如何让一个EntityManager被注入？

MonsterEJB.java：

package model; 

import java.util.List; 

import javax.ejb.LocalBean; 
import javax.ejb.Stateless; 
import javax.inject.Inject; 
import javax.inject.Named; 
import javax.persistence.EntityManager; 
import javax.persistence.EntityManagerFactory; 
import javax.persistence.PersistenceContext; 
import javax.persistence.PersistenceUnit; 
import javax.persistence.Query; 

@Stateless 
@LocalBean 
@Named 
public class MonsterEJB 
{ 
    @PersistenceUnit(unitName="mongo") 
    private EntityManager em; 

    @Inject 
    private Monster injectableMonster; 

    public MonsterEJB() 
    { 

    } 

    public void create() 
    { 
     em.getTransaction().begin(); 
     Monster en = new Monster(); 
     en.setDescription(injectableMonster.getDescription()); 
     em.persist(en); 
     em.getTransaction().commit(); 
    } 

    public List<Monster> getList() 
    { 
     Query query = em.createQuery("Select m from Monster m"); 
     List<Monster> Monsters = query.getResultList(); 

     return Monsters; 
    } 

    public void remove() 
    { 
     em.getTransaction().begin(); 
     Monster en = em.find(Monster.class, injectableMonster.getId()); 
     em.remove(en); 
     em.getTransaction().commit(); 
    } 

    public void update() 
    { 
     em.getTransaction().begin(); 
     Monster en = em.find(Monster.class, injectableMonster.getId()); 
     en.setDescription(injectableMonster.getDescription()); 
     em.getTransaction().commit(); 
    } 
}

Monster.java：

package model; 

import java.io.Serializable; 

import javax.enterprise.context.RequestScoped; 
import javax.inject.Named; 
import javax.persistence.*; 

import org.eclipse.persistence.nosql.annotations.*; 

@Entity 
@Named 
@RequestScoped 
@NoSql(dataFormat = DataFormatType.MAPPED) 
public class Monster implements Serializable 
{ 
    private static final long serialVersionUID = 1L; 

    @Id 
    @GeneratedValue 
    @Field(name = "_id") 
    private String id; 

    @Version 
    private long version; 

    @Basic 
    private String description; 

    public Monster() 
    { 

    } 

    public String getId() 
    { 
     return id; 
    } 

    public void setId(String id) 
    { 
     this.id = id; 
    } 

    public String getDescription() 
    { 
     return description; 
    } 

    public void setDescription(String description) 
    { 
     this.description = description; 
    } 

    @Override 
    public String toString() 
    { 
     return "Monster [id=" + id + ", version=" + version + ", description="+ description; 
    } 
}

的persistence.xml：

<?xml version="1.0" encoding="UTF-8" ?> 
<persistence xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
     xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" 
     version="2.0" xmlns="http://java.sun.com/xml/ns/persistence"> 
    <persistence-unit name="mongo" transaction-type="RESOURCE_LOCAL"> 
     <class>model.Monster</class> 
     <properties> 
      <property name="eclipselink.target-database" value="org.eclipse.persistence.nosql.adapters.mongo.MongoPlatform"/> 
      <property name="eclipselink.nosql.connection-spec" value="org.eclipse.persistence.nosql.adapters.mongo.MongoConnectionSpec"/> 
      <property name="eclipselink.nosql.property.mongo.port" value="27017"/> 
      <property name="eclipselink.nosql.property.mongo.host" value="localhost"/> 
      <property name="eclipselink.nosql.property.mongo.db" value="MonsterDatabase"/> 
      <property name="eclipselink.logging.level" value="FINEST"/> 
     </properties> 
    </persistence-unit> 
</persistence>

Show.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

<html xmlns="http://www.w3.org/1999/xhtml" 
    xmlns:ui="http://java.sun.com/jsf/facelets" 
    xmlns:h="http://java.sun.com/jsf/html" 
    xmlns:f="http://java.sun.com/jsf/core"> 

<ui:composition template="WEB-INF/templates/BasicTemplate.xhtml"> 

    <ui:define name="header"> 
     <div style="width:100%;font-size:36px;line-height:48px;background-color:navy;color:white">Showing Monsters</div> 
    </ui:define> 

    <ui:define name="content"> 
     <h:dataTable var="f2" value="#{MonsterEJB.list}"> 
      <h:column>#{f2.id}, #{f2.description}</h:column> 
     </h:dataTable> 
    </ui:define> 

</ui:composition> 
</html>

错误该网页显示

type Exception report 

message 

descriptionThe server encountered an internal error() that prevented it from fulfilling this request. 

exception 

javax.servlet.ServletException: javax.ejb.EJBException: javax.ejb.CreateException: Could not create stateless EJB 
root cause 

javax.ejb.EJBException: javax.ejb.EJBException: javax.ejb.CreateException: Could not create stateless EJB 
root cause 

javax.ejb.EJBException: javax.ejb.CreateException: Could not create stateless EJB 
root cause 

javax.ejb.CreateException: Could not create stateless EJB 
root cause 

java.lang.IllegalStateException: Exception attempting to inject Env-Prop: model.MonsterEJB/[email protected] Resource. Class name = model.MonsterEJB Field [email protected]@@@ into class model.MonsterEJB 
root cause 

com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting to inject Env-Prop: model.MonsterEJB/[email protected] Resource. Class name = model.ElnotEJB Field [email protected]@@@ into class model.MonsterEJB 
root cause 

java.lang.IllegalArgumentException: Can not set javax.persistence.EntityManager field model.MonsterEJB.em to com.sun.enterprise.container.common.impl.EntityManagerFactoryWrapper

问：如何让我的MonsterEJB.java注入与NoSQL的一个EntityManager的？

来源

2012-07-25 stackoverflow

我不确定这是否是您例外的原因，但您的MonsterEJB类同时注释为@Named和@Stateless。 @Named用于定义JSF Managed Bean和@Stateless对于Enterprise Java Beans，这是不同的事情。

使用一个或另一个注释。

此外，Monster类是在定义为同一时间：一个Entity，作为ManagedBean通过@Named注释，并通过javax.enterprise.context.RequestScoped注释的CDI豆。而且这也没有意义。

为了澄清这些概念，我建议学习一些Java EE 6教程（如this）。

来源

2012-07-25 15:19:10 perissf

应该如何Monster.java和MonsterEJB正确地然后注释？我在我的Java EE 6应用程序中使用java服务器面。给我的印象是我需要这样才能正常工作。 – stackoverflow 2012-07-25 15:41:48

在你学习了一个教程之后，你可以实现这个来自Adam Bien博客的[基本JPA应用]（http://www.adam-bien.com/roller/abien/entry/ejb_3_persistence_jpa_for），如果你想要更多的东西完成，那么[this]（http://wiki.netbeans.org/DevelopJavaEE6App）是一个使用JPA和其他Java EE 6功能的完整Web应用程序... – perissf 2012-07-25 17:08:16

尝试使用@PersistenceContext，而不是@PersistenceUnit

来源

2015-08-14 14:57:05

谢谢！作品 – 2016-10-24 14:02:57

如何让一个EntityManager被注入？

回答

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