如何使用 JPA 配置 Spring 应用程序？答案

【问题标题】：How to configure a spring application with JPA?如何使用 JPA 配置 Spring 应用程序？
【发布时间】：2016-05-16 16:34:35
【问题描述】：

我正在尝试使用持久性 API 部署 Spring 应用程序，但配置存在一些问题。我不知道为什么找不到DAOS... 可能是上下文有问题..

这是道：

@Component
public interface AccountDAO extends JpaRepository<Account, String> {
}

应用上下文：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd">

    <context:component-scan base-package="ro.academy.service" />
    <context:component-scan base-package="ro.academy.model.daos" />
    <context:annotation-config/>
</beans>

另一个配置上下文：

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(basePackages = {
        "ro.academy.model.daos"
})
public class PersistenceContext {
    @Bean(destroyMethod = "close")
    DataSource dataSource(Environment env) {
        BasicDataSource dataSourceConfig = new BasicDataSource();
        dataSourceConfig.setDriverClassName(env.getRequiredProperty("db.driver"));
        dataSourceConfig.setUrl(env.getRequiredProperty("db.url"));
        dataSourceConfig.setUsername(env.getRequiredProperty("db.username"));
        dataSourceConfig.setPassword(env.getRequiredProperty("db.password"));

        return dataSourceConfig;
    }
}

我应该在 web xml 中配置持久性上下文吗？这是 web xml 文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            /WEB-INF/applicationContext.xml
        </param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

还有错误：

  Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private ro.academy.model.daos.AccountDAO ro.academy.service.MyService.accountsDAO; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [ro.academy.model.daos.AccountDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:573)
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
        ... 58 more
    Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [ro.academy.model.daos.AccountDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1373)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1119)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014)
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:545)
        ... 60 more

【问题讨论】：

标签： java spring hibernate jpa

【解决方案1】：

我没有将组件放在 Repository 类中。相反，从 SpringBoot 原型中，我一直在创建这些类，如下所示：

@Component("countryService")
@Transactional
public class CountryServiceImpl implements CountryService {
    private CountryRepository countryRepository;
    private RegionRepository regionRepository;

    @Autowired
    public CountryServiceImpl(CountryRepository countryRepository, RegionRepository regionRepository) {
        this.countryRepository = countryRepository;
        this.regionRepository = regionRepository;
    }

Repository 类没有特殊的注解：

public interface CountryRepository extends PagingAndSortingRepository<Country, Long> {

}

按照这个模板，它应该适合你。否则这个答案对 cmets 有帮助：

Unable to Autowire ServiceImpl Class Bean with Service Class Object

【讨论】：