为什么我需要一个 entityManagerFactory？答案

【问题标题】：Why do I need an entityManagerFactory?为什么我需要一个 entityManagerFactory？
【发布时间】：2016-01-03 19:04:36
【问题描述】：

我的 src/main/resources 中有以下 xml（这是正确的位置吗？）

<?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:jpa="http://www.springframework.org/schema/data/jpa"
   xsi:schemaLocation="http://www.springframework.org/schema/beans     http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/data/jpa     http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

   <jpa:repositories base-package="com.parrit.models"/>

</beans>

由于缺少 bean，我无法构建，并且我在这个 xml 中收到警告，上面写着 Referenced bean 'entityManagerFactory' not found。

据我所知，我没有引用entityManagerFactory。我错过了什么？

据我所知，这是引用的 bean。它位于 srd/main/java/com.parrit.models

package com.parrit.models;

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

public interface WorkspaceRepository extends JpaRepository<Workspace, Long> {

}

应 Ali Deghani 的要求添加了 Stacktrace。 entityManagerFactory 警告没有堆栈跟踪，它只是一个编译器警告。

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'workspaceController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.parrit.models.WorkspaceRepository com.parrit.WorkspaceController.repository; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.parrit.models.WorkspaceRepository] 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.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839) ~[spring-context-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538) ~[spring-context-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:118) ~[spring-boot-1.3.1.RELEASE.jar:1.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:764) [spring-boot-1.3.1.RELEASE.jar:1.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.doRun(SpringApplication.java:357) [spring-boot-1.3.1.RELEASE.jar:1.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:305) [spring-boot-1.3.1.RELEASE.jar:1.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1124) [spring-boot-1.3.1.RELEASE.jar:1.3.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1113) [spring-boot-1.3.1.RELEASE.jar:1.3.1.RELEASE]
    at com.parrit.ParritApplication.main(ParritApplication.java:10) [classes/:na]
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.parrit.models.WorkspaceRepository com.parrit.WorkspaceController.repository; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.parrit.models.WorkspaceRepository] 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) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    ... 17 common frames omitted
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.parrit.models.WorkspaceRepository] 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) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1119) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:545) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    ... 19 common frames omitted

【问题讨论】：

添加更多细节，包括可能的堆栈跟踪、更多配置等
@AliDehghani 添加了。不确定还有哪些其他配置有用。有什么建议吗？

标签： java spring jpa spring-data-jpa

【解决方案1】：

存储库需要实体管理器才能运行。您必须至少将一个实体管理器工厂明确定义为 bean。如果定义了多个，那么您应该通过将其 bean 引用作为属性 'entity-manager-factory-ref' 添加到 'jpa:repositories' 元素来指定使用哪一个。另见http://docs.spring.io/spring-data/jpa/docs/1.3.0.RELEASE/reference/html/jpa.repositories.html

【讨论】：

【解决方案2】：

JPA 存储库将在哪里查找数据源？实体管理器工厂需要显示获取数据的位置。此外，使用 JPA，我们需要一个 org.springframework.orm.jpa.JpaTransactionManager，例如可以这样配置：

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
            p:driverClassName="com.mysql.jdbc.Driver" p:url="jdbc:mysql://localhost/test"
            p:username="root" p:password="" p:initialSize="5" p:maxActive="10">
</bean>

<bean
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
        id="entityManagerFactory">
        <property name="dataSource" ref="dataSource" />
</bean>

<bean class="org.springframework.orm.jpa.JpaTransactionManager"
        id="transactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

【讨论】：

你的基本想法是有效的，但你有两个dataSourcees 可用
谢谢，我改了