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1、 畢業(yè)設(shè)計(jì)說明書 英文文獻(xiàn)及中文翻譯 班 級(jí)： 學(xué)號(hào)： 軟件學(xué)院 姓 名： 軟件工程 學(xué) 院： 專 業(yè)： 指導(dǎo)教師： 2014年 6 月 第 2 頁 共 12 頁 Explore On

2、JAVA, JSP Technology And Three Frameworks Duke, the Java mascot James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991. Java was originally designed for interactive television, but it was too advanced for the digital cable television industry at the time

3、. The language was initially called Oak after an oak tree that stood outside Gosling's office; it went by the name Green later, and was later renamed Java, from a list of random words. Gosling aimed to implement a virtual machine and a language that had a familiar C/C++ style of notation. Sun Micro

4、systems released the first public implementation as Java 1.0 in 1995. It promised "Write Once, Run Anywhere" , providing no-cost run-times on popular platforms. Fairly secure and featuring configurable security, it allowed network- and file-access restrictions. Major web browsers soon incorporated t

5、he ability to run Java applets within web pages, and Java quickly became popular. With the advent of Java 2, new versions had multiple configurations built for different types of platforms. For example, J2EE targeted enterprise applications and the greatly stripped-down version J2ME for mobile appli

6、cations , J2SE designated the Standard Edition. In 2006, for marketing purposes, Sun renamed new J2 versions as Java EE, Java ME, and Java SE, respectively. In 1997, Sun Microsystems approached the ISO/IEC JTC1 standards body and later the Ecma International to formalize Java, but it soon withdrew

7、from the process. Java remains a de facto standard, controlled through the Java Community Process. At one time, Sun made most of its Java implementations available without charge, despite their proprietary software status. Sun generated revenue from Java through the selling of licenses for specializ

8、ed products such as the Java Enterprise System. Sun distinguishes between its Software Development Kit (SDK) and Runtime Environment (JRE) (a subset of the SDK); the primary distinction involves the JRE's lack of the compiler, utility programs, and header files. On November 13, 2006, Sun released mu

9、ch of Java as open source software under the terms of the GNU General Public License (GPL). On May 8, 2007, Sun finished the process, making all of Java's core code available under free software/open-source distribution terms, aside from a small portion of code to which Sun did not hold the copyrigh

10、t. Sun's vice-president Rich Green has said that Sun's ideal role with regards to Java is as an "evangelist." Following Oracle Corporation's acquisition of Sun Microsystems in 2009–2010, Oracle has described itself as the "steward of Java technology with a relentless commitment to fostering a commun

11、ity of participation and transparency". Principles There were five primary goals in the creation of the Java language:1.It should be "simple, object oriented, and familiar"2.It should be "robust and secure". 3.It should be "architecture neutral and portable"4.It should execute with "high performan

12、ce"5.It should be "interpreted, threaded, and dynamic". Java Platform Main articles: Java (software platform) and Java Virtual Machine One characteristic of Java is portability, which means that computer programs written in the Java language must run similarly on any supported hardware/operating-sy

13、stem platform. This is achieved by compiling the Java language code to an intermediate representation called Java byte code, instead of directly to platform-specific machine code. Java byte code instructions are analogous to machine code, but are intended to be interpreted by a virtual machine (VM)

14、written specifically for the host hardware. End-users commonly use a Java Runtime Environment (JRE) installed on their own machine for standalone Java applications, or in a Web browser for Java applets. Standardized libraries provide a generic way to access host-specific features such as graphics, t

15、hreading, and networking. A major benefit of using byte code is porting. However, the overhead of interpretation means that interpreted programs almost always run more slowly than programs compiled to native executables would. Just-in-Time compilers were introduced from an early stage that compile

16、byte codes to machine code during runtime. Implementations Sun Microsystems officially licenses the Java Standard Edition platform for Linux, Mac OS X, and Solaris. Although in the past Sun has licensed Java to Microsoft, the license has expired and has not been renewed. Through a network of third-p

17、arty vendors and licensees, alternative Java environments are available for these and other platforms. Sun's trademark license for usage of the Java brand insists that all implementations be "compatible". This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implement

18、ation did not support RMI or JNI and had added platform-specific features of their own. Sun sued in 1997, and in 2001 won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun. As a result, Microsoft no longer ships Java with Windows, and in recent versi

19、ons of Windows, Internet Explorer cannot support Java applets without a third-party plugin . Sun, and others, have made available free Java run-time systems for those and other versions of Windows. Platform-independent Java is essential to the Java EE strategy, and an even more rigorous validation i

20、s required to certify an implementation. This environment enables portable server-side applications, such as Web services, Java Servlets, and Enterprise JavaBeans, as well as with embedded systems based on OSGi, using Embedded Java environments. Through the new GlassFish project, Sun is working to c

21、reate a fully functional, unified open source implementation of the Java EE technologies. Sun also distributes a superset of the JRE called the Java Development Kit (commonly known as the JDK), which includes development tools such as the Java compiler, Java doc, Jar, and debugger. Java performance

22、 and garbage collectors Programs written in Java have a reputation for being slower and requiring more memory than those written in C. However, Java programs' execution speed improved significantly with the introduction of Just-in-time compilation in 1997/1998 for Java1.1, the addition of language

23、features supporting better code analysis (such as inner classes, String Buffer class, optional assertions, etc.), and optimizations in the Java Virtual Machine itself, such as Hot Spot becoming the default for Sun's JVM in 2000. Currently, Java code has approximately half the performance of C code.

24、 Some platforms offer direct hardware support for Java; there are microcontrollers that can run java in hardware instead of a software JVM, and ARM based processors can have hardware support for executing Java byte code through its Jazelle option. Automatic memory management java uses an automatic

25、 garbage collector to manage memory in the object lifecycle. The programmer determines when objects are created, and the Java runtime is responsible for recovering the memory once objects are no longer in use. Once no references to an object remain, the unreachable memory becomes eligible to be free

26、d automatically by the garbage collector. Something similar to a memory leak may still occur if a programmer's code holds a reference to an object that is no longer needed, typically when objects that are no longer needed are stored in containers that are still in use. If methods for a nonexistent o

27、bject are called, a "null pointer exception" is thrown. One of the ideas behind Java's automatic memory management model is that programmers can be spared the burden of having to perform manual memory management. In some languages, memory for the creation of objects is implicitly allocated on the s

28、tack, or explicitly allocated and deal located from the heap. In the latter case the responsibility of managing memory resides with the programmer. If the program does not deal locate an object, a memory leak occurs. If the program attempts to access or deal locate memory that has already been deal

29、located, the result is undefined and difficult to predict, and the program is likely to become unstable and/or crash. This can be partially remedied by the use of smart pointers, but these add overhead and complexity. Note that garbage collection does not prevent "logical" memory leaks, i.e. those w

30、here the memory is still referenced but never used. Garbage collection may happen at any time. Ideally, it will occur when a program is idle. It is guaranteed to be triggered if there is insufficient free memory on the heap to allocate a new object; this can cause a program to stall momentarily. Ex

31、plicit memory management is not possible in Java. Java does not support C/C++ style pointer arithmetic, where object addresses and unsigned integers (usually long integers) can be used interchangeably. This allows the garbage collector to relocate referenced objects and ensures type safety and secu

32、rity. As in C++ and some other object-oriented languages, variables of Java's primitive data types are not objects. Values of primitive types are either stored directly in fields (for objects) or on the stack (for methods) rather than on the heap, as commonly true for objects (but see Escape analysi

33、s). This was a conscious decision by Java's designers for performance reasons. Because of this, Java was not considered to be a pure object-oriented programming language. However, as of Java 5.0, auto boxing enables programmers to proceed as if primitive types were instances of their wrapper class.

34、Java contains multiple types of garbage collectors. By default, Hot Spot uses the Concurrent Mark Sweep collector, also known as the CMS Garbage Collector. However, there are also several other garbage collectors that can be used to manage the Heap. For 90% of applications in Java, the CMS Garbage C

35、ollector is good enough. A class that is not declared public may be stored in any .java file. The compiler will generate a class file for each class defined in the source file. The name of the class file is the name of the class, with .class appended. For class file generation, anonymous classes ar

36、e treated as if their name were the concatenation of the name of their enclosing class and an integer. The keyword public denotes that a method can be called from code in other classes, or that a class may be used by classes outside the class hierarchy. The class hierarchy is related to the name of

37、 the directory in which the .java file is located. The keyword static in front of a method indicates a static method, which is associated only with the class and not with any specific instance of that class. Only static methods can be invoked without a reference to an object. Static methods cannot

38、access any method variables that are not static. The keyword void indicates that the main method does not return any value to the caller. If a Java program is to exit with an error code, it must call System. The method name "main" is not a keyword in the Java language. It is simply the name of the

39、 method the Java launcher calls to pass control to the program. Java classes that run in managed environments such as applets and Enterprise Java Bean do not use or need a main() method. A java program may contain multiple classes that have main methods, which means that the VM needs to be explicitl

40、y told which class to launch from. The main method must accept an array of String objects. By convention, it is referenced as args although any other legal identifier name can be used. Since Java 5, the main method can also use variable arguments, in the form of public static void main(String... ar

41、gs), allowing the main method to be invoked with an arbitrary number of String arguments. The effect of this alternate declaration is semantically identical (the args parameter is still an array of String objects), but allows an alternative syntax for creating and passing the array. The Java launch

42、er launches Java by loading a given class (specified on the command line or as an attribute in a JAR) and starting its public static void main(String[]) method. Stand-alone programs must declare this method explicitly. The String[] args parameter is an array of String objects containing any argument

43、s passed to the class. The parameters to main are often passed by means of a command line. Criticism of Java A number of criticisms have been leveled at Java programming language for various design choices in the language and platform. Such criticisms include the implementation of generics, the h

44、andling of unsigned numbers, the implementation of floating-point arithmetic, and security vulnerabilities. Class libraries Java Platform and Class libraries diagram Java libraries are the compiled byte codes of source code developed by the JRE implementor to support application development in Jav

45、a. Examples of these libraries are: The core libraries, which include: Collection libraries that implement data structures such as lists, dictionaries, trees, sets, queues and double-ended queue, or stacks XML Processing (Parsing, Transforming, Validating) libraries Security Internationalization

46、 and localization libraries The integration libraries, which allow the application writer to communicate with external systems. These libraries include: The Java Database Connectivity (JDBC) API for database access Java Naming and Directory Interface (JNDI) for lookup and discovery RMI and CORBA

47、 for distributed application development JMX for managing and monitoring applications User interface libraries, which include: The (heavyweight, or native) Abstract Window Toolkit (AWT), which provides GUI components, the means for laying out those components and the means for handling events fro

48、m those components The (lightweight) Swing libraries, which are built on AWT but provide (non-native) implementations of the AWT widgetry APIs for audio capture, processing, and playback A platform dependent implementation of Java Virtual Machine (JVM) that is the means by which the byte codes of

49、 the Java libraries and third party applications are executed Plugins, which enable applets to be run in Web browsers Java Web Start, which allows Java applications to be efficiently distributed to end-users across the Internet Licensing and documentation. DocumentationMain article: Javadoc Jav

50、adoc is a comprehensive documentation system, created by Sun Microsystems, used by many Java developers. It provides developers with an organized system for documenting their code. Javadoc comments have an extra asterisk at the beginning, i.e. the tags are /** and */, whereas the normal multi-line c

51、omment tags comments in Java and C are set off with /* and */. Sun has defined and supports four editions of Java targeting different application environments and segmented many of its APIs so that they belong to one of the platforms. The platforms are: Java Card for smartcards. Java Platform, Micr

52、o Edition (Java ME) — targeting environments with limited resources Java Platform, Standard Edition (Java SE) — targeting workstation environmentJava Platform, Enterprise Edition (Java EE) — targeting large distributed enterprise or Internet environments. The classes in the Java APIs are organized i

53、nto separate groups called packages. Each package contains a set of related interfaces, classes and exceptions. Refer to the separate platforms for a description of the packages available. The set of APIs is controlled by Sun Microsystems in cooperation with others through the Java Community Process

54、 program. Companies or individuals participating in this process can influence the design and development of the APIs. This process has been a subject of controversy. Sun also provided an edition called PersonalJava that has been superseded by later, standards-based Java ME configuration-profile pai

55、rings. JSP Profile JSP (Java Server Pages) is initiated by Sun Microsystems, Inc., with many companies to participate in the establishment of a dynamic web page technical standards. JSP technology somewhat similar to ASP technology, it is in the traditional HTML web page document (*. htm, *. html

56、) to insert the Java programming paragraph (Scriptlet) and JSP tag (tag), thus JSP documents (*. jsp). Using JSP development of the Web application is cross-platform that can run on Linux, is also available for other operating systems. JSP technology to use the Java programming language prepared by

57、 the category of XML tags and scriptlets, to produce dynamic pages package processing logic. Page also visit by tags and scriptlets exist in the services side of the resources of logic. JSP page logic and web page design and display separation, support reusable component-based design, Web-based appl

58、ication development is rapid and easy. Web server in the face of visits JSP page request, the first implementation of the procedures of, and then together with the results of the implementation of JSP documents in HTML code with the return to the customer. Insert the Java programming operation of t

59、he database can be re-oriented websites, in order to achieve the establishment of dynamic pages needed to function.JSP and Java Servlet, is in the implementation of the server, usually returned to the client is an HTML text, as long as the client browser will be able to visit. JSP 1.0 specification

60、 of the final version is launched in September 1999, December has introduced 1.1 specifications. At present relatively new is JSP1.2 norms, JSP2.0 norms of the draft has also been introduced. JSP pages from HTML code and Java code embedded in one of the components. The server was in the pages of c

61、lient requests after the Java code and then will generate the HTML pages to return to the client browser. Java Servlet JSP is the technical foundation and large-scale Web application development needs of Java Servlet and JSP support to complete. JSP with the Java technology easy to use, fully object

62、-oriented, and a platform-independent and secure, mainly for all the characteristics of the Internet. JSP technology strength:(1) time to prepare, run everywhere. At this point Java better than PHP, in addition to systems, the code not to make any changes.(2) the multi-platform support. Basically on

63、 all platforms of any development environment, in any environment for deployment in any environment in the expansion. Compared ASP / PHP limitations are obvious. (3) a strong scalability. From only a small Jar documents can run Servlet / JSP, to the multiple servers clustering and load balancing, to

64、 multiple Application for transaction processing, information processing, a server to numerous servers, Java shows a tremendous Vitality. (4) diversification and powerful development tools support. This is similar to the ASP, Java already have many very good development tools, and many can be free,

65、and many of them have been able to run on a variety of platforms under. JSP technology vulnerable:(1) and the same ASP, Java is the advantage of some of its fatal problem. It is precisely because in order to cross-platform functionality, in order to extreme stretching capacity, greatly increasing th

66、e complexity of the product. (2) Java's speed is class to complete the permanent memory, so in some cases by the use of memory compared to the number of users is indeed a "minimum cost performance." On the other hand, it also needs disk space to store a series of. Java documents and. Class, as well as the corresponding versions of documents. Spring Framework The Spring Framework is an open source application framework for the Java platform. The first version was written by Rod Johnson who re