spring-data-jpa 如何检测某个字段是否变动？

Question

如题，在spring-data-jpa 框架中，是否存在一种较好的实践，能够非常方便的检测某个字段的变动。只需要写一个变化逻辑，而不需要自己写代码检测是否存在变动。有相关类似的功能可以提取出相关抽象也行。

Answer 1

import java.util.Arrays;
import java.util.Date;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;

import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.mapping.PersistentClass;
import org.hibernate.tuple.entity.EntityMetamodel;
import org.hibernate.tuple.entity.PojoEntityTuplizer;
import org.springframework.util.ReflectionUtils;

public class TuplizerImpl extends PojoEntityTuplizer {

    private final ConcurrentHashMap<Integer, Object[]> map = new ConcurrentHashMap<>();
    private final ConcurrentHashMap<Integer, Boolean> bMap = new ConcurrentHashMap<>();

    public TuplizerImpl(EntityMetamodel entityMetamodel, PersistentClass mappedEntity) {
        super(entityMetamodel, mappedEntity);
    }

    @Override
    public void setPropertyValues(Object entity, Object[] values) throws HibernateException {

        if (bMap.containsKey(entity.hashCode()) && map.containsKey(entity.hashCode())) {
            Arrays.stream(entity.getClass().getDeclaredFields())
                    .filter(f -> f.getAnnotation(Record.class) != null)
                    .peek(f -> f.setAccessible(true))
                    .map(s -> this.getEntityMetamodel().getPropertyIndex(s.getName()))
                    .filter(i -> !Objects.equals(map.get(entity.hashCode())[i], values[i]))
                    .map(i -> ReflectionUtils.findField(entity.getClass(),
                            this.getEntityMetamodel().getPropertyNames()[i])).filter(Objects::nonNull)
                    .map(f -> f.getAnnotation(Record.class))
                    .map(Record::field)
                    .map(s -> this.getEntityMetamodel().getPropertyIndex(s))
                    .forEach(i -> values[i] = new Date());
            map.remove(entity.hashCode());
            bMap.remove(entity.hashCode());
        } else {
            map.put(entity.hashCode(), values);
        }
        super.setPropertyValues(entity, values);

    }

    @Override
    public void afterInitialize(Object entity, SharedSessionContractImplementor session) {
        bMap.put(entity.hashCode(), true);
        super.afterInitialize(entity, session);
    }

}

@Entity
@Getter
@Setter
@ToString
@Tuplizer(impl = TuplizerImpl.class)
public class Account {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Record(field = "nameChange")
    private String name;
    
    @Setter(AccessLevel.NONE)
    private Date nameChange;

    @OneToMany( mappedBy = "fromAccount")
    private Set<Transaction> transactions;
}

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Record {
    
    String field() default "";

}