1. Computer Language
Languages : communication way
Computer languages: of communication between people and computers
java is a computer programming language, but also the Italian cycling brand
Software engineers, the Java Development Engineer
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2. C / S conceptual architecture
C / S is the Client / Server , i.e., a client / server architecture, a typical two-tier structure.
A client comprising one or more programs running on a user's computer
Server has two, one is a server-side database, the data access server via the client database; the other is Socket server, the server-side program by Socket that communicate with the client.
C / S can be seen as a fat client architecture
Because the client needs to implement the vast majority of business logic and interface display. As part of the client's needs under great pressure, because the display logic and transaction processing are contained therein,
By interaction with the database (usually the SQL implementation or stored procedure) to achieve persistent data, in order to meet the needs of the actual project.
C / S advantages and disadvantages
advantage:
( 1 ) interface and operation can be very rich
( 2 ) ensure safety performance can easily achieve multi-layer authentication is not difficult
( 3 ) Since there is only one layer interacting, so response speed.
Disadvantages:
( 1 ) Applicable narrow, typically used in LAN
( 2 ) user group is fixed. Since the need to be installed before use, and therefore not suitable for users of some unknown
( 3 high) maintenance costs. The occurrence of an upgrade, all client programs need to be changed.
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3. B / S conceptual framework
B / S is a Browser / Server , that is, the browser / server architecture.
Browser refers to a Web browser, a handful of business logic in the front-end implementation, but the main business logic on the server side, Browser Client, WebApp server and DB end constitute the so-called three-tier architecture.
B / S -based systems without special installation, only the Web browser.
B / S can be seen as a thin client architecture
B / S architecture, the display logic to the Web browser, transaction processing logic on the WebApp on, thus avoiding the huge fat client, reducing the client's pressure. Because the client contains very little logic, it is also known as thin clients.
B / S advantages and disadvantages
advantage:
( 1 ) client without having to install, there are Web browser to
( 2 ) BS architecture can be placed directly over the WAN, to achieve the purpose of multi-client access through certain access control, strong interaction.
( 3 ) BS architecture eliminates the need to upgrade multiple clients, you can upgrade the server.
Disadvantages:
( 1 ) in the cross-browser, BS architecture is not satisfactory.
( 2 ) the performance to be achieved CS degree program takes a lot of energy.
( 3 ) on the speed and security need to spend a significant design cost, this is BS biggest problem architecture.
( 4 ) B and S interaction is a request - response pattern, usually need to refresh the page, this is not the customer would like to see. (At Ajax after the popularity of this problem to a certain degree of ease)
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4. the Java Introduction (History of)
- sun 1991 established a program called Green project team, specializing in computer embedded applications in home appliances (TV set-top boxes) developed a technique called Oak of object-oriented language
- 1996 Nian 1 Yue, Sun has released Java first development kit ( the JDK 1.0 ) , which is Java important milestone in the development process, marking Java to become a stand-alone development tool
- 1997 Nian 2 Yue, the JDK 1.1 available
- 1998 Nian 12 Yue 8 days, the second generation of Java Platform Enterprise Edition J2EE release
- 1999 Nian 6 Yue, Sun released the second generation of Java platform (referred to as Java2 ) in 3 versions
- 2000 Nian 5 Yue, JDK1.3 , JDK1.4 and J2SE1.3 have been released
- 2001 Nian 9 Yue 24- Ri, J2EE1.3 release. 2002 Nian 2 Yue 26 Ri, J2SE1.4 release
- 2004 Nian 9 Yue 30 Ri, J2SE1.5 release
- 2005 Nian 6 months, at the Java One conference, Sun has released the Java SE 6 . In this case, the Java various versions have been renamed, which has been canceled figures 2 , such as J2EE renamed JavaEE , J2SE renamed JavaSE , J2ME renamed JavaME .
- 2006 Nian 11 Yue 13 Ri, Java technology inventor Sun announced the Java technology as free software released
- 2009 years, the Oracle announced the acquisition of Sun
- 2014 year Oracle released Java8 official version
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5. The Java features
- Simplicity absorbed the C ++ various advantages languages, also abandoned C ++ was difficult to understand multiple inheritance , pointers , etc.
- Object-Oriented
- Platform-independent portability (cross-platform)
- Multithreading
- safety
- Java can write desktop applications , Web applications , distributed systems , and embedded systems applications, etc.
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6. the Java three technologies infrastructure languages
1 .Java SE is the Java Platform Standard Edition for short ( Java Platform, Standard Edition) (Also Known AS Java 2 Platform), for the development and deployment of desktops, servers and embedded devices and real-time environment of Java applications. Including the development of Java SE class library for Java Web services, at the same time, Java SE provides the foundation for Java EE.
Java SE (Java Platform, Standard Edition, Java Standard Edition) is based on the JDK and JRE
2 J2EE is a use of Java 2 platform enterprise solutions to simplify the development, deployment architecture and complex issues related to the management. J2EE technology base is the core Java platform or Java 2 Platform, Standard Edition, J2EE is not only consolidated the Standard Edition of the many advantages, such as "write once, run anywhere" features, easy to access database JDBC API, CORBA technology and the ability to protect data in Internet applications, security mode , and so on, and also provides EJB (Enterprise JavaBeans), Java Servlets API, JSP (Java Server Pages) and XML technology fully supported. The ultimate goal is to become an enabling enterprise developers to significantly shorten time to market architecture.
3 Java ME is short for Java Micro Edition (Java Platform, Enterprise Edition), is a collection of technologies and specifications, it is a mobile device (including consumer products, embedded devices provide, and advanced mobile devices, etc.) based on the Java environment development and application platform. Java ME configuration currently divided into two categories, one is for small mobile devices CLDC (Connected Limited Device Profile), a face type category is more powerful devices such as mobile smart phones and and top boxes, known as CDC (Connected Device Profile CDC
Put it more simply point
Java SE software running on the computer to do.
Java EE is used to make websites - (our common JSP technology)
Java ME is doing mobile phone software.
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7. JAVA language Why cross-platform?
Because Java code is compiled after the program code is not a hardware system that can be run directly, but a " midamble " - bytecode. It is then mounted on different hardware platforms different Java Virtual Machine (JVM) , the JVM to the byte code and then " translated " code into the corresponding hardware platform capable of executing. So for Java programmers, it does not need to consider the hardware platform is. So Java cross-platform.
Because it has a Virtual Machine ( the JVM ), JAVA program is not run directly on the computer, is performed on a virtual machine, each system has its own platform is a virtual machine ( the JVM ), so JAVA language can be cross-platform.
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8. Jre
(Java Runtime Environment acronym refers to the Java Runtime Environment )
Including the java virtual machine (jvm) and class libraries needed java program, if just run a good development program, as long as the computer can be installed jre
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9. Jdk
Write source code ---- compilation
(Java Development Kit is the Java language Software Development Kit ( SDK ))
Includes jre, no JDK, it can not compile Java program (refer .java java source files), only if you want to run a Java program (refer to class or jar or other archives), to ensure that the appropriate JRE is installed. (Includes compilation tools javac.exe)
Jdk > jre >jvm
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