嵌套异常是java.lang.StackOverflowError

问题描述

我有一堂课

@Entity
@Table(name = "movies")
@Data
public class MovieEntity implements Serializable {
    ...

    @OneToMany(mappedBy = "movie", cascade = CascadeType.ALL)
    private Set<MovieRate> ratings;
}

可映射列表

@Entity
@Table(name = "movies_ratings")
@Data
public class MovieRate {
    ...
}

加载 movie.getRatings（）列表将我拒之门外

    ...
at org.eclipse.persistence.indirection.IndirectSet.buildDelegate(IndirectSet.java:225) ~[org.eclipse.persistence.core-2.7.0.jar:na]
    at org.eclipse.persistence.indirection.IndirectSet.getDelegate(IndirectSet.java:436) ~[org.eclipse.persistence.core-2.7.0.jar:na]
    at org.eclipse.persistence.indirection.IndirectSet.hashCode(IndirectSet.java:485) ~[org.eclipse.persistence.core-2.7.0.jar:na]
    at com.core.jpa.entity.MovieEntity.hashCode(MovieEntity.java:21) ~[classes/:na]
    at com.core.jpa.entity.movie.MovieRate.hashCode(MovieRate.java:16) ~[classes/:na]
    at java.util.HashMap.hash(HashMap.java:338) ~[na:1.8.0_144]
    at java.util.HashMap.put(HashMap.java:611) ~[na:1.8.0_144]
    at java.util.HashSet.add(HashSet.java:219) ~[na:1.8.0_144]
    at org.eclipse.persistence.queries.ReadAllQuery.registerResultInUnitOfWork(ReadAllQuery.java:968) ~[org.eclipse.persistence.core-2.7.0.jar:na]
...

所有错误

问题可能出在Lombok注释上。但是我不知道是什么。

The problem is probably with the Lombok annotations. But I do not know what.

推荐答案

显然，该异常是由 MovieRate.hashcode（ ）和 MovieEntity.hascode（）由，要解决您的问题，您可以在 MovieRate 或<$ c中添加 @EqualsAndHashCode $ c> MovieEntity 或两者都：

Apparently, the exception is caused by both MovieRate.hashcode() and MovieEntity.hascode() which is generated by Lombok, to solve your issue you may add @EqualsAndHashCode in MovieRate or in MovieEntity or both :

@Entity
@Table(name = "movies")
@Data @EqualsAndHashCode(exclude = "ratings")
public class MovieEntity implements Serializable {
    // Your code
}

或

@Entity
@Table(name = "movies_ratings")
@Data @EqualsAndHashCode(exclude = "movie")
public class MovieRate {
    ...
}

为什么？ （因为它使用）生成 hashCode（）：

Why? @Data (as it use @EqualsAndHashCode) in order to generate hashCode():

也使用 MovieEntity.ratings 和 MovieRate.movi​​e ，并且每次调用 hashCode（）一侧的方法将调用另一侧的 hashCode（），并且由于它是双向关联，它将无限运行直到 java.lang.StackOverflowError 。

So it will use MovieEntity.ratings and MovieRate.movie as well, and each call of hashCode() method of the one side will call the other side's hashCode(), and as it's bidirectional association, it will run infinitely till java.lang.StackOverflowError.

注意： toString（）（也由 @Data 生成）方法，这两个实体都将尝试打印另一面。要解决此问题，您可以添加以排除相同的字段。

Note: You will have the same error for toString() (which also generated by @Data) method for both entities, as each one will attempt to print the other side. To solve it, you can add @ToString to exclude the same fields.

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