Mybatis DataSource

  • Author: HuiFer
  • Description: 该文介绍 mybatis DataSource 源码

  • 源码阅读工程: SourceHot-Mybatis

  • org.apache.ibatis.datasource.DataSourceFactory

  1. /**
  2.  * 数据源工厂
  3.  * @author Clinton Begin
  4.  */
  5. public interface DataSourceFactory {
  7.     /**
  8.      * 设置 dataSource 属性
  9.      * @param props
  10.      */
  11.     void setProperties(Properties props);
  13.     /**
  14.      * 获取 dataSource
  15.      * @return {@link DataSource}
  16.      */
  17.     DataSource getDataSource();
  19. }

类图如下

image-20191223081023730

  • setProperties会将下列标签放入datasource中
  1.       <dataSource type="POOLED">
  2.         <property name="driver" value="com.mysql.jdbc.Driver"/>
  3.         <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false"/>
  4.         <property name="username" value="mybatis"/>
  5.         <property name="password" value="mybatis"/>
  6.       </dataSource>
  • 在org.apache.ibatis.session.Configuration中有配置下面三个信息
  1.         typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);
  2.         typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);
  3.         typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);

JndiDataSourceFactory

  1. /**
  2.  * @author Clinton Begin
  3.  */
  4. public class JndiDataSourceFactory implements DataSourceFactory {
  6.     public static final String INITIAL_CONTEXT = "initial_context";
  7.     public static final String DATA_SOURCE = "data_source";
  8.     public static final String ENV_PREFIX = "env.";
  10.     /**
  11.      * 直接 java 数据源
  12.      */
  13.     private DataSource dataSource;
  15.     /**
  16.      * 获取数据源的配置信息
  17.      * @param allProps
  18.      * @return
  19.      */
  20.     private static Properties getEnvProperties(Properties allProps) {
  21.         final String PREFIX = ENV_PREFIX;
  22.         Properties contextProperties = null;
  23.         for (Entry<Object, Object> entry : allProps.entrySet()) {
  24.             String key = (String) entry.getKey();
  25.             String value = (String) entry.getValue();
  26.             // 只获取前缀`env`
  27.             if (key.startsWith(PREFIX)) {
  28.                 if (contextProperties == null) {
  29.                     contextProperties = new Properties();
  30.                 }
  31.                 // 放入数据
  32.                 contextProperties.put(key.substring(PREFIX.length()), value);
  33.             }
  34.         }
  35.         return contextProperties;
  36.     }
  38.     /**
  39.      * 设置数据源属性
  40.      * @param properties
  41.      */
  42.     @Override
  43.     public void setProperties(Properties properties) {
  44.         try {
  45.             InitialContext initCtx;
  46.             Properties env = getEnvProperties(properties);
  47.             if (env == null) {
  48.                 initCtx = new InitialContext();
  49.             } else {
  50.                 initCtx = new InitialContext(env);
  51.             }
  53.             if (properties.containsKey(INITIAL_CONTEXT)
  54.                     && properties.containsKey(DATA_SOURCE)) {
  55.                 // 如果包含`initial_context`和`data_source`
  56.                 Context ctx = (Context) initCtx.lookup(properties.getProperty(INITIAL_CONTEXT));
  57.                 dataSource = (DataSource) ctx.lookup(properties.getProperty(DATA_SOURCE));
  58.             } else if (properties.containsKey(DATA_SOURCE)) {
  59.                 dataSource = (DataSource) initCtx.lookup(properties.getProperty(DATA_SOURCE));
  60.             }
  62.         } catch (NamingException e) {
  63.             throw new DataSourceException("There was an error configuring JndiDataSourceTransactionPool. Cause: " + e, e);
  64.         }
  65.     }
  67.     @Override
  68.     public DataSource getDataSource() {
  69.         return dataSource;
  70.     }
  72. }

PooledDataSource

  1.     protected int poolMaximumActiveConnections = 10;
  2.     protected int poolMaximumIdleConnections = 5;
  3.     protected int poolMaximumCheckoutTime = 20000;
  4.     protected int poolTimeToWait = 20000;
  5.     protected int poolMaximumLocalBadConnectionTolerance = 3;
  6.     protected String poolPingQuery = "NO PING QUERY SET";
  7.     protected boolean poolPingEnabled;
  8.     protected int poolPingConnectionsNotUsedFor;

PooledDataSourceFactory

  1. public class PooledDataSourceFactory extends UnpooledDataSourceFactory {
  4.     public PooledDataSourceFactory() {
  5.         this.dataSource = new PooledDataSource();
  6.     }
  8. }
  10.     // 初始化
  11.     public PooledDataSource() {
  12.         dataSource = new UnpooledDataSource();
  13.     }

UnpooledDataSourceFactory

  1.     @Override
  2.     public void setProperties(Properties properties) {
  3.         Properties driverProperties = new Properties();
  4.         //metaDataSource 现在是一个dataSource
  5.         MetaObject metaDataSource = SystemMetaObject.forObject(dataSource);
  6.         for (Object key : properties.keySet()) {
  7.             String propertyName = (String) key;
  8.             if (propertyName.startsWith(DRIVER_PROPERTY_PREFIX)) {
  9.                 // 如果是 driver. 前缀开头
  10.                 String value = properties.getProperty(propertyName);
  11.                 driverProperties.setProperty(propertyName.substring(DRIVER_PROPERTY_PREFIX_LENGTH), value);
  12.             } else if (metaDataSource.hasSetter(propertyName)) {
  13.                 String value = (String) properties.get(propertyName);
  14.                 Object convertedValue = convertValue(metaDataSource, propertyName, value);
  15.                 // 通过 metaDataSource 来对 dataSource 进行设置属性
  16.                 metaDataSource.setValue(propertyName, convertedValue);
  17.             } else {
  18.                 throw new DataSourceException("Unknown DataSource property: " + propertyName);
  19.             }
  20.         }
  21.         if (driverProperties.size() > 0) {
  22.             metaDataSource.setValue("driverProperties", driverProperties);
  23.         }
  24.     }

UnpooledDataSource

  • org.apache.ibatis.datasource.unpooled.UnpooledDataSource主要定义数据库连接相关的一些属性,以及与数据库的链接对象创建

    1.     // 一些配置信息
    2.     private ClassLoader driverClassLoader;
    3.     private Properties driverProperties;
    4.     private String driver;
    5.     private String url;
    6.     private String username;
    7.     private String password;
    8.     private Boolean autoCommit;
    9.     private Integer defaultTransactionIsolationLevel;
    10.     private Integer defaultNetworkTimeout;

  • 初始化连接对象

    1.     /**
    2.      * 加载链接驱动 如 mysql 链接驱动
    3.      * @throws SQLException
    4.      */
    5.     private synchronized void initializeDriver() throws SQLException {
    6.         if (!registeredDrivers.containsKey(driver)) {
    7.             Class<?> driverType;
    8.             try {
    9.                 if (driverClassLoader != null) {
    10.                     driverType = Class.forName(driver, true, driverClassLoader);
    11.                 } else {
    12.                     driverType = Resources.classForName(driver);
    13.                 }
    14.                 // DriverManager requires the driver to be loaded via the system ClassLoader.
    15.                 // http://www.kfu.com/~nsayer/Java/dyn-jdbc.html
    16.                 Driver driverInstance = (Driver) driverType.getDeclaredConstructor().newInstance();
    17.                 DriverManager.registerDriver(new DriverProxy(driverInstance));
    18.                 registeredDrivers.put(driver, driverInstance);
    19.             } catch (Exception e) {
    20.                 throw new SQLException("Error setting driver on UnpooledDataSource. Cause: " + e);
    21.             }
    22.         }
    23.     }

  • 设置连接对象的属性

    1.     /**
    2.      * 设置连接对象 , 超时时间,是否自动提交事物
    3.      * @param conn
    4.      * @throws SQLException
    5.      */
    6.     private void configureConnection(Connection conn) throws SQLException {
    7.         if (defaultNetworkTimeout != null) {
    8.             conn.setNetworkTimeout(Executors.newSingleThreadExecutor(), defaultNetworkTimeout);
    9.         }
    10.         if (autoCommit != null && autoCommit != conn.getAutoCommit()) {
    11.             conn.setAutoCommit(autoCommit);
    12.         }
    13.         if (defaultTransactionIsolationLevel != null) {
    14.             conn.setTransactionIsolation(defaultTransactionIsolationLevel);
    15.         }
    16.     }

  • 获取连接对象

    1.     /**
    2.      * 获取链接对象
    3.      * @param username
    4.      * @param password
    5.      * @return
    6.      * @throws SQLException
    7.      */
    8.     private Connection doGetConnection(String username, String password) throws SQLException {
    9.         Properties props = new Properties();
    10.         if (driverProperties != null) {
    11.             props.putAll(driverProperties);
    12.         }
    13.         if (username != null) {
    14.             props.setProperty("user", username);
    15.         }
    16.         if (password != null) {
    17.             props.setProperty("password", password);
    18.         }
    19.         return doGetConnection(props);
    20.     }

解析流程

  • 在 xml 解析的过程中会执行DataSourceFactory相关内容
  1.     /**
  2.      * 解析 dataSourceElement 标签
  3.      * <dataSource type="POOLED">
  4.      * <property name="driver" value="com.mysql.jdbc.Driver"/>
  5.      * <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
  6.      * <property name="username" value="root"/>
  7.      * <property name="password" value="root"/>
  8.      * </dataSource>
  9.      *
  10.      * @param context
  11.      * @return
  12.      * @throws Exception
  13.      */
  14.     private DataSourceFactory dataSourceElement(XNode context) throws Exception {
  15.         if (context != null) {
  16.             String type = context.getStringAttribute("type");
  17.             Properties props = context.getChildrenAsProperties();
  18.             //org.apache.ibatis.session.Configuration.Configuration()
  19.             DataSourceFactory factory = (DataSourceFactory) resolveClass(type).getDeclaredConstructor().newInstance();
  21.             // PooledDataSourceFactory -> UnpooledDataSourceFactory
  22.             factory.setProperties(props);
  23.             return factory;
  24.         }
  25.         throw new BuilderException("Environment declaration requires a DataSourceFactory.");
  26.     }

从类图上或者代码中我们可以发现PooledDataSourceFactory是继承UnpooledDataSourceFactory那么方法应该也是UnpooledDataSourceFactory的。看看设置属性方法

image-20191223083610214

方法直接走完

image-20191223083732972