Java createEntityManagerFactory（“某物”）返回null

我正在学习JPA与样本项目。每当我执行程序时，它都返回null。我检查了跟踪

，但这并没有帮助。请帮帮我。我被困了两天。我不知道我在哪里犯错

以下异常总是发生

1605 [main] DEBUG org.hibernate.boot.internal.BootstrapContextImpl  - Injecting ScanEnvironment [org.hibernate.jpa.boot.internal.StandardJpaScanEnvironmentImpl@482e36] into BootstrapContext; was [null]
1606 [main] DEBUG org.hibernate.boot.internal.BootstrapContextImpl  - Injecting ScanOptions [org.hibernate.boot.archive.scan.internal.StandardScanOptions@967906] into BootstrapContext; was [org.hibernate.boot.archive.scan.internal.StandardScanOptions@18dfcc1]
Exception in thread "main" java.lang.NullPointerException
        at org.hibernate.boot.archive.scan.spi.ClassFileArchiveEntryHandler.toClassDescriptor(ClassFileArchiveEntryHandler.java:84)
        at org.hibernate.boot.archive.scan.spi.ClassFileArchiveEntryHandler.toClassDescriptor(ClassFileArchiveEntryHandler.java:67)
        at org.hibernate.boot.archive.scan.spi.ClassFileArchiveEntryHandler.handleEntry(ClassFileArchiveEntryHandler.java:53)
        at org.hibernate.boot.archive.internal.JarFileBasedArchiveDescriptor.visitArchive(JarFileBasedArchiveDescriptor.java:147)
        at org.hibernate.boot.archive.scan.spi.AbstractScannerImpl.scan(AbstractScannerImpl.java:47)
        at org.hibernate.boot.model.process.internal.ScanningCoordinator.coordinateScan(ScanningCoordinator.java:76)
        at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.prepare(MetadataBuildingProcess.java:98)
        at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:242)
        at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:175)
        at org.hibernate.jpa.boot.spi.Bootstrap.getEntityManagerFactoryBuilder(Bootstrap.java:76)
        at org.hibernate.jpa.HibernatePersistenceProvider.getEntityManagerFactoryBuilder(HibernatePersistenceProvider.java:171)
        at org.hibernate.jpa.HibernatePersistenceProvider.getEntityManagerFactoryBuilderOrNull(HibernatePersistenceProvider.java:119)
        at org.hibernate.jpa.HibernatePersistenceProvider.getEntityManagerFactoryBuilderOrNull(HibernatePersistenceProvider.java:61)
        at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:50)
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
        at com.test.jpa.App.main(App.java:19)

这是映射类

package com.test.jpa;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;


@Entity
@Table(name = "client")
public class User {

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Column(name = "age")
    private int age = 0;

    @Id
    @Column(name = "No")
    private int No = 0;

    public int getNo() {
        return No;
    }

    public void setNo(int no) {
     No = no;
   }
}

pom文件

<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.test</groupId>
  <artifactId>jpa</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>jpa</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.slf4j</groupId>
             <artifactId>slf4j-api</artifactId>
             <version>1.7.30</version>
        </dependency>
        <dependency>
               <groupId>org.hibernate</groupId>
               <artifactId>hibernate-core</artifactId>
               <version>5.4.11.Final</version>
        </dependency>   
         <dependency>
            <groupId>postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>9.1-901-1.jdbc4</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>    
            <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
                <optimize>true</optimize>
                <debug>true</debug>
                <encoding>${project.build.sourceEncoding}</encoding>
            </configuration>
            </plugin>      
            <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-assembly-plugin</artifactId>
              <configuration>
                  <descriptorRefs>
                      <descriptorRef>jar-with-dependencies</descriptorRef>
                  </descriptorRefs>
                  <dependencySets>
                      <dependencySet>
                          <includes>
                              <include>*:jar:*</include>
                          </includes>
                          <excludes>
                              <exclude>*:sources</exclude>
                              <exclude>*:javadoc</exclude>
                          </excludes>
                      </dependencySet>
                  </dependencySets>
                 <archive>
                   <manifest>
                     <addClasspath>true</addClasspath>
                     <mainClass>com.test.jpa.App</mainClass>
                   </manifest>
                 </archive>
               </configuration>
                 <executions>
                     <execution>
                         <id>make-assembly</id>
                         <phase>package</phase>
                         <goals>
                             <goal>single</goal>
                         </goals>
                     </execution>
                 </executions>
            </plugin>        
        </plugins>
   </build>
</project>

当它被执行时，不会抛出空指针异常。它像follow一样打印，然后传递到successive execution

844 [main] DEBUG org.hibernate.boot.internal.BootstrapContextImpl  - Injecting ScanEnvironment [org.hibernate.jpa.boot.internal.StandardJpaScanEnvironmentImpl@45312be2] into BootstrapContext; was [null]
844 [main] DEBUG org.hibernate.boot.internal.BootstrapContextImpl  - Injecting ScanOptions [org.hibernate.boot.archive.scan.internal.StandardScanOptions@7fb95505] into BootstrapContext; was [org.hibernate.boot.archive.scan.internal.StandardScanOptions@58be6e8]
903 [main] DEBUG org.hibernate.boot.internal.BootstrapContextImpl  - Injecting JPA temp ClassLoader [null] into BootstrapContext; was [null]
903 [main] DEBUG org.hibernate.boot.internal.ClassLoaderAccessImpl  - ClassLoaderAccessImpl#injectTempClassLoader(null) [was null]

但当在命令行中使用包装良好的jar执行时，会抛出exeception

1605 [main] DEBUG org.hibernate.boot.internal.BootstrapContextImpl  - Injecting ScanEnvironment [org.hibernate.jpa.boot.internal.StandardJpaScanEnvironmentImpl@482e36] into BootstrapContext; was [null]
1606 [main] DEBUG org.hibernate.boot.internal.BootstrapContextImpl  - Injecting ScanOptions [org.hibernate.boot.archive.scan.internal.StandardScanOptions@967906] into BootstrapContext; was [org.hibernate.boot.archive.scan.internal.StandardScanOptions@18dfcc1]
Exception in thread "main" java.lang.NullPointerException

---

谢谢

构建期间的打包问题

你的配置看起来不错。可能是包装问题。尝试使用以下命令构建并运行您的项目，它将正常工作：

mvn clean compile assembly:single
java -jar target/jpa-0.0.1-SNAPSHOT-jar-with-dependencies.jar

看看这个答案，了解更多关于如何创建具有依赖项的jar的信息。

为了正确起见，请提供更多详细信息：

hibernate:hibernate核心是要使用的正确依赖项。 hibernate:hibernate entitymanager不推荐使用，实际上只指向hibernate核心

jar内的引用：

Hibernate的JPA支持已经合并到Hibernate核心中 模块，使此hibernate entitymanager模块过时。这 模块将在Hibernate ORM 6.0中删除。它只在这里保存了一段时间 不同的使用者期望在一个数据库中有一组静态的工件名称 Hibernate版本的数量。看见

---

我解决了这个问题。这是依赖性问题。在pom文件中，我添加了以下内容

   <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.4.12.Final</version>
        </dependency>

org.hibernate
休眠实体管理器
5.4.12.最终版本

并删除了以下依赖项

<dependency>
               <groupId>org.hibernate</groupId>
               <artifactId>hibernate-core</artifactId>
               <version>5.4.11.Final</version>
        </dependency>   

org.hibernate
冬眠核心
5.4.11.最终版本

---

hibernate entitymanager将添加所有必要的依赖项。

我看不出JPA配置中有任何错误。看起来问题出在你的包装上。你是如何运行这段代码的？@LeonardoCruz谢谢，使用maven汇编插件打包，并在命令行java-jar-jarname中运行。jar@LeonardoCruz文件名为persistence.xml。不是persistent.xml。我更新了问题内容还可以，只是我输入了问题。嗨，谢谢，但是，pom文件已经如你所建议的那样了。你是否也像建议的那样生成jar并运行？是的，兄弟，我修复了依赖关系。clean安装也和你们建议的一样谢谢你们的回答，但，我只使用了hibernate内核，它给了我空指针异常。我不知道为什么。hibernate entitymanager只解决了我的问题。应该在hibernate core中添加任何其他依赖项吗？我不这么认为，只有hibernate core是必需的，所有其他依赖项都是可传递加载的。您可以使用mvn依赖项来检查这一点：treeHi jagadeesh，它现在工作很好，但我认为它不是解决方案。请看一下我的答案。我添加了更多细节以使其更精确。这是。正如您所发现的，使用hibernate entitymanager 5.4.12.Final修复了这个问题，但只是因为版本冲突；它应该与hibernate core 5.4.12.Final一起工作，避免使用不推荐的hibernate entitymanager。

mvn clean compile assembly:single
java -jar target/jpa-0.0.1-SNAPSHOT-jar-with-dependencies.jar

   <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.4.12.Final</version>
        </dependency>

<dependency>
               <groupId>org.hibernate</groupId>
               <artifactId>hibernate-core</artifactId>
               <version>5.4.11.Final</version>
        </dependency>