JBoss7.1.0: Can't find a persistence unit named null in subdeployment

问题

I have a project with 3 modules inside: factory-ear, factory-ejb and factory-web. It deployed to JBoss7 as EAR with ejb.jar and web.war inside. When I trying to get EntityManager in my EJB class

@PersistenceContext(unitName = "manager1")
private EntityManager em;

I get error

JBAS011440: Can't find a persistence unit named manager1 in subdeployment "factory-ejb-1.0-SNAPSHOT.jar" of deployment "factory.ear"

My persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
    xmlns="http://java.sun.com/xml/ns/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">
    <persistence-unit name="manager1" transaction-type="JTA">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <jta-data-source>java:jboss/datasources/PostgresDS</jta-data-source>
        <class>com.test.model.Car</class>
        <class>com.test.model.Engine</class>
        <class>com.test.model.Body</class>
        <class>com.test.model.Transmission</class>
        <properties>
         <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
         <property name="hibernate.show_sql" value="true" />
         <property name="hibernate.hbm2ddl.auto" value="update"/>
        </properties>
    </persistence-unit>
</persistence>

The persistence.xml is in the app_name/factory_ear/META-INF.

I have read that this can be a problem of classloaders. I have same JPA API dependency with provided scope in ear and web modules

  <dependency>
     <groupId>org.hibernate.javax.persistence</groupId>
     <artifactId>hibernate-jpa-2.0-api</artifactId>
     <scope>provided</scope>
  </dependency> 

But I was not able to remove one of them. Both are necessary for build.

Body.java

@Entity
@Table(name = "body")
public class Body {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "type")
    private String type;

    @Column(name = "color")
    private String color;

    @Column(name = "doors_num")
    private Integer doorsNumber;

    @Column(name = "vin")
    private Integer vin;

    @OneToMany(mappedBy = "body")
    private Set<Car> cars;

    /**
     * @return the id
     */
    public Integer getId() {
        return id;
    }

    /**
     * @param id the id to set
     */
    public void setId(Integer id) {
        this.id = id;
    }

    /**
     * @return the type
     */
    public String getType() {
        return type;
    }

    /**
     * @param type the type to set
     */
    public void setType(String type) {
        this.type = type;
    }

    /**
     * @return the color
     */
    public String getColor() {
        return color;
    }

    /**
     * @param color the color to set
     */
    public void setColor(String color) {
        this.color = color;
    }

    /**
     * @return the doorsNumber
     */
    public Integer getDoorsNumber() {
        return doorsNumber;
    }

    /**
     * @param doorsNumber the doorsNumber to set
     */
    public void setDoorsNumber(Integer doorsNumber) {
        this.doorsNumber = doorsNumber;
    }

    /**
     * @return the vin
     */
    public Integer getVin() {
        return vin;
    }

    /**
     * @param vin the vin to set
     */
    public void setVin(Integer vin) {
        this.vin = vin;
    }

    /**
     * @return the cars
     */
    public Set<Car> getCars() {
        return cars;
    }

    /**
     * @param cars the cars to set
     */
    public void setCars(Set<Car> cars) {
        this.cars = cars;
    }
}

Car.java

public class Car {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "model")
    private String model;

    @ManyToOne
    @JoinColumn(name = "engine_id")
    private Engine engine;

    @ManyToOne
    @JoinColumn(name = "body_id")
    private Body body;

    @ManyToOne
    @JoinColumn(name = "transmission_id")
    private Transmission transmission;

    /**
     * @return the id
     */
    public Integer getId() {
        return id;
    }

    /**
     * @param id the id to set
     */
    public void setId(Integer id) {
        this.id = id;
    }

    /**
     * @return the model
     */
    public String getModel() {
        return model;
    }

    /**
     * @param model the model to set
     */
    public void setModel(String model) {
        this.model = model;
    }

    /**
     * @return the engine
     */
    public Engine getEngine() {
        return engine;
    }

    /**
     * @param engine the engine to set
     */
    public void setEngine(Engine engine) {
        this.engine = engine;
    }

    /**
     * @return the body
     */
    public Body getBody() {
        return body;
    }

    /**
     * @param body the body to set
     */
    public void setBody(Body body) {
        this.body = body;
    }

    /**
     * @return the transmission
     */
    public Transmission getTransmission() {
        return transmission;
    }

    /**
     * @param transmission the transmission to set
     */
    public void setTransmission(Transmission transmission) {
        this.transmission = transmission;
    }
}

回答1:

This problem is not caused by your maven dependencies.

The content of the META-INF directory in an EAR file is generally inaccessible to any class loader.

Therefore, you cannot put your persistence.xml file in the META-INF directory of the EAR file. Move it into the META-INF directory of the EJB jar file instead.

来源：https://stackoverflow.com/questions/39880595/jboss7-1-0-cant-find-a-persistence-unit-named-null-in-subdeployment