RegionBean


1   package edu.rice.rubis.beans;
2   
3   import java.rmi.*;
4   import javax.ejb.*;
5   import javax.rmi.PortableRemoteObject  ;
6   import javax.naming.InitialContext  ;
7   
8   /**
9    * RegionBean is an entity bean with "container managed persistence". 
10   * The state of an instance is stored into a relational database. 
11   * The following table should exist:<p>
12   * <pre>
13   * CREATE TABLE regions (
14   *    id   INTEGER UNSIGNED NOT NULL UNIQUE,
15   *    name VARCHAR(20),
16   *    PRIMARY KEY(id)
17   * );
18   * </pre>
19   * @author <a HREF="mailto:cecchet@rice.edu">Emmanuel Cecchet</a> and <a HREF="mailto:julie.marguerite@inrialpes.fr">Julie Marguerite</a>
20   * @version 1.0
21   */
22  
23  public class RegionBean implements EntityBean 
24  {
25    private EntityContext entityContext;
26    private transient boolean isDirty; // used for the isModified function
27  
28    /* Class member variables */
29  
30    public Integer   id;
31    public String    name;
32  
33    /**
34     * Get region's id.
35     *
36     * @return region id
37     * @exception RemoteException if an error occurs
38     */
39    public Integer   getId() throws RemoteException
40    {
41      return id;
42    }
43  
44    /**
45     * Get region name.
46     *
47     * @return region name
48     * @exception RemoteException if an error occurs
49     */
50    public String   getName() throws RemoteException
51    {
52      return name;
53    }
54  
55    /**
56     * Set region's name
57     *
58     * @param newName region name
59     * @exception RemoteException if an error occurs
60     */
61    public void setName(String   newName) throws RemoteException 
62    {
63      name = newName;
64      isDirty = true; // the bean content has been modified
65    }
66  
67  
68    /**
69     * This method is used to create a new Region Bean. Note that the region
70     * id is automatically generated by the database (AUTO_INCREMENT) on the
71     * primary key.
72     *
73     * @param regionName Region name
74     *
75     * @return pk primary key set to null
76     * @exception CreateException if an error occurs
77     * @exception RemoteException if an error occurs
78     * @exception RemoveException if an error occurs
79     */
80    public RegionPK ejbCreate(String   regionName) throws CreateException, RemoteException, RemoveException
81    {
82       // Connecting to IDManager Home interface thru JNDI
83        IDManagerHome home = null;
84        IDManager idManager = null;
85        
86        try 
87        {
88          InitialContext   initialContext = new InitialContext  ();
89          home = (IDManagerHome)PortableRemoteObject.narrow(initialContext.lookup(
90                 "java:comp/env/ejb/IDManager"), IDManagerHome.class);
91        } 
92        catch (Exception   e)
93        {
94          throw new EJBException("Cannot lookup IDManager: " +e);
95        }
96       try 
97        {
98          IDManagerPK idPK = new IDManagerPK();
99          idManager = home.findByPrimaryKey(idPK);
100         id = idManager.getNextRegionID();
101         name = regionName;
102       }
103      catch (Exception   e)
104       {
105         throw new EJBException("Cannot create region: " +e);
106       }
107      return null;
108   }
109 
110   /** This method just set an internal flag to 
111       reload the id generated by the DB */
112   public void ejbPostCreate(String   regionName)
113   {
114     isDirty = true; // the id has to be reloaded from the DB
115   }
116 
117   /** Persistence is managed by the container and the bean
118       becomes up to date */
119   public void ejbLoad() throws RemoteException 
120   {
121     isDirty = false;
122   }
123 
124   /** Persistence is managed by the container and the bean
125       becomes up to date */
126   public void ejbStore() throws RemoteException
127   {
128     isDirty = false;
129   }
130 
131   /** This method is empty because persistence is managed by the container */
132   public void ejbActivate() throws RemoteException {}
133   /** This method is empty because persistence is managed by the container */
134   public void ejbPassivate() throws RemoteException {}
135   /** This method is empty because persistence is managed by the container */
136   public void ejbRemove() throws RemoteException, RemoveException {}
137 
138 
139   /**
140    * Sets the associated entity context. The container invokes this method 
141    *  on an instance after the instance has been created. 
142    * 
143    * This method is called in an unspecified transaction context. 
144    * 
145    * @param context An EntityContext interface for the instance. The instance should 
146    *                store the reference to the context in an instance variable. 
147    * @exception EJBException  Thrown by the method to indicate a failure 
148    *                          caused by a system-level error.
149    * @exception RemoteException - This exception is defined in the method signature
150    *                           to provide backward compatibility for enterprise beans
151    *                           written for the EJB 1.0 specification. 
152    *                           Enterprise beans written for the EJB 1.1 and 
153    *                           higher specification should throw the javax.ejb.EJBException 
154    *                           instead of this exception. 
155    */
156   public void setEntityContext(EntityContext context) throws RemoteException
157   {
158     entityContext = context;
159   }
160 
161 
162   /**
163    * Unsets the associated entity context. The container calls this method 
164    *  before removing the instance. This is the last method that the container 
165    *  invokes on the instance. The Java garbage collector will eventually invoke 
166    *  the finalize() method on the instance. 
167    *
168    * This method is called in an unspecified transaction context. 
169    * 
170    * @exception EJBException  Thrown by the method to indicate a failure 
171    *                          caused by a system-level error.
172    * @exception RemoteException - This exception is defined in the method signature
173    *                           to provide backward compatibility for enterprise beans
174    *                           written for the EJB 1.0 specification. 
175    *                           Enterprise beans written for the EJB 1.1 and 
176    *                           higher specification should throw the javax.ejb.EJBException 
177    *                           instead of this exception.
178    */
179   public void unsetEntityContext() throws RemoteException
180   {
181     entityContext = null;
182   }
183 
184 
185   /**
186    * Returns true if the beans has been modified.
187    * It prevents the EJB server from reloading a bean
188    * that has not been modified.
189    *
190    * @return a <code>boolean</code> value
191    */
192   public boolean isModified() 
193   {
194     return isDirty;
195   }
196 
197 }
198
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