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：
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
/**
* 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));
}
}
/**
* 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);
}
}
}
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);
}
}
}
}
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface CascadeSave {
}
@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。
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，谢谢大家对脚本之家的支持。
参考：http://www.baeldung.com/cascading-with-dbref-and-lifecycle-events-in-spring-data-mongodb
