在filter里关闭session

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package com.upstate.cellculture.om.persist;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.JDBCException;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
* This class is used to get Hibernate Sessions and may
* also contain methods (in the future) to get DBConnections
* or Transactions from JNDI.
*/
public class ServiceLocator
{
//~ Static fields/initializers =============================================
public final static String SESSION_FACTORY = "hibernate/sessionFactory";
public static final ThreadLocal session = new ThreadLocal();
private static SessionFactory sf = null;
private static ServiceLocator me;
private static Log log = LogFactory.getLog(ServiceLocator.class);

static {
try
{
me = new ServiceLocator();
}
catch (Exception e)
{
log.fatal("Error occurred initializing ServiceLocator");
e.printStackTrace();
}
}

//~ Constructors ===========================================================

private ServiceLocator() throws HibernateException, JDBCException
{}

//~ Methods ================================================================

public static Session currentSession() throws PersistenceException
{
Session s = (Session) session.get();

if (s == null)
{
s = PersistenceManager.openSession();
if (log.isDebugEnabled())
{
log.debug("Opened hibernate session.");
}

session.set(s);
}

return s;
}

public static void closeSession() throws HibernateException, JDBCException
{
Session s = (Session) session.get();
session.set(null);

if (s != null)
{
if (s.isOpen())
{
s.flush();
s.close();

if (log.isDebugEnabled())
{
log.debug("Closed hibernate session.");
}
}
}
else
{
log.warn("Hibernate session was inadvertently already closed.");

}
}
}

如果你使用对象的lazy loading你需要使用一个servlet filter

java代码:

package com.upstate.cellculture.filter; 

import java.io.IOException; 

import javax.servlet.Filter; 
import javax.servlet.FilterChain; 
import javax.servlet.FilterConfig; 
import javax.servlet.ServletException; 
import javax.servlet.ServletRequest; 
import javax.servlet.ServletResponse; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpSession; 

import net.sf.hibernate.Session; 

import org.apache.commons.logging.Log; 
import org.apache.commons.logging.LogFactory; 

import com.upstate.cellculture.om.persist.PersistenceException; 
import com.upstate.cellculture.om.persist.ServiceLocator; 

public class ActionFilter implements Filter 
{ 
    //~ Static fields/initializers ============================================= 

    //~ Instance fields ======================================================== 

    /** 
     * The <code>Log</code> instance for this class 
     */ 
    private Log log = LogFactory.getLog(ActionFilter.class); 
    private FilterConfig filterConfig = null; 

    //~ Methods ================================================================ 

    public void init(FilterConfig filterConfig) throws ServletException 
    { 
        this.filterConfig = filterConfig; 

    } 

    /** 
     * Destroys the filter. 
     */ 
    public void destroy() 
    { 
        filterConfig = null; 
    } 

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException 
    { 
        // cast to the types I want to use 
        HttpServletRequest request = (HttpServletRequest) req; 
        HttpServletResponse response = (HttpServletResponse) resp; 
        HttpSession session = request.getSession(true); 

        Session ses = null; 
        boolean sessionCreated = false; 

        try 
        { 
            chain.doFilter(request, response); 
        } 
        finally 
        { 
            try 
            { 
                ServiceLocator.closeSession(); 
            } 
            catch (Exception exc) 
            { 
                log.error("Error closing hibernate session.", exc); 
                exc.printStackTrace(); 
            } 
        } 
    } 

    public static Session getSession() throws PersistenceException 
    { 
        try 
        { 

            return ServiceLocator.currentSession(); 
        } 
        catch (Exception e) 
        { 
            throw new PersistenceException("Could not find current Hibernate session.", e); 
        } 

    } 
} 

此外，为了把数据库访问集中起来，我们会使用一些manager类，也就是DAO

java代码:

/* 
* Created on Apr 28, 2003 
* 
*/ 
package com.upstate.cellculture.om.persist; 
import java.util.List; 

import net.sf.hibernate.Query; 
import net.sf.hibernate.Session; 

import com.upstate.cellculture.om.Technician; 
/** 
* @author tmckinney 
* 
* Centralizes all access to the Technicians table 
*/ 
public class TechnicianManager 
{ 
    private static List allTechnicians; 
    public static void save(Technician technician) throws PersistenceException 
    { 
        try 
        { 

            ServiceLocator.currentSession().save(technician); 

        } 
        catch (Exception e) 
        { 
            throw new PersistenceException("Could not save.", e); 
        } 
    } 

    public static Technician retrieveByPK(long technicianId) throws PersistenceException 
       { 
           try 
             { 
                 Technician technician= (Technician) ServiceLocator.currentSession().load(Technician.class, new Long(technicianId)); 
                 return technician; 
             } 
             catch (Exception e) 
             { 
                 throw new PersistenceException("Could not retrieve.", e); 
             } 
       } 


    public static List retrieveAllTechnicians() throws PersistenceException 
    { 
        if (allTechnicians == null) 
        { 
            try 
            { 
                Query q = ServiceLocator.currentSession().createQuery("from technician in class " + Technician.class +" order by upper(technician.name)"); 
                allTechnicians = q.list(); 
                session.flush(); 
            } 
            catch (Exception e) 
            { 
                e.printStackTrace(); 
                throw new PersistenceException(e); 
            } 
        } 
        return allTechnicians; 

    } 


} 

如果能够使用一个 TechnicianManager接口和一个TechnicianManagerImpl class. 那就更好了。

通过自己定义的一个异常来包装了所有抛出的异常。

java代码:

package com.upstate.cellculture.om.persist; 

import org.apache.commons.lang.exception.NestableException; 
/** 
* A general PersistenceException that is thrown by all Manager classes. 
* 
*/ 
public class PersistenceException extends NestableException 
{ 
    //~ Constructors =========================================================== 

    /** 
     * Constructor for PersistenceException. 
     */ 
    public PersistenceException() 
    { 
        super(); 
    } 

    /** 
     * Constructor for PersistenceException. 
     * 
     * @param message 
     */ 
    public PersistenceException(String message) 
    { 
        super(message); 
    } 

    /** 
     * Constructor for PersistenceException. 
     * 
     * @param message 
     * @param cause 
     */ 
    public PersistenceException(String message, Throwable cause) 
    { 
        super(message, cause); 
    } 

    /** 
     * Constructor for PersistenceException. 
     * 
     * @param cause 
     */ 
    public PersistenceException(Throwable cause) 
    { 
        super(cause); 
    } 

} 