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