JDK8/Java8源码在线阅读
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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*
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package java.sql;
import java.util.Iterator;
import java.util.ServiceLoader;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.concurrent.CopyOnWriteArrayList;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
/**
* <P>The basic service for managing a set of JDBC drivers.<br>
* <B>NOTE:</B> The {@link javax.sql.DataSource} interface, new in the
* JDBC 2.0 API, provides another way to connect to a data source.
* The use of a <code>DataSource</code> object is the preferred means of
* connecting to a data source.
*
* <P>As part of its initialization, the <code>DriverManager</code> class will
* attempt to load the driver classes referenced in the "jdbc.drivers"
* system property. This allows a user to customize the JDBC Drivers
* used by their applications. For example in your
* ~/.hotjava/properties file you might specify:
* <pre>
* <CODE>jdbc.drivers=foo.bah.Driver:wombat.sql.Driver:bad.taste.ourDriver</CODE>
* </pre>
*<P> The <code>DriverManager</code> methods <code>getConnection</code> and
* <code>getDrivers</code> have been enhanced to support the Java Standard Edition
* <a href="../../../technotes/guides/jar/jar.html#Service%20Provider">Service Provider</a> mechanism. JDBC 4.0 Drivers must
* include the file <code>META-INF/services/java.sql.Driver</code>. This file contains the name of the JDBC drivers
* implementation of <code>java.sql.Driver</code>. For example, to load the <code>my.sql.Driver</code> class,
* the <code>META-INF/services/java.sql.Driver</code> file would contain the entry:
* <pre>
* <code>my.sql.Driver</code>
* </pre>
*
* <P>Applications no longer need to explicitly load JDBC drivers using <code>Class.forName()</code>. Existing programs
* which currently load JDBC drivers using <code>Class.forName()</code> will continue to work without
* modification.
*
* <P>When the method <code>getConnection</code> is called,
* the <code>DriverManager</code> will attempt to
* locate a suitable driver from amongst those loaded at
* initialization and those loaded explicitly using the same classloader
* as the current applet or application.
*
* <P>
* Starting with the Java 2 SDK, Standard Edition, version 1.3, a
* logging stream can be set only if the proper
* permission has been granted. Normally this will be done with
* the tool PolicyTool, which can be used to grant <code>permission
* java.sql.SQLPermission "setLog"</code>.
* @see Driver
* @see Connection
*/
public class DriverManager {
// List of registered JDBC drivers
private final static CopyOnWriteArrayList<DriverInfo> registeredDrivers = new CopyOnWriteArrayList<>();
private static volatile int loginTimeout = 0;
private static volatile java.io.PrintWriter logWriter = null;
private static volatile java.io.PrintStream logStream = null;
// Used in println() to synchronize logWriter
private final static Object logSync = new Object();
/* Prevent the DriverManager class from being instantiated. */
private DriverManager(){}
/**
* Load the initial JDBC drivers by checking the System property
* jdbc.properties and then use the {@code ServiceLoader} mechanism
*/
static {
loadInitialDrivers();
println("JDBC DriverManager initialized");
}
/**
* The <code>SQLPermission</code> constant that allows the
* setting of the logging stream.
* @since 1.3
*/
final static SQLPermission SET_LOG_PERMISSION =
new SQLPermission("setLog");
/**
* The {@code SQLPermission} constant that allows the
* un-register a registered JDBC driver.
* @since 1.8
*/
final static SQLPermission DEREGISTER_DRIVER_PERMISSION =
new SQLPermission("deregisterDriver");
//--------------------------JDBC 2.0-----------------------------
/**
* Retrieves the log writer.
*
* The <code>getLogWriter</code> and <code>setLogWriter</code>
* methods should be used instead
* of the <code>get/setlogStream</code> methods, which are deprecated.
* @return a <code>java.io.PrintWriter</code> object
* @see #setLogWriter
* @since 1.2
*/
public static java.io.PrintWriter getLogWriter() {
return logWriter;
}
/**
* Sets the logging/tracing <code>PrintWriter</code> object
* that is used by the <code>DriverManager</code> and all drivers.
* <P>
* There is a minor versioning problem created by the introduction
* of the method <code>setLogWriter</code>. The
* method <code>setLogWriter</code> cannot create a <code>PrintStream</code> object
* that will be returned by <code>getLogStream</code>---the Java platform does
* not provide a backward conversion. As a result, a new application
* that uses <code>setLogWriter</code> and also uses a JDBC 1.0 driver that uses
* <code>getLogStream</code> will likely not see debugging information written
* by that driver.
*<P>
* Starting with the Java 2 SDK, Standard Edition, version 1.3 release, this method checks
* to see that there is an <code>SQLPermission</code> object before setting
* the logging stream. If a <code>SecurityManager</code> exists and its
* <code>checkPermission</code> method denies setting the log writer, this
* method throws a <code>java.lang.SecurityException</code>.
*
* @param out the new logging/tracing <code>PrintStream</code> object;
* <code>null</code> to disable logging and tracing
* @throws SecurityException
* if a security manager exists and its
* <code>checkPermission</code> method denies
* setting the log writer
*
* @see SecurityManager#checkPermission
* @see #getLogWriter
* @since 1.2
*/
public static void setLogWriter(java.io.PrintWriter out) {
SecurityManager sec = System.getSecurityManager();
if (sec != null) {
sec.checkPermission(SET_LOG_PERMISSION);
}
logStream = null;
logWriter = out;
}
//---------------------------------------------------------------
/**
* Attempts to establish a connection to the given database URL.
* The <code>DriverManager</code> attempts to select an appropriate driver from
* the set of registered JDBC drivers.
*<p>
* <B>Note:</B> If a property is specified as part of the {@code url} and
* is also specified in the {@code Properties} object, it is
* implementation-defined as to which value will take precedence.
* For maximum portability, an application should only specify a
* property once.
*
* @param url a database url of the form
* <code> jdbc:<em>subprotocol</em>:<em>subname</em></code>
* @param info a list of arbitrary string tag/value pairs as
* connection arguments; normally at least a "user" and
* "password" property should be included
* @return a Connection to the URL
* @exception SQLException if a database access error occurs or the url is
* {@code null}
* @throws SQLTimeoutException when the driver has determined that the
* timeout value specified by the {@code setLoginTimeout} method
* has been exceeded and has at least tried to cancel the
* current database connection attempt
*/
@CallerSensitive
public static Connection getConnection(String url,
java.util.Properties info) throws SQLException {
return (getConnection(url, info, Reflection.getCallerClass()));
}
/**
* Attempts to establish a connection to the given database URL.
* The <code>DriverManager</code> attempts to select an appropriate driver from
* the set of registered JDBC drivers.
*<p>
* <B>Note:</B> If the {@code user} or {@code password} property are
* also specified as part of the {@code url}, it is
* implementation-defined as to which value will take precedence.
* For maximum portability, an application should only specify a
* property once.
*
* @param url a database url of the form
* <code>jdbc:<em>subprotocol</em>:<em>subname</em></code>
* @param user the database user on whose behalf the connection is being
* made
* @param password the user's password
* @return a connection to the URL
* @exception SQLException if a database access error occurs or the url is
* {@code null}
* @throws SQLTimeoutException when the driver has determined that the
* timeout value specified by the {@code setLoginTimeout} method
* has been exceeded and has at least tried to cancel the
* current database connection attempt
*/
@CallerSensitive
public static Connection getConnection(String url,
String user, String password) throws SQLException {
java.util.Properties info = new java.util.Properties();
if (user != null) {
info.put("user", user);
}
if (password != null) {
info.put("password", password);
}
return (getConnection(url, info, Reflection.getCallerClass()));
}
/**
* Attempts to establish a connection to the given database URL.
* The <code>DriverManager</code> attempts to select an appropriate driver from
* the set of registered JDBC drivers.
*
* @param url a database url of the form
* <code> jdbc:<em>subprotocol</em>:<em>subname</em></code>
* @return a connection to the URL
* @exception SQLException if a database access error occurs or the url is
* {@code null}
* @throws SQLTimeoutException when the driver has determined that the
* timeout value specified by the {@code setLoginTimeout} method
* has been exceeded and has at least tried to cancel the
* current database connection attempt
*/
@CallerSensitive
public static Connection getConnection(String url)
throws SQLException {
java.util.Properties info = new java.util.Properties();
return (getConnection(url, info, Reflection.getCallerClass()));
}
/**
* Attempts to locate a driver that understands the given URL.
* The <code>DriverManager</code> attempts to select an appropriate driver from
* the set of registered JDBC drivers.
*
* @param url a database URL of the form
* <code>jdbc:<em>subprotocol</em>:<em>subname</em></code>
* @return a <code>Driver</code> object representing a driver
* that can connect to the given URL
* @exception SQLException if a database access error occurs
*/
@CallerSensitive
public static Driver getDriver(String url)
throws SQLException {
println("DriverManager.getDriver(\"" + url + "\")");
Class<?> callerClass = Reflection.getCallerClass();
// Walk through the loaded registeredDrivers attempting to locate someone
// who understands the given URL.
for (DriverInfo aDriver : registeredDrivers) {
// If the caller does not have permission to load the driver then
// skip it.
if(isDriverAllowed(aDriver.driver, callerClass)) {
try {
if(aDriver.driver.acceptsURL(url)) {
// Success!
println("getDriver returning " + aDriver.driver.getClass().getName());
return (aDriver.driver);
}
} catch(SQLException sqe) {
// Drop through and try the next driver.
}
} else {
println(" skipping: " + aDriver.driver.getClass().getName());
}
}
println("getDriver: no suitable driver");
throw new SQLException("No suitable driver", "08001");
}
/**
* Registers the given driver with the {@code DriverManager}.
* A newly-loaded driver class should call
* the method {@code registerDriver} to make itself
* known to the {@code DriverManager}. If the driver is currently
* registered, no action is taken.
*
* @param driver the new JDBC Driver that is to be registered with the
* {@code DriverManager}
* @exception SQLException if a database access error occurs
* @exception NullPointerException if {@code driver} is null
*/
public static synchronized void registerDriver(java.sql.Driver driver)
throws SQLException {
registerDriver(driver, null);
}
/**
* Registers the given driver with the {@code DriverManager}.
* A newly-loaded driver class should call
* the method {@code registerDriver} to make itself
* known to the {@code DriverManager}. If the driver is currently
* registered, no action is taken.
*
* @param driver the new JDBC Driver that is to be registered with the
* {@code DriverManager}
* @param da the {@code DriverAction} implementation to be used when
* {@code DriverManager#deregisterDriver} is called
* @exception SQLException if a database access error occurs
* @exception NullPointerException if {@code driver} is null
* @since 1.8
*/
public static synchronized void registerDriver(java.sql.Driver driver,
DriverAction da)
throws SQLException {
/* Register the driver if it has not already been added to our list */
if(driver != null) {
registeredDrivers.addIfAbsent(new DriverInfo(driver, da));
} else {
// This is for compatibility with the original DriverManager
throw new NullPointerException();
}
println("registerDriver: " + driver);
}
/**
* Removes the specified driver from the {@code DriverManager}'s list of
* registered drivers.
* <p>
* If a {@code null} value is specified for the driver to be removed, then no
* action is taken.
* <p>
* If a security manager exists and its {@code checkPermission} denies
* permission, then a {@code SecurityException} will be thrown.
* <p>
* If the specified driver is not found in the list of registered drivers,
* then no action is taken. If the driver was found, it will be removed
* from the list of registered drivers.
* <p>
* If a {@code DriverAction} instance was specified when the JDBC driver was
* registered, its deregister method will be called
* prior to the driver being removed from the list of registered drivers.
*
* @param driver the JDBC Driver to remove
* @exception SQLException if a database access error occurs
* @throws SecurityException if a security manager exists and its
* {@code checkPermission} method denies permission to deregister a driver.
*
* @see SecurityManager#checkPermission
*/
@CallerSensitive
public static synchronized void deregisterDriver(Driver driver)
throws SQLException {
if (driver == null) {
return;
}
SecurityManager sec = System.getSecurityManager();
if (sec != null) {
sec.checkPermission(DEREGISTER_DRIVER_PERMISSION);
}
println("DriverManager.deregisterDriver: " + driver);
DriverInfo aDriver = new DriverInfo(driver, null);
if(registeredDrivers.contains(aDriver)) {
if (isDriverAllowed(driver, Reflection.getCallerClass())) {
DriverInfo di = registeredDrivers.get(registeredDrivers.indexOf(aDriver));
// If a DriverAction was specified, Call it to notify the
// driver that it has been deregistered
if(di.action() != null) {
di.action().deregister();
}
registeredDrivers.remove(aDriver);
} else {
// If the caller does not have permission to load the driver then
// throw a SecurityException.
throw new SecurityException();
}
} else {
println(" couldn't find driver to unload");
}
}
/**
* Retrieves an Enumeration with all of the currently loaded JDBC drivers
* to which the current caller has access.
*
* <P><B>Note:</B> The classname of a driver can be found using
* <CODE>d.getClass().getName()</CODE>
*
* @return the list of JDBC Drivers loaded by the caller's class loader
*/
@CallerSensitive
public static java.util.Enumeration<Driver> getDrivers() {
java.util.Vector<Driver> result = new java.util.Vector<>();
Class<?> callerClass = Reflection.getCallerClass();
// Walk through the loaded registeredDrivers.
for(DriverInfo aDriver : registeredDrivers) {
// If the caller does not have permission to load the driver then
// skip it.
if(isDriverAllowed(aDriver.driver, callerClass)) {
result.addElement(aDriver.driver);
} else {
println(" skipping: " + aDriver.getClass().getName());
}
}
return (result.elements());
}
/**
* Sets the maximum time in seconds that a driver will wait
* while attempting to connect to a database once the driver has
* been identified.
*
* @param seconds the login time limit in seconds; zero means there is no limit
* @see #getLoginTimeout
*/
public static void setLoginTimeout(int seconds) {
loginTimeout = seconds;
}
/**
* Gets the maximum time in seconds that a driver can wait
* when attempting to log in to a database.
*
* @return the driver login time limit in seconds
* @see #setLoginTimeout
*/
public static int getLoginTimeout() {
return (loginTimeout);
}
/**
* Sets the logging/tracing PrintStream that is used
* by the <code>DriverManager</code>
* and all drivers.
*<P>
* In the Java 2 SDK, Standard Edition, version 1.3 release, this method checks
* to see that there is an <code>SQLPermission</code> object before setting
* the logging stream. If a <code>SecurityManager</code> exists and its
* <code>checkPermission</code> method denies setting the log writer, this
* method throws a <code>java.lang.SecurityException</code>.
*
* @param out the new logging/tracing PrintStream; to disable, set to <code>null</code>
* @deprecated Use {@code setLogWriter}
* @throws SecurityException if a security manager exists and its
* <code>checkPermission</code> method denies setting the log stream
*
* @see SecurityManager#checkPermission
* @see #getLogStream
*/
@Deprecated
public static void setLogStream(java.io.PrintStream out) {
SecurityManager sec = System.getSecurityManager();
if (sec != null) {
sec.checkPermission(SET_LOG_PERMISSION);
}
logStream = out;
if ( out != null )
logWriter = new java.io.PrintWriter(out);
else
logWriter = null;
}
/**
* Retrieves the logging/tracing PrintStream that is used by the <code>DriverManager</code>
* and all drivers.
*
* @return the logging/tracing PrintStream; if disabled, is <code>null</code>
* @deprecated Use {@code getLogWriter}
* @see #setLogStream
*/
@Deprecated
public static java.io.PrintStream getLogStream() {
return logStream;
}
/**
* Prints a message to the current JDBC log stream.
*
* @param message a log or tracing message
*/
public static void println(String message) {
synchronized (logSync) {
if (logWriter != null) {
logWriter.println(message);
// automatic flushing is never enabled, so we must do it ourselves
logWriter.flush();
}
}
}
//------------------------------------------------------------------------
// Indicates whether the class object that would be created if the code calling
// DriverManager is accessible.
private static boolean isDriverAllowed(Driver driver, Class<?> caller) {
ClassLoader callerCL = caller != null ? caller.getClassLoader() : null;
return isDriverAllowed(driver, callerCL);
}
private static boolean isDriverAllowed(Driver driver, ClassLoader classLoader) {
boolean result = false;
if(driver != null) {
Class<?> aClass = null;
try {
aClass = Class.forName(driver.getClass().getName(), true, classLoader);
} catch (Exception ex) {
result = false;
}
result = ( aClass == driver.getClass() ) ? true : false;
}
return result;
}
private static void loadInitialDrivers() {
String drivers;
try {
drivers = AccessController.doPrivileged(new PrivilegedAction<String>() {
public String run() {
return System.getProperty("jdbc.drivers");
}
});
} catch (Exception ex) {
drivers = null;
}
// If the driver is packaged as a Service Provider, load it.
// Get all the drivers through the classloader
// exposed as a java.sql.Driver.class service.
// ServiceLoader.load() replaces the sun.misc.Providers()
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
ServiceLoader<Driver> loadedDrivers = ServiceLoader.load(Driver.class);
Iterator<Driver> driversIterator = loadedDrivers.iterator();
/* Load these drivers, so that they can be instantiated.
* It may be the case that the driver class may not be there
* i.e. there may be a packaged driver with the service class
* as implementation of java.sql.Driver but the actual class
* may be missing. In that case a java.util.ServiceConfigurationError
* will be thrown at runtime by the VM trying to locate
* and load the service.
*
* Adding a try catch block to catch those runtime errors
* if driver not available in classpath but it's
* packaged as service and that service is there in classpath.
*/
try{
while(driversIterator.hasNext()) {
driversIterator.next();
}
} catch(Throwable t) {
// Do nothing
}
return null;
}
});
println("DriverManager.initialize: jdbc.drivers = " + drivers);
if (drivers == null || drivers.equals("")) {
return;
}
String[] driversList = drivers.split(":");
println("number of Drivers:" + driversList.length);
for (String aDriver : driversList) {
try {
println("DriverManager.Initialize: loading " + aDriver);
Class.forName(aDriver, true,
ClassLoader.getSystemClassLoader());
} catch (Exception ex) {
println("DriverManager.Initialize: load failed: " + ex);
}
}
}
// Worker method called by the public getConnection() methods.
private static Connection getConnection(
String url, java.util.Properties info, Class<?> caller) throws SQLException {
/*
* When callerCl is null, we should check the application's
* (which is invoking this class indirectly)
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