Question

我是JPA的新手，我创建了一个类似下面的类

/**
 * 
 */
package programme;

import javax.persistence.Access;
import javax.persistence.AccessType;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Transient;

/**
 * @author anoop
 *
 */
@Entity
@Table(name="course")
@Access(AccessType.FIELD)
public class programme {
    @Id private int id;
    private String name;
    private int year;
    @Transient private String comments;

    //getters and setters for the fields.
}

我注意到另一个名为class的实体java类Programme.java，带有下划线，即Programme_.java。什么是这个类，为什么会这样生成。有什么方法可以阻止它的产生吗？

Programme_.java类的代码如下。

package programme;

import javax.annotation.Generated;
import javax.persistence.metamodel.SingularAttribute;
import javax.persistence.metamodel.StaticMetamodel;

@Generated(value="Dali", date="2014-04-27T21:32:59.433+0530")
@StaticMetamodel(programme.class)
public class programme_ {
    public static volatile SingularAttribute<programme, Integer> id;
    public static volatile SingularAttribute<programme, String> name;
    public static volatile SingularAttribute<programme, Integer> year;
    public static volatile SingularAttribute<programme, String> comments;
}

Answer 1

这是你的“Canonical Metamodel”。它可以与JPA 2.x规范（第6.2节）中描述的JPA Criteria API一起使用。

阻止Eclipse生成这些类：编辑Eclipse项目属性＆gt; JPA＆gt; Canonical metamodel（JPA 2.0）＆gt;源文件夹 - 将文件夹的值设置为“”。

Answer 2

这是我对persistence.xml进行的更改prevent Java文件和使用下划线生成的类文件（导致我a problem）：

diff --git a/examples/javaee7/src/main/resources/META-INF/persistence.xml b/examples/javaee7/src/main/resources/META-INF/persistence.xml index 86d3c0c..a477432 100644 --- a/examples/javaee7/src/main/resources/META-INF/persistence.xml +++ b/examples/javaee7/src/main/resources/META-INF/persistence.xml @@ -1,9 +1,9 @@ <?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="javaee7addressbookPersistenceUnit" transaction-type="JTA"> - <exclude-unlisted-classes>false</exclude-unlisted-classes> + <exclude-unlisted-classes>true</exclude-unlisted-classes> <properties> <property name="javax.persistence.schema-generation.database.action" value="create"/> </properties> </persistence-unit> </persistence>

在此更改之前，正在生成以下文件：

目标/生成来源/注解/ COM / greptilian / addressbookmvc / javaee7 / Person_.java
目标/类/ COM / greptilian / addressbookmvc / javaee7 / Person_.class

为什么有一个具有实体名称的类加上JPA实体类的下划线

2 个答案: