Question

当我获取一个类似于另一个实体的“父”实体时，我有一个奇怪的行为。这些是我的实体类：

父实体（“一侧”）

package so.lazy;

import java.util.LinkedHashSet;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.OneToMany;

@Entity
public class Parent extends Base {

    private static final long serialVersionUID = -1111542804002616234L;

    @OneToMany(mappedBy = "one")
    private Set<Child> children = new LinkedHashSet<Child>();

    // more fields

    public Set<Child> getChildren() {
        return children;
    }

    public void setChildren(Set<Child> children) {
        this.children = children;
    }

    @Override
    public String toString() {
        return "Parent{" +
                "dataId=" + getDataId() +
                '}';
    }
    // more getters and setters
}

子实体（“多面”）

package so.lazy;

import javax.persistence.*;

@Entity
public class Child extends Base {

    private static final long serialVersionUID = -8798542804002616234L;

    @ManyToOne(fetch = FetchType.LAZY)
    private Parent parent;

    // more fields

    public Parent getParent() {
        return parent;
    }

    public void setParent(Parent parent) {
        this.parent = parent;
    }
    // more getters and setters
}

抽象基类

package so.lazy;

import java.io.Serializable;
import java.util.UUID;
import javax.persistence.*;

import org.hibernate.annotations.Type;

@MappedSuperclass
public abstract class Base implements Serializable {
    @Id
    @Column(name = "data_id")
    @Type(type = "pg-uuid")
    private java.util.UUID dataId;

    public Base() {
        dataId = UUID.randomUUID();  // production: com.fasterxml.uuid.generators UUID Type 1
    }

    public UUID getDataId() {
        return dataId;
    }

    public void setDataId(UUID dataId) {
        this.dataId = dataId;
    }
}

使用此代码时：

Child child=childrepository.findOne(uuid);
Parent parent=child.getParent();

System.out.println("Parent: " + parent.toString());        // Output A
System.out.println("ID in parent: " + parent.getDataId);   // Output B

输出为输出A和B中的父级包含两个完全不同的UUID 。
方法Parent#toString()给出正确的UUID，getter给出错误的UUID。

为什么？

如果我在@ManyToOne(fetch = FetchType.EAGER)中将parent的{{1}}切换到Child，则可以正常工作。

我的依赖项：
春天4.3.8
Spring DataJPA 1.11.0
PostgreSQL 9.4-1202-jdbc42

错误的UUID（主键）是从Spring存储库中以fetchtype LAZY和@ManyToOne

0 个答案: