mybatis datasource

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+# Mybatis DataSource
+- `org.apache.ibatis.datasource.DataSourceFactory`
+```java
+/**
+ * 数据源工厂
+ * @author Clinton Begin
+ */
+public interface DataSourceFactory {
+
+    /**
+     * 设置 dataSource 属性
+     * @param props
+     */
+    void setProperties(Properties props);
+
+    /**
+     * 获取 dataSource
+     * @return {@link DataSource}
+     */
+    DataSource getDataSource();
+
+}
+
+```
+
+类图如下
+
+![image-20191223081023730](/images/mybatis/image-20191223081023730.png)
+
+- `setProperties`会将下列标签放入`datasource`中
+
+```java
+      <dataSource type="POOLED">
+        <property name="driver" value="com.mysql.jdbc.Driver"/>
+        <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false"/>
+        <property name="username" value="mybatis"/>
+        <property name="password" value="mybatis"/>
+      </dataSource>
+```
+
+
+
+
+
+
+
+
+
+- 在`org.apache.ibatis.session.Configuration`中有配置下面三个信息
+```java
+        typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);
+        typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);
+        typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);
+
+```
+
+
+
+
+
+
+
+
+
+## JndiDataSourceFactory
+
+```java
+/**
+ * @author Clinton Begin
+ */
+public class JndiDataSourceFactory implements DataSourceFactory {
+
+    public static final String INITIAL_CONTEXT = "initial_context";
+    public static final String DATA_SOURCE = "data_source";
+    public static final String ENV_PREFIX = "env.";
+
+    /**
+     * 直接 java 数据源
+     */
+    private DataSource dataSource;
+
+    /**
+     * 获取数据源的配置信息
+     * @param allProps
+     * @return
+     */
+    private static Properties getEnvProperties(Properties allProps) {
+        final String PREFIX = ENV_PREFIX;
+        Properties contextProperties = null;
+        for (Entry<Object, Object> entry : allProps.entrySet()) {
+            String key = (String) entry.getKey();
+            String value = (String) entry.getValue();
+            // 只获取前缀`env`
+            if (key.startsWith(PREFIX)) {
+                if (contextProperties == null) {
+                    contextProperties = new Properties();
+                }
+                // 放入数据
+                contextProperties.put(key.substring(PREFIX.length()), value);
+            }
+        }
+        return contextProperties;
+    }
+
+    /**
+     * 设置数据源属性
+     * @param properties
+     */
+    @Override
+    public void setProperties(Properties properties) {
+        try {
+            InitialContext initCtx;
+            Properties env = getEnvProperties(properties);
+            if (env == null) {
+                initCtx = new InitialContext();
+            } else {
+                initCtx = new InitialContext(env);
+            }
+
+            if (properties.containsKey(INITIAL_CONTEXT)
+                    && properties.containsKey(DATA_SOURCE)) {
+                // 如果包含`initial_context`和`data_source`
+                Context ctx = (Context) initCtx.lookup(properties.getProperty(INITIAL_CONTEXT));
+                dataSource = (DataSource) ctx.lookup(properties.getProperty(DATA_SOURCE));
+            } else if (properties.containsKey(DATA_SOURCE)) {
+                dataSource = (DataSource) initCtx.lookup(properties.getProperty(DATA_SOURCE));
+            }
+
+        } catch (NamingException e) {
+            throw new DataSourceException("There was an error configuring JndiDataSourceTransactionPool. Cause: " + e, e);
+        }
+    }
+
+    @Override
+    public DataSource getDataSource() {
+        return dataSource;
+    }
+
+}
+```
+
+## PooledDataSource
+
+```java
+	protected int poolMaximumActiveConnections = 10;
+    protected int poolMaximumIdleConnections = 5;
+    protected int poolMaximumCheckoutTime = 20000;
+    protected int poolTimeToWait = 20000;
+    protected int poolMaximumLocalBadConnectionTolerance = 3;
+    protected String poolPingQuery = "NO PING QUERY SET";
+    protected boolean poolPingEnabled;
+    protected int poolPingConnectionsNotUsedFor;
+```
+
+
+
+## PooledDataSourceFactory
+
+```java
+public class PooledDataSourceFactory extends UnpooledDataSourceFactory {
+
+
+    public PooledDataSourceFactory() {
+        this.dataSource = new PooledDataSource();
+    }
+
+}
+
+	// 初始化
+    public PooledDataSource() {
+        dataSource = new UnpooledDataSource();
+    }
+```
+
+
+
+## UnpooledDataSourceFactory
+
+```java
+    @Override
+    public void setProperties(Properties properties) {
+        Properties driverProperties = new Properties();
+        //metaDataSource 现在是一个dataSource
+        MetaObject metaDataSource = SystemMetaObject.forObject(dataSource);
+        for (Object key : properties.keySet()) {
+            String propertyName = (String) key;
+            if (propertyName.startsWith(DRIVER_PROPERTY_PREFIX)) {
+                // 如果是 driver. 前缀开头
+                String value = properties.getProperty(propertyName);
+                driverProperties.setProperty(propertyName.substring(DRIVER_PROPERTY_PREFIX_LENGTH), value);
+            } else if (metaDataSource.hasSetter(propertyName)) {
+                String value = (String) properties.get(propertyName);
+                Object convertedValue = convertValue(metaDataSource, propertyName, value);
+                // 通过 metaDataSource 来对 dataSource 进行设置属性
+                metaDataSource.setValue(propertyName, convertedValue);
+            } else {
+                throw new DataSourceException("Unknown DataSource property: " + propertyName);
+            }
+        }
+        if (driverProperties.size() > 0) {
+            metaDataSource.setValue("driverProperties", driverProperties);
+        }
+    }
+
+```
+
+
+
+## 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
+
+  ```java
+      // 一些配置信息
+      private ClassLoader driverClassLoader;
+      private Properties driverProperties;
+      private String driver;
+      private String url;
+      private String username;
+      private String password;
+      private Boolean autoCommit;
+      private Integer defaultTransactionIsolationLevel;
+      private Integer defaultNetworkTimeout;
+  ```
+
+  
+
+- 初始化连接对象
+
+  ```java
+      /**
+       * 加载链接驱动 如 mysql 链接驱动
+       * @throws SQLException
+       */
+      private synchronized void initializeDriver() throws SQLException {
+          if (!registeredDrivers.containsKey(driver)) {
+              Class<?> driverType;
+              try {
+                  if (driverClassLoader != null) {
+                      driverType = Class.forName(driver, true, driverClassLoader);
+                  } else {
+                      driverType = Resources.classForName(driver);
+                  }
+                  // DriverManager requires the driver to be loaded via the system ClassLoader.
+                  // http://www.kfu.com/~nsayer/Java/dyn-jdbc.html
+                  Driver driverInstance = (Driver) driverType.getDeclaredConstructor().newInstance();
+                  DriverManager.registerDriver(new DriverProxy(driverInstance));
+                  registeredDrivers.put(driver, driverInstance);
+              } catch (Exception e) {
+                  throw new SQLException("Error setting driver on UnpooledDataSource. Cause: " + e);
+              }
+          }
+      }
+  
+  ```
+
+  
+
+- 设置连接对象的属性
+
+  ```java
+      /**
+       * 设置连接对象 , 超时时间,是否自动提交事物
+       * @param conn
+       * @throws SQLException
+       */
+      private void configureConnection(Connection conn) throws SQLException {
+          if (defaultNetworkTimeout != null) {
+              conn.setNetworkTimeout(Executors.newSingleThreadExecutor(), defaultNetworkTimeout);
+          }
+          if (autoCommit != null && autoCommit != conn.getAutoCommit()) {
+              conn.setAutoCommit(autoCommit);
+          }
+          if (defaultTransactionIsolationLevel != null) {
+              conn.setTransactionIsolation(defaultTransactionIsolationLevel);
+          }
+      }
+  
+  ```
+
+  
+
+- 获取连接对象
+
+  ```java
+      /**
+       * 获取链接对象
+       * @param username
+       * @param password
+       * @return
+       * @throws SQLException
+       */
+      private Connection doGetConnection(String username, String password) throws SQLException {
+          Properties props = new Properties();
+          if (driverProperties != null) {
+              props.putAll(driverProperties);
+          }
+          if (username != null) {
+              props.setProperty("user", username);
+          }
+          if (password != null) {
+              props.setProperty("password", password);
+          }
+          return doGetConnection(props);
+      }
+  
+  ```
+
+  
+
+
+
+
+
+## 解析流程
+
+- 在xml解析的过程中会执行`DataSourceFactory`相关内容
+
+```java
+    /**
+     * 解析 dataSourceElement 标签
+     * <dataSource type="POOLED">
+     * <property name="driver" value="com.mysql.jdbc.Driver"/>
+     * <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
+     * <property name="username" value="root"/>
+     * <property name="password" value="root"/>
+     * </dataSource>
+     *
+     * @param context
+     * @return
+     * @throws Exception
+     */
+    private DataSourceFactory dataSourceElement(XNode context) throws Exception {
+        if (context != null) {
+            String type = context.getStringAttribute("type");
+            Properties props = context.getChildrenAsProperties();
+            //org.apache.ibatis.session.Configuration.Configuration()
+            DataSourceFactory factory = (DataSourceFactory) resolveClass(type).getDeclaredConstructor().newInstance();
+
+            // PooledDataSourceFactory -> UnpooledDataSourceFactory
+            factory.setProperties(props);
+            return factory;
+        }
+        throw new BuilderException("Environment declaration requires a DataSourceFactory.");
+    }
+
+```
+
+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](/images/mybatis/image-20191223083610214.png)
+
+方法直接走完
+
+![image-20191223083732972](/images/mybatis/image-20191223083732972.png)
+
--- a/images/mybatis/image-20191223081023730.png
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--- a/images/mybatis/image-20191223083610214.png
+++ b/images/mybatis/image-20191223083610214.png
--- a/images/mybatis/image-20191223083732972.png
+++ b/images/mybatis/image-20191223083732972.png