前言
Spring Data MongoDB 项目提供与MongoDB文档数据库的集成,Spring与Hibernate集成时,Spring提供了org.springframework.orm.hibernate3.HibernateTemplate
实现了对数据的CRUD操作, Spring Data MongoDB提供了org.springframework.data.mongodb.core.MongoTemplate
对MongoDB的CRUD的操作,包括对集成的对象映射文件和POJO之间的CRUD的操作。
在使用Spring Data操作MongoDB中:
- 在保存一个实体的时候,如果被@DBRef标识的类只传入Id,保存后返回的结果并没有全部的引用类内容,只有Id。
- 保存实体,不能保存引用实体。
例如:我们有一个实体Person,有一个实体EmailAddress。
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@Document (collection = "test_person" ) public class Person { private String name; @DBRef private EmailAddress emailAddress; ... getter setter 方法 } |
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@Document (collection = "test_email" ) public class EmailAddress { @Id private String id; private String value; ... getter setter 方法 } |
当我们调用保存方法的时候:
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public Person test() { Person person = new Person(); person.setName( "test" ); EmailAddress emailAddress = new EmailAddress(); emailAddress.setId( "5a05108d4dcc5dece03c9e69" ); person.setEmailAddress(emailAddress); testRepository.save(person); return person; } |
上述的代码中,返回的person只有id,没有emailAddress的其他值。
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public Person test() { Person person = new Person(); person.setName( "test" ); EmailAddress emailAddress = new EmailAddress(); emailAddress.setName( "afafa" ); person.setEmailAddress(emailAddress); testRepository.save(person); return person; } |
上述的代码中,emailAddress不能被保存。
解决
生命周期事件
Spring Data MongoDB中存在一些生命周期事件,如:onBeforeConvert, onBeforeSave, onAfterSave, onAfterLoad and onAfterConvert等。我们可以继承AbstractMappingEventListener,然后重写这些方法,即可以实现。
代码
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/** * MongoDB级联控制 * Created by guanzhenxing on 2017/11/9. */ public class CascadeControlMongoEventListener extends AbstractMongoEventListener<Object> { @Autowired private MongoOperations mongoOperations; @Override public void onAfterSave(AfterSaveEvent<Object> event) { super .onAfterSave(event); Object source = event.getSource(); ReflectionUtils.doWithFields(source.getClass(), new CascadeAfterSaveCallback(source, mongoOperations)); } @Override public void onBeforeConvert(BeforeConvertEvent<Object> event) { super .onBeforeConvert(event); Object source = event.getSource(); ReflectionUtils.doWithFields(source.getClass(), new CascadeBeforeConvertCallback(source, mongoOperations)); } } |
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/** * 级联控制的回调 * Created by guanzhenxing on 2017/11/10. */ public class CascadeAfterSaveCallback implements ReflectionUtils.FieldCallback { private Object source; private MongoOperations mongoOperations; public CascadeAfterSaveCallback( final Object source, final MongoOperations mongoOperations) { this .source = source; this .mongoOperations = mongoOperations; } @Override public void doWith( final Field field) throws IllegalArgumentException, IllegalAccessException { ReflectionUtils.makeAccessible(field); if (field.isAnnotationPresent(DBRef. class )) { final Object fieldValue = field.get(source); //获得值 if (fieldValue != null ) { doCascadeLoad(field); } } } /** * 级联查询 * * @param field */ private void doCascadeLoad(Field field) throws IllegalAccessException { Object fieldValue = field.get(source); List<Field> idFields = ReflectionUtil.getAnnotationField(fieldValue, Id. class ); //该方法是为了获得所有的被@Id注解的属性 if (idFields.size() == 1 ) { //只处理一个Id Object idValue = ReflectionUtil.getFieldValue(fieldValue, idFields.get( 0 ).getName()); Object value = mongoOperations.findById(idValue, fieldValue.getClass()); //查询获得值 ReflectionUtil.setFieldValue(source, field.getName(), value); } } } |
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public class CascadeBeforeConvertCallback implements ReflectionUtils.FieldCallback { private Object source; private MongoOperations mongoOperations; public CascadeBeforeConvertCallback(Object source, MongoOperations mongoOperations) { this .source = source; this .mongoOperations = mongoOperations; } @Override public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException { ReflectionUtils.makeAccessible(field); if (field.isAnnotationPresent(DBRef. class )) { final Object fieldValue = field.get(source); //获得值 if (fieldValue != null ) { doCascadeSave(field); } } } /** * 级联保存 * * @param field * @throws IllegalAccessException */ private void doCascadeSave(Field field) throws IllegalAccessException { if (field.isAnnotationPresent(CascadeSave. class )) { //如果有标识@CascadeSave注解 Object fieldValue = field.get(source); List<Field> idFields = ReflectionUtil.getAnnotationField(fieldValue, Id. class ); if (idFields.size() == 1 ) { mongoOperations.save(fieldValue); } } } } |
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@Retention (RetentionPolicy.RUNTIME) @Target (ElementType.FIELD) public @interface CascadeSave { } |
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@Configuration public class MongoConfig { @Bean public CascadeControlMongoEventListener userCascadingMongoEventListener() { return new CascadeControlMongoEventListener(); } } |
以上是核心代码。至此,我们就可以解决上述的问题了。
总结
以上就是这篇文章的全部内容了,希望本文的内容对大家的学习或者工作具有一定的参考学习价值,如果有疑问大家可以留言交流,谢谢大家对服务器之家的支持。
参考:http://www.baeldung.com/cascading-with-dbref-and-lifecycle-events-in-spring-data-mongodb
原文链接:http://webfuse.cn/2017/11/10/Spring%20Data%20MongoDB中的自定义级联