Question

我在META-INF目录下使用toplink创建了具有相同名称的persistence.xml。然后我用我的代码调用它......

public class DBConnect {
    @PersistenceUnit
    EntityManagerFactory emf;

    public DBConnect()
    {
        emf = null;
    }
    public void startConnection()
    {
        emf = Persistence.createEntityManagerFactory
                (
                    "cvut.fel.pjv.persistence.xml"
                );
    }
    public void closeConnection()
    {
        emf.close();
    }
    public EntityManagerFactory getEMF()
    {
        return emf;
    }
}

我收到以下错误消息：

Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named cvut.fel.pjv.persistence.xml
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:85)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
    at utils.DBConnect.startConnection(DBConnect.java:30)
    at utils.Server.<init>(Server.java:32)
    at utils.Server.main(Server.java:58)

这是我的persistence.xml - 我认为它应该是正确的

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
  <persistence-unit name="cvut.fel.pjv_LibrarySystem_server_jar_1.0-SNAPSHOTPU" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>model.Vydani</class>
    <class>model.Nosic</class>
    <class>model.Vypujcka</class>
    <class>model.Adresa</class>
    <class>model.Casopis</class>
    <class>model.Kategorie</class>
    <class>model.Kniha</class>
    <class>model.Nakladatelstvi</class>
    <class>model.Zamestnanec</class>
    <class>model.Ctenar</class>
    <class>model.Vytisk</class>
    <class>model.Autor</class>
    <class>model.SpisovatelePocetDel</class>
    <class>model.UzivateleAdresy</class>
    <class>model.Osoba</class>
    <class>model.DigitalniNosic</class>
    <properties>
      <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://slon.felk.cvut.cz:5432/db18_koresmi1"/>
      <property name="javax.persistence.jdbc.user" value="db18_koresmi1"/>
      <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/>
      <property name="javax.persistence.jdbc.password" value="Hk2JsA"/>
    </properties>
  </persistence-unit>
</persistence>

还有一个pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>cvut.fel.pjv</groupId>
    <artifactId>LibrarySystem_server</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <dependencies>
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>eclipselink</artifactId>
            <version>2.5.2</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
            <version>2.5.2</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.googlecode.json-simple</groupId>
            <artifactId>json-simple</artifactId>
            <version>1.1.1</version>
            <type>jar</type>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>9.4.1212</version>
        </dependency>
    </dependencies>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
</project>

我非常感谢你的帮助 - 我在netbeans中做了一个maven项目

Answer 1

Persistence.createEntityManagerFactory的参数是持久性单元的名称。根据您的persistence.xml，您的持久性单元名为 cvut.fel.pjv_LibrarySystem_server_jar_1.0-SNAPSHOTPU 。以下代码应该有效：

emf = Persistence.createEntityManagerFactory("cvut.fel.pjv_LibrarySystem_server_jar_1.0-SNAPSHOTPU");

没有为EntityManager命名的持久性提供程序 - 我做错了什么？

1 个答案: