怎么将属性注入到 JPA entity 中

如何将属性注入到 JPA entity 中

1、定义一个注入的接口

  public interface DependencyInjector {void performInjection(Object existingBean); }

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2、定义一个实现了注入接口 DependencyInjector 及 BeanFactoryAware 的属性注射器 bean

public class AutowireDependencyInjector implements DependencyInjector, BeanFactoryAware{  private AutowireCapableBeanFactory beanFactory;  public void setBeanFactory(BeanFactory beanFactory) {    if (!(beanFactory instanceof AutowireCapableBeanFactory))      throw new IllegalArgumentException("BeanFactory must" + " be an AutowireCapableBeanFactory");    this.beanFactory = (AutowireCapableBeanFactory) beanFactory;  }  //将属性（spring中注册过的）绑定到 bean 上  public void performInjection(Object existingBean) {    beanFactory.autowireBeanProperties(existingBean,      AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE, false);  }}

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3、定义一个监听器，监听 entity 生成后不同的事件类型，然后将属性注入

public class DependencyInjectionEntityListener {  private static DependencyInjector _injector;  public static void setInjector(DependencyInjector injector) {    _injector = injector;  }  //如果需要监听不同的事件，以下方式类推  @PrePersist  @PostLoad  public void performInjection(Object entity) {    if (_injector == null)      throw new IllegalStateException("EntityListener cannot"       + " be used without an injector");    _injector.performInjection(entity);  }}

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4、定义一个监听配置类，将属性注射器注入到监听器中

public class DependencyInjectionEntityListenerConfigurer implements InitializingBean{  private DependencyInjector injector;  public void setInjector(DependencyInjector injector) {    if (injector == null)      throw new NullPointerException("Injector cannot be null");    this.injector = injector;  }  public void afterPropertiesSet() throws Exception {    DependencyInjectionEntityListener.setInjector(injector);  }}

5、entity 类使用

@Entity// 自定义的 listener@EntityListeners(DependencyInjectionEntityListener.class)public class DomainObject {  @Id   private long id;  DomainObject() {  }  public DomainObject(long id) {    this.id = id;  }  public long getId() {    return id;  }    //需要注入的属性  @Transient  private SomeService service;  public void setService(SomeService service) {    this.service = service;  }}

关键点在于 AutowireCapableBeanFactory.autowireBeanProperties(existingBean, AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE, false);, 将spring中的属性注入到 JPA entity， 以及用到了JPA 的? EntityListeners.

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