ejblocator.java

以前做的一个j2ee的项目

package gov.gdlt.ssgly.taxcore.comm.servicelocator;

import java.util.Map;
import java.util.HashMap;
import java.util.Properties;
import javax.ejb.EJBLocalHome;
import javax.ejb.EJBHome;
import javax.rmi.PortableRemoteObject;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import gov.gdlt.ssgly.taxcore.comm.log.LogWritter;
import gov.gdlt.ssgly.taxcore.comm.config.ApplicationContext;


/**
 * Service Locator模式的实现，在此提供给客户端定位后台EJB的方法。
 *
 * <p>Title: EJBLocator</p>
 * <p>Description: 税收管理员系统</p>
 * <p>Copyright: Copyright (c) 2005 广州市地方税务局</p>
 * <p>Company: 信息中心</p>
 * @author Lemon
 * @version 1.0
 * @since 2005.8.8.
 */

public class EJBLocator {

    private static EJBLocator instance;
    private Map homeInterfaces;
    private Context context;

    // This is private, and can't be instantiated directly
    private void initRemote() throws NamingException {
        homeInterfaces = new HashMap();

        // Get the context for caching purposes
        String url = ApplicationContext.singleton().getValueAsString(ApplicationContext.EJB_PROVIDER_URL);
        Properties properties = null;
        try {
            properties = new Properties();
            properties.put(Context.INITIAL_CONTEXT_FACTORY,
                           ApplicationContext.WEBLOGIC_INITIAL_CONTEXT_FACTORY);
            properties.put(Context.PROVIDER_URL, url);
            context = new InitialContext(properties);
        } catch (Exception e) {
            LogWritter.sysError("Unable to connect to WebLogic server at " +
                                url +
                                "Please make sure that the server is running.",
                                e);
            //throw e;
        }

    }

    private void initLocal() throws NamingException {
        homeInterfaces = new HashMap();

        // Get the context for caching purposes
        context = new InitialContext();
    }

    private EJBLocator() {
    }

    public static EJBLocator getInstance() throws NamingException {
        if (instance == null) {
            instance = new EJBLocator();
            instance.initLocal();
        }
        return instance;
    }

    public static EJBLocator getRemoteInstance() throws NamingException {
            if (instance == null) {
                instance = new EJBLocator();
                instance.initRemote();
            }
            return instance;
    }

    public EJBLocalHome getLocalHome(String jndiName, Class localHomeClass) throws
            NamingException {

        // See if we already have this interface cached
        EJBLocalHome localHome = (EJBLocalHome) homeInterfaces.get(
                localHomeClass);

        // If not, look up with the supplied JNDI name
        if (localHome == null) {
            localHome = (EJBLocalHome) context.lookup(jndiName);
            // If this is a new ref, save for caching purposes
            homeInterfaces.put(localHomeClass, localHome);
        }
        return localHome;
    }

    public EJBHome getRemoteHome(String jndiName, Class homeClass) throws
            NamingException {

        // See if we already have this interface cached
        EJBHome remoteHome = (EJBHome) homeInterfaces.get(
                homeClass);

        // If not, look up with the supplied JNDI name
        if (remoteHome == null) {
            remoteHome = (EJBHome) context.lookup(jndiName);

            Object objref = context.lookup(jndiName);
            remoteHome = (EJBHome) PortableRemoteObject.narrow(objref,
                    homeClass);

            // If this is a new ref, save for caching purposes
            homeInterfaces.put(homeClass, remoteHome);
        }

        return remoteHome;
    }

}