# Mybatis DataSource
- Author: [HuiFer](https://github.com/huifer)
- Description: 该文介绍 mybatis DataSource 源码
- 源码阅读工程: [SourceHot-Mybatis](https://github.com/SourceHot/mybatis-read.git)
- `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
- `setProperties`会将下列标签放入`datasource`中
```java
```
- 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 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
*
*
*
*
*
*
*
* @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
方法直接走完
