java - Persistence.createEntityManagerFactory("something") 返回 null
问题描述
我正在通过示例项目学习 JPA。每当我执行程序时，它都会返回 null。我检查了关注
JPA - createEntityManagerFactory 返回 Null，但是，这没有帮助。请帮我。我被困了两天。我不知道我在哪里做错了。
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)
主班
public class App
{
public static void main( String[] args )
{
System.out.println( "I am going to connect" );
BasicConfigurator.configure();
Logger.getLogger("org").setLevel(Level.ALL);
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("boom");
if(entityManagerFactory !=null ) {
System.out.println( "lalala" );
}else {
System.out.println( "nullllllllllllll" );
}
}
}
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>
持久性.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="boom" >
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<class>com.test.jpa.User</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost:6767/User"/>
<property name="javax.persistence.jdbc.user" value="postgres"/>
<property name="javax.persistence.jdbc.password" value="atis"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
<property name="hibernate.show_sql" value="false"/>
<property name="hibernate.format_sql" value="true"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
<property name="hibernate.connection.autocommit" value="false"/>
<property name="hibernate.connection.provider_disables_autocommit" value="true"/>
</properties>
</persistence-unit>
</persistence>
我创建了名为 User 的数据库，表是 "client" ，cloumn 是 "No","age"-integer 数据类型，"name"-string 数据类型
更新：
我使用带有跟随类的junit工具进行了测试。
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class PersonTest {
private EntityManagerFactory emf;
private EntityManager em;
@Before
public void initEmfAndEm() {
BasicConfigurator.configure();
Logger.getLogger("org").setLevel(Level.ALL);
emf = Persistence.createEntityManagerFactory("boom");
if(emf !=null)
System.out.println("wooooooooooooooooooooo ");
em = emf.createEntityManager();
}
@After
public void cleanup() {
em.close();
}
@Test
public void emptyTest() {
}
}
当它被执行时，它不会抛出空指针异常。它像跟随一样打印，然后传递给连续执行。
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]
但是当在命令行中使用打包好的jar执行时，会抛出异常
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
解决方案
我解决了问题。这是依赖问题。在 pom 文件中，在我添加以下内容后
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>5.4.12.Final</version>
</dependency>
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>
hibernate-entitymanager 将添加所有必要的依赖项。
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