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Wednesday December 21, 2005

Primary key generation in EJB 3.0blo I and John Jullion-Ceccarelli wrote a tutorial about primary key generation in EJB 2.1. It was very pretty painful stuff, you should create table with appropriate data type column, use Object primary key and other. In EJB 3.0 is generation of PK different, it's easy to use. Let's go through all options that are for this in EJB 3.0. Primary key you can define in Entity bean with @Id annotation. There are five options for GeneratorType: NONE, AUTO, IDENTITY, SEQUENCE and TABLE. First one is NONE, it means that application is responsible for generation of primary key. Next one is AUTO that leaves the job to the container. This strategy indicates that a persistence provider should pick up appropriate strategy according to the database. It means that you need not setup your id and container generates it. I would like to describe SEQUENCE and TABLE strategy in more details below. SEQUENCE or IDENTITY strategy use a database sequence or identity column. I will show this strategy for Oracle database. We need to create new sequence with this command:

    CREATE SEQUENCE EMPL_ID INCREMENT BY 1 START WITH 100;
  

     @Id(generate=GeneratorType.SEQUENCE, generator="EMPL_GEN")
     @SequenceGenerator(name="EMPL_GEN",sequenceName="EMPL_ID")
  

     CREATE TABLE GEN_ID(
     GEN_KEY VARCHAR(20),
     GEN_VALUE INTEGER,
     PRIMARY KEY(GEN_KEY))
  

   @Id(generate=GeneratorType.TABLE,generator="ORDER_GEN")
    @Column(name="ID")
    @TableGenerator(name="ORDER_GEN",pkColumnName="GEN_KEY",
            pkColumnValue="ORDER_ID",allocationSize=1,
            initialValue=1,valueColumnName="GEN_VALUE",
            table=@Table(name="GEN_ID"))
 
All attributes are very intuitive and can be guessed from this sample. 
 Generation of primary key in EJB 3.0 is simple, isn't it?
              Posted by pblaha
   (     Dec 21 2005, 06:07:37 PM CET     )
       Permalink
           

    
    

Monday December 19, 2005

EJB 3.0 client in J2SE project Today, I would like to show how you can create client for EJB 3.0 in J2SE project. First, we will need to create a bean with remote interface. Since, we are using EJB 3.0 this is very simple. Create business interface with Remote annotation and then create bean's implementation class of your bean and specify JNDI name of this bean:

  @Stateless(name="ejb/ProcessHello")
  public class ProcessHelloBean implements org.netbeans.ProcessHello {

  public void String getHello(){
   ....
 

    @EJB(name="ejb/ProcessHello")
    private org.netbeans.ProcessHello hello;

    hello.getHello();
  

    InitialContext ctx = new InitialContext();
    Object obj = ctx.lookup("org.netbeans.ProcessHello");
    ProcessHello hello = (TestTableRemote)PortableRemoteObject.narrow(obj, ProcessHello.class);
    hello.getHello();
 

Thursday December 15, 2005

Persistence in J2SE project The big advantage of the EJB 3.0 is using entity beans out of container. This new feature will allow to test your business objects outside of application server. I would like to show how you can write simple J2SE project that uses EntityManager in NetBeans 5.0. Let's create new J2SE project in NetBeans.

• We need to add persistence.xml file in META-INF directory in jar file. This can be simple done in NetBeans. Create new META-INF directory in src directory of your NetBeans project and add new persistence.xml into it. This file will be copied in correct place during building. In the properties.xml file we need to specify provider class name and persistence classes:

       <persistence xmlns="http://java.sun.com/xml/ns/persistence">
      <persistence-unit name="pu1">
          <!-- Provider class name is required in Java SE -->
          <provider>oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider</provider>
          <!-- All persistence classes must be listed -->
          <class>persistence.Product</class>
          <properties>
              <!-- Provider-specific connection properties -->
              <property name="jdbc.driver" value="com.mysql.jdbc.Driver"/>
              <property name="jdbc.connection.string" value="jdbc:mysql://localhost:3306/EJB"/>
              <property name="jdbc.user" value="blaha"/>
              <property name="jdbc.password" value="passw"/>
              <!-- Provider-specific settings -->
              <property name="toplink.logging.level" value="INFO"/>
          </properties>
      </persistence-unit>
  </persistence>
  

• Add javaee.jar on project classpath. The jar is located in lib directory in Glassfish installation. Now, we can use persistence. The EntityManager need to be call first and then you can get EntityManager. See code snapshot:

  36 EntityManagerFactory emF = Persistence.createEntityManagerFactory("pu1");
  37         EntityManager em = emF.createEntityManager();
  38         EntityTransaction tx = em.getTransaction();
  39         tx.begin();
  40         Product product = new Product();
  41         product.setId(1);
  42         product.setPartNumber("ADSD-64464");
  43         product.setDescription("HAMMER");
  44         product.setPrice(12);
  45          em.persist(product); 
  46         tx.commit();
  47         
  48         // try to find product
  49         Query query = em.createQuery("select p from Product p where p.description =:descr");
  50         query.setParameter("descr","hammer");
  51         List results = query.getResultList();
  52         
  

• Don't forget to add JDBC driver on project classpath.
• The persistence projects must be run with -javaagent:${GLASSFISH_HOME}/lib/toplink-essentials-agent.jar. Add this option in project properties - Run - VM Options in NetBeans.

Wednesday December 14, 2005

How to use EntityManager API in web module The javax.persistence.Entitymanager API is used for creating, finding and updating entity bean instances. I would like to show how EntityManager can be used in web module. I will focus only to Glassfish implementation. I know that Oracle App server uses a little bit different approach. They use EntityManager that is bind to java:comp/ejb/<module-name>/EntityManager.
First, some actions with EntityManager API are required to be used in a transaction, so the web module must manually demarcate the transaction using the UserTransaction API.
In objects that are managed by container like servlets, JSF beans and EJB bean you can use simple injection. Following sample explains how to use EntityManager in servlet:

     @PersistenceContext
     EntityManager em;
     @Resource
     UserTransaction tx;
     ....
     tx.begin();
     em.persist(new YourObject());
     tx.commit();
   

    InitialContext ctx = new InitialContext();
    UserTransaction tx = (UserTransaction)ctx.lookup("UserTransaction");
    EntityManager em = em = (EntityManager) ctx.lookup("java:comp/env/persistence/EntityManager");
     tx.begin();
     YourObject o1 = em.merge(yourObject); // merge object to the new context
     em.remove(o1);
     tx.commit();
 

  <persistence-context-ref>
  <persistence-context-ref-name>persistence/EntityManager</persistence-context-ref-name>
     <persistence-unit-name>unitName</persistence-unit-name>
  </persistence-context-ref>
 

Thursday December 08, 2005

Develop Custom Realm in NetBeans I will write simple custom realm for Sun Application server in NetBeans. This realm will be used for authentication of users. I will implement very simple realm that will check password that are stored in Hashtable. I guess, extending this realm for using JDBC or other technology is easy task.
Implementation involves the following three steps:

• Implement a JAAS LoginModule
• Implement a Realm class
• Configure the Realm and LoginModule into the server

• Add appserv-rt.jar on project's classpath. This jar is located under lib directory in you App server.
• First, create new class SimpleLoginModule in simplerealm package. This class must extend PasswordLoginModule. In this class we should implement authenticate() method that performs actual authentication. Our implementation calls method in Realm Class that did authentication itself. See attached sources for more info.
• Create new class SimpleRealm in package simplerealm. The realm class is used to hook the custom realm into the Application Server. In this class the properties from domain.xml are read and authentication is performed.
• Build project. In next steps we should register new realm in Application server.
• I created targets that allow to register and delete realm in Application server. These tasks are in realm-targets.xml file in mentioned sources. Download sources and copy this file in project directory. You should copy login.conf, adminpw.txt and build.properties too in same directory. These files are needed for realm's targets.
• Import realm targets in build.xml file. Open this file and add these lines in the file:

        <!DOCTYPE project [<!ENTITY RealmTargets SYSTEM "realm-targets.xml">]>
        .......
        &RealmTargets;
      

• Run create-realm target. The target copies realm jar in App server directory and register realm
• Logg in web console and go to Application server -- JVM Settings -- Path Settings and this ${com.sun.aas.installRoot}/domains/domain1/lib/SimpleRealm.jar in suffix classpath text field. Save and restart server.
• Now, you can change realm config in your application and test new Simple realm. How you can change realm for web application? Very simple, open web.xml file and change realm-name value in SimpleRealm.

Tuesday December 06, 2005

How to use CMP beans with generated primary key I saw a question about using CMP beans with generated primary key. Therefore, I decided to write one simple application that can explain how to use this feature. More info about generating primary key values in CMP beans is avalaible here here. I would like to note that the user should never rely on the internals of the container code. And if the user chooses to use a generated PK for CMP, it means they do not care about the value, and should not try to access it (other than as an Object).
In this post we will develop EJB module that creates product and purchase order. See Entity relationship diagram:

• Create requested tables with following DDL:

        CREATE TABLE PRODUCT(
        ID BIGINT(19) NOT NULL,
        PART_NUMBER VARCHAR(19) UNIQUE NOT NULL,
        DESCRIPTION VARCHAR(25),
        PRICE FLOAT,
        PRIMARY KEY (ID),
        INDEX PART_NUMBER (PART_NUMBER)
        );
        
        CREATE TABLE PURCHASEORDER(
        ID BIGINT(19) NOT NULL,
        CUSTOMER VARCHAR(20) NOT NULL,
        PRODUCT_ID BIGINT(19) NOT NULL,
        AMOUNT FLOAT,
        PRIMARY KEY (ID),
        INDEX CUST (CUSTOMER),
        FOREIGN KEY (PRODUCT_ID) REFERENCES PRODUCT(ID))
     

  Primary key column should be mapped to column with NUMERIC data type with a precision of 19 or more.
• Generete CMP beans from database and make changes that are described in above tutorial.
• Add session facade bean and implement business method that creates order:

        public void createProduct(String partNr, String description, float price) throws EJBException {
          try {
              productHome.create(partNr,description, new Float(price));
          } catch (CreateException ex) {
              ex.printStackTrace();
              throw new EJBException(ex.getMessage());
          }
         }
  
         public void createOrder(String customer, String partNr, float amount) throws EJBException {
          try {
              ProductLocal product = productHome.findByPartNumber(partNr);
              purchaseHome.create(customer,new Float(amount),product);
          } catch (FinderException ex) {
              ex.printStackTrace();
              throw new EJBException(ex.getMessage());
          }catch(CreateException ex){
              ex.printStackTrace();
              throw new EJBException(ex.getMessage());
          }
      }  
    

• Write client or JUnit tests and check the bean's functionality. Sources and tests are avalaible here.

Monday December 05, 2005

LDAP authentication in Sun Application server Today, I would like to describe the steps to enable LDAP authentication in web module that is deployed in Sun Application server. Authentication is the way an entity determines that another entity is who it claims to be.
Very important for understanding security for SJAS is Realm. A realm, also called a security policy domain or security domain, is a scope over which the server defines and enforces a common security policy. In practical terms, a realm is a repository where the server stores user and group information. The Application Server comes pre-configured with three realms: file (the initial default realm), certificate, and admin-realm. In this post we will add and setup new ldap realm.
I will use open source implementation of the Lightweight Directory Access Protocol server that is avalaible here.

• First, we should create new user. I created users.ldif file with one entry that represents user:

       dn: uid=blaha,ou=people,dc=netbeans,dc=cz
       uid: blaha
       givenName: blaha
       objectClass: top
       objectClass: person
       objectClass: organizationalPerson
       objectClass: inetorgperson
       sn: blaha
       cn: Petr Blaha
       userPassword: {SSHA}Z9RXgOsVA6395NtLw6ot7XjkO3dJAeUIqDdWdA==
     

  The entry should have defined uid attribute. The container will search entry according to this attribute during authentication.
• Add this entry in ldap server, execute folowing command:
  ldapadd -x -D "cn=Manager,dc=netbeans,dc=cz" -W -f users.ldif
• Open web admin console (bu default http://localhost:4848) and go to Security -- Realms page and click New button. Specify name, class name should be com.sun.enterprise.security.auth.realm.ldap.LDAPRealm and add these properties:
  directory: ldap://localhost:389 (change to right name)
  base-dn: ou=people,dc=netbeans,dc=cz (base distinguished name it represents from whence the search will start)
  jaas-context: ldapRealm (type of login module to use for this realm. Use ldapRealm)
• Create new web application. I will use form authentication method. Therefore, I created new login page contains HTML form with these fields:

      <form method="POST" action="j_security_check">
        Username: <input type="text" name="j_username"/>
   
        Password: <input type="password" name="j_password"/>
        <input type="submit" value="Submit"/>
      
    

• Update web.xml file according to new realm:

  18 <security-role>
  19     <role-name>USER</role-name>
  20   </security-role>
  21 
  22   <security-constraint>
  23     <web-resource-collection>
  24       <web-resource-name>protected area</web-resource-name>
  25       <url-pattern>/index.jsp</url-pattern>
  26       <http-method>GET</http-method>
  27       <http-method>POST</http-method>
  28     </web-resource-collection>
  29     <auth-constraint>
  30       <role-name>USER</role-name>
  31     </auth-constraint>
  32   </security-constraint>
  33 
  34   <login-config>
  35     <auth-method>FORM</auth-method>
  36     <realm-name>ldaprealmperapp</realm-name><!-- name of LDAP realm-->
  37     <form-login-config>
  38       <form-login-page>/login.jsp</form-login-page>
  39       <form-error-page>/error.jsp</form-error-page>
  40     </form-login-config>
  41   </login-config>
  

• Now you can test LDAP authentication.

Thursday December 01, 2005

Hibernate plugin for NetBeans 5.0 Many developers don't like EJB, JDO technologies and they are using other object/relational persistance and query service for Java like Hibernate. Hibernate lets you develop persistant classes following common Java idiom. The plugin for Hibernate in NetBeans was missing. Recently, I have seen on project of my colleague.
Petr Zajac develops xdoclet plugin for NetBeans that enables Attribute-Oriented Programming for Java. The plugin parses your source code and generates many artifacts such as XML and other stuff. Based on this plugin he did Hibernate plugin.
This plugin allows you to create new POJO beans, add relationships, fields, ....code completion