Java Web Services & Java EE Microservices: JSP Servlets JBDC

Now let’s talk about Web services are. Web services are tools that you can use several different ways. The most popular styles are SOA, REST and RPC. They are architectural elements. The type of web service that you choose will make or break your internet company. It will make it easier or harder for your clients to purchase items from you over the internet. It is a good idea for you to understand and know what each type of web service can do before you can really make up your mind.

Web services can be executed in different ways. Web services can be classified as “Big” web services and “RESTful” web services.

Big web services

Big web services depend on SOAP standard and frequently contain a WSDL to portray the interface that the web service offers. The points of interest of the contract may include messages, operations, bindings, and the location of the web service.

Basically, you would need to utilize RESTful web services for integration over the web and utilize enormous web services in enterprise application integration scenarios that have propelled quality of service (QoS) requirements.

Java API for XML Web Services (JAX-WS) is a technology for building web administrations and customers that impart utilizing XML. JAX-WS enables designers to compose message-situated and also Remote Procedure Call-arranged (RPC-arranged) web services.

There are many options to initialize Jersey in your servlet container. Some of them require no XML configuration at all. For my application, I simply configured the Jersey Servlet in web.xml as follows:

Written in the Java programming language, an enterprise bean is a server-side component that encapsulates the business logic of an application. The business logic is the code that fulfills the purpose of the application. In an inventory control application, for example, the enterprise beans might implement the business logic in methods called checkInventoryLevel and orderProduct. 

Session beans provide a simple but powerful way to encapsulate business logic within an application. They can be accessed from remote Java clients, web service clients, and components running in the same server.

Message-driven beans can implement any messaging type. Most commonly, they implement the Java Message Service (JMS) technology. The example in this chapter uses JMS technology, so you should be familiar with basic JMS concepts such as queues and messages.

This section demonstrates how to use the embedded enterprise bean container to run enterprise bean applications in the Java SE environment, outside of a Java EE server.

This section discusses how to implement asynchronous business methods in session beans and call them from enterprise bean clients.

Java Persistence API (JPA) provides Plain Old Java Object standard and object relational mapping (OR mapping) for data persistence among applications. JPA is a specification and several implementations are available. 

This sub-section explains how to use the Java Persistence API. The material here focuses on the source code and settings of three examples. The first example, order, is an application that uses a stateful session bean to manage entities related to an ordering system. The second example, roster, is an application that manages a community sports system. The third example, address-book, is a web application that stores contact data.

The Java Persistence query language defines queries for entities and their persistent state. The query language allows you to write portable queries that work regardless of the underlying data store.

The Criteria API is used to define queries for entities and their persistent state by creating query-defining objects. Criteria queries are written using Java programming language APIs, are typesafe, and are portable. Such queries work regardless of the underlying data store.

String-based Criteria API queries (“string-based queries”) are Java programming language queries that use strings rather than strongly-typed metamodel objects to specify entity attributes when traversing a data hierarchy. String-based queries are constructed similarly to metamodel queries, can be static or dynamic, and can express the same kind of queries and operations as strongly-typed metamodel queries.

Enterprise tier and web tier applications are made up of components that are deployed into various containers. These components are combined to build a multitier enterprise application. Security for components is provided by their containers. A container provides two kinds of security: declarative and programmatic.

Web applications contain resources that can be accessed by many users. These resources often traverse unprotected, open networks, such as the Internet. In such an environment, a substantial number of web applications will require some type of security. 

The following parties are responsible for administering security for enterprise applications:

• System administrator: Responsible for setting up a database of users and assigning them to the proper group. The system administrator is also responsible for setting GlassFish Serverproperties that enable the applications to run properly. Some security-related examples set up a default principal-to-role mapping, anonymous users, default users, and propagated identities. When needed for this tutorial, the steps for performing specific tasks are provided.

Digital certificates for the GlassFish Server have already been generated and can be found in the directory domain-dir/config/. These digital certificates are self-signed and are intended for use in a development environment; they are not intended for production purposes. For production purposes, generate your own certificates and have them signed by a certificate authority (CA).

In a Java EE application, a transaction is a series of actions that must all complete successfully, or else all the changes in each action are backed out. Transactions end in either a commit or a rollback. 

This overview defines the concept of messaging, describes the JMS API and when it can be used, and explains how the JMS API works within the Java EE platform.

This section shows how to create, package, and run simple JMS clients that are packaged as application clients and deployed to a Java EE server. The clients demonstrate the basic tasks a JMS application must perform:

Typical enterprise application accesses and stores information in one or more databases, because this information is critical for business operations, it must be accurate, current, and reliable. Data integrity would be lost if multiple programs were allowed to update the same information simultaneously or if a system that failed while processing a business transaction were to leave the affected data only partially updated. By preventing both of these scenarios, software transactions ensure data integrity. Transactions control the concurrent access of data by multiple programs. In the event of a system failure, transactions make sure that after recovery, the data will be in a consistent state.

Interceptors are used in conjunction with Java EE managed classes to allow developers to invoke interceptor methods on an associated target class, in conjunction with method invocations or lifecycle events. Common uses of interceptors are logging, auditing, and profiling.