源码分析-Mybatis初始化过程

这里进行的分析我们会在下面代码处进行断点

sqlSessionFactory= new SqlSessionFactoryBuilder().build(inputStream);

1。步入后首先来到

public SqlSessionFactoryBuilder() {
}

我们在这里构造一个SqlSessionFactoryBuilder实例。

2。接下来来到

public SqlSessionFactory build(InputStream inputStream) {
return this.build((InputStream)inputStream, (String)null, (Properties)null);
}

我们通过刚才SqlSessionFactoryBuilder的实例中的build方法，然后调用重载的build方法

public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
SqlSessionFactory var5;
try {
XMLConfigBuilder e = new XMLConfigBuilder(inputStream, environment, properties);
var5 = this.build((Configuration)e.parse());
} catch (Exception var14) {
throw ExceptionFactory.wrapException("Error building SqlSession.", var14);
} finally {
ErrorContext.instance().reset();

try {
inputStream.close();
} catch (IOException var13) {
;
}

}

return var5;
}

在这里首先会创建一个XMLConfigBuilder,然后继续调用build的重载方法传入XMLConfigBuilder的解析，也就是对我们XMLconfig的解析，返回的是Configuration类型。在Mybatis中是使用的DOM4J的解析。

3.真正的Build,

public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}

在这里返回的是默认SqlSessionFactory,进入构造函数中看。这里需要说明一下什么是Configuration

public class Configuration {
protected Environment environment;
protected boolean safeRowBoundsEnabled;
protected boolean safeResultHandlerEnabled;
protected boolean mapUnderscoreToCamelCase;
protected boolean aggressiveLazyLoading;
protected boolean multipleResultSetsEnabled;
protected boolean useGeneratedKeys;
protected boolean useColumnLabel;
protected boolean cacheEnabled;
protected boolean callSettersOnNulls;
protected String logPrefix;
protected Class<? extends Log> logImpl;
protected LocalCacheScope localCacheScope;
protected JdbcType jdbcTypeForNull;
protected Set<String> lazyLoadTriggerMethods;
protected Integer defaultStatementTimeout;
protected Integer defaultFetchSize;
protected ExecutorType defaultExecutorType;
protected AutoMappingBehavior autoMappingBehavior;
protected Properties variables;
protected ReflectorFactory reflectorFactory;
protected ObjectFactory objectFactory;
protected ObjectWrapperFactory objectWrapperFactory;
protected MapperRegistry mapperRegistry;
protected boolean lazyLoadingEnabled;
protected ProxyFactory proxyFactory;
protected String databaseId;
protected Class<?> configurationFactory;
protected final InterceptorChain interceptorChain;
protected final TypeHandlerRegistry typeHandlerRegistry;
protected final TypeAliasRegistry typeAliasRegistry;
protected final LanguageDriverRegistry languageRegistry;
protected final Map<String, MappedStatement> mappedStatements;
protected final Map<String, Cache> caches;
protected final Map<String, ResultMap> resultMaps;
protected final Map<String, ParameterMap> parameterMaps;
protected final Map<String, KeyGenerator> keyGenerators;
protected final Set<String> loadedResources;
protected final Map<String, XNode> sqlFragments;
protected final Collection<XMLStatementBuilder> incompleteStatements;
protected final Collection<CacheRefResolver> incompleteCacheRefs;
protected final Collection<ResultMapResolver> incompleteResultMaps;
protected final Collection<MethodResolver> incompleteMethods;
protected final Map<String, String> cacheRefMap;

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

public Configuration() {
this.safeRowBoundsEnabled = false;
this.safeResultHandlerEnabled = true;
this.mapUnderscoreToCamelCase = false;
this.aggressiveLazyLoading = true;
this.multipleResultSetsEnabled = true;
this.useGeneratedKeys = false;
this.useColumnLabel = true;
this.cacheEnabled = true;
this.callSettersOnNulls = false;
this.localCacheScope = LocalCacheScope.SESSION;
this.jdbcTypeForNull = JdbcType.OTHER;
this.lazyLoadTriggerMethods = new HashSet(Arrays.asList(new String[]{"equals", "clone", "hashCode", "toString"}));
this.defaultExecutorType = ExecutorType.SIMPLE;
this.autoMappingBehavior = AutoMappingBehavior.PARTIAL;
this.variables = new Properties();
this.reflectorFactory = new DefaultReflectorFactory();
this.objectFactory = new DefaultObjectFactory();
this.objectWrapperFactory = new DefaultObjectWrapperFactory();
this.mapperRegistry = new MapperRegistry(this);
this.lazyLoadingEnabled = false;
this.proxyFactory = new JavassistProxyFactory();
this.interceptorChain = new InterceptorChain();
this.typeHandlerRegistry = new TypeHandlerRegistry();
this.typeAliasRegistry = new TypeAliasRegistry();
this.languageRegistry = new LanguageDriverRegistry();
this.mappedStatements = new Configuration.StrictMap("Mapped Statements collection");
this.caches = new Configuration.StrictMap("Caches collection");
this.resultMaps = new Configuration.StrictMap("Result Maps collection");
this.parameterMaps = new Configuration.StrictMap("Parameter Maps collection");
this.keyGenerators = new Configuration.StrictMap("Key Generators collection");
this.loadedResources = new HashSet();
this.sqlFragments = new Configuration.StrictMap("XML fragments parsed from previous mappers");
this.incompleteStatements = new LinkedList();
this.incompleteCacheRefs = new LinkedList();
this.incompleteResultMaps = new LinkedList();
this.incompleteMethods = new LinkedList();
this.cacheRefMap = new HashMap();
this.typeAliasRegistry.registerAlias("JDBC", JdbcTransactionFactory.class);
this.typeAliasRegistry.registerAlias("MANAGED", ManagedTransactionFactory.class);
this.typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);
this.typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);
this.typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);
this.typeAliasRegistry.registerAlias("PERPETUAL", PerpetualCache.class);
this.typeAliasRegistry.registerAlias("FIFO", FifoCache.class);
this.typeAliasRegistry.registerAlias("LRU", LruCache.class);
this.typeAliasRegistry.registerAlias("SOFT", SoftCache.class);
this.typeAliasRegistry.registerAlias("WEAK", WeakCache.class);
this.typeAliasRegistry.registerAlias("DB_VENDOR", VendorDatabaseIdProvider.class);
this.typeAliasRegistry.registerAlias("XML", XMLLanguageDriver.class);
this.typeAliasRegistry.registerAlias("RAW", RawLanguageDriver.class);
this.typeAliasRegistry.registerAlias("SLF4J", Slf4jImpl.class);
this.typeAliasRegistry.registerAlias("COMMONS_LOGGING", JakartaCommonsLoggingImpl.class);
this.typeAliasRegistry.registerAlias("LOG4J", Log4jImpl.class);
this.typeAliasRegistry.registerAlias("LOG4J2", Log4j2Impl.class);
this.typeAliasRegistry.registerAlias("JDK_LOGGING", Jdk14LoggingImpl.class);
this.typeAliasRegistry.registerAlias("STDOUT_LOGGING", StdOutImpl.class);
this.typeAliasRegistry.registerAlias("NO_LOGGING", NoLoggingImpl.class);
this.typeAliasRegistry.registerAlias("CGLIB", CglibProxyFactory.class);
this.typeAliasRegistry.registerAlias("JAVASSIST", JavassistProxyFactory.class);
this.languageRegistry.setDefaultDriverClass(XMLLanguageDriver.class);
this.languageRegistry.register(RawLanguageDriver.class);
}

上面我将Configuration所有信息以及构造函数列出来，具体包含了我们我们所有的在Mybatis-config.xml所配置的信息，MapperRegistry包含了我们所配置所有的Mapper信息，在MapperRegistry中维护了一个HashMap()如下：

private final Map<Class<?>, MapperProxyFactory<?>> knownMappers = new HashMap();

在我们sqlsessio中会详细讲解。

4.DefaultSqlSessionFactory是我们的SqlSession工厂，其中主要的方法是opensession();

public SqlSession openSession() {
return this.openSessionFromDataSource(this.configuration.getDefaultExecutorType(), (TransactionIsolationLevel)null, false);
}

这个我们以后会详细讲解。