更改代码时Maven的问题？

Question

我正在尝试使用NetBeans运行一个小型Maven测试程序。现在，NetBeans提供的代码在Maven中运行得非常好。编译，运行，一切顺利。但是，当我更改任何内容，比如添加FXML或添加JPA持久性时，在启动程序时都会出现错误。编译似乎有效，但我无法启动程序。我希望错误在Maven的配置中，但我找不到它。代码本身应该工作得很好。

好吧，告诉你们我到底是什么意思，这是密码。我只是在MySQL-数据库中添加了一个JPA-持久性。添加之后，程序就不再运行了。

App.java

package com.myproject.mavenproject;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        System.out.println( "Hello new World!" );

        EntityManagerFactory emf = Persistence.createEntityManagerFactory( "GlassesPU" );
        try {
            EntityManager     em = emf.createEntityManager();
            EntityTransaction tx = null;
            try {
                tx = em.getTransaction();
                tx.begin();

                Hund hund = new Hund();
                hund.setFormerName("Albert");
                hund.setNewName("Einstein");
                em.persist(hund);

                //em.persist( entity1 );
                //em.merge( entity2 );
                //em.find( MyEntity.class, id );
                tx.commit();
            } catch( RuntimeException ex ) {
                if( tx != null && tx.isActive() ) tx.rollback();
                throw ex;
            } finally {
                em.close();
            }
        } finally {
            emf.close();
        }
    }
}

Hund.java

package com.myproject.mavenproject;

import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Hund implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String formerName;
    private String newName;

    public Long getId() {
        return id;
    }

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

    public String getFormerName() {
        return formerName;
    }

    public void setFormerName(String formerName) {
        this.formerName = formerName;
    }

    public String getNewName() {
        return newName;
    }

    public void setNewName(String newName) {
        this.newName = newName;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Hund)) {
            return false;
        }
        Hund other = (Hund) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "com.myproject.mavenproject.Hund[ id=" + id + " ]";
    }

}

persistence.xml

<?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="com.myproject_MavenProject_jar_1.0-SNAPSHOTPU" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>com.myproject.mavenproject.Hund</class>
    <properties>
      <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/glasses?zeroDateTimeBehavior=convertToNull"/>
      <property name="javax.persistence.jdbc.password" value="mypassword"/>
      <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
      <property name="javax.persistence.jdbc.user" value="root"/>
      <property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>
    </properties>
  </persistence-unit>
</persistence>

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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.myproject</groupId>
  <artifactId>MavenProject</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>MavenProject</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.eclipse.persistence</groupId>
      <artifactId>eclipselink</artifactId>
      <version>2.5.1</version>
    </dependency>
    <dependency>
      <groupId>org.eclipse.persistence</groupId>
      <artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
      <version>2.5.1</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
</project>

错误消息

cd /home/myuser/NetBeansProjects/MavenProject; JAVA_HOME=/usr/lib/jvm/jdk1.7.0_51 /home/myuser/netbeans-7.4/java/maven/bin/mvn "-Dexec.args=-classpath %classpath com.myproject.mavenproject.App" -Dexec.executable=/usr/lib/jvm/jdk1.7.0_51/bin/java org.codehaus.mojo:exec-maven-plugin:1.2.1:exec
Running NetBeans Compile On Save execution. Phase execution is skipped and output directories of dependency projects (with Compile on Save turned on) will be used instead of their jar artifacts.
Scanning for projects...

------------------------------------------------------------------------
Building MavenProject 1.0-SNAPSHOT
------------------------------------------------------------------------

--- exec-maven-plugin:1.2.1:exec (default-cli) @ MavenProject ---
Hello new World!
Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named GlassesPU
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:85)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
    at com.myproject.mavenproject.App.main(App.java:18)
------------------------------------------------------------------------
BUILD FAILURE
------------------------------------------------------------------------
Total time: 0.891s
Finished at: Mon Feb 03 21:35:25 CET 2014
Final Memory: 5M/111M
------------------------------------------------------------------------
Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:exec (default-cli) on project MavenProject: Command execution failed. Process exited with an error: 1 (Exit value: 1) -> [Help 1]

To see the full stack trace of the errors, re-run Maven with the -e switch.
Re-run Maven using the -X switch to enable full debug logging.

For more information about the errors and possible solutions, please read the following articles:
[Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

有人知道问题出在哪里吗？

Answer 1

Maven没有问题。只是报告了错误。它说它找不到一个叫做"GlassesPU“的持久性提供者。

Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named GlassesPU

您的persistence.xml有另一个名称：

<persistence-unit name="com.myproject_MavenProject_jar_1.0-SNAPSHOTPU" ... >

尝试将其更改为"GlassesPU"：

<persistence-unit name="GlassesPU" ...>

如果Maven再次抱怨，可能是由于其他原因。