* Example: *
*
* RowSetFactory aFactory = RowSetProvider.newFactory();
* CachedRowSet crs = aFactory.createCachedRowSet();
* ...
* RowSetFactory rsf = RowSetProvider.newFactory("com.sun.rowset.RowSetFactoryImpl", null);
* WebRowSet wrs = rsf.createWebRowSet();
*
** Tracing of this class may be enabled by setting the System property * {@code javax.sql.rowset.RowSetFactory.debug} to any value but {@code false}. *
* * @author Lance Andersen * @since 1.7 */ public class RowSetProvider { private static final String ROWSET_DEBUG_PROPERTY = "javax.sql.rowset.RowSetProvider.debug"; private static final String ROWSET_FACTORY_IMPL = "com.sun.rowset.RowSetFactoryImpl"; private static final String ROWSET_FACTORY_NAME = "javax.sql.rowset.RowSetFactory"; /** * Internal debug flag. */ private static boolean debug = true; static { // Check to see if the debug property is set String val = getSystemProperty(ROWSET_DEBUG_PROPERTY); // Allow simply setting the prop to turn on debug debug = val != null && !"false".equals(val); } protected RowSetProvider () { } /** *Creates a new instance of a RowSetFactory
* implementation. This method uses the following
* look up order to determine
* the RowSetFactory implementation class to load:
RowSetFactory instance.
* Once an application has obtained a reference to a {@code RowSetFactory}, * it can use the factory to obtain RowSet instances.
* * @return New instance of aRowSetFactory
*
* @throws SQLException if the default factory class cannot be loaded,
* instantiated. The cause will be set to actual Exception
*
* @see ServiceLoader
* @since 1.7
*/
public static RowSetFactory newFactory()
throws SQLException {
// Use the system property first
RowSetFactory factory = null;
String factoryClassName = null;
try {
trace("Checking for Rowset System Property...");
factoryClassName = getSystemProperty(ROWSET_FACTORY_NAME);
if (factoryClassName != null) {
trace("Found system property, value=" + factoryClassName);
factory = (RowSetFactory) getFactoryClass(factoryClassName, null, true).newInstance();
}
} catch (ClassNotFoundException e) {
throw new SQLException(
"RowSetFactory: " + factoryClassName + " not found", e);
} catch (Exception e) {
throw new SQLException(
"RowSetFactory: " + factoryClassName + " could not be instantiated: " + e,
e);
}
// Check to see if we found the RowSetFactory via a System property
if (factory == null) {
// If the RowSetFactory is not found via a System Property, now
// look it up via the ServiceLoader API and if not found, use the
// Java SE default.
factory = loadViaServiceLoader();
factory =
factory == null ? newFactory(ROWSET_FACTORY_IMPL, null) : factory;
}
return (factory);
}
/**
* Creates a new instance of a RowSetFactory from the
* specified factory class name.
* This function is useful when there are multiple providers in the classpath.
* It gives more control to the application as it can specify which provider
* should be loaded.
Once an application has obtained a reference to a RowSetFactory
* it can use the factory to obtain RowSet instances.
javax.sql.rowset.RowSetFactory.
*
* @param cl ClassLoader used to load the factory
* class. If null current Thread's context
* classLoader is used to load the factory class.
*
* @return New instance of a RowSetFactory
*
* @throws SQLException if factoryClassName is
* null, or the factory class cannot be loaded, instantiated.
*
* @see #newFactory()
*
* @since 1.7
*/
public static RowSetFactory newFactory(String factoryClassName, ClassLoader cl)
throws SQLException {
trace("***In newInstance()");
try {
Class providerClass = getFactoryClass(factoryClassName, cl, false);
RowSetFactory instance = (RowSetFactory) providerClass.newInstance();
if (debug) {
trace("Created new instance of " + providerClass +
" using ClassLoader: " + cl);
}
return instance;
} catch (ClassNotFoundException x) {
throw new SQLException(
"Provider " + factoryClassName + " not found", x);
} catch (Exception x) {
throw new SQLException(
"Provider " + factoryClassName + " could not be instantiated: " + x,
x);
}
}
/*
* Returns the class loader to be used.
* @return The ClassLoader to use.
*
*/
static private ClassLoader getContextClassLoader() throws SecurityException {
return (ClassLoader) AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
ClassLoader cl = null;
cl = Thread.currentThread().getContextClassLoader();
if (cl == null) {
cl = ClassLoader.getSystemClassLoader();
}
return cl;
}
});
}
/**
* Attempt to load a class using the class loader supplied. If that fails
* and fall back is enabled, the current (i.e. bootstrap) class loader is
* tried.
*
* If the class loader supplied is null, first try using the
* context class loader followed by the current class loader.
* @return The class which was loaded
*/
static private Class getFactoryClass(String factoryClassName, ClassLoader cl,
boolean doFallback) throws ClassNotFoundException {
try {
if (cl == null) {
cl = getContextClassLoader();
if (cl == null) {
throw new ClassNotFoundException();
} else {
return cl.loadClass(factoryClassName);
}
} else {
return cl.loadClass(factoryClassName);
}
} catch (ClassNotFoundException e) {
if (doFallback) {
// Use current class loader
return Class.forName(factoryClassName, true, RowSetFactory.class.getClassLoader());
} else {
throw e;
}
}
}
/**
* Use the ServiceLoader mechanism to load the default RowSetFactory
* @return default RowSetFactory Implementation
*/
static private RowSetFactory loadViaServiceLoader() {
RowSetFactory theFactory = null;
trace("***in loadViaServiceLoader()");
for (RowSetFactory factory : ServiceLoader.load(javax.sql.rowset.RowSetFactory.class)) {
trace(" Loading done by the java.util.ServiceLoader :" + factory.getClass().getName());
theFactory = factory;
break;
}
return theFactory;
}
/**
* Returns the requested System Property. If a {@code SecurityException}
* occurs, just return NULL
* @param propName - System property to retrieve
* @return The System property value or NULL if the property does not exist
* or a {@code SecurityException} occurs.
*/
static private String getSystemProperty(final String propName) {
String property = null;
try {
property = (String) AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
return System.getProperty(propName);
}
});
} catch (SecurityException se) {
if (debug) {
se.printStackTrace();
}
}
return property;
}
/**
* Debug routine which will output tracing if the System Property
* -Djavax.sql.rowset.RowSetFactory.debug is set
* @param msg - The debug message to display
*/
private static void trace(String msg) {
if (debug) {
System.err.println("###RowSets: " + msg);
}
}
}