Question

我是jpa和hibernate的新手，我花了一段时间来设置xml文件（可能不是完整的），降低错误，并尝试全部解决。我使用mariadb并拥有一个名为jpadb的数据库，我试图创建并传递一个＆＃34; Employee＆＃34;来自java的对象。我收到了错误

：org.hibernate.PersistentObjectException：传递给的分离实体坚持：model.Employee

我的代码如下：

的persistence.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="sample" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

        <class>model.Employee</class>


        <properties>


            <property name="javax.persistence.jdbc.driver" value="org.mariadb.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:mariadb://localhost:3306/jpadb" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="root" />


        </properties>

    </persistence-unit>
</persistence>

的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>sqlDemo</groupId>
    <artifactId>demo</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>loader.MainApp</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
    <dependencies>
        <dependency>
            <groupId>org.mariadb.jdbc</groupId>
            <artifactId>mariadb-java-client</artifactId>
            <version>2.2.3</version>
        </dependency>
        <dependency>
            <groupId>javax.persistence</groupId>
            <artifactId>persistence-api</artifactId>
            <version>1.0.2</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.2.17.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-c3p0</artifactId>
            <version>5.2.17.Final</version>
        </dependency>
    </dependencies>



</project>

Employee.java

package model;
import javax.persistence.*;

@Entity
@Table (name="user")
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private int eid;

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

    @Column(name = "salary")
    private double salary;

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

    public Employee(int eid, String ename, double salary, String deg) {
        super( );
        this.eid = eid;
        this.ename = ename;
        this.salary = salary;
        this.deg = deg;
    }

    public Employee( ) {
        super();
    }

    public int getEid( ) {
        return eid;
    }

    public void setEid(int eid) {
        this.eid = eid;
    }

    public String getEname( ) {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public double getSalary( ) {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public String getDeg( ) {
        return deg;
    }

    public void setDeg(String deg) {
        this.deg = deg;
    }

    @Override
    public String toString() {
        return "Employee [eid=" + eid + ", ename=" + ename + ", salary=" + salary + ", deg=" + deg + "]";
    }
}

CreateEmployee.java

package service;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import model.Employee;

public class CreateEmployee {

    public static void main( String[ ] args ) {

        EntityManagerFactory emfactory = Persistence.createEntityManagerFactory( "sample" );

        EntityManager entitymanager = emfactory.createEntityManager( );
        entitymanager.getTransaction( ).begin( );

        Employee employee = new Employee( );
        employee.setEid( 1201 );
        employee.setEname( "Maria" );
        employee.setSalary( 40000 );
        employee.setDeg( "Technical Manager" );

        entitymanager.persist( employee );
        entitymanager.getTransaction( ).commit( );

        entitymanager.close( );
        emfactory.close( );
    }
}

我试图通过教程，但由于hibernate-property版本不匹配，我很难过。我花了一段时间才找到mariadb的属性才能使它工作。提前谢谢。

Answer 1

您的ID是自动生成的，您在插入新行时不必通过它。删除行employee.setEid( 1201 );，它应该这样做。您应该看看实体生命周期。 https://www.javabullets.com/jpa-entity-lifecycle/

Answer 2

设置 @GeneratedValue（strategy = GenerationType.IDENTITY）并删除 employee.setEid（1201）;

行

无法将对象传递给数据库;传递给持久化的分离实体

2 个答案: