J2EE, MVC, design pattern, UML, CORBA, and Linux

1. What technologies are used to implement each part of MVC? How to implement it?
A: MVC is short for Model-View-controller. "Model" indicates the business logic of the application (implemented by the JavaBean and EJB components), and "View" indicates the application surface (generated by the JSP page ), "controller" provides application processing process control (generally a servlet). This design model divides the application logic, processing process and display logic into different components for implementation. These components can be used for interaction and reuse.
2. What is J2EE?
A: je22 is a multi-layer (Multi-diered), distributed (distributed), component-based enterprise-level application model (enterpriese application model) proposed by Sun ). in such an application system, different components can be divided by function. These components can be located on different computers and at the corresponding level (Tier. The hierarchy includes the Client layer (clietn tier) components, web layer and components, business layer and components, and Enterprise Information System (EIS) layer.
3. Web Service terminology. Jswdl Development Kit introduction. JAXP and jaxm. Soap, UDDI, and WSDL.
Answer: Web Service Description Language (WSDL)
Soap is the Simple Object Access Protocol. It is a lightweight protocol used to exchange XML encoding information.
The purpose of UDDI is to establish standards for e-commerce. UDDI is a set of web-based, distributed, and standard standards for implementing information registration centers for Web Services, it also contains a set of access protocols that enable enterprises to register their own web services so that other enterprises can discover.
4. Is J2EE a technology, a platform, or a framework?
A: J2EE is a standard platform for enterprise distributed application development.
J2EE is also a framework, including JDBC, JNDI, RMI, JMS, EJB, JTA and other technologies.
5. Struts applications (such as Struts Architecture)
A: struts uses the Java Servlet/JavaServer Pages technology to develop the open source code framework for Web applications. Struts can be used to develop an application architecture based on the Model-View-controller design pattern. Struts has the following main functions:
1. Include a controller servlet that can send user requests to corresponding action objects.
II. the JSP free tag Library provides Association support in the Controller servlet to help developers create interactive form applications.
3. provides a series of practical objects: XML processing, automatic processing of JavaBeans attributes through Java reflection APIs, and International prompts and messages.
6. Web Service terminology. Jswdl Development Kit introduction. JAXP and jaxm. Soap, UDDI, and WSDL.
A: Web serviceweb service is a network-based, distributed modular component that executes specific tasks and complies with specific technical specifications, these specifications Enable Web Services to interoperate with other compatible components.
JAXP (Java API for XML parsing) defines a common interface for using Dom, sax, and XSLT in Java. In this way, you only need to use these universal interfaces in your program, and you do not need to modify the code when you need to change the specific implementation.
Jaxm (Java API for XML messaging) is an API that provides access methods and transmission mechanisms for soap communication.
WSDL is an XML format used to describe network services as a group of endpoints that operate on messages that contain document-oriented or process-oriented information. This format first abstracts the operation and message, and then binds it to a specific network protocol and Message format to define the endpoint. The specific endpoints are combined into abstract endpoints (services ).
Soap is the Simple Object Access Protocol. It is a lightweight protocol used to exchange XML encoding information.
The purpose of UDDI is to establish standards for e-commerce. UDDI is a set of web-based, distributed, and standard standards for implementing information registration centers for Web Services, it also contains a set of access protocols that enable enterprises to register their own web services so that other enterprises can discover.
7. Differences between C/S and B/S:
A: There are eight differences:
1. Different hardware environments:
C/s is generally built on a dedicated network. In a small network environment, the LAN provides connection and data exchange services through dedicated servers.
B/S is built on a wide area network. It does not need to be a dedicated network hardware environment, such as accessing the Internet over the phone and renting equipment. information management. it has a stronger adaptability than C/S. Generally, only the operating system and browser are available.
2. Different security requirements
C/s is generally oriented to relatively fixed user groups and has strong information security control capabilities. generally, the C/S structure is suitable for highly confidential information systems. some public information can be published through B/S.
B/S is built on a wide area network, which has relatively weak security control capabilities and may be intended for unknown users.
3. Different program Architectures
The C/S program can focus more on processes, perform multi-level permission verification, and minimize the system running speed.
B/S's multiple considerations for security and access speed are based on the need for more optimization. higher requirements for B/S architecture than c/s is a development trend, from Ms. net series of BizTalk 2000 Exchange 2000 and so on, fully support the system built by network components. the JavaBean Component Technology pushed by Sun and IBM makes B/S more mature.
4. Different Software Reuse
The reusability of components is not as good as that of components under B/S requirements.
The multiple structures of B/S pairs require relatively independent components and can be reused relatively well. You can purchase a dining table instead of a stone table on the wall.
5. Different system maintenance
Due to the integrity of the C/S program, it is necessary to make an overall investigation to solve the problems and system upgrades. Upgrading is difficult. It may be necessary to create a new system.
B/S components, which can be replaced individually to achieve seamless system upgrade. The system maintenance overhead is minimized. Users can download and install the components online to achieve the upgrade.
6. Different handling problems
The c/s program can fix the user surface and meet high security requirements in the same region. It is related to the operating system and should be the same system.
B/S is built on the Wide Area Network. It targets different user groups and is scattered across regions. This is what C/S cannot do. It has the least relationship with the operating system platform.
7. Different user interfaces
C/s is mostly built on Windows platforms, with limited performance methods and high requirements on programmers.
B/S is built on a browser, with richer and more vivid expressions to communicate with users, and most of the difficulties are reduced to reduce development costs.
8. Different information flows
C/S programs are generally typical centralized mechanical processing, with relatively low interaction.
B/S information flow to changeable, B-B B-C B-G and other information, flow changes, more like the transaction center.
8. What is a Web container?
A: provide an environment for the application components (JSP and Servlet) in the container, so that JSP and servlet can directly connect to the environment variables in the container **. You do not need to pay attention to other system problems. It is mainly implemented by Web servers. For example, tomcat, WebLogic, and websphere. The interface provided by the container strictly complies with the Web application standard in J2EE specifications. We call the web server that complies with the above standards the Web Container in J2EE. 122 what is an EJB container
A: Enterprise Java Bean container. More industry-specific characteristics. It provides various management functions for the component EJB running in it. As long as the EJB meeting the J2EE specification is put into the container, it will be managed efficiently by the container immediately. In addition, system-level services can be obtained through ready-made interfaces. For example, mail service and transaction management
9. What is JNDI?
A: (Java Naming & Directory Interface) Java Naming directory service. The main function is to provide a directory system that allows applications from other places to leave their own indexes on it to quickly find and locate distributed applications.
10. What is JMS?
A: (Java Message Service) Java Message Service. Communication between applications. Including point-to-point and broadcast.
11. What is JTA?
A: (Java transaction API) Java transaction service. Provides various distributed transaction services. An application only needs to call the interfaces it provides.
12. What is JAF?
A: (Java Action Framework) Java security authentication framework. Provides some security control frameworks. Developers can implement their own personalized security control policies through various deployment and customization.
RMI/IIOP :( Remote Method Invocation/Internet object request mediation protocol) They are mainly used to call services remotely. For example, if a program runs on a remote computer that provides the Stock Analysis Service, we can directly call it on a local computer. Of course, this requires certain specifications to communicate between heterogeneous systems. RMI is unique to Java.
13. What technologies are used to implement MVC? How to implement it?
A: MVC is short for Model-View-controller. "Model" indicates the business logic of the application (implemented by the JavaBean and EJB components), and "View" indicates the application surface (generated by the JSP page ), "controller" provides application processing process control (generally a servlet). This design model divides the application logic, processing process and display logic into different components for implementation. These components can be used for interaction and reuse.

14. What design patterns are used in development? In what scenarios?
A: each mode describes a problem that is constantly emerging in our environment, and then describes the core solution of the problem. In this way, you can use existing solutions countless times without repeating the same work. The MVC design mode is mainly used. Used to develop JSP/servlet or J2EE applications. Simple factory mode.
15. Are you familiar with or have heard of several common J2EE models? And some opinions on the Design Model
A: Session Facade Pattern: Use sessionbean to access entitybean.
Message Facade Pattern: asynchronous call
EJB Command pattern: replace sessionbean with command JavaBeans for Lightweight Access
Data transfer object Factory: Using DTO factory to simplify entitybean data provision features
Generic attribute access: the attibuteaccess interface simplifies entitybean data provision features
Business interface: Use Remote (local) interfaces and bean classes to implement the same interface and standardize business logic consistency
The design of the EJB architecture directly affects the system performance, scalability, maintainability, component reusability, and development efficiency. The more complex the project, the larger the project team, the more important the design is.
16. Common J2EE design patterns? Describe the factory model.
A: There are 23 Design Patterns in Java:
Factory (factory mode), Builder (construction mode), factory method (Factory method mode ),
Prototype (original model mode), Singleton (Singleton mode), facade (facade mode ),
Adapter (adapter mode), bridge (Bridge Mode), composite (merging mode ),
Decorator, flyweight, proxy ),
Command (command mode), Interpreter (Interpreter mode), visitor (visitor mode ),
Iterator, mediator, memento ),
Observer (Observer mode), State (State mode), Strategy (Policy mode ),
Template Method (template method mode), chain of responsibleity (responsibility chain mode)
Factory mode: The factory mode is a frequently used mode. Classes implemented based on the factory mode can generate instances of a class in a group based on the provided data, generally, this group of classes has a common abstract parent class that implements the same method, but these methods perform different operations on different data. First, you need to define a base class. The subclass of this class implements the methods in the base class through different methods. Define a factory class. The factory class can generate different subclass instances according to the conditions. After obtaining the subclass instance, developers can call the methods in the base class without having to consider which subclass instance is returned.
17. UML
A: Standard Modeling Language (UML. Use case diagram, static diagram (including class diagram, object diagram, and package diagram), behavior diagram, InterAction diagram (sequence diagram, cooperation diagram), implementation diagram,
 

18. What is CORBA? What is the purpose?
A: The CORBA standard is a Common Object Request Broker Architecture, which is standardized by Object Management Group (OMG. It is composed of an Interface Definition Language (IDL), a language binding (binding: also translated as associated encoding), and a protocol that allows interoperation between applications. The purpose is:
Write in different programming languages
Run in different processes
Development for different operating systems

19. Linux thread and GDI class explanation.
A: Linux implements the "one-to-one" thread model based on the core lightweight process. A thread entity corresponds to a core Lightweight Process, and management between threads is implemented in the off-core function library.
The GDI class is the image device programming interface class library.
134. Linux thread and GDI class explanation.
Linux implements the "one-to-one" thread model based on the core lightweight process. A thread entity corresponds to a core Lightweight Process, and management between threads is implemented in the off-core function library.
The GDI class is the image device programming interface class library.