JAKARTAEE API of Java Library: Details of Function and Usage
JAKARTAEE API of Java Library: Detailed function and usage explanation
Jakartaee API is a Java class library that provides rich functions and tools to help developers quickly build enterprise -level applications.In this article, we will explore the functions of these APIs and provide some cases to show their usage.
1. What is Jakartaee API?
Jakartaee (formerly Javaee) is a Java platform for developing enterprise -level applications.Jakartaee API is its core part. It provides a series of libraries and tools to build strong, secure, scalable and high -performance applications.These APIs cover various functions, including web development, message transmission, security, transaction management, etc.
2. Jakartaee API feature overview
Here are some commonly used functional modules in the Jakartaee API:
-Servlet API: Used to develop Java -based web applications.It provides a simple way to handle HTTP requests and responses, and supports functions such as session management, filters, listeners, and other functions.
-JPA API: Java persistent API, used to process object relationship mapping (ORM).Developers can use JPA API to define the physical class, access the database, and conduct query and transaction management.
-EJB API: Application of enterprise JavaBean API for developing distributed, transaction and security management applications.It provides component -oriented programming models that enable developers to build components with reused, scalable and high -performance.
-JMS API: Java Message Service API, used to build an asynchronous and reliable message transmission system.It supports the sending and receiving of the message, and provides a variety of message modes and reliability guarantee mechanisms.
-JDBC API: Java database is connected to API for access and operation database.Developers can use JDBC API to perform SQL query, update and transaction processing.
-JSF API: Javaseerver Faces API, used to build a user interface.It provides a set of components and event models for creating an interactive web page.
-JAX-RS API: Java API for Restful Web Services, web services used to build RESTFUL-style.It provides a set of annotations and classes to handle HTTP requests, routes and serialization.
This is just a small part of the Jakartaee API, and there are more modules for developers.
3. Example of Jakartaee API
Here are some example code, which shows the function of how to use the Jakartaee API:
// Use Servlet API to process HTTP request
@WebServlet("/hello")
public class HelloWorldServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
response.setContentType("text/plain");
response.getWriter().print("Hello, World!");
}
}
// Use JPA API to implement object relationship mapping
@Entity
@Table(name = "employees")
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private int age;
// omit the getter and setter method
}
// Query employee information in the application
EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPU");
EntityManager em = emf.createEntityManager();
Employee employee = em.find(Employee.class, 1L);
System.out.println("Employee name: " + employee.getName());
// Use JMS API to send and receive message
@Stateless
@MessageDriven(mappedName = "jms/MyQueue")
public class MessageReceiver implements MessageListener {
public void onMessage(Message message) {
if (message instanceof TextMessage) {
try {
String text = ((TextMessage) message).getText();
System.out.println("Received message: " + text);
} catch (JMSException e) {
e.printStackTrace();
}
}
}
}
// Send a message
InitialContext context = new InitialContext();
ConnectionFactory connectionFactory = (ConnectionFactory) context.lookup("jms/ConnectionFactory");
Connection connection = connectionFactory.createConnection();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
Destination destination = (Destination) context.lookup("jms/MyQueue");
MessageProducer producer = session.createProducer(destination);
TextMessage textMessage = session.createTextMessage();
textMessage.setText("Hello, JakartaEE!");
producer.send(textMessage);
These examples show the usage of several commonly used modules in the Jakartaee API.Developers can choose appropriate APIs according to their needs and use their functions to develop powerful enterprise -level applications.
Summarize
Jakartaee API provides extensive functions and tools to help developers build high -performance, secure and scalable enterprise -level applications.This article introduces some functional modules of the Jakartaee API and provides use cases to show its usage.Through in -depth understanding of these APIs, developers can better use them to develop high -quality applications.
