RELEASE_2_1_13/src/java/org/apache/cocoon/components/modules/output/SessionAttributeOutputModule.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.cocoon.components.modules.output;

import java.util.Iterator;
import java.util.Map;

import org.apache.avalon.framework.configuration.Configuration;
import org.apache.avalon.framework.logger.Logger;
import org.apache.cocoon.environment.ObjectModelHelper;
import org.apache.cocoon.environment.Session;

/**
 * Abstraction layer to encapsulate different output
 * destinations. Configuration option <key-prefix> defaults to
 * "org.apache.cocoon.components.modules.output.OutputModule"+":"
 *
 * Can be used with different isolation-level: default is "0" being
 * no isolation at all, values are immediately visible but are removed
 * on a rollback; "1" keeps the values at a save place until either
 * rollback or commit is called. Then values are either discarded or
 * copied to the final destination.
 *
 * @author <a href="mailto:haul@apache.org">Christian Haul</a>
 * @version CVS $Id$
 */
public class SessionAttributeOutputModule extends AbstractOutputModule {
    
    public final String PREFIX = "org.apache.cocoon.components.modules.output.OutputModule";
    public final String TRANS_PREFIX = "org.apache.cocoon.components.modules.output.OutputModule.SessionAttributeOutputModule.transient";
    public final String ROLLBACK_LIST = "org.apache.cocoon.components.modules.output.OutputModule.SessionAttributeOutputModule.rollback";
    
    /**
     * communicate an attribute value to further processing logic.
     * @param modeConf column's mode configuration from resource
     * description. This argument is optional.
     * @param objectModel The objectModel
     * @param name The attribute's label, consisting of "table.column"
     * or "table.column[index]" in case of multiple attributes of the
     * same spec.
     * @param value The attriute's value.
     * */
    public void setAttribute( Configuration modeConf, Map objectModel, String name, Object value ) {
        if (this.settings.get("isolation-level","0").equals("1")) {
            if (getLogger().isDebugEnabled())
                getLogger().debug("setting transient ['"+name+"'] to ['"+value+"']");
            this.transientSetAttribute(objectModel, TRANS_PREFIX, name, value);
        } else {
            // use read uncommitted isolation level

            Session session = ObjectModelHelper.getRequest(objectModel).getSession();

            name = getName(name);

            if (!this.attributeExists(objectModel, ROLLBACK_LIST, name)) {
                Object tmp = session.getAttribute(name);
                this.transientSetAttribute(objectModel, ROLLBACK_LIST, name, tmp);
            }

            if (getLogger().isDebugEnabled())
                getLogger().debug("setting ['"+name+"'] to ['"+value+"']");
            session.setAttribute(name, value);
        }

    }
    
    
    
    /**
     * If a database transaction needs to rollback, this is called to
     * inform the further processing logic about this fact. All
     * already set attribute values are invalidated. <em>This is difficult
     * because only the request object can be used to synchronize this
     * and build some kind of transaction object. Beaware that sending
     * your data straight to some beans or other entities could result
     * in data corruption!</em>
     * */
    public void rollback( Configuration modeConf, Map objectModel, Exception e ) {
        if (this.settings.get("isolation-level","0").equals("1")) {
            if (getLogger().isDebugEnabled()) {
                getLogger().debug("rolling back");
            }
            this.rollback(objectModel, TRANS_PREFIX);
        } else {
            if (getLogger().isDebugEnabled()) {
                getLogger().debug("start rolling back");
            }
            Session session = ObjectModelHelper.getRequest(objectModel).getSession();
            Map rollbackList = this.prepareCommit(objectModel,ROLLBACK_LIST);
            if (rollbackList != null) {
                for (Iterator i = rollbackList.entrySet().iterator(); i.hasNext(); ) {
                    Map.Entry me = (Map.Entry)i.next();
                    String key = (String)me.getKey();
                    Object val = me.getValue();
                    if (val != null) {
                        if (getLogger().isDebugEnabled()) {
                            getLogger().debug("rolling back ['" + key + "'] to ['" + val + "']");
                        }
                        session.setAttribute(key, val);
                    } else {
                        if (getLogger().isDebugEnabled()) {
                            getLogger().debug("rolling back ['" + key + "']");
                        }
                        session.removeAttribute(key);
                    }
                }
            }
        }
        if (getLogger().isDebugEnabled()) {
            getLogger().debug("done rolling back");
        }
        String prefix = (String) this.settings.get("key-prefix", PREFIX);
        if (!(prefix.equals(""))) {
            ObjectModelHelper.getRequest(objectModel).getSession().setAttribute(prefix+":",e.getMessage());
        } else {
            ObjectModelHelper.getRequest(objectModel).getSession().setAttribute("errorMessage",e.getMessage());
        }
    }
    
    
    /**
     * Signal that the database transaction completed
     * successfully. See notes on @link{rollback}.
     * */
    public void commit( Configuration modeConf, Map objectModel ) {
        if (this.settings.get("isolation-level","0").equals("1")) {

            Logger logger = getLogger();
            if (logger.isDebugEnabled()) {
                logger.debug("prepare commit");
            }
            Map aMap = this.prepareCommit(objectModel, TRANS_PREFIX);
            if (aMap == null || aMap.isEmpty()) {
                return;
            }
            String prefix = (String)this.settings.get("key-prefix", PREFIX );
            if (prefix.length() > 0) {
                prefix = prefix + ":";
            } else {
                prefix = null;
            }
            Session session = ObjectModelHelper.getRequest(objectModel).getSession();
            for (Iterator i = aMap.entrySet().iterator(); i.hasNext(); ) {
                Map.Entry me = (Map.Entry)i.next();
                String key = (String)me.getKey();
                Object value = me.getValue();
                if (prefix != null) {
                    key = prefix + key;
                }
                if (logger.isDebugEnabled()) {
                    logger.debug("committing ['" + key + "'] to ['" + value + "']");
                }
                session.setAttribute(key, value);
            }
            if (logger.isDebugEnabled()) {
                logger.debug("done commit");
            }
        } else {
            if (getLogger().isDebugEnabled())
                getLogger().debug("commit");
            this.prepareCommit(objectModel, ROLLBACK_LIST);
        }
    }
    
    protected String getName( String name ) {
        String prefix = (String) this.settings.get("key-prefix", PREFIX );
        return (prefix.length() == 0 ? name : prefix+":"+name);
    }

}