Mybatis的Environment解析详解

今天来具体看一下如何解析environments 
//XMLConfigBuilder 

Java代码  

1. private void parseConfiguration(XNode root)  

2.     {  

3.         try  

4.         {  

5.             propertiesElement(root.evalNode("properties"));  

6.             typeAliasesElement(root.evalNode("typeAliases"));  

7.             pluginElement(root.evalNode("plugins"));  

8.             objectFactoryElement(root.evalNode("objectFactory"));  

9.             objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));  

10.             settingsElement(root.evalNode("settings"));  

11.         //解析environments  

12.             environmentsElement(root.evalNode("environments"));  

13.             databaseIdProviderElement(root.evalNode("databaseIdProvider"));  

14.             typeHandlerElement(root.evalNode("typeHandlers"));  

15.             mapperElement(root.evalNode("mappers"));  

16.         }  

17.         catch(Exception e)  

18.         {  

19.             throw new BuilderException((new StringBuilder()).append("Error parsing SQL Mapper Configuration. Cause: ").append(e).toString(), e);  

20.         }  

21.     }  

22. //解析environments  

23. private void environmentsElement(XNode context)  

24.         throws Exception  

25.     {  

26.         if(context != null)  

27.         {  

28.             if(C == null)  

29.                 environment = context.getStringAttribute("default");  

30.             Iterator i$ = context.getChildren().iterator();  

31.         //遍历environments的child节点environment，并解析  

32.             do  

33.             {  

34.                 if(!i$.hasNext())  

35.                     break;  

36.                 XNode child = (XNode)i$.next();  

37.                 String id = child.getStringAttribute("id");  

38.         //如果environment的id属性，与environments的default相同时，才解析  

39.                 if(isSpecifiedEnvironment(id))  

40.                 {  

41.             //解析transactionManager  

42.                     TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));  

43.                     //解析dataSource  

44.             DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));  

45.                     javax.sql.DataSource dataSource = dsFactory.getDataSource();  

46.                     org.apache.ibatis.mapping.Environment.Builder environmentBuilder = (new org.apache.ibatis.mapping.Environment.Builder(id)).transactionFactory(txFactory).dataSource(dataSource);  

47.                     configuration.setEnvironment(environmentBuilder.build());  

48.                 }  

49.             } while(true);  

50.         }  

51.     }  

//解析transactionManager 
先看configuration的构造，启动有JDBC，POOLED类型的映射关系，这个在解析environment节点时，需要用到下载 

Java代码  

1. typeAliasRegistry.registerAlias("JDBC", org/apache/ibatis/transaction/jdbc/JdbcTransactionFactory);  

2. typeAliasRegistry.registerAlias("POOLED", org/apache/ibatis/datasource/pooled/PooledDataSourceFactory);  

Java代码  

1. public Configuration()  

2.     {  

3.         safeRowBoundsEnabled = false;  

4.         safeResultHandlerEnabled = true;  

5.         mapUnderscoreToCamelCase = false;  

6.         aggressiveLazyLoading = true;  

7.         multipleResultSetsEnabled = true;  

8.         useGeneratedKeys = false;//允许JDBC支持生成的键  

9.         useColumnLabel = true;  

10.         cacheEnabled = true;//全局的映射器启用或禁用缓存  

11.         callSettersOnNulls = false;  

12.         localCacheScope = LocalCacheScope.SESSION;//本地一级缓存作用域  

13.         jdbcTypeForNull = JdbcType.OTHER;  

14.         lazyLoadTriggerMethods = new HashSet(Arrays.asList(new String[] {  

15.             "equals", "clone", "hashCode", "toString"  

16.         }));  

17.         defaultExecutorType = ExecutorType.SIMPLE;  

18.         autoMappingBehavior = AutoMappingBehavior.PARTIAL;  

19.         variables = new Properties();  

20.         objectFactory = new DefaultObjectFactory();//默认ObjectFactory  

21.         objectWrapperFactory = new DefaultObjectWrapperFactory();//默认DefaultObjectWrapperFactory  

22.         mapperRegistry = new MapperRegistry(this);  

23.         lazyLoadingEnabled = false;  

24.         interceptorChain = new InterceptorChain();//插件链  

25.         typeHandlerRegistry = new TypeHandlerRegistry();//类型处理注册器  

26.         typeAliasRegistry = new TypeAliasRegistry();//类型别名注册器  

27.         languageRegistry = new LanguageDriverRegistry();  

28.     //mappedStatements Map  

29.         mappedStatements = new StrictMap("Mapped Statements collection");  

30.     //mappedStatements，method，二级缓存  

31.         caches = new StrictMap("Caches collection");  

32.     //MapperInterface 方法返回结果类型Map  

33.         resultMaps = new StrictMap("Result Maps collection");  

34.         //MapperInterface 方法参数类型Map  

35.         parameterMaps = new StrictMap("Parameter Maps collection");  

36.     //主键生成器Map  

37.         keyGenerators = new StrictMap("Key Generators collection");  

38.         loadedResources = new HashSet();  

39.     //Mapper.xml 中statement片段  

40.         sqlFragments = new StrictMap("XML fragments parsed from previous mappers");  

41.     //未解析处理的statements  

42.         incompleteStatements = new LinkedList();  

43.     //未解析处理的CacheRefs  

44.         incompleteCacheRefs = new LinkedList();  

45.     //未解析处理的ResultMaps  

46.         incompleteResultMaps = new LinkedList();  

47.     //未解析处理的Methods  

48.         incompleteMethods = new LinkedList();  

49.         cacheRefMap = new HashMap();  

50.         typeAliasRegistry.registerAlias("JDBC", org/apache/ibatis/transaction/jdbc/JdbcTransactionFactory);  

51.         typeAliasRegistry.registerAlias("MANAGED", org/apache/ibatis/transaction/managed/ManagedTransactionFactory);  

52.         typeAliasRegistry.registerAlias("JNDI", org/apache/ibatis/datasource/jndi/JndiDataSourceFactory);  

53.         typeAliasRegistry.registerAlias("POOLED", org/apache/ibatis/datasource/pooled/PooledDataSourceFactory);  

54.         typeAliasRegistry.registerAlias("UNPOOLED", org/apache/ibatis/datasource/unpooled/UnpooledDataSourceFactory);  

55.         typeAliasRegistry.registerAlias("PERPETUAL", org/apache/ibatis/cache/impl/PerpetualCache);  

56.         typeAliasRegistry.registerAlias("FIFO", org/apache/ibatis/cache/decorators/FifoCache);  

57.         typeAliasRegistry.registerAlias("LRU", org/apache/ibatis/cache/decorators/LruCache);  

58.         typeAliasRegistry.registerAlias("SOFT", org/apache/ibatis/cache/decorators/SoftCache);  

59.         typeAliasRegistry.registerAlias("WEAK", org/apache/ibatis/cache/decorators/WeakCache);  

60.         typeAliasRegistry.registerAlias("VENDOR", org/apache/ibatis/mapping/VendorDatabaseIdProvider);  

61.         typeAliasRegistry.registerAlias("XML", org/apache/ibatis/scripting/xmltags/XMLLanguageDriver);  

62.         typeAliasRegistry.registerAlias("RAW", org/apache/ibatis/scripting/defaults/RawLanguageDriver);  

63.         typeAliasRegistry.registerAlias("SLF4J", org/apache/ibatis/logging/slf4j/Slf4jImpl);  

64.         typeAliasRegistry.registerAlias("COMMONS_LOGGING", org/apache/ibatis/logging/commons/JakartaCommonsLoggingImpl);  

65.         typeAliasRegistry.registerAlias("LOG4J", org/apache/ibatis/logging/log4j/Log4jImpl);  

66.         typeAliasRegistry.registerAlias("JDK_LOGGING", org/apache/ibatis/logging/jdk14/Jdk14LoggingImpl);  

67.         typeAliasRegistry.registerAlias("STDOUT_LOGGING", org/apache/ibatis/logging/stdout/StdOutImpl);  

68.         typeAliasRegistry.registerAlias("NO_LOGGING", org/apache/ibatis/logging/nologging/NoLoggingImpl);  

69.         typeAliasRegistry.registerAlias("CGLIB", org/apache/ibatis/executor/loader/CglibProxyFactory);  

70.         typeAliasRegistry.registerAlias("JAVASSIST", org/apache/ibatis/executor/loader/JavassistProxyFactory);  

71.         languageRegistry.setDefaultDriverClass(org/apache/ibatis/scripting/xmltags/XMLLanguageDriver);  

72.         languageRegistry.register(org/apache/ibatis/scripting/defaults/RawLanguageDriver);  

73.     }  

从上可以看出JDBC，POOLED类型别名的映射关系如下： 
JDBC，JdbcTransactionFactory 下载
POOLED，PooledDataSourceFactory 

Java代码  

1. <environments default="development">  

2.         <environment id="development">  

3.             <transactionManager type="JDBC" />  

4.             <dataSource type="POOLED">  

5.                 <property name="driver" value="${driver}" />  

6.                 <property name="url" value="${url}" />  

7.                 <property name="username" value="${username}" />  

8.                 <property name="password" value="${password}" />  

9.             </dataSource>  

10.         </environment>  

11. </environments>  

Java代码  

1. private TransactionFactory transactionManagerElement(XNode context)  

2.         throws Exception  

3.     {  

4.         if(context != null)  

5.         {  

6.             String type = context.getStringAttribute("type");  

7.             Properties props = context.getChildrenAsProperties();  

8.         //从类型解决器中，获取type对应的类型的实例，从上面的配置来看  

9.         //实际为JdbcTransactionFactory  

10.             TransactionFactory factory = (TransactionFactory)resolveClass(type).newInstance();  

11.         //设置JdbcTransactionFactory属性  

12.             factory.setProperties(props);  

13.             return factory;  

14.         } else  

15.         {  

16.             throw new BuilderException("Environment declaration requires a TransactionFactory.");  

17.         }  

18.     }  

//JdbcTransactionFactory 

Java代码  下载

1. public class JdbcTransactionFactory  

2.     implements TransactionFactory  

3. {  

4.     public void setProperties(Properties properties)  

5.     {  

6.     }  

7.    //根据数据连接新建事务  

8.     public Transaction newTransaction(Connection conn)  

9.     {  

10.         return new JdbcTransaction(conn);  

11.     }  

12.     //根据数据源和事务级别和是否自动提交，新建事务  

13.     public Transaction newTransaction(DataSource ds, TransactionIsolationLevel level, boolean autoCommit)  

14.     {  

15.         return new JdbcTransaction(ds, level, autoCommit);  

16.     }  

17. }  

//TransactionFactory 

Java代码  

1. public interface TransactionFactory  

2. {  

3.     public abstract void setProperties(Properties properties);  

4.     public abstract Transaction newTransaction(Connection connection);  

5.     public abstract Transaction newTransaction(DataSource datasource, TransactionIsolationLevel transactionisolationlevel, boolean flag);  

6. }  

现在来看一下jdbc事务 

Java代码  下载

1. public class JdbcTransaction  

2.     implements Transaction  

3. {  

4.     private static final Log log = LogFactory.getLog(org/apache/ibatis/transaction/jdbc/JdbcTransaction);  

5.     protected Connection connection;//数据库连接  

6.     protected DataSource dataSource;//数据源  

7.     protected TransactionIsolationLevel level;//事务级别  

8.     protected boolean autoCommmit;//自动提交属性  

9.   

10.     public JdbcTransaction(DataSource ds, TransactionIsolationLevel desiredLevel, boolean desiredAutoCommit)  

11.     {  

12.         dataSource = ds;  

13.         level = desiredLevel;  

14.         autoCommmit = desiredAutoCommit;  

15.     }  

16.   

17.     public JdbcTransaction(Connection connection)  

18.     {  

19.         this.connection = connection;  

20.     }  

21.   

22.     public Connection getConnection()  

23.         throws SQLException  

24.     {  

25.         if(connection == null)  

26.             openConnection();  

27.         return connection;  

28.     }  

29.   

30.     public void commit()  

31.         throws SQLException  

32.     {  

33.         if(connection != null && !connection.getAutoCommit())  

34.         {  

35.             if(log.isDebugEnabled())  

36.                 log.debug((new StringBuilder()).append("Committing JDBC Connection [").append(connection).append("]").toString());  

37.             connection.commit();  

38.         }  

39.     }  

40.   

41.     public void rollback()  

42.         throws SQLException  

43.     {  

44.         if(connection != null && !connection.getAutoCommit())  

45.         {  

46.             if(log.isDebugEnabled())  

47.                 log.debug((new StringBuilder()).append("Rolling back JDBC Connection [").append(connection).append("]").toString());  

48.             connection.rollback();  

49.         }  

50.     }  

51.   

52.     public void close()  

53.         throws SQLException  

54.     {  

55.         if(connection != null)  

56.         {  

57.             resetAutoCommit();  

58.             if(log.isDebugEnabled())  

59.                 log.debug((new StringBuilder()).append("Closing JDBC Connection [").append(connection).append("]").toString());  

60.             connection.close();  

61.         }  

62.     }  

63.   

64.     protected void setDesiredAutoCommit(boolean desiredAutoCommit)  

65.     {  

66.         try  

67.         {  

68.             if(connection.getAutoCommit() != desiredAutoCommit)  

69.             {  

70.                 if(log.isDebugEnabled())  

71.                     log.debug((new StringBuilder()).append("Setting autocommit to ").append(desiredAutoCommit).append(" on JDBC Connection [").append(connection).append("]").toString());  

72.                 connection.setAutoCommit(desiredAutoCommit);  

73.             }  

74.         }  

75.         catch(SQLException e)  

76.         {  

77.             throw new TransactionException((new StringBuilder()).append("Error configuring AutoCommit.  Your driver may not support getAutoCommit() or setAutoCommit(). Requested setting: ").append(desiredAutoCommit).append(".  Cause: ").append(e).toString(), e);  

78.         }  

79.     }  

80.   

81.     protected void resetAutoCommit()  

82.     {  

83.         try  

84.         {  

85.             if(!connection.getAutoCommit())  

86.             {  

87.                 if(log.isDebugEnabled())  

88.                     log.debug((new StringBuilder()).append("Resetting autocommit to true on JDBC Connection [").append(connection).append("]").toString());  

89.                 connection.setAutoCommit(true);  

90.             }  

91.         }  

92.         catch(SQLException e)  

93.         {  

94.             log.debug((new StringBuilder()).append("Error resetting autocommit to true before closing the connection.  Cause: ").append(e).toString());  

95.         }  

96.     }  

97.     //获取connection  

98.     protected void openConnection()  

99.         throws SQLException  

100.     {  

101.         if(log.isDebugEnabled())  

102.             log.debug("Openning JDBC Connection");  

103.         connection = dataSource.getConnection();  

104.         if(level != null)  

105.             connection.setTransactionIsolation(level.getLevel());  

106.         setDesiredAutoCommit(autoCommmit);  

107.     }  

108. }  

//Transaction 

Java代码  

1. public interface Transaction  

2. {  

3.   

4.     public abstract Connection getConnection()  

5.         throws SQLException;  

6.   

7.     public abstract void commit()  

8.         throws SQLException;  

9.   

10.     public abstract void rollback()  

11.         throws SQLException;  

12.   

13.     public abstract void close()  

14.         throws SQLException;  

15. }  

从上面可以看出jdbc对应的事务工厂为JdbcTransactionFactory，由JdbcTransactionFactory，根据数据源，事务级别以及自动提交属性来，创建JdbcTransaction，而JdbcTransaction的事务管理，是通过数据连接connection，而connection是从datasource获取，JdbcTransaction的事务管理，就是依靠相应的数据库driver，来管理，实际依赖于数据库。 下载

//解析dataSource 

Java代码  

1. private DataSourceFactory dataSourceElement(XNode context)  

2.         throws Exception  

3.     {  

4.         if(context != null)  

5.         {  

6.         //获取数据源的类型，和属性  

7.             String type = context.getStringAttribute("type");  

8.             Properties props = context.getChildrenAsProperties();  

9.         //根据type从configuration的类型处理器，获取具体的DataSourceFactory  

10.         //从上文，我们看一看到type为POOLED，对应的是PooledDataSourceFactory  

11.             DataSourceFactory factory = (DataSourceFactory)resolveClass(type).newInstance();  

12.             factory.setProperties(props);  

13.             return factory;  

14.         } else  

15.         {  

16.             throw new BuilderException("Environment declaration requires a DataSourceFactory.");  

17.         }  

18.     }  

// PooledDataSourceFactory 

Java代码  

1. public class PooledDataSourceFactory extends UnpooledDataSourceFactory  

2. {  

3.   

4.     public PooledDataSourceFactory()  

5.     {  

6.         dataSource = new PooledDataSource();  

7.     }  

8. }  

Mybatis的Environment解析详解

原文：http://12064211.blog.51cto.com/12054211/1867309