看看这个吧:java.sql包中的 java.sql.Driver, jdbc.sql.Connection等提供给程序开发人员统一的开发接口
数据库提供商提供相应的实现,对程序开发人员来讲只要知道这些接口都有哪些方法就可以了
但我们可以深入一些 看看到底这里面都做了那些事, 同时也可以学习其中的编程模式(如Interface模式等)1 Class.forName(String classname) 的源码为:
public final
class Class implements java.io.Serializable {
...
public static Class forName(String className)
throws ClassNotFoundException {
return forName0(className, true, ClassLoader.getCallerClassLoader());
}...
}
关于forName0 请自己查看jdk source.目的是把指定的Class装载到JVM中来。(注意class的装载、初始化过程)
在装载过程中将执行被装载类的static块(如下)2 sun的JdbcOdbcDriver 源码:
public class JdbcOdbcDriver extends JdbcOdbcObject
implements JdbcOdbcDriverInterface
{
...
/**
* connect to DB
*/
public synchronized Connection connect(String s, Properties properties)
throws SQLException
{
if(JdbcOdbcObject.isTracing())
JdbcOdbcObject.trace("*Driver.connect (" + s + ")");
if(!acceptsURL(s))
return null;
if(hDbc != 0)
{
disconnect(hDbc);
closeConnection(hDbc);
hDbc = 0;
}
if(!initialize())
{
return null;
}
else
{
JdbcOdbcConnection jdbcodbcconnection = new JdbcOdbcConnection(OdbcApi, hEnv, this);
jdbcodbcconnection.initialize(getSubName(s), properties, DriverManager.getLoginTimeout());
jdbcodbcconnection.setURL(s);
return jdbcodbcconnection;
}
}static
{
if(JdbcOdbcObject.isTracing())
JdbcOdbcObject.trace("JdbcOdbcDriver class loaded");
JdbcOdbcDriver jdbcodbcdriver = new JdbcOdbcDriver();
try
{
DriverManager.registerDriver(jdbcodbcdriver);
}
catch(SQLException sqlexception)
{
if(JdbcOdbcObject.isTracing())
JdbcOdbcObject.trace("Unable to register driver");
}
}
}public interface JdbcOdbcDriverInterface
extends Driver
{
...
}3 连接过程
jdbc.sql.Connection con =
DriverManager.getConnection("jdbc:odbc:pubs","sa","");public class DriverManager {
public static synchronized Connection getConnection(String url,
String user, String password) throws SQLException {
java.util.Properties info = new java.util.Properties();// Gets the classloader of the code that called this method, may
// be null.
ClassLoader callerCL = DriverManager.getCallerClassLoader();if (user != null) {
info.put("user", user);
}
if (password != null) {
info.put("password", password);
}return (getConnection(url, info, callerCL));
}
private static synchronized Connection getConnection(
String url,
java.util.Properties info,
ClassLoader callerCL) throws SQLException
{
...
Connection result = di.driver.connect(url, info);
...
}
}
数据库提供商提供相应的实现,对程序开发人员来讲只要知道这些接口都有哪些方法就可以了
但我们可以深入一些 看看到底这里面都做了那些事, 同时也可以学习其中的编程模式(如Interface模式等)1 Class.forName(String classname) 的源码为:
public final
class Class implements java.io.Serializable {
...
public static Class forName(String className)
throws ClassNotFoundException {
return forName0(className, true, ClassLoader.getCallerClassLoader());
}...
}
关于forName0 请自己查看jdk source.目的是把指定的Class装载到JVM中来。(注意class的装载、初始化过程)
在装载过程中将执行被装载类的static块(如下)2 sun的JdbcOdbcDriver 源码:
public class JdbcOdbcDriver extends JdbcOdbcObject
implements JdbcOdbcDriverInterface
{
...
/**
* connect to DB
*/
public synchronized Connection connect(String s, Properties properties)
throws SQLException
{
if(JdbcOdbcObject.isTracing())
JdbcOdbcObject.trace("*Driver.connect (" + s + ")");
if(!acceptsURL(s))
return null;
if(hDbc != 0)
{
disconnect(hDbc);
closeConnection(hDbc);
hDbc = 0;
}
if(!initialize())
{
return null;
}
else
{
JdbcOdbcConnection jdbcodbcconnection = new JdbcOdbcConnection(OdbcApi, hEnv, this);
jdbcodbcconnection.initialize(getSubName(s), properties, DriverManager.getLoginTimeout());
jdbcodbcconnection.setURL(s);
return jdbcodbcconnection;
}
}static
{
if(JdbcOdbcObject.isTracing())
JdbcOdbcObject.trace("JdbcOdbcDriver class loaded");
JdbcOdbcDriver jdbcodbcdriver = new JdbcOdbcDriver();
try
{
DriverManager.registerDriver(jdbcodbcdriver);
}
catch(SQLException sqlexception)
{
if(JdbcOdbcObject.isTracing())
JdbcOdbcObject.trace("Unable to register driver");
}
}
}public interface JdbcOdbcDriverInterface
extends Driver
{
...
}3 连接过程
jdbc.sql.Connection con =
DriverManager.getConnection("jdbc:odbc:pubs","sa","");public class DriverManager {
public static synchronized Connection getConnection(String url,
String user, String password) throws SQLException {
java.util.Properties info = new java.util.Properties();// Gets the classloader of the code that called this method, may
// be null.
ClassLoader callerCL = DriverManager.getCallerClassLoader();if (user != null) {
info.put("user", user);
}
if (password != null) {
info.put("password", password);
}return (getConnection(url, info, callerCL));
}
private static synchronized Connection getConnection(
String url,
java.util.Properties info,
ClassLoader callerCL) throws SQLException
{
...
Connection result = di.driver.connect(url, info);
...
}
}
我以前学了挺长时间vc,所以现在改学j2ee感觉还行。
to hoxisoft:
现在大一刚开始,高深啊,不过还是万分感谢;
to mailbornb:
能推荐一本吗?
to jsbyl:
校园网进不了哦。
to neuhawk:
多多指教。[email protected]