JPA瞬态信息在创建时丢失
我有一个带有瞬变场的实体。当我想创建一个新的对象实例时,我会丢失暂时的信息。下面的示例演示了这个问题。为了便于示例,我们假设barness是一个瞬态场JPA瞬态信息在创建时丢失,jpa,Jpa,我有一个带有瞬变场的实体。当我想创建一个新的对象实例时,我会丢失暂时的信息。下面的示例演示了这个问题。为了便于示例,我们假设barness是一个瞬态场 FooEntity fooEntity = new FooEntity(); fooEntity.setFoobosity(5); fooEntity.setBarness(2); fooEntity = fooEntityManager.merge(fooEntity); System.out.println(fooEntity.getFoob
FooEntity fooEntity = new FooEntity();
fooEntity.setFoobosity(5);
fooEntity.setBarness(2);
fooEntity = fooEntityManager.merge(fooEntity);
System.out.println(fooEntity.getFoobosity()); //5
System.out.println(fooEntity.getBarness()); //0 (or whatever default barness is)
有什么方法可以维护我的临时信息吗?这或多或少是按设计工作的。transient的语义正是如此。从
entityManager.merge(obj)
返回的实体实际上是一个全新的实体,它维护传递到merge中的对象的状态(在本文中,状态是不属于持久对象的任何内容)。详细信息请参见。注意:可能有JPA实现在对象合并后维护瞬态字段(仅仅因为它们返回相同的对象),但是规范不保证这种行为
基本上你可以做两件事:
最后一件事:我发现域类上的临时字段的主要用例是划分派生字段,即可以根据类的持久字段重新计算的字段。加入讨论较晚,但这就是我使用spring AOP和JPA提供的@PreUpdate annotation实现它的方式。(增加详细版本) 用例
package security;
import config.Constants;
import org.springframework.data.domain.AuditorAware;
import org.springframework.stereotype.Component;
/**
* Implementation of AuditorAware based on Spring Security.
*/
@Component
public class SpringSecurityAuditorAware implements AuditorAware<String> {
@Override
public String getCurrentAuditor() {
String userName = SecurityUtils.getCurrentUserLogin();
return userName != null ? userName : Constants.SYSTEM_ACCOUNT;
}
}
package config;
import io.github.jhipster.config.JHipsterConstants;
import io.github.jhipster.config.liquibase.AsyncSpringLiquibase;
import liquibase.integration.spring.SpringLiquibase;
import org.h2.tools.Server;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.liquibase.LiquibaseProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Profile;
import org.springframework.core.env.Environment;
import org.springframework.core.task.TaskExecutor;
import org.springframework.data.jpa.repository.config.EnableJpaAuditing;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import javax.sql.DataSource;
import java.sql.SQLException;
@Configuration
@EnableJpaRepositories("repository")
@EnableJpaAuditing(auditorAwareRef = "springSecurityAuditorAware")
@EnableTransactionManagement
public class DatabaseConfiguration {
private final Logger log = LoggerFactory.getLogger(DatabaseConfiguration.class);
private final Environment env;
public DatabaseConfiguration(Environment env) {
this.env = env;
}
/* Other code */
}
用于注入用户名的SpringSecurityAuditorAware
package security;
import config.Constants;
import org.springframework.data.domain.AuditorAware;
import org.springframework.stereotype.Component;
/**
* Implementation of AuditorAware based on Spring Security.
*/
@Component
public class SpringSecurityAuditorAware implements AuditorAware<String> {
@Override
public String getCurrentAuditor() {
String userName = SecurityUtils.getCurrentUserLogin();
return userName != null ? userName : Constants.SYSTEM_ACCOUNT;
}
}
合并数据以在合并后保留的方面这将截取对象(实体)并重置字段
package aop.security.audit;
import domain.AbstractAuditingEntity;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import java.time.Instant;
@Aspect
@Component
public class ExternalDataInflowAudit {
private final Logger log = LoggerFactory.getLogger(ExternalDataInflowAudit.class);
// As per our requirements, we need to override @LastModifiedBy and @LastModifiedDate
// https://stackoverflow.com/questions/2581665/jpa-transient-information-lost-on-create?answertab=active#tab-top
@Around("execution(public !void javax.persistence.EntityManager.merge(..))")
private Object resetAuditFromExternal(ProceedingJoinPoint joinPoint) throws Throwable {
Object[] args = joinPoint.getArgs();
AbstractAuditingEntity abstractAuditingEntity;
Instant lastModifiedDate = null;
String lastModifiedBy = null;
if (args.length > 0 && args[0] instanceof AbstractAuditingEntity) {
abstractAuditingEntity = (AbstractAuditingEntity) args[0];
lastModifiedBy = abstractAuditingEntity.getBackendAuditor();
lastModifiedDate = abstractAuditingEntity.getBackendModifiedDate();
}
Object proceed = joinPoint.proceed();
if (proceed instanceof AbstractAuditingEntity) {
abstractAuditingEntity = (AbstractAuditingEntity) proceed;
if (null != lastModifiedBy) {
abstractAuditingEntity.setLastModifiedBy(lastModifiedBy);
abstractAuditingEntity.setBackendAuditor(lastModifiedBy);
log.debug("Setting the Modified auditor from [{}] to [{}] for Entity [{}]",
abstractAuditingEntity.getLastModifiedBy(), lastModifiedBy, abstractAuditingEntity);
}
if (null != lastModifiedDate) {
abstractAuditingEntity.setLastModifiedDate(lastModifiedDate);
abstractAuditingEntity.setBackendModifiedDate(lastModifiedDate);
log.debug("Setting the Modified date from [{}] to [{}] for Entity [{}]",
abstractAuditingEntity.getLastModifiedDate(), lastModifiedDate, abstractAuditingEntity);
}
}
return proceed;
}
}
用法如果实体设置了backendAuditor和/或backendModifiedDate,则将使用此值,否则将采用Spring Audit提供的值 最后,由于它简化了很多事情,因此您可以专注于业务逻辑 免责声明:我只是Jhipster的粉丝,与它没有任何关系。基于惊人的发现,我创建了一个更通用的代码: 我需要在实体上允许一些临时字段(我指的是我们不保留在数据库中的字段,但我们允许用户使用我们发送到服务器[使用/]并上传到文件存储的数据填充这些字段) 这些字段将使用以下注释进行注释(.RUNTIME在此处使用,因此我可以在运行时对这些字段使用反射): 然后,我使用apache遍历这些字段:
如果有必要,Hibernate和MySQL是底层技术。感谢您的确认。我们已经将字段移到了object之外。
@Retention(RetentionPolicy.RUNTIME)
public @interface PreservePostMerge { }
@Aspect
@Component
public class PreservePostMergeData {
private final Logger log = LoggerFactory.getLogger(PreservePostMergeData.class);
@Around("execution(public !void javax.persistence.EntityManager.merge(..))")
private Object preserveTransientDataPostMerge(ProceedingJoinPoint joinPoint) throws Throwable {
Object[] args = joinPoint.getArgs();
Object afterMerge = joinPoint.proceed();
if (args.length > 0) {
Object beforeMerge = args[0];
Field[] annotatedFieldsToPreserve = FieldUtils.getFieldsWithAnnotation(beforeMerge.getClass(), PreservePostMerge.class);
Arrays.stream(annotatedFieldsToPreserve).forEach(field -> {
try {
FieldUtils.writeField(field, afterMerge, FieldUtils.readField(field, beforeMerge, true), true);
} catch (IllegalAccessException exception) {
log.warn("Illegal accesss to field: {}, of entity: {}. Data was not preserved.", field.getName(), beforeMerge.getClass());
}
});
}
return afterMerge;
}
}