J2SE综合——关于private构造函数

王朝java/jsp·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

看下面的类:

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() {

}

}

在这个类中,用到了私有构造函数,如粗体部分.

我的调用类:

package zy.pro.td.plugin;

/*

* Created on Oct 4, 2004

*

* To change the template for this generated file go to

* WindowPreferencesJavaCode GenerationCode 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 HibernateSessionFactoryhsf;

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;

}

}

在调用类中,我创建了一个HibernateSessionFactory的对象,但是在初始化时,却出了问题.总提示说:

HibernateSessionFactory() hasprivateaccessin zy.pro.td.util.HibernateSessionFactoryatline35(35:9)

然后,我就将HibernateSessionFactory的构造函数由private改成了public,调试通过.

构造函数为私有,就不能创建该类的对象.

 
 
 
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