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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。
@Document(collection = "test_person")public class Person { private String name; @DBRef private EmailAddress emailAddress; ... getter setter 方法}
@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:
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。
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
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)); }}
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); } } } 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); } }}
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); } } } 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); } } }}
@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.FIELD)public @interface CascadeSave {}
@Configurationpublic class MongoConfig { @Bean public CascadeControlMongoEventListener userCascadingMongoEventListener() { return new CascadeControlMongoEventListener(); }}
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