Mybatis的Environment解析詳解

今天來具體看一下如何解析environments 
//XMLConfigBuilder 

Java代碼

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.         //遍歷environments的child節點environment，並解析  
32.             do  
33.             {  
34.                 if(!i$.hasNext())  
35.                     break;  
36.                 XNode child = (XNode)i$.next();  
37.                 String id = child.getStringAttribute("id");  
38.         //若是environment的id屬性，與environments的default相同時，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的構造，啓動有JDBC，POOLED類型的映射關係，這個在解析environment節點時，須要用到  下載

Java代碼

1. typeAliasRegistry.registerAlias("JDBC", org/apache/ibatis/transaction/jdbc/JdbcTransactionFactory);  
2. typeAliasRegistry.registerAlias("POOLED", org/apache/ibatis/datasource/pooled/PooledDataSourceFactory);  

 

Java代碼

1. public Configuration()  
2.     {  
3.         safeRowBoundsEnabled = false;  
4.         safeResultHandlerEnabled = true;  
5.         mapUnderscoreToCamelCase = false;  
6.         aggressiveLazyLoading = true;  
7.         multipleResultSetsEnabled = true;  
8.         useGeneratedKeys = false;//容許JDBC支持生成的鍵  
9.         useColumnLabel = true;  
10.         cacheEnabled = true;//全局的映射器啓用或禁用緩存  
11.         callSettersOnNulls = false;  
12.         localCacheScope = LocalCacheScope.SESSION;//本地一級緩存做用域  
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();//默認ObjectFactory  
21.         objectWrapperFactory = new DefaultObjectWrapperFactory();//默認DefaultObjectWrapperFactory  
22.         mapperRegistry = new MapperRegistry(this);  
23.         lazyLoadingEnabled = false;  
24.         interceptorChain = new InterceptorChain();//插件鏈  
25.         typeHandlerRegistry = new TypeHandlerRegistry();//類型處理註冊器  
26.         typeAliasRegistry = new TypeAliasRegistry();//類型別名註冊器  
27.         languageRegistry = new LanguageDriverRegistry();  
28.     //mappedStatements Map  
29.         mappedStatements = new StrictMap("Mapped Statements collection");  
30.     //mappedStatements，method，二級緩存  
31.         caches = new StrictMap("Caches collection");  
32.     //MapperInterface 方法返回結果類型Map  
33.         resultMaps = new StrictMap("Result Maps collection");  
34.         //MapperInterface 方法參數類型Map  
35.         parameterMaps = new StrictMap("Parameter Maps collection");  
36.     //主鍵生成器Map  
37.         keyGenerators = new StrictMap("Key Generators collection");  
38.         loadedResources = new HashSet();  
39.     //Mapper.xml 中statement片斷  
40.         sqlFragments = new StrictMap("XML fragments parsed from previous mappers");  
41.     //未解析處理的statements  
42.         incompleteStatements = new LinkedList();  
43.     //未解析處理的CacheRefs  
44.         incompleteCacheRefs = new LinkedList();  
45.     //未解析處理的ResultMaps  
46.         incompleteResultMaps = new LinkedList();  
47.     //未解析處理的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.     }  

從上能夠看出JDBC，POOLED類型別名的映射關係以下： 
JDBC，JdbcTransactionFactory  下載
POOLED，PooledDataSourceFactory 
 

Java代碼

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代碼

 

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.         //從類型解決器中，獲取type對應的類型的實例，從上面的配置來看  
9.         //實際爲JdbcTransactionFactory  
10.             TransactionFactory factory = (TransactionFactory)resolveClass(type).newInstance();  
11.         //設置JdbcTransactionFactory屬性  
12.             factory.setProperties(props);  
13.             return factory;  
14.         } else  
15.         {  
16.             throw new BuilderException("Environment declaration requires a TransactionFactory.");  
17.         }  
18.     }  

//JdbcTransactionFactory 

Java代碼

下載

1. public class JdbcTransactionFactory  
2.     implements TransactionFactory  
3. {  
4.     public void setProperties(Properties properties)  
5.     {  
6.     }  
7.    //根據數據鏈接新建事務  
8.     public Transaction newTransaction(Connection conn)  
9.     {  
10.         return new JdbcTransaction(conn);  
11.     }  
12.     //根據數據源和事務級別和是否自動提交，新建事務  
13.     public Transaction newTransaction(DataSource ds, TransactionIsolationLevel level, boolean autoCommit)  
14.     {  
15.         return new JdbcTransaction(ds, level, autoCommit);  
16.     }  
17. }  

//TransactionFactory 

Java代碼

 

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. }  

如今來看一下jdbc事務 
 

Java代碼

下載

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;//數據庫鏈接  
6.     protected DataSource dataSource;//數據源  
7.     protected TransactionIsolationLevel level;//事務級別  
8.     protected boolean autoCommmit;//自動提交屬性  
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.     //獲取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代碼

 

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. }  

從上面能夠看出jdbc對應的事務工廠爲JdbcTransactionFactory，由JdbcTransactionFactory，根據數據源，事務級別以及自動提交屬性來，建立JdbcTransaction，而JdbcTransaction的事務管理，是經過數據鏈接connection，而connection是從datasource獲取，JdbcTransaction的事務管理，就是依靠相應的數據庫driver，來管理，實際依賴於數據庫。  下載

//解析dataSource 

Java代碼

 

1. private DataSourceFactory dataSourceElement(XNode context)  
2.         throws Exception  
3.     {  
4.         if(context != null)  
5.         {  
6.         //獲取數據源的類型，和屬性  
7.             String type = context.getStringAttribute("type");  
8.             Properties props = context.getChildrenAsProperties();  
9.         //根據type從configuration的類型處理器，獲取具體的DataSourceFactory  
10.         //從上文，咱們看一看到type爲POOLED，對應的是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代碼

 

1. public class PooledDataSourceFactory extends UnpooledDataSourceFactory  
2. {  
3.   
4.     public PooledDataSourceFactory()  
5.     {  
6.         dataSource = new PooledDataSource();  
7.     }  
8. }