不带注释的JPA ORM映射是否可行？

在c#（dotnetcore）中，我可以定义一个assembly/csproj

仅包含POCO（又名POJO）类

没有对任何其他库的引用

Poco对象上没有ORM属性（也称为注释）

然后在另一个assembly/csproj中，我可以“流利地”定义poco和ORM之间的映射。（例如实体框架或NHibernate）

例如：（实体框架核心）

都在同一个模块中（我正在使用gradle，仅供参考），aka，都在同一个.jar中

java（8或11或其他）中是否有将POCO与ORM分开的方法

像这样的pojo：

package com.mycompany.pojosandjpaannotationsmixed;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import java.time.OffsetDateTime;

@Entity
@Table(name = "SomeEntityTable")
public class SomeEntity {

    @Id
    @Column(name = "SomeEntityKey", unique = true)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long someEntityKey;

    @Column(name = "SomeEntityName", unique = true)
    private String someEntityName;

    @Column(name = "CreateOffsetDateTime", columnDefinition = "TIMESTAMP WITH TIME ZONE" )
    private OffsetDateTime createOffsetDateTime;

    public long getSomeEntityKey() {
        return someEntityKey;
    }

    public void setSomeEntityKey(long someEntityKey) {
        this.someEntityKey = someEntityKey;
    }

    public String getSomeEntityName() {
        return someEntityName;
    }

    public void setSomeEntityName(String someEntityName) {
        this.someEntityName = someEntityName;
    }

    public OffsetDateTime getCreateOffsetDateTime() {
        return createOffsetDateTime;
    }

    public void setCreateOffsetDateTime(OffsetDateTime createOffsetDateTime) {
        this.createOffsetDateTime = createOffsetDateTime;
    }
}

public class SomeEntity {

    private long someEntityKey;

    private String someEntityName;

    private OffsetDateTime createOffsetDateTime;


    public long getSomeEntityKey() {
        return someEntityKey;
    }

    public void setSomeEntityKey(long someEntityKey) {
        this.someEntityKey = someEntityKey;
    }

    public String getSomeEntityName() {
        return someEntityName;
    }

    public void setSomeEntityName(String someEntityName) {
        this.someEntityName = someEntityName;
    }

    public OffsetDateTime getCreateOffsetDateTime() {
        return createOffsetDateTime;
    }

    public void setCreateOffsetDateTime(OffsetDateTime createOffsetDateTime) {
        this.createOffsetDateTime = createOffsetDateTime;
    }

}

还有其他地方的ORM映射代码？（在另一个模块/.jar中）

我发现：

---

但同样，POJO似乎充满了注释。

是的。JPA规范规定：

对象/关系映射信息可以采用以下形式： 中包含的托管持久性类的注释 持久化单元，META-INF目录中包含的orm.xml文件 在持久化单元的根目录中，位于 类路径，并从持久性中引用。xml文件，或 这些因素的组合

注释只是一种选择。所有映射信息都可以在xml文件中定义，或者两者的组合。在后一种情况下，xml文件上的映射信息将覆盖注释

例如，这可能是一个

META-INF/orm.xml

文件：

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings xmlns="http://xmlns.jcp.org/xml/ns/persistence/orm"
                 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence/orm 
                 http://xmlns.jcp.org/xml/ns/persistence/orm_2_2.xsd"
                 version="2.2">
    <entity class="com.mycompany.pojosandjpaannotationsmixed.SomeEntity">
        <table name="SomeEntityTable" />
        <attributes>
            <id name="someEntityKey">
                <column name="SomeEntityKey" unique="true" />
                <generated-value strategy="AUTO" />
            </id>
            <basic name="someEntityName">
                <column name="SomeEntityName" unique="true" />
            </basic>
            <!--
             .... 
             -->
        </attributes>
    </entity>
</entity-mappings>

public class SomeEntity {

    private long someEntityKey;

    private String someEntityName;

    private OffsetDateTime createOffsetDateTime;


    public long getSomeEntityKey() {
        return someEntityKey;
    }

    public void setSomeEntityKey(long someEntityKey) {
        this.someEntityKey = someEntityKey;
    }

    public String getSomeEntityName() {
        return someEntityName;
    }

    public void setSomeEntityName(String someEntityName) {
        this.someEntityName = someEntityName;
    }

    public OffsetDateTime getCreateOffsetDateTime() {
        return createOffsetDateTime;
    }

    public void setCreateOffsetDateTime(OffsetDateTime createOffsetDateTime) {
        this.createOffsetDateTime = createOffsetDateTime;
    }

}

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings xmlns="http://xmlns.jcp.org/xml/ns/persistence/orm"
                 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence/orm 
                 http://xmlns.jcp.org/xml/ns/persistence/orm_2_2.xsd"
                 version="2.2">
    <entity class="com.mycompany.pojosandjpaannotationsmixed.SomeEntity">
        <table name="SomeEntityTable" />
        <attributes>
            <id name="someEntityKey">
                <column name="SomeEntityKey" unique="true" />
                <generated-value strategy="AUTO" />
            </id>
            <basic name="someEntityName">
                <column name="SomeEntityName" unique="true" />
            </basic>
            <!--
             .... 
             -->
        </attributes>
    </entity>
</entity-mappings>