Configuration.java

/*
 *    Copyright 2009-2014 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.session;

import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import org.apache.ibatis.binding.MapperRegistry;
import org.apache.ibatis.builder.CacheRefResolver;
import org.apache.ibatis.builder.ResultMapResolver;
import org.apache.ibatis.builder.annotation.MethodResolver;
import org.apache.ibatis.builder.xml.XMLStatementBuilder;
import org.apache.ibatis.cache.Cache;
import org.apache.ibatis.cache.decorators.FifoCache;
import org.apache.ibatis.cache.decorators.LruCache;
import org.apache.ibatis.cache.decorators.SoftCache;
import org.apache.ibatis.cache.decorators.WeakCache;
import org.apache.ibatis.cache.impl.PerpetualCache;
import org.apache.ibatis.datasource.jndi.JndiDataSourceFactory;
import org.apache.ibatis.datasource.pooled.PooledDataSourceFactory;
import org.apache.ibatis.datasource.unpooled.UnpooledDataSourceFactory;
import org.apache.ibatis.executor.BatchExecutor;
import org.apache.ibatis.executor.CachingExecutor;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.executor.ReuseExecutor;
import org.apache.ibatis.executor.SimpleExecutor;
import org.apache.ibatis.executor.keygen.KeyGenerator;
import org.apache.ibatis.executor.loader.ProxyFactory;
import org.apache.ibatis.executor.loader.cglib.CglibProxyFactory;
import org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory;
import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.resultset.DefaultResultSetHandler;
import org.apache.ibatis.executor.resultset.ResultSetHandler;
import org.apache.ibatis.executor.statement.RoutingStatementHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.logging.commons.JakartaCommonsLoggingImpl;
import org.apache.ibatis.logging.jdk14.Jdk14LoggingImpl;
import org.apache.ibatis.logging.log4j.Log4jImpl;
import org.apache.ibatis.logging.log4j2.Log4j2Impl;
import org.apache.ibatis.logging.nologging.NoLoggingImpl;
import org.apache.ibatis.logging.slf4j.Slf4jImpl;
import org.apache.ibatis.logging.stdout.StdOutImpl;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ParameterMap;
import org.apache.ibatis.mapping.ResultMap;
import org.apache.ibatis.mapping.VendorDatabaseIdProvider;
import org.apache.ibatis.parsing.XNode;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.InterceptorChain;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.factory.DefaultObjectFactory;
import org.apache.ibatis.reflection.factory.ObjectFactory;
import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;
import org.apache.ibatis.scripting.LanguageDriver;
import org.apache.ibatis.scripting.LanguageDriverRegistry;
import org.apache.ibatis.scripting.defaults.RawLanguageDriver;
import org.apache.ibatis.scripting.xmltags.XMLLanguageDriver;
import org.apache.ibatis.transaction.Transaction;
import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;
import org.apache.ibatis.transaction.managed.ManagedTransactionFactory;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.TypeAliasRegistry;
import org.apache.ibatis.type.TypeHandlerRegistry;

/**
 * @author Clinton Begin
 */
/**
 * 配置，里面好多配置项
 * 
 */
public class Configuration {

  //环境
  protected Environment environment;

  //---------以下都是<settings>节点-------
  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;
  //默认启用缓存
  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;
  //默认为简单执行器
  protected ExecutorType defaultExecutorType = ExecutorType.SIMPLE;
  protected AutoMappingBehavior autoMappingBehavior = AutoMappingBehavior.PARTIAL;
  //---------以上都是<settings>节点-------

  protected Properties variables = new Properties();
  //对象工厂和对象包装器工厂
  protected ObjectFactory objectFactory = new DefaultObjectFactory();
  protected ObjectWrapperFactory objectWrapperFactory = new DefaultObjectWrapperFactory();
  //映射注册机
  protected MapperRegistry mapperRegistry = new MapperRegistry(this);

  //默认禁用延迟加载
  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 href='https://code.google.com/p/mybatis/issues/detail?id=300'>Issue 300</a> (google code)
   */
  protected Class<?> configurationFactory;

  protected final InterceptorChain interceptorChain = new InterceptorChain();
  //类型处理器注册机
  protected final TypeHandlerRegistry typeHandlerRegistry = new TypeHandlerRegistry();
  //类型别名注册机
  protected final TypeAliasRegistry typeAliasRegistry = new TypeAliasRegistry();
  protected final LanguageDriverRegistry languageRegistry = new LanguageDriverRegistry();

  //映射的语句,存在Map里
  protected final Map<String, MappedStatement> mappedStatements = new StrictMap<MappedStatement>("Mapped Statements collection");
  //缓存,存在Map里
  protected final Map<String, Cache> caches = new StrictMap<Cache>("Caches collection");
  //结果映射,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语句
  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() {
    //注册更多的类型别名，至于为何不直接在TypeAliasRegistry里注册，还需进一步研究
    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);
  }

  public String getLogPrefix() {
    return logPrefix;
  }

  public void setLogPrefix(String logPrefix) {
    this.logPrefix = logPrefix;
  }

  public Class<? extends Log> getLogImpl() {
    return logImpl;
  }

  @SuppressWarnings("unchecked")
  public void setLogImpl(Class<?> logImpl) {
    if (logImpl != null) {
      this.logImpl = (Class<? extends Log>) logImpl;
      LogFactory.useCustomLogging(this.logImpl);
    }
  }

  public boolean isCallSettersOnNulls() {
    return callSettersOnNulls;
  }

  public void setCallSettersOnNulls(boolean callSettersOnNulls) {
    this.callSettersOnNulls = callSettersOnNulls;
  }

  public String getDatabaseId() {
    return databaseId;
  }

  public void setDatabaseId(String databaseId) {
    this.databaseId = databaseId;
  }

  public Class<?> getConfigurationFactory() {
    return configurationFactory;
  }

  public void setConfigurationFactory(Class<?> configurationFactory) {
    this.configurationFactory = configurationFactory;
  }

  public boolean isSafeResultHandlerEnabled() {
    return safeResultHandlerEnabled;
  }

  public void setSafeResultHandlerEnabled(boolean safeResultHandlerEnabled) {
    this.safeResultHandlerEnabled = safeResultHandlerEnabled;
  }

  public boolean isSafeRowBoundsEnabled() {
    return safeRowBoundsEnabled;
  }

  public void setSafeRowBoundsEnabled(boolean safeRowBoundsEnabled) {
    this.safeRowBoundsEnabled = safeRowBoundsEnabled;
  }

  public boolean isMapUnderscoreToCamelCase() {
    return mapUnderscoreToCamelCase;
  }

  public void setMapUnderscoreToCamelCase(boolean mapUnderscoreToCamelCase) {
    this.mapUnderscoreToCamelCase = mapUnderscoreToCamelCase;
  }

  public void addLoadedResource(String resource) {
    loadedResources.add(resource);
  }

  public boolean isResourceLoaded(String resource) {
    return loadedResources.contains(resource);
  }

  public Environment getEnvironment() {
    return environment;
  }

  public void setEnvironment(Environment environment) {
    this.environment = environment;
  }

  public AutoMappingBehavior getAutoMappingBehavior() {
    return autoMappingBehavior;
  }

  public void setAutoMappingBehavior(AutoMappingBehavior autoMappingBehavior) {
    this.autoMappingBehavior = autoMappingBehavior;
  }

  public boolean isLazyLoadingEnabled() {
    return lazyLoadingEnabled;
  }

  public void setLazyLoadingEnabled(boolean lazyLoadingEnabled) {
    this.lazyLoadingEnabled = lazyLoadingEnabled;
  }

  public ProxyFactory getProxyFactory() {
    return proxyFactory;
  }

  public void setProxyFactory(ProxyFactory proxyFactory) {
    if (proxyFactory == null) {
      proxyFactory = new JavassistProxyFactory();
    }
    this.proxyFactory = proxyFactory;
  }

  public boolean isAggressiveLazyLoading() {
    return aggressiveLazyLoading;
  }

  public void setAggressiveLazyLoading(boolean aggressiveLazyLoading) {
    this.aggressiveLazyLoading = aggressiveLazyLoading;
  }

  public boolean isMultipleResultSetsEnabled() {
    return multipleResultSetsEnabled;
  }

  public void setMultipleResultSetsEnabled(boolean multipleResultSetsEnabled) {
    this.multipleResultSetsEnabled = multipleResultSetsEnabled;
  }

  public Set<String> getLazyLoadTriggerMethods() {
    return lazyLoadTriggerMethods;
  }

  public void setLazyLoadTriggerMethods(Set<String> lazyLoadTriggerMethods) {
    this.lazyLoadTriggerMethods = lazyLoadTriggerMethods;
  }

  public boolean isUseGeneratedKeys() {
    return useGeneratedKeys;
  }

  public void setUseGeneratedKeys(boolean useGeneratedKeys) {
    this.useGeneratedKeys = useGeneratedKeys;
  }

  public ExecutorType getDefaultExecutorType() {
    return defaultExecutorType;
  }

  public void setDefaultExecutorType(ExecutorType defaultExecutorType) {
    this.defaultExecutorType = defaultExecutorType;
  }

  public boolean isCacheEnabled() {
    return cacheEnabled;
  }

  public void setCacheEnabled(boolean cacheEnabled) {
    this.cacheEnabled = cacheEnabled;
  }

  public Integer getDefaultStatementTimeout() {
    return defaultStatementTimeout;
  }

  public void setDefaultStatementTimeout(Integer defaultStatementTimeout) {
    this.defaultStatementTimeout = defaultStatementTimeout;
  }

  public boolean isUseColumnLabel() {
    return useColumnLabel;
  }

  public void setUseColumnLabel(boolean useColumnLabel) {
    this.useColumnLabel = useColumnLabel;
  }

  public LocalCacheScope getLocalCacheScope() {
    return localCacheScope;
  }

  public void setLocalCacheScope(LocalCacheScope localCacheScope) {
    this.localCacheScope = localCacheScope;
  }

  public JdbcType getJdbcTypeForNull() {
    return jdbcTypeForNull;
  }

  public void setJdbcTypeForNull(JdbcType jdbcTypeForNull) {
    this.jdbcTypeForNull = jdbcTypeForNull;
  }

  public Properties getVariables() {
    return variables;
  }

  public void setVariables(Properties variables) {
    this.variables = variables;
  }

  public TypeHandlerRegistry getTypeHandlerRegistry() {
    return typeHandlerRegistry;
  }

  public TypeAliasRegistry getTypeAliasRegistry() {
    return typeAliasRegistry;
  }

  /**
   * @since 3.2.2
   */
  public MapperRegistry getMapperRegistry() {
    return mapperRegistry;
  }

  public ObjectFactory getObjectFactory() {
    return objectFactory;
  }

  public void setObjectFactory(ObjectFactory objectFactory) {
    this.objectFactory = objectFactory;
  }

  public ObjectWrapperFactory getObjectWrapperFactory() {
    return objectWrapperFactory;
  }

  public void setObjectWrapperFactory(ObjectWrapperFactory objectWrapperFactory) {
    this.objectWrapperFactory = objectWrapperFactory;
  }

  /**
   * @since 3.2.2
   */
  public List<Interceptor> getInterceptors() {
    return interceptorChain.getInterceptors();
  }

  public LanguageDriverRegistry getLanguageRegistry() {
    return languageRegistry;
  }

  public void setDefaultScriptingLanguage(Class<?> driver) {
    if (driver == null) {
      driver = XMLLanguageDriver.class;
    }
    getLanguageRegistry().setDefaultDriverClass(driver);
  }

  public LanguageDriver getDefaultScriptingLanuageInstance() {
    return languageRegistry.getDefaultDriver();
  }

  //创建元对象
  public MetaObject newMetaObject(Object object) {
    return MetaObject.forObject(object, objectFactory, objectWrapperFactory);
  }

  //创建参数处理器
  public ParameterHandler newParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
    //创建ParameterHandler
    ParameterHandler parameterHandler = mappedStatement.getLang().createParameterHandler(mappedStatement, parameterObject, boundSql);
    //插件在这里插入
    parameterHandler = (ParameterHandler) interceptorChain.pluginAll(parameterHandler);
    return parameterHandler;
  }

  //创建结果集处理器
  public ResultSetHandler newResultSetHandler(Executor executor, MappedStatement mappedStatement, RowBounds rowBounds, ParameterHandler parameterHandler,
      ResultHandler resultHandler, BoundSql boundSql) {
    //创建DefaultResultSetHandler(稍老一点的版本3.1是创建NestedResultSetHandler或者FastResultSetHandler)
    ResultSetHandler resultSetHandler = new DefaultResultSetHandler(executor, mappedStatement, parameterHandler, resultHandler, boundSql, rowBounds);
    //插件在这里插入
    resultSetHandler = (ResultSetHandler) interceptorChain.pluginAll(resultSetHandler);
    return resultSetHandler;
  }

  //创建语句处理器
  public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
    //创建路由选择语句处理器
    StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
    //插件在这里插入
    statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
    return statementHandler;
  }

  public Executor newExecutor(Transaction transaction) {
    return newExecutor(transaction, defaultExecutorType);
  }

  //产生执行器
  public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
    executorType = executorType == null ? defaultExecutorType : executorType;
    //这句再做一下保护,囧,防止粗心大意的人将defaultExecutorType设成null?
    executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
    Executor executor;
    //然后就是简单的3个分支，产生3种执行器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);
    }
    //如果要求缓存，生成另一种CachingExecutor(默认就是有缓存),装饰者模式,所以默认都是返回CachingExecutor
    if (cacheEnabled) {
      executor = new CachingExecutor(executor);
    }
    //此处调用插件,通过插件可以改变Executor行为
    executor = (Executor) interceptorChain.pluginAll(executor);
    return executor;
  }

  public void addKeyGenerator(String id, KeyGenerator keyGenerator) {
    keyGenerators.put(id, keyGenerator);
  }

  public Collection<String> getKeyGeneratorNames() {
    return keyGenerators.keySet();
  }

  public Collection<KeyGenerator> getKeyGenerators() {
    return keyGenerators.values();
  }

  public KeyGenerator getKeyGenerator(String id) {
    return keyGenerators.get(id);
  }

  public boolean hasKeyGenerator(String id) {
    return keyGenerators.containsKey(id);
  }

  public void addCache(Cache cache) {
    caches.put(cache.getId(), cache);
  }

  public Collection<String> getCacheNames() {
    return caches.keySet();
  }

  public Collection<Cache> getCaches() {
    return caches.values();
  }

  public Cache getCache(String id) {
    return caches.get(id);
  }

  public boolean hasCache(String id) {
    return caches.containsKey(id);
  }

  public void addResultMap(ResultMap rm) {
    resultMaps.put(rm.getId(), rm);
    checkLocallyForDiscriminatedNestedResultMaps(rm);
    checkGloballyForDiscriminatedNestedResultMaps(rm);
  }

  public Collection<String> getResultMapNames() {
    return resultMaps.keySet();
  }

  public Collection<ResultMap> getResultMaps() {
    return resultMaps.values();
  }

  public ResultMap getResultMap(String id) {
    return resultMaps.get(id);
  }

  public boolean hasResultMap(String id) {
    return resultMaps.containsKey(id);
  }

  public void addParameterMap(ParameterMap pm) {
    parameterMaps.put(pm.getId(), pm);
  }

  public Collection<String> getParameterMapNames() {
    return parameterMaps.keySet();
  }

  public Collection<ParameterMap> getParameterMaps() {
    return parameterMaps.values();
  }

  public ParameterMap getParameterMap(String id) {
    return parameterMaps.get(id);
  }

  public boolean hasParameterMap(String id) {
    return parameterMaps.containsKey(id);
  }

  public void addMappedStatement(MappedStatement ms) {
    mappedStatements.put(ms.getId(), ms);
  }

  public Collection<String> getMappedStatementNames() {
    buildAllStatements();
    return mappedStatements.keySet();
  }

  public Collection<MappedStatement> getMappedStatements() {
    buildAllStatements();
    return mappedStatements.values();
  }

  public Collection<XMLStatementBuilder> getIncompleteStatements() {
    return incompleteStatements;
  }

  public void addIncompleteStatement(XMLStatementBuilder incompleteStatement) {
    incompleteStatements.add(incompleteStatement);
  }

  public Collection<CacheRefResolver> getIncompleteCacheRefs() {
    return incompleteCacheRefs;
  }

  public void addIncompleteCacheRef(CacheRefResolver incompleteCacheRef) {
    incompleteCacheRefs.add(incompleteCacheRef);
  }

  public Collection<ResultMapResolver> getIncompleteResultMaps() {
    return incompleteResultMaps;
  }

  public void addIncompleteResultMap(ResultMapResolver resultMapResolver) {
    incompleteResultMaps.add(resultMapResolver);
  }

  public void addIncompleteMethod(MethodResolver builder) {
    incompleteMethods.add(builder);
  }

  public Collection<MethodResolver> getIncompleteMethods() {
    return incompleteMethods;
  }

  //由DefaultSqlSession.selectList调用过来
  public MappedStatement getMappedStatement(String id) {
    return this.getMappedStatement(id, true);
  }

  public MappedStatement getMappedStatement(String id, boolean validateIncompleteStatements) {
    //先构建所有语句，再返回语句
    if (validateIncompleteStatements) {
      buildAllStatements();
    }
    return mappedStatements.get(id);
  }

  public Map<String, XNode> getSqlFragments() {
    return sqlFragments;
  }

  public void addInterceptor(Interceptor interceptor) {
    interceptorChain.addInterceptor(interceptor);
  }

  //将包下所有类加入到mapper
  public void addMappers(String packageName, Class<?> superType) {
    mapperRegistry.addMappers(packageName, superType);
  }

  public void addMappers(String packageName) {
    mapperRegistry.addMappers(packageName);
  }

  public <T> void addMapper(Class<T> type) {
    mapperRegistry.addMapper(type);
  }

  public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    return mapperRegistry.getMapper(type, sqlSession);
  }

  public boolean hasMapper(Class<?> type) {
    return mapperRegistry.hasMapper(type);
  }

  public boolean hasStatement(String statementName) {
    return hasStatement(statementName, true);
  }

  public boolean hasStatement(String statementName, boolean validateIncompleteStatements) {
    if (validateIncompleteStatements) {
      buildAllStatements();
    }
    return mappedStatements.containsKey(statementName);
  }

  public void addCacheRef(String namespace, String referencedNamespace) {
    cacheRefMap.put(namespace, referencedNamespace);
  }
  
  /*
   * Parses all the unprocessed statement nodes in the cache. It is recommended
   * to call this method once all the mappers are added as it provides fail-fast
   * statement validation.
   */
  protected void buildAllStatements() {
    if (!incompleteResultMaps.isEmpty()) {
      synchronized (incompleteResultMaps) {
        // This always throws a BuilderException.
        incompleteResultMaps.iterator().next().resolve();
      }
    }
    if (!incompleteCacheRefs.isEmpty()) {
      synchronized (incompleteCacheRefs) {
        // This always throws a BuilderException.
        incompleteCacheRefs.iterator().next().resolveCacheRef();
      }
    }
    if (!incompleteStatements.isEmpty()) {
      synchronized (incompleteStatements) {
        // This always throws a BuilderException.
        incompleteStatements.iterator().next().parseStatementNode();
      }
    }
    if (!incompleteMethods.isEmpty()) {
      synchronized (incompleteMethods) {
        // This always throws a BuilderException.
        incompleteMethods.iterator().next().resolve();
      }
    }
  }

  /*
   * Extracts namespace from fully qualified statement id.
   *
   * @param statementId
   * @return namespace or null when id does not contain period.
   */
  protected String extractNamespace(String statementId) {
    int lastPeriod = statementId.lastIndexOf('.');
    return lastPeriod > 0 ? statementId.substring(0, lastPeriod) : null;
  }

  // Slow but a one time cost. A better solution is welcome.
  protected void checkGloballyForDiscriminatedNestedResultMaps(ResultMap rm) {
    if (rm.hasNestedResultMaps()) {
      for (Map.Entry<String, ResultMap> entry : resultMaps.entrySet()) {
        Object value = entry.getValue();
        if (value instanceof ResultMap) {
          ResultMap entryResultMap = (ResultMap) value;
          if (!entryResultMap.hasNestedResultMaps() && entryResultMap.getDiscriminator() != null) {
            Collection<String> discriminatedResultMapNames = entryResultMap.getDiscriminator().getDiscriminatorMap().values();
            if (discriminatedResultMapNames.contains(rm.getId())) {
              entryResultMap.forceNestedResultMaps();
            }
          }
        }
      }
    }
  }

  // Slow but a one time cost. A better solution is welcome.
  protected void checkLocallyForDiscriminatedNestedResultMaps(ResultMap rm) {
    if (!rm.hasNestedResultMaps() && rm.getDiscriminator() != null) {
      for (Map.Entry<String, String> entry : rm.getDiscriminator().getDiscriminatorMap().entrySet()) {
        String discriminatedResultMapName = entry.getValue();
        if (hasResultMap(discriminatedResultMapName)) {
          ResultMap discriminatedResultMap = resultMaps.get(discriminatedResultMapName);
          if (discriminatedResultMap.hasNestedResultMaps()) {
            rm.forceNestedResultMaps();
            break;
          }
        }
      }
    }
  }

  //静态内部类,严格的Map，不允许多次覆盖key所对应的value
  protected static class StrictMap<V> extends HashMap<String, V> {

    private static final long serialVersionUID = -4950446264854982944L;
    private String name;

    public StrictMap(String name, int initialCapacity, float loadFactor) {
      super(initialCapacity, loadFactor);
      this.name = name;
    }

    public StrictMap(String name, int initialCapacity) {
      super(initialCapacity);
      this.name = name;
    }

    public StrictMap(String name) {
      super();
      this.name = name;
    }

    public StrictMap(String name, Map<String, ? extends V> m) {
      super(m);
      this.name = name;
    }

    @SuppressWarnings("unchecked")
    public V put(String key, V value) {
      if (containsKey(key)) {
        //如果已经存在此key了，直接报错
        throw new IllegalArgumentException(name + " already contains value for " + key);
      }
      if (key.contains(".")) {
        //如果有.符号，取得短名称，大致用意就是包名不同，类名相同，提供模糊查询的功能
        final String shortKey = getShortName(key);
        if (super.get(shortKey) == null) {
          //如果没有这个缩略，则放一个缩略
          super.put(shortKey, value);
        } else {
          //如果已经有此缩略，表示模糊，放一个Ambiguity型的
          super.put(shortKey, (V) new Ambiguity(shortKey));
        }
      }
      //再放一个全名
      return super.put(key, value);
      //可以看到，如果有包名，会放2个key到这个map，一个缩略，一个全名
    }

    public V get(Object key) {
      V value = super.get(key);
      //如果找不到相应的key，直接报错
      if (value == null) {
        throw new IllegalArgumentException(name + " does not contain value for " + key);
      }
      //如果是模糊型的，也报错，提示用户
      //原来这个模糊型就是为了提示用户啊
      if (value instanceof Ambiguity) {
        throw new IllegalArgumentException(((Ambiguity) value).getSubject() + " is ambiguous in " + name
            + " (try using the full name including the namespace, or rename one of the entries)");
      }
      return value;
    }

    //取得短名称，也就是取得最后那个句号的后面那部分
    private String getShortName(String key) {
      final String[] keyparts = key.split("\\.");
      return keyparts[keyparts.length - 1];
    }

    //模糊，居然放在Map里面的一个静态内部类，
    protected static class Ambiguity {
      //提供一个主题
      private String subject;

      public Ambiguity(String subject) {
        this.subject = subject;
      }

      public String getSubject() {
        return subject;
      }
    }
  }

}