Question

我有pom.xml

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>net.vyhn</groupId>
    <artifactId>jpa</artifactId>
    <packaging>war</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>jpa Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>eclipselink</artifactId>
            <version>2.6.3</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>org.eclipse.persistence.core</artifactId>
            <version>2.6.3</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>org.eclipse.persistence.jpa</artifactId>
            <version>2.6.3</version>
        </dependency>
        <dependency>
            <groupId>javax.persistence</groupId>
            <artifactId>persistence-api</artifactId>
            <version>1.0.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.2</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>jpa</finalName>
    </build>
</project>

Employee.java

package example.com.domain;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;

@Entity
public class Employee {

    @Id
    @GeneratedValue
    private Long id;
    private String name;

    @ManyToOne
    private Department department;

    public Employee() {
    }

    public Employee(String name, Department department) {
        this.name = name;
        this.department = department;
    }


    public Employee(String name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    @Override
    public String toString() {
        return "Employee [id=" + id + ", name=" + name + ", department="
                + department.getName() + "]";
    }

}

Department.java

package example.com.domain;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import java.util.ArrayList;
import java.util.List;

@Entity
public class Department {

    @Id
    @GeneratedValue
    private Long id;


    private String name;

    @OneToMany(mappedBy = "department", cascade = CascadeType.PERSIST)
    private List<Employee> employees = new ArrayList<Employee>();


    public Department() {
        super();
    }

    public Department(String name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<Employee> getEmployees() {
        return employees;
    }

    public void setEmployees(List<Employee> employees) {
        this.employees = employees;
    }

}

JpaTest.java

package example.com.jpa;

import example.com.domain.Department;
import example.com.domain.Employee;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import java.util.List;

public class JpaTest {

    private EntityManager manager;

    public JpaTest(EntityManager manager) {
        this.manager = manager;
    }

    public static void main(String[] args) {
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("persistenceUnit");
        EntityManager manager = factory.createEntityManager();
        JpaTest test = new JpaTest(manager);
        EntityTransaction tx = manager.getTransaction();
        tx.begin();
        try {
            test.createEmployees();
        } catch (Exception e) {
            e.printStackTrace();
        }
        tx.commit();
        test.listEmployees();
        System.out.println(".. done");
    }

    private void createEmployees() {
        int numOfEmployees = manager.createQuery("Select a From Employee a", Employee.class).getResultList().size();
        if (numOfEmployees == 0) {
            Department department = new Department("java");
            manager.persist(department);
            manager.persist(new Employee("Jakab Gipsz", department));
            manager.persist(new Employee("Captain Nemo", department));
        }
    }

    private void listEmployees() {
        List<Employee> resultList = manager.createQuery("Select a From Employee a", Employee.class).getResultList();
        System.out.println("num of employess:" + resultList.size());
        for (Employee next : resultList) {
            System.out.println("next employee: " + next);
        }
    }

}

当我运行JpaTest.java时，出现错误：

"C:\Program Files\Java\jdk1.8.0_92\bin\java" -Didea.launcher.port=7533 "-Didea.launcher.bin.path=C:\Program Files (x86)\JetBrains\IntelliJ IDEA 2016.1.2\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_92\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_92\jre\lib\rt.jar;C:\Users\Administrator\IdeaProjects\demo_jpa\target\classes;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\eclipselink\2.6.3\eclipselink-2.6.3.jar;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\javax.persistence\2.1.1\javax.persistence-2.1.1.jar;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\commonj.sdo\2.1.1\commonj.sdo-2.1.1.jar;C:\Users\Administrator\.m2\repository\javax\validation\validation-api\1.1.0.Final\validation-api-1.1.0.Final.jar;C:\Users\Administrator\.m2\repository\org\glassfish\javax.json\1.0.4\javax.json-1.0.4.jar;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\org.eclipse.persistence.core\2.6.3\org.eclipse.persistence.core-2.6.3.jar;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\org.eclipse.persistence.asm\2.6.3\org.eclipse.persistence.asm-2.6.3.jar;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\org.eclipse.persistence.jpa\2.6.3\org.eclipse.persistence.jpa-2.6.3.jar;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\org.eclipse.persistence.antlr\2.6.3\org.eclipse.persistence.antlr-2.6.3.jar;C:\Users\Administrator\.m2\repository\org\eclipse\persistence\org.eclipse.persistence.jpa.jpql\2.6.3\org.eclipse.persistence.jpa.jpql-2.6.3.jar;C:\Users\Administrator\.m2\repository\javax\persistence\persistence-api\1.0.2\persistence-api-1.0.2.jar;C:\Users\Administrator\.m2\repository\mysql\mysql-connector-java\6.0.2\mysql-connector-java-6.0.2.jar;C:\Program Files (x86)\JetBrains\IntelliJ IDEA 2016.1.2\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain example.com.jpa.JpaTest
Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named persistenceUnit
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:85)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
    at example.com.jpa.JpaTest.main(JpaTest.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

帮我解决这个错误，谢谢！

Answer 1

您必须将persistence.xml放入java/resources文件夹。

<persistence-unit name="persistenceUnit" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>

我希望这会起作用

JPA persistence.xml出错没有EntityManager的持久性提供程序

1 个答案: