2017.12.27 sqlSessionFactory和sqlSession（to be continued）

參考來自：《深刻淺出MyBatis技術原理與實踐-第6章 》

 

1.SqlSessionFactory

SqlSessionFactory是一個接口，最重要的功能是提供SqlSession。

 1 public interface SqlSessionFactory {
 2 
 3   SqlSession openSession();
 4 
 5   SqlSession openSession(boolean autoCommit);
 6   SqlSession openSession(Connection connection);
 7   SqlSession openSession(TransactionIsolationLevel level);
 8 
 9   SqlSession openSession(ExecutorType execType);
10   SqlSession openSession(ExecutorType execType, boolean autoCommit);
11   SqlSession openSession(ExecutorType execType, TransactionIsolationLevel level);
12   SqlSession openSession(ExecutorType execType, Connection connection);
13 
14  Configuration getConfiguration(); 15 
16 }

 

SqlSessionFactory有一個默認的實現類DefaultSqlSessionFactory。

 16 package org.apache.ibatis.session.defaults;
 17 
 18 import java.sql.Connection;
 19 import java.sql.SQLException;
 20 
 21 import org.apache.ibatis.exceptions.ExceptionFactory;
 22 import org.apache.ibatis.executor.ErrorContext;
 23 import org.apache.ibatis.executor.Executor;
 24 import org.apache.ibatis.mapping.Environment;
 25 import org.apache.ibatis.session.Configuration;
 26 import org.apache.ibatis.session.ExecutorType;
 27 import org.apache.ibatis.session.SqlSession;
 28 import org.apache.ibatis.session.SqlSessionFactory;
 29 import org.apache.ibatis.session.TransactionIsolationLevel;
 30 import org.apache.ibatis.transaction.Transaction;
 31 import org.apache.ibatis.transaction.TransactionFactory;
 32 import org.apache.ibatis.transaction.managed.ManagedTransactionFactory;
 33 
 34 /**
 35  * @author Clinton Begin
 36  */
 37 public class DefaultSqlSessionFactory implements SqlSessionFactory {
 38 
 39   private final Configuration configuration;  40 
 41   public DefaultSqlSessionFactory(Configuration configuration) {
 42     this.configuration = configuration;
 43   } 84 
 85   @Override
 86   public Configuration getConfiguration() {
 87     return configuration;
 88   }
 89   //其他略
144 
145 }

 

在對SqlSessionFactory的構建中，直接使用構造方法去構建是有困難的，這樣會將大量的邏輯放在構造方法中。所以採用的是builder模式，使用SqlSessionFactoryBuilder來構建。

SqlSessionFactory中提供了不少build方法，最終調用的都是下面兩個中的一個，而後調用第三個build：生成一個defaultSqlSessionFactory(configuration config)。

Configuration類中則保存了配置相關的參數，全局惟一。

 1 package org.apache.ibatis.session;
 2 
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 import java.io.Reader;
 6 import java.util.Properties;
 7 
 8 import org.apache.ibatis.builder.xml.XMLConfigBuilder;
 9 import org.apache.ibatis.exceptions.ExceptionFactory;
10 import org.apache.ibatis.executor.ErrorContext;
11 import org.apache.ibatis.session.defaults.DefaultSqlSessionFactory;
12 
13 public class SqlSessionFactoryBuilder {
14 
15   public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
16     try {
17       XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
18       return build(parser.parse());
19     } catch (Exception e) {
20       throw ExceptionFactory.wrapException("Error building SqlSession.", e);
21     } finally {
22       ErrorContext.instance().reset();
23       try {
24         reader.close();
25       } catch (IOException e) {
26         // Intentionally ignore. Prefer previous error.
27       }
28     }
29   }
30 
31   public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
32     try {
33       XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
34       return build(parser.parse());
35     } catch (Exception e) {
36       throw ExceptionFactory.wrapException("Error building SqlSession.", e);
37     } finally {
38       ErrorContext.instance().reset();
39       try {
40         inputStream.close();
41       } catch (IOException e) {
42         // Intentionally ignore. Prefer previous error.
43       }
44     }
45   }
46     
47   public SqlSessionFactory build(Configuration config) {
48     return new DefaultSqlSessionFactory(config);
49   }
50   //其他略
51 }

 

綜上所述，SqlSessionFactory的構建過程：

• mybatis經過SqlSessionFactoryBuilder去構建SqlSessionFactory。
• SqlSessionFactoryBuilder中提供了SqlXMLConfigBuilder讀取XML配置文件中的信息，保存至Configuration類的單例中。
• 而後SqlSessionFactoryBuilder實例化DefaultSqlSessionFactory。