UnpooledDataSource.java

/*
 *    Copyright 2009-2012 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.datasource.unpooled;

import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.DriverPropertyInfo;
import java.sql.SQLException;
import java.util.Enumeration;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Logger;

import javax.sql.DataSource;

import org.apache.ibatis.io.Resources;

/**
 * @author Clinton Begin
 * @author Eduardo Macarron
 */
/**
 * 没有池化的数据源
 */
public class UnpooledDataSource implements DataSource {
  
  private ClassLoader driverClassLoader;
  //作为可选项,你可以传递数据库驱动的属性。要这样做,属性的前缀是以“driver.”开 头的,例如
  //driver.encoding=UTF8
  private Properties driverProperties;
  private static Map<String, Driver> registeredDrivers = new ConcurrentHashMap<String, Driver>();

  private String driver;
  private String url;
  private String username;
  private String password;

  private Boolean autoCommit;
  private Integer defaultTransactionIsolationLevel;

  static {
    Enumeration<Driver> drivers = DriverManager.getDrivers();
    while (drivers.hasMoreElements()) {
      Driver driver = drivers.nextElement();
      registeredDrivers.put(driver.getClass().getName(), driver);
    }
  }

  public UnpooledDataSource() {
  }

  public UnpooledDataSource(String driver, String url, String username, String password) {
    this.driver = driver;
    this.url = url;
    this.username = username;
    this.password = password;
  }

  public UnpooledDataSource(String driver, String url, Properties driverProperties) {
    this.driver = driver;
    this.url = url;
    this.driverProperties = driverProperties;
  }

  public UnpooledDataSource(ClassLoader driverClassLoader, String driver, String url, String username, String password) {
    this.driverClassLoader = driverClassLoader;
    this.driver = driver;
    this.url = url;
    this.username = username;
    this.password = password;
  }

  public UnpooledDataSource(ClassLoader driverClassLoader, String driver, String url, Properties driverProperties) {
    this.driverClassLoader = driverClassLoader;
    this.driver = driver;
    this.url = url;
    this.driverProperties = driverProperties;
  }

  @Override
  public Connection getConnection() throws SQLException {
    return doGetConnection(username, password);
  }

  @Override
  public Connection getConnection(String username, String password) throws SQLException {
    return doGetConnection(username, password);
  }

  @Override
  public void setLoginTimeout(int loginTimeout) throws SQLException {
    DriverManager.setLoginTimeout(loginTimeout);
  }

  @Override
  public int getLoginTimeout() throws SQLException {
    return DriverManager.getLoginTimeout();
  }

  @Override
  public void setLogWriter(PrintWriter logWriter) throws SQLException {
    DriverManager.setLogWriter(logWriter);
  }

  @Override
  public PrintWriter getLogWriter() throws SQLException {
    return DriverManager.getLogWriter();
  }

  public ClassLoader getDriverClassLoader() {
    return driverClassLoader;
  }

  public void setDriverClassLoader(ClassLoader driverClassLoader) {
    this.driverClassLoader = driverClassLoader;
  }

  public Properties getDriverProperties() {
    return driverProperties;
  }

  public void setDriverProperties(Properties driverProperties) {
    this.driverProperties = driverProperties;
  }

  public String getDriver() {
    return driver;
  }

  public synchronized void setDriver(String driver) {
    this.driver = driver;
  }

  public String getUrl() {
    return url;
  }

  public void setUrl(String url) {
    this.url = url;
  }

  public String getUsername() {
    return username;
  }

  public void setUsername(String username) {
    this.username = username;
  }

  public String getPassword() {
    return password;
  }

  public void setPassword(String password) {
    this.password = password;
  }

  public Boolean isAutoCommit() {
    return autoCommit;
  }

  public void setAutoCommit(Boolean autoCommit) {
    this.autoCommit = autoCommit;
  }

  public Integer getDefaultTransactionIsolationLevel() {
    return defaultTransactionIsolationLevel;
  }

  public void setDefaultTransactionIsolationLevel(Integer defaultTransactionIsolationLevel) {
    this.defaultTransactionIsolationLevel = defaultTransactionIsolationLevel;
  }

  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);
  }

  private Connection doGetConnection(Properties properties) throws SQLException {
    initializeDriver();
    //属性的前缀是以“driver.”开 头的,它 是 通 过 DriverManager.getConnection(url,driverProperties)方法传递给数据库驱动
    Connection connection = DriverManager.getConnection(url, properties);
    configureConnection(connection);
    return connection;
  }

  private synchronized void initializeDriver() throws SQLException {
	  //这里便是大家熟悉的初学JDBC时的那几句话了 Class.forName newInstance()
    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.newInstance();
        DriverManager.registerDriver(new DriverProxy(driverInstance));
        registeredDrivers.put(driver, driverInstance);
      } catch (Exception e) {
        throw new SQLException("Error setting driver on UnpooledDataSource. Cause: " + e);
      }
    }
  }

  private void configureConnection(Connection conn) throws SQLException {
    if (autoCommit != null && autoCommit != conn.getAutoCommit()) {
      conn.setAutoCommit(autoCommit);
    }
    if (defaultTransactionIsolationLevel != null) {
      conn.setTransactionIsolation(defaultTransactionIsolationLevel);
    }
  }

  /**
   * 驱动代理
   * 不是很懂
   *
   */
  private static class DriverProxy implements Driver {
    private Driver driver;

    DriverProxy(Driver d) {
      this.driver = d;
    }

    @Override
    public boolean acceptsURL(String u) throws SQLException {
      return this.driver.acceptsURL(u);
    }

    @Override
    public Connection connect(String u, Properties p) throws SQLException {
      return this.driver.connect(u, p);
    }

    @Override
    public int getMajorVersion() {
      return this.driver.getMajorVersion();
    }

    @Override
    public int getMinorVersion() {
      return this.driver.getMinorVersion();
    }

    @Override
    public DriverPropertyInfo[] getPropertyInfo(String u, Properties p) throws SQLException {
      return this.driver.getPropertyInfo(u, p);
    }

    @Override
    public boolean jdbcCompliant() {
      return this.driver.jdbcCompliant();
    }

    // @Override only valid jdk7+
    public Logger getParentLogger() {
      return Logger.getLogger(Logger.GLOBAL_LOGGER_NAME);
    }
  }

  @Override
  public <T> T unwrap(Class<T> iface) throws SQLException {
    throw new SQLException(getClass().getName() + " is not a wrapper.");
  }

  @Override
  public boolean isWrapperFor(Class<?> iface) throws SQLException {
    return false;
  }

  // @Override only valid jdk7+
  public Logger getParentLogger() {
    // requires JDK version 1.6
    return Logger.getLogger(Logger.GLOBAL_LOGGER_NAME);
  }

}