Question

我在Eclipse的服务器选项卡中运行的Glassfish v3上遇到以下错误。

javax.servlet.ServletException: javax.persistence.PersistenceException: No Persistence provider for EntityManager named chatroom

当我尝试从@Stateless bean和@Entity运行此代码时。我已经将bean的代码包含在最后作为参考（虽然我不认为这是问题！）

    EntityManagerFactory factory = Persistence.createEntityManagerFactory("chatroom");

下面是我的persistence.xml。我尽力配置这个，但我不确定我在做什么。我知道我将实体类ChatHistory连接到数据库，但我不确定如何检查与数据库的连接，并确保它正常工作。我运行了数据库，可以在Data Source Explorer中看到它。用户名和密码是正确的。

http://oi44.tinypic.com/5nyq9.jpg

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
  <persistence-unit name="chatroom" transaction-type="JTA">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>org.janp.castlerock.ChatHistory</class>
    <properties>
      <property name="eclipselink.target-database" value="DERBY"/>
      <property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
      <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
      <property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/MyDB;create=true"/>
      <property name="javax.persistence.jdbc.user" value="username"/>
      <property name="javax.persistence.jdbc.password" value="password"/>
    </properties>
  </persistence-unit>
</persistence>

ChatHistory.java

package org.janp.castlerock;

import java.util.List;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.validation.constraints.NotNull;

@Entity
public class ChatHistory {

    private int id;
    private List<String> messages;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public int getId() {
        return id;
    }

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

    @NotNull
    public List<String> getMessages() {
        return messages;
    }

    public void setMessages(List<String> messages) {
        this.messages = messages;
    }
}

Chatroom.java

package org.janp.castlerock;

import java.util.ArrayList;
import java.util.List;

import javax.ejb.EJB;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;

@Path("/chatrooms")
@Stateless
public class Chatroom {
    ChatHistory history;
    @EJB
    ConverterBean converterBean;
    @GET
    @Produces("text/plain")
    public String getClichedMessage() {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("chatroom");
        EntityManager em = factory.createEntityManager();
        Query q = em.createQuery("select t from Todo t");
        List<ChatHistory> messages = q.getResultList();
        for (ChatHistory element : messages) {
            System.out.println(element);
        }
        System.out.println("Size: " + messages.size());

        ArrayList<String> temp = new ArrayList<String>();
        temp.add("HELLO WORLD");
        temp.add("I AM FINE");
        em.getTransaction().begin();

        ChatHistory messagehistory = new ChatHistory();
        messagehistory.setMessages(temp);
        em.persist(messagehistory);
        em.getTransaction().commit();
        em.close();

        messages = q.getResultList();
        for (ChatHistory element : messages) {
            System.out.println(element);
        }
        System.out.println("Size: " + messages.size());

        return "SUCCESS!:" + messages;
//      System.out.println("blahblha");
//      converterBean.dollarToYen(new BigDecimal(5.0));
//      return "Success!";
    }
}

Answer 1

您应该注入EntityManager注释

@Stateless
public class Chatroom 
{  
   @PersistenceContext(unitName = "chatroom")
   private EntityManager entityManager;

还要检查类路径中存在的类org.eclipse.persistence.jpa.PersistenceProvider

没有使用glassfish v3的EntityManager错误的持久性提供程序

1 个答案: