程式師世界 >> 編程語言 >> JAVA編程 >> J2SE >> J2SE綜合：關於private構造函數

J2SE綜合：關於private構造函數

編輯：J2SE

看下面的類:

HibernateSessionFactory.Java
package zy.pro.wd.util;
import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;
import net.sf.hibernate.cfg.Configuration;
/**
* Configures and provides Access to Hibernate sessions, tIEd to the
* current thread of execution.　Follows the Thread Local Session
* pattern, see {@link http://hibernate.org/42.Html}.
*/
public class HibernateSessionFactory {
/**
* Location of hibernate.cfg.XML file.
* NOTICE: Location should be on the classpath as Hibernate uses
* #resourceAsStream style lookup for its configuration file. That
* is place the config file in a Java package - the default location
* is the default Java package.
* Examples:
* CONFIG_FILE_LOCATION = "/hibernate.conf.XML".
* CONFIG_FILE_LOCATION = "/com/foo/bar/myhiberstuff.conf.XML".
*/
private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.XML";
/** Holds a single instance of Session */
private static final ThreadLocal threadLocal = new ThreadLocal();
/** The single instance of hibernate configuration */
private static final Configuration cfg = new Configuration();
/** The single instance of hibernate SessionFactory */
private static net.sf.hibernate.SessionFactory sessionFactory;
/**
* Returns the ThreadLocal Session instance.　Lazy initialize
* the SessionFactory if needed.
*
*　@return Session
*　@throws HibernateException
*/
public static Session currentSession() throws HibernateException {
Session session = (Session) threadLocal.get();
if (session == null) {
if (sessionFactory == null) {
try {
cfg.configure(CONFIG_FILE_LOCATION);
sessionFactory = cfg.buildSessionFactory();
}
catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
session = sessionFactory.openSession();
threadLocal.set(session);
}
return session;
}
/**
*　Close the single hibernate session instance.
*
*　@throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);
if (session != null) {
session.close();
}
}
/**
* Default constructor.
*/
private HibernateSessionFactory() {
}
}

在這個類中,用到了私有構造函數,如粗體部分.

我的調用類:

package zy.pro.td.plugin;
/*
* Created on Oct 4, 2004
*
* To change the template for this generated file go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
import Javax.servlet.ServletException;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.action.PlugIn;
import org.apache.struts.config.ModuleConfig;
import Javax.naming.Context;
import Javax.naming.InitialContext;
import zy.pro.td.util.HibernateSessionFactory;
/**
* @author sunil
*
*　　This class will initialize hibernate and bind SessionFactory in JNDI at the
*　　time of application and startup and unbind it from JNDI at the time of application
*　shutdown
*/
public class HibernatePlugin
implements PlugIn {
private static final String jndi_hibernate = "jndi_hibernate_factory";
private　 HibernateSessionFactory　hsf;
private String name;
public HibernatePlugin() {
hsf=new HibernateSessionFactory();
}
// This method will be called at the time of application shutdown
public void destroy() {
System.out.println("Entering HibernatePlugIn.destroy()");
//Put hibernate cleanup code here
System.out.println("Exiting HibernatePlugIn.destroy()");
}
//This method will be called at the time of application startup
public void init(ActionServlet actionServlet, ModuleConfig config) throws
ServletException {
System.out.println("Entering HibernatePlugIn.init()");
System.out.println("Value of init parameter " + getName());
//Uncomment next two lines if you want to throw UnavailableException from your servlet
//　　　　if(true)
//　　　　　　throw new ServletException("Error configuring HibernatePlugIn");
System.out.println("Exiting HibernatePlugIn.init()");
}
private void bindFactoryToJNDI() {
try {
Context ctx = new InitialContext();
}
catch (Exception e) {
e.printStackTrace();
}
}
public String getName() {
return name;
}
public void setName(String string) {
name = string;
}
}