Geronimo! Part 1th: Let Java EE programming simpler

Java EE is a platform-independent environment designed to develop and configure web-based applications that are used in an enterprise-wide environment. This platform has been dubbed a meta language or a language superset. In essence, however, Java EE is only the smallest set of JavaScript and some specific Java classes. (See Resources for a link to the Java EE Class document.) ）

Java EE consists of application programming interfaces (APIs), services, and protocols for developing multi-tier and web-based applications. It's a complex standard, and it's not easy to write a simplified article that's as difficult as writing an article that simplifies the federal tax code. But let's start with some of its basic principles, and the entire journey will be inspired by the small amount of implementation details. Now buckle up and let's get started!

Basic principles

Java EE Multilayer Design The client layer is represented by a pure HTML protocol, which is generated by the JavaServer Pages (JSP) and the Java servlet, and potentially deploys multiple Java applets with a transport protocol (TCP/IP, of course). Any Web browser that conforms to the standard can function as a client of the Java EE system.

The server layer contains Enterprise JavaBean (EJB) technology, which defines the platform logic for enterprise applications. The EJB server provides thread management, concurrency management, memory management, and security features and automates these tasks so that application programmers can get rid of these details. This is the power of Java EE design.

At the bottom is the core of the enterprise's precious data, where standard database tools, such as ibm®db2®, Oracle, MySQL, can be accessed through the Java database connection (Java DB Connectivity,jdbc) interface. or any number of other database engines that are based on the Structured Query language (structured queries language,sql).

Java EE is all about defining WEB services--This is a nice name for defining a dynamic page, in which case the program dynamically generates the Web page, instead of just returning a generic HTML text file to the calling client browser. Java EE is a veritable hodgepodge of various technical acronyms, each of which is described by an acronym that is easy to remember. As a programmer, you don't need to master all these technologies to make a glorious career in the Java EE environment, but if you learn more about this, you can benefit your career.

Quick reference: Java EE technology

The next thing to introduce is a lot of Java technology, a quick reference to some technology. Programmers who have mastered all these technologies are in great demand in today's workplace. These technologies are so popular that I think it's because of their importance and the simplicity of deployment, which is purely my subjective point of view.

I provide this list both to explain the complexities of Java EE and to provide a rough map to help you continue to learn these techniques. Important technologies include:

A file of the jsp:html template that contains embedded Java code that is compiled into a servlet before execution.

EJB: Represents the platform logic of an enterprise Web application. The two types of EJB technology are entity beans and session beans.

JDBC: An API for connecting to a database from the Java environment. It is a substitute for a Java programmer for Open Database Connectivity (open DB CONNECTIVITY,ODBC).

Java API for XML processing (Java API for XML PROCESSING,JAXP): Used to assist application analysis and transformation of XML documents.

Java Naming and Directory interfaces (Java naming and directory Interface,jndi): Used to define methods for performing directory operations, such as using their properties to search for objects and associating properties with objects.

Java API for xml-based remote procedure invocation (Java API for xml-based remote Procedure CALL,JAX-RPC): Allows developers to create Web Service Description Language (Web services Descripti On LANGUAGE,WSDL) describes the client and service. WSDL describes the service as a set of endpoints that operate on messages and are defined in XML.

Java API for xml-based Web services (Java API for xml-based Web SERVICES,JAX-WS): It allows developers to implement clients and services described by WSDL, similar to Jax-RPC at this point, but JA X-WS does not require a deployment descriptor because it uses annotations such as @WebService to declare WEB service endpoints. When using JAX-WS, you can deploy WEB services without using a deployment descriptor!

XML-bound Java schema (Java Architecture for XML BINDING,JAXB): Provides a bound compiler and a run-time framework to map Java objects to XML documents. This feature ensures that only valid messages are accepted and processed by the system. The compiler automatically converts the XML schema of the World Wide Web consortium,w3c into Java classes so that you do not have to write any complex parsing code yourself.

Java API for XML messages (Java API for XML MESSAGING,JAXM): Allows applications to exchange XML-form business documents on the Internet. Examples include inventory lists, invoices and countless other business documents, which enable modern business to function effectively.

The Java API for the >xml registry (Java API for XML REGISTRIES,JAXR): Provides a standard API for accessing different kinds of XML registries, which is useful for building, deploying, and discovering Web services.

Java Messaging Service (Java message SERVICE,JMS): Allows the use of a unified API to write message-based applications that can access common features of many messaging system products.

Java Management extensions (Java Management extensions,jmx): This is a Java standard that is created specifically to monitor and manage the application services of the EE app.