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Enterprise JavaBeans in Java Creator barcode 39 in Java Enterprise JavaBeans




How to generate, print barcode using .NET, Java sdk library control with example project source code free download:
Enterprise JavaBeans using barcode integrating for jsp control to generate, create code 3/9 image in jsp applications. Code 3/9 Now that we have seen the USS Code 39 for Java session bean and its corresponding business interface, let"s take a look at a client sample application:. package net.ensode.glassfi shbook; import javax.

ejb.EJB; public class SessionBeanClient { @EJB private static SimpleSession simpleSession; private void invokeSessionBeanMethods() { System.out.

println(simpleSession.getMessage()); System.out.

println("\nSimpleSession is of type: " + simpleSession.getClass().getName()); } public static void main(String[] args) { new SessionBeanClient().

invokeSessionBeanMethods(); } }. The above code simply decl bar code 39 for Java ares an instance variable of type net.ensode. SimpleSession, which is the business interface for our session bean.

The instance variable is decorated with the @EJB annotation; this annotation lets the EJB container know that this variable is a business interface for a session bean. The EJB container then injects an implementation of the business interface for the client code to use. As our client is a stand-alone application (as opposed to a Java EE artifact such as a WAR file) in order for it to be able to access code deployed in the server, it must be placed in a JAR file and executed through the appclient utility.

This utility can be found at [glassfish installation directory]/glassfish/bin/. Assuming this path is in the PATH environment variable, and assuming we placed our client code in a JAR file called simplesessionbeanclient.jar, we would execute the above client code by typing the following command in the command line:.

appclient -client simplesessionbeanclient.jar Executing the above comman Code-39 for Java d results in the following console output:. If you don"t see this, it didn"t work! SimpleSession is of type: net.ensode.glassfishbook.

_SimpleSession_Wrapper. which is the output of the SessionBeanClient class. [ 294 ]. 9 . The first line of output i s simply the return value of the getMessage() method we implemented in the session bean. The second line of output displays the fully qualified class name of the class implementing the business interface. Notice that the class name is not the fully qualified name of the session bean we wrote; instead, what is actually provided is an implementation of the business interface created behind the scenes by the EJB container.

. A More Realistic Example In the previous section, w e saw a very simple, "Hello world" type of example. In this section, we will show a more realistic example. Session beans are frequently used as Data Access Objects (DAOs).

Sometimes, they are used as a wrapper for JDBC calls, other times they are used to wrap calls to obtain or modify JPA entities. In this section, we will take the latter approach. The following example illustrates how to implement the DAO design pattern in a session bean.

Before looking at the bean implementation, let"s look at the business interface corresponding to it:. package net.ensode.glassfi jar Code 3/9 shbook; import javax.

ejb.Remote; @Remote public interface CustomerDao { public void saveCustomer(Customer customer); public Customer getCustomer(Long customerId); public void deleteCustomer(Customer customer); }. As we can see, the above i s a remote interface implementing three methods; the saveCustomer() method saves customer data to the database, the getCustomer() method obtains data for a customer from the database, and the deleteCustomer() method deletes customer data from the database. All of these methods take or return an instance of the Customer entity we developed in 4 as a parameter. Let"s now take a look at the session bean implementing the above business interface.

As we are about to see, there are some differences between the way JPA code is implemented in a session bean versus in a plain old Java object.. package net.ensode.glassfi jsp 39 barcode shbook; import import import import java.

sql.Connection; java.sql.

PreparedStatement; java.sql.ResultSet; java.

sql.SQLException; [ 295 ]. Enterprise JavaBeans impor t import import import import javax.annotation.Resource; javax.

ejb.Stateless; javax.persistence.

EntityManager; javax.persistence.PersistenceContext; javax.

sql.DataSource;. @Stateless public class Cu tomcat Code 39 Full ASCII stomerDaoBean implements CustomerDao { @PersistenceContext private EntityManager entityManager; @Resource(name = "jdbc/__CustomerDBPool") private DataSource dataSource; public void saveCustomer(Customer customer) { if (customer.getCustomerId() == null) { saveNewCustomer(customer); } else { updateCustomer(customer); } } private void saveNewCustomer(Customer customer) { customer.setCustomerId(getNewCustomerId()); entityManager.

persist(customer); } private void updateCustomer(Customer customer) { entityManager.merge(customer); } public Customer getCustomer(Long customerId) { Customer customer; customer = entityManager.find(Customer.

class, customerId); return customer; } public void deleteCustomer(Customer customer) { entityManager.remove(customer); } [ 296 ]. 9 private Long getNewCust omerId() { Connection connection; Long newCustomerId = null; try { connection = dataSource.getConnection(); PreparedStatement preparedStatement = connection .prepareStatement( "select max(customer_id)+1 as new_customer_id " + "from customers"); ResultSet resultSet = preparedStatement.

executeQuery(); if (resultSet != null && resultSet.next()) { newCustomerId = resultSet.getLong("new_customer_id"); } connection.

close(); } catch (SQLException e) { e.printStackTrace(); } return newCustomerId; } }. The first difference we sh jvm 3 of 9 ould notice is that an instance of javax.persistence. EntityManager is directly injected into the session bean.

In previous JPA examples, we had to inject an instance of javax.persistence.EntityManagerFactory, then use the injected EntityManagerFactory instance to obtain an instance of EntityManager.

The reason we had to do this was that our previous examples were not thread safe. What this means is that potentially the same code could be executed concurrently by more than one user. As EntityManager is not designed to be used concurrently by more than one thread, we used an EntityManagerFactory instance to provide each thread with its own instance of EntityManager.

Since the EJB container assigns a session bean to a single client at time, session beans are inherently thread safe, therefore, we can inject an instance of EntityManager directly into a session bean.. [ 297 ].
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