Mybatis源碼分析[05.Configuration]

Mybatis的配置類

public class Configuration {

  //環境
  protected Environment environment;

  //---------<settings>節點-------
  protected boolean safeRowBoundsEnabled = false;
  protected boolean safeResultHandlerEnabled = true;
  protected boolean mapUnderscoreToCamelCase = false;
  protected boolean aggressiveLazyLoading = true;
  protected boolean multipleResultSetsEnabled = true;
  protected boolean useGeneratedKeys = false;
  protected boolean useColumnLabel = true;

  //默認啟用緩存
  protected boolean cacheEnabled = true;
  protected boolean callSettersOnNulls = false;

  protected String logPrefix;
  protected Class <? extends Log> logImpl;
  protected LocalCacheScope localCacheScope = LocalCacheScope.SESSION;
  protected JdbcType jdbcTypeForNull = JdbcType.OTHER;
  protected Set<String> lazyLoadTriggerMethods = new HashSet<String>(Arrays.asList(new String[] { "equals", "clone", "hashCode", "toString" }));
  protected Integer defaultStatementTimeout;

  //默認為簡單執行器
  protected ExecutorType defaultExecutorType = ExecutorType.SIMPLE;
  protected AutoMappingBehavior autoMappingBehavior = AutoMappingBehavior.PARTIAL;
  //---------<settings>節點-------

  protected Properties variables = new Properties();

  //對象工廠和對象包裝器工廠
  protected ObjectFactory objectFactory = new DefaultObjectFactory();
  protected ObjectWrapperFactory objectWrapperFactory = new DefaultObjectWrapperFactory();

  //映射注冊機
  protected MapperRegistry mapperRegistry = new MapperRegistry(this);

  //默認禁用延遲加載
  protected boolean lazyLoadingEnabled = false;
  protected ProxyFactory proxyFactory = new JavassistProxyFactory(); // #224 Using internal Javassist instead of OGNL

  protected String databaseId;
  /**
   * Configuration factory class.
   * Used to create Configuration for loading deserialized unread properties.
   *
   * @see <a >Issue 300</a> (google code)
   */
  protected Class<?> configurationFactory;

  protected final InterceptorChain interceptorChain = new InterceptorChain();

  //類型處理器注冊機
  protected final TypeHandlerRegistry typeHandlerRegistry = new TypeHandlerRegistry();

  //類型別名注冊機
  protected final TypeAliasRegistry typeAliasRegistry = new TypeAliasRegistry();
  protected final LanguageDriverRegistry languageRegistry = new LanguageDriverRegistry();

  //映射的語句,存在Map里
  protected final Map<String, MappedStatement> mappedStatements = new StrictMap<MappedStatement>("Mapped Statements collection");

  //緩存,存在Map里
  protected final Map<String, Cache> caches = new StrictMap<Cache>("Caches collection");

  //結果映射,存在Map里
  protected final Map<String, ResultMap> resultMaps = new StrictMap<ResultMap>("Result Maps collection");
  protected final Map<String, ParameterMap> parameterMaps = new StrictMap<ParameterMap>("Parameter Maps collection");
  protected final Map<String, KeyGenerator> keyGenerators = new StrictMap<KeyGenerator>("Key Generators collection");

  protected final Set<String> loadedResources = new HashSet<String>();
  protected final Map<String, XNode> sqlFragments = new StrictMap<XNode>("XML fragments parsed from previous mappers");

  //不完整的SQL語句
  protected final Collection<XMLStatementBuilder> incompleteStatements = new LinkedList<XMLStatementBuilder>();
  protected final Collection<CacheRefResolver> incompleteCacheRefs = new LinkedList<CacheRefResolver>();
  protected final Collection<ResultMapResolver> incompleteResultMaps = new LinkedList<ResultMapResolver>();
  protected final Collection<MethodResolver> incompleteMethods = new LinkedList<MethodResolver>();

  /*
   * A map holds cache-ref relationship. The key is the namespace that
   * references a cache bound to another namespace and the value is the
   * namespace which the actual cache is bound to.
   */
  protected final Map<String, String> cacheRefMap = new HashMap<String, String>();

  public Configuration(Environment environment) {
    this();
    this.environment = environment;
  }

  public Configuration() {
    //注冊更多的類型別名
    typeAliasRegistry.registerAlias("JDBC", JdbcTransactionFactory.class);
    typeAliasRegistry.registerAlias("MANAGED", ManagedTransactionFactory.class);

    typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);
    typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);
    typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);

    typeAliasRegistry.registerAlias("PERPETUAL", PerpetualCache.class);
    typeAliasRegistry.registerAlias("FIFO", FifoCache.class);
    typeAliasRegistry.registerAlias("LRU", LruCache.class);
    typeAliasRegistry.registerAlias("SOFT", SoftCache.class);
    typeAliasRegistry.registerAlias("WEAK", WeakCache.class);

    typeAliasRegistry.registerAlias("DB_VENDOR", VendorDatabaseIdProvider.class);

    typeAliasRegistry.registerAlias("XML", XMLLanguageDriver.class);
    typeAliasRegistry.registerAlias("RAW", RawLanguageDriver.class);

    typeAliasRegistry.registerAlias("SLF4J", Slf4jImpl.class);
    typeAliasRegistry.registerAlias("COMMONS_LOGGING", JakartaCommonsLoggingImpl.class);
    typeAliasRegistry.registerAlias("LOG4J", Log4jImpl.class);
    typeAliasRegistry.registerAlias("LOG4J2", Log4j2Impl.class);
    typeAliasRegistry.registerAlias("JDK_LOGGING", Jdk14LoggingImpl.class);
    typeAliasRegistry.registerAlias("STDOUT_LOGGING", StdOutImpl.class);
    typeAliasRegistry.registerAlias("NO_LOGGING", NoLoggingImpl.class);

    typeAliasRegistry.registerAlias("CGLIB", CglibProxyFactory.class);
    typeAliasRegistry.registerAlias("JAVASSIST", JavassistProxyFactory.class);

    languageRegistry.setDefaultDriverClass(XMLLanguageDriver.class);
    languageRegistry.register(RawLanguageDriver.class);
  }
}

Configuration類具有產生執行器的功能

  //產生執行器
  public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
    executorType = executorType == null ? defaultExecutorType : executorType;
    executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
    Executor executor;

    //然后就是簡單的3個分支，產生3種執行器BatchExecutor/ReuseExecutor/SimpleExecutor
    if (ExecutorType.BATCH == executorType) {
      executor = new BatchExecutor(this, transaction);
    } else if (ExecutorType.REUSE == executorType) {
      executor = new ReuseExecutor(this, transaction);
    } else {
      executor = new SimpleExecutor(this, transaction);
    }

    //如果要求緩存，生成另一種CachingExecutor(默認就是有緩存),裝飾者模式,所以默認都是返回CachingExecutor
    if (cacheEnabled) {
      executor = new CachingExecutor(executor);
    }
    //此處調用插件,通過插件可以改變Executor行為
    executor = (Executor) interceptorChain.pluginAll(executor);
    return executor;
  }