expressionassignmenthandler.java

workflow first jbpm

/*
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 * Copyright 2005, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jbpm.identity.assignment;

import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jbpm.JbpmContext;
import org.jbpm.graph.exe.ExecutionContext;
import org.jbpm.graph.exe.Token;
import org.jbpm.identity.Entity;
import org.jbpm.identity.Group;
import org.jbpm.identity.User;
import org.jbpm.identity.hibernate.IdentitySession;
import org.jbpm.security.SecurityHelper;
import org.jbpm.taskmgmt.def.AssignmentHandler;
import org.jbpm.taskmgmt.exe.Assignable;
import org.jbpm.taskmgmt.exe.SwimlaneInstance;

/**
 * implements an expression language for assigning actors to tasks based 
 * on this identity component.
 * 
 * <pre>syntax : first-term --> next-term --> next-term --> ... --> next-term
 * 
 * first-term ::= previous |
 *                swimlane(swimlane-name) |
 *                variable(variable-name) |
 *                user(user-name) |
 *                group(group-name)
 * 
 * next-term ::= group(group-type) |
 *               member(role-name)
 * </pre> 
 */
public class ExpressionAssignmentHandler implements AssignmentHandler {

  private static final long serialVersionUID = 1L;
  
  protected String expression;
  protected ExecutionContext executionContext = null;
  protected ExpressionSession expressionSession = null;
  protected TermTokenizer tokenizer;
  protected Entity entity = null;

  public void assign(Assignable assignable, ExecutionContext executionContext) {

    try {
      expressionSession = getExpressionSession();
      if (expressionSession==null) {
        throw new NullPointerException("getIdentitySession returned null");
      }
      this.tokenizer = new TermTokenizer(expression);
      this.executionContext = executionContext;
      entity = resolveFirstTerm(tokenizer.nextTerm());
      while( tokenizer.hasMoreTerms()
             && (entity!=null) ) {
        entity = resolveNextTerm(tokenizer.nextTerm());
      }
      // if the expression did not resolve to an actor
      if (entity==null) {
        // throw an exception
        throw new RuntimeException("couldn't resolve assignment expression '"+expression+"'");
        
      // else if the expression evaluated to a user
      } else if (entity instanceof User) {
        // do direct assignment
        assignable.setActorId(entity.getName());
        
      // else if the expression evaluated to a group
      } else if (entity instanceof Group) {
        // put the group in the pool
        assignable.setPooledActors(new String []{entity.getName()});
      }
      
    } catch (RuntimeException e) {
      throw new ExpressionAssignmentException("couldn't resolve assignment expression '"+expression+"'", e);
    }
  }

  /**
   * serves as a hook for customizing the way the identity session is retrieved.
   * overload this method to reuse this expression assignment handler for your 
   * user data store.
   */
  protected ExpressionSession getExpressionSession() {
    JbpmContext jbpmContext = JbpmContext.getCurrentJbpmContext();
    if (jbpmContext==null) {
      throw new RuntimeException("no active JbpmContext for resolving assignment expression'"+expression+"'");
    }
    return new IdentitySession(jbpmContext.getSession());
  }

  protected Entity resolveFirstTerm(String term) {
    Entity entity = null;
    
    log.debug("resolving first term '"+term+"'");
    
    if (term.equalsIgnoreCase("previous")) {
    String userName = SecurityHelper.getAuthenticatedActorId();
    entity = getUserByName(userName);
    
    } else if ( (term.startsWith("swimlane("))
         && (term.endsWith(")")) ) {
      String swimlaneName = term.substring(9,term.length()-1).trim();
      String userName = getSwimlaneActorId(swimlaneName);
      entity = getUserByName(userName);

    } else if ( (term.startsWith("variable("))
                && (term.endsWith(")")) ) {
      String variableName = term.substring(9,term.length()-1).trim();
      Object value = getVariable(variableName);
      
      if (value==null) {
        throw new ExpressionAssignmentException("variable '"+variableName+"' is null");
        
      } else if (value instanceof String) {
        entity = getUserByName((String) value);
        
      } else if (value instanceof Entity) {
        entity = (Entity) value;
      }

    } else if ( (term.startsWith("user("))
                && (term.endsWith(")")) ) {
      String userName = term.substring(5,term.length()-1).trim();
      entity = getUserByName(userName);

    } else if ( (term.startsWith("group("))
                && (term.endsWith(")")) ) {
      String groupName = term.substring(6,term.length()-1).trim();
      entity = getGroupByName(groupName);

    } else {
      throw new ExpressionAssignmentException("couldn't interpret first term in expression '"+expression+"'");
    }

    return entity;
  }

  protected Entity resolveNextTerm(String term) {

    log.debug("resolving next term '"+term+"'");

    if ( (term.startsWith("group("))
            && (term.endsWith(")")) ) {
      String groupType = term.substring(6,term.length()-1).trim();
      User user = (User) entity;
      Set groups = user.getGroupsForGroupType(groupType);
      if (groups.size()==0) {
        throw new ExpressionAssignmentException("no groups for group-type '"+groupType+"'");
      }
      entity = (Entity) groups.iterator().next();
      
    } else if ( (term.startsWith("member("))
            && (term.endsWith(")")) ) {
      String role = term.substring(7,term.length()-1).trim();
      Group group = (Group) entity;
      entity = expressionSession.getUserByGroupAndRole(group.getName(), role);
      if (entity==null) {
        throw new ExpressionAssignmentException("no users in role '"+role+"'");
      }

    } else {
      throw new ExpressionAssignmentException("couldn't interpret term '"+term+"' in expression '"+expression+"'");
    }
    
    return entity;
  }

  protected Object getVariable(String variableName) {
    Token token = executionContext.getToken();
    return executionContext.getContextInstance().getVariable(variableName, token);
  }

  protected Entity getGroupByName(String groupName) {
    Group group = null;
    group = expressionSession.getGroupByName(groupName);
    if (group==null) {
      throw new ExpressionAssignmentException("group '"+groupName+"' couldn't be fetched from the user db");
    }
    return group;
  }

  protected Entity getUserByName(String userName) {
    User user = null;
    user = expressionSession.getUserByName(userName);
    if (user==null) {
      throw new ExpressionAssignmentException("user '"+userName+"' couldn't be fetched from the user db");
    }
    return user;
  }

  protected String getSwimlaneActorId(String swimlaneName) {
    SwimlaneInstance swimlaneInstance = executionContext
          .getTaskMgmtInstance()
          .getSwimlaneInstance(swimlaneName);
    if (swimlaneInstance==null) {
      throw new ExpressionAssignmentException("no swimlane instance '"+swimlaneName+"'");
    }
    return swimlaneInstance.getActorId();
  }
  
  private static final Log log = LogFactory.getLog(ExpressionAssignmentHandler.class);
}