本文分析的是 spring-data-mongodb-1.9.2.RELEASE.jar 和 mongodb-driver-core-3.2.2.jar。
一、UML Class Diagram
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);
}
}
}
可以看到，这个构造方法至少需要一个参数 mongoDbFactory，MongoTemplate 类中其他字段都可以内部构造出来。
（2）MongoDbFactory
MongoDbFactory 是一个接口，用于新建 DB 实例。
它的实现之一是 SimpleMongoDbFactory。
public interface MongoDbFactory {
/**
* Creates a default {@link DB} instance.
*
* @return
* @throws DataAccessException
*/
DB getDb() throws DataAccessException;
/**
* Creates a {@link DB} instance to access the database with the given name.
*
* @param dbName must not be {@literal null} or empty.
* @return
* @throws DataAccessException
*/
DB getDb(String dbName) throws DataAccessException;
/**
* Exposes a shared {@link MongoExceptionTranslator}.
*
* @return will never be {@literal null}.
*/
PersistenceExceptionTranslator getExceptionTranslator();
}
（3） SimpleMongoDbFactory
SimpleMongoDbFactory 实现了 MongoDbFactory 接口（以下省略了部分代码）：
public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
private final Mongo mongo;
private final String databaseName;
private final boolean mongoInstanceCreated;
private final UserCredentials credentials;
private final PersistenceExceptionTranslator exceptionTranslator;
private final String authenticationDatabaseName;
private WriteConcern writeConcern;
/**
* Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoClientURI}.
*
* @param uri must not be {@literal null}.
* @throws UnknownHostException
* @since 1.7
*/
public SimpleMongoDbFactory(MongoClientURI uri) throws UnknownHostException {
this(new MongoClient(uri), uri.getDatabase(), true);
}
/**
* Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoClient}.
*
* @param mongoClient must not be {@literal null}.
* @param databaseName must not be {@literal null}.
* @since 1.7
*/
public SimpleMongoDbFactory(MongoClient mongoClient, String databaseName) {
this(mongoClient, databaseName, false);
}
private SimpleMongoDbFactory(Mongo mongo, String databaseName, UserCredentials credentials,
boolean mongoInstanceCreated, String authenticationDatabaseName) {
if (mongo instanceof MongoClient && (credentials != null && !UserCredentials.NO_CREDENTIALS.equals(credentials))) {
throw new InvalidDataAccessApiUsageException(
"Usage of 'UserCredentials' with 'MongoClient' is no longer supported. Please use 'MongoCredential' for 'MongoClient' or just 'Mongo'.");
}
Assert.notNull(mongo, "Mongo must not be null");
Assert.hasText(databaseName, "Database name must not be empty");
Assert.isTrue(databaseName.matches("[\\w-]+"),
"Database name must only contain letters, numbers, underscores and dashes!");
this.mongo = mongo;
this.databaseName = databaseName;
this.mongoInstanceCreated = mongoInstanceCreated;
this.credentials = credentials == null ? UserCredentials.NO_CREDENTIALS : credentials;
this.exceptionTranslator = new MongoExceptionTranslator();
this.authenticationDatabaseName = StringUtils.hasText(authenticationDatabaseName) ? authenticationDatabaseName
: databaseName;
Assert.isTrue(this.authenticationDatabaseName.matches("[\\w-]+"),
"Authentication database name must only contain letters, numbers, underscores and dashes!");
}
/**
* @param client
* @param databaseName
* @param mongoInstanceCreated
* @since 1.7
*/
private SimpleMongoDbFactory(MongoClient client, String databaseName, boolean mongoInstanceCreated) {
Assert.notNull(client, "MongoClient must not be null!");
Assert.hasText(databaseName, "Database name must not be empty!");
this.mongo = client;
this.databaseName = databaseName;
this.mongoInstanceCreated = mongoInstanceCreated;
this.exceptionTranslator = new MongoExceptionTranslator();
this.credentials = UserCredentials.NO_CREDENTIALS;
this.authenticationDatabaseName = databaseName;
}
}
核心构造方法：
/**
* @param client
* @param databaseName
* @param mongoInstanceCreated
* @since 1.7
*/
private SimpleMongoDbFactory(MongoClient client, String databaseName, boolean mongoInstanceCreated) { Assert.notNull(client, "MongoClient must not be null!");
Assert.hasText(databaseName, "Database name must not be empty!"); this.mongo = client;
this.databaseName = databaseName;
this.mongoInstanceCreated = mongoInstanceCreated;
this.exceptionTranslator = new MongoExceptionTranslator();
this.credentials = UserCredentials.NO_CREDENTIALS;
this.authenticationDatabaseName = databaseName;
}
第一个参数 MongoClient client（MongoClient）: 包含 host, port, username, password 等信息。
（4）MongoClient 与 Mongo
MongoClient 继承了 Mongo。
/**
* Creates a Mongo instance based on a (single) mongo node using a given ServerAddress and default options.
*
* @param addr the database address
* @param credentialsList the list of credentials used to authenticate all connections
* @param options default options
* @see com.mongodb.ServerAddress
* @since 2.11.0
*/
public MongoClient(final ServerAddress addr, final List<MongoCredential> credentialsList, final MongoClientOptions options) {
super(addr, credentialsList, options);
}
这个核心构造方法接收三个参数：
final ServerAddress addr：可以由 new ServerAddress(host, port) 构造。
final List<MongoCredential> credentialsList： 包含 username, password 等信息。
final MongoClientOptions options： 包含 MongoDB 数据库的配置信息。
（5） MongoCredential
MongoCredential 包含 username, password 等信息。
public final class MongoCredential {
private final AuthenticationMechanism mechanism;
private final String userName;
private final String source;
private final char[] password;
private final Map<String, Object> mechanismProperties;
// Other code
}
三、其他
Spring-MongoDB 整合与 Spring-MyBatis 相似。
Spring-MyBatis 的核心类是 SqlSessionTemplate，作用与 MongoTemplate 一样。