implements UserDAO {
}
GenericRepositoryInterface.java:
public interface GenericRepositoryInterface<T> {
T save(T emp);
Boolean delete(T emp);
T edit(T emp);
T find(Long empId);
}
GenericRepositoryImplementation.java:
@Repository
public class GenericRepositoryImplementation<T> implements GenericRepositoryInterface<T> {
protected EntityManager entityManager;
private T type;
public GenericRepositoryImplementation(T type) {
// TODO Auto-generated constructor stub
this.type = type;
}
public EntityManager getEntityManager() {
return entityManager;
}
@PersistenceContext
public void setEntityManager(EntityManager entityManager) {
this.entityManager = entityManager;
}
@Override
public T save(T emp) {
// TODO Auto-generated method stub
entityManager.persist(emp);
entityManager.flush();
return emp;
}
@Override
public Boolean delete(T emp) {
// TODO Auto-generated method stub
try {
entityManager.remove(emp);
} catch (Exception ex) {
return false;
}
return true;
}
@Override
public T edit(T emp) {
// TODO Auto-generated method stub
try{
return entityManager.merge(emp);
} catch(Exception ex) {
return null;
}
}
@Override
public T find(Long empId) {
// TODO Auto-generated method stub
return (T) entityManager.find(type.getClass(), empId);
}
}
我不确定我的实现哪里出了问题,但是每当我运行应用程序时,它都会崩溃并显示以下日志:
2018-06-24 18:12:14.748 DEBUG 72491 --- [ restartedMain] o.s.b.d.LoggingFailureAnalysisReporter : Application failed to start due to an exception
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.example.test.dao.UserDAO' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1509) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1104) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1065) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:584) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:91) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:373) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1350) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:580) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:503) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:251) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1065) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:584) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:91) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:373) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1350) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:580) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:503) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:760) ~[spring-beans-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869) ~[spring-context-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.1.0.BUILD-SNAPSHOT.jar:5.1.0.BUILD-SNAPSHOT]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.1.0.BUILD-SNAPSHOT.jar:2.1.0.BUILD-SNAPSHOT]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762) [spring-boot-2.1.0.BUILD-SNAPSHOT.jar:2.1.0.BUILD-SNAPSHOT]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:398) [spring-boot-2.1.0.BUILD-SNAPSHOT.jar:2.1.0.BUILD-SNAPSHOT]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:330) [spring-boot-2.1.0.BUILD-SNAPSHOT.jar:2.1.0.BUILD-SNAPSHOT]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1234) [spring-boot-2.1.0.BUILD-SNAPSHOT.jar:2.1.0.BUILD-SNAPSHOT]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1222) [spring-boot-2.1.0.BUILD-SNAPSHOT.jar:2.1.0.BUILD-SNAPSHOT]
at com.example.test.Application.main(Application.java:11) [classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_171]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.1.0.BUILD-SNAPSHOT.jar:2.1.0.BUILD-SNAPSHOT]
2018-06-24 18:12:14.749 ERROR 72491 --- [ restartedMain] o.s.b.d.LoggingFailureAnalysisReporter :
***************************
APPLICATION FAILED TO START
***************************
Description:
Field userDAO in com.example.test.service.impl.UserServiceImpl required a bean of type 'com.example.test.dao.UserDAO' that could not be found.
Action:
Consider defining a bean of type 'com.example.test.dao.UserDAO' in your configuration.
我不知道为什么,但在提到的位置有一个 UserDAO 类,它无法识别它。我错过了任何注释或任何东西吗?
解决方案
没有UserDAO
找到实现。
你想扩展你的通用 DAO 实现:
@Repository
public class UserDAOImpl extends GenericRepositoryImplementation< UsersEntity> implements UserDAO {
public UserDaoImpl() {
super(UsersEntity.class);
}
}
你的通用 DAO 实现应该接受一个类型的类<T>
而不是一个实例T
:
public class GenericRepositoryImplementation<T> implements GenericRepositoryInterface<T> {
protected EntityManager entityManager;
private Class<T> type;
public GenericRepositoryImplementation(Class<T> type) {
// TODO Auto-generated constructor stub
this.type = type;
}
}
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