核心类是 MongoTemplate，下面这张 UML 类图涉及了主要的类，省略了次要的类。
涉及的类： MongoTemplate,
MongoOperations,
MongoDbFactory,
SimpleMongoDbFactory,
Mongo,
MongoClient,
MongoCredential,
ServerAddress。
二、源码分析
（1） MongoTemplate
MongoTemplate 是 Spring-MongoDB 整合的核心类，它实现了 MongoOperations 接口（该接口定义了 CRUD 操作）。
MongoTemplate 有个核心的构造方法（其他重载的构造方法最终都会调用这个构造方法）：
/** * Constructor used for a basic template configuration. * * @param mongoDbFactory must not be {@literal null}. * @param mongoConverter */ public MongoTemplate(MongoDbFactory mongoDbFactory, MongoConverter mongoConverter) { Assert.notNull(mongoDbFactory); this.mongoDbFactory = mongoDbFactory; this.exceptionTranslator = mongoDbFactory.getExceptionTranslator(); this.mongoConverter = mongoConverter == null ? getDefaultMongoConverter(mongoDbFactory) : mongoConverter; this.queryMapper = new QueryMapper(this.mongoConverter); this.updateMapper = new UpdateMapper(this.mongoConverter); // We always have a mapping context in the converter, whether it's a simple one or not mappingContext = this.mongoConverter.getMappingContext(); // We create indexes based on mapping events if (null != mappingContext && mappingContext instanceof MongoMappingContext) { indexCreator = new MongoPersistentEntityIndexCreator((MongoMappingContext) mappingContext, mongoDbFactory); eventPublisher = new MongoMappingEventPublisher(indexCreator); if (mappingContext instanceof ApplicationEventPublisherAware) { ((ApplicationEventPublisherAware) mappingContext).setApplicationEventPublisher(eventPublisher); } } }